# Atkinson frustrations



## Gordon (Jul 9, 2018)

This post is to vent my frustration but if someone has some insight it is certainly welcome. I am building the Atkinson Differential engine from the Gingery plans and I am not having any luck in getting to run. Gingery said that he had to turn the engine over with an electric motor and a belt to the flywheel for up to 40 hours to seat the rings before it would start dependably. I have been doing that for quite a few hours (25-30) but I am not seeing any improvement. I am sure that the problem is compression but a solution escapes me. Due to the unique design you can only feel the compression on the last portion of the compression stroke because the spark plug hole is covered until the last part of the stroke. There seems to be good suction at the spark plug hole on what would be the exhaust stroke.


At this point it kind of fires about 1/3 of the time and even that is intermittent. If fires for a while and then quits firing until something like carburetor adjustment or cool off occurs. I have tried different spark timing and different carburetors and carburetor adjustments but nothing seems to change. I am using the S&S ignition and there seems to be a good spark.


At this point I am reluctant to remove the pistons/rings for inspection because if they are actually seating the rings are going to be in a different rotation when it is reassembled which I assume would at least partially disturb the seating in process.


There seems to be a surprising lack of information and build logs on an engine which has been built by quite a few others. There are quite a few Youtube videos. There are several errors or at lest omissions on the drawings but I have not seen any reference to this by any others. I have been over by engine and checked it to the drawings many times and as far as I can tell it is made correctly.


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## ThomasSK (Jul 9, 2018)

Does it move the intake valve? that is just moved by the suction from the cylinder, and the spring is important.  Too stiff a spring here would make it not get enough gas.  Make sure there isn't too much friction on the intake valve.

Does it run assisted? given that it has gas available, does it run when connected to a electric motor?
Have you tried running it on a dab of starting fluid? 

As long as you can feel the push of the compression, that should be fine.  Is your timing of the spark correct? The way that the timing is explained in the book its faily easy to set it up 180 degree wrong, there is a youtube video around that explains it, but I was not able to dig it up.

The Atkinson differential is perhaps one of the worst engines to get running reliably, but it's a fun engine!


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## Gordon (Jul 9, 2018)

Intake valve seems to move well. Visible movement and I have tried stronger and weaker springs.

It kind of runs with the electric motor. I can hear it fire about 25% to 50% of the time. I cannot get it to fire when turned over by hand. I have also tried weaker and stronger exhaust valve springs. I does not really try to run on starting fluid. Just one pop. It only seems to fire with the carburetor adjustment just barely open. I have tried making a smaller orifice but that has not made much difference. I have also tried choke plates on the intake throat.

I am sure that the ignition timing is correct or at least not 180° off. I have tried running it both up to 15° BTDC and ATDC.


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## ThomasSK (Jul 9, 2018)

Just to cover all the basics, power stroke should be the long stroke, and compression stroke the short stroke. 

What kind of fuel do you use?  
It may be that it needs more time to run in, but I would expect it to fire and run for a short time after 30hr.


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## Gordon (Jul 9, 2018)

I am using Coleman fuel. I also thought that after running with an electric motor for that long it should show more of a tenancy to fire. I guess I will just try running with the electric motor for a while more.

Am I correct in my assumption that removing and reinstalling the rings would affect the seating or are the rings rotating in the grooves as it is running?


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## ThomasSK (Jul 9, 2018)

The rings should be rotating.


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## Cogsy (Jul 10, 2018)

In my mind, the procedure for "running the rings in" is completely wrong and is likely to be the direct cause of poor compression. Best full size practice (and what I use successfully in model size) is not run the rings in at all and use combustion forces to provide correct ring pressure to create a seal. The absence of these combustion forces means the rings will wear in without creating an effective seal and will most likely never seal fully. In a full size engine, excessive idling/low load of a brand new engine results in the same thing and is known as 'glazing'. I wonder if the specified running in procedure is why this engine is known as difficult to get running?

If it was my engine, I think I'd be pulling it down, lightly honing the bore (as I'm thinking it will be highly polished from the running in procedure) and trying a fresh set of rings, with zero running-in and see if it runs then.

In my models (and this is all based on cast iron rings which I assume yours is) I lap the valves in and assemble the engine without spinning it at all. Once fuel and spark is set I try to start and the first few pops and bangs seem to increase the valve sealing and compression increases, as does the frequency of the pops and bangs. A few tweaks of the carb and maybe the timing later and it (hopefully) starts. After a few runs (maybe 10-15 minutes total running) compression is noticeably higher than what it first was, due to the rings bedding in properly. I've included 2 videos of the same engine using this procedure. The first is the very first start of it, and the second is with around 15 minutes of running on it. In the second I attempt the first hand-start of the engine around the 1:45 mark.


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## Gordon (Jul 10, 2018)

Cogsy: Actually that is pretty much what I have done. I honed the cylinder and lapped the valves. I have remade the rings twice. I have been running it with the electric motor with both ignition and fuel operating. I have not run it at all just spinning free without fuel and spark. As I stated it fires part of the time but not enough to actually run on it's own. I does seem to be improving. If I try to hand start it it will keep spinning for several revolutions because the firing is at lest helping to keep it turning.


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## colby15642 (Jul 10, 2018)

Also make sure that the entire ignition system is working properly, as the plug may not be firing under compression pressure.  That has fooled me a couple of times in the past.

If you're spinning the engine with an electric motor, it should fire consistently even if it has no piston rings installed.

Does it emit black smoke or unburned fuel from the exhaust?  If not, try enriching the mixture until it does smoke, so you know where you are in the range of fuel / air mixtures.

Try propane as a fuel (but not in your enclosed basement) to eliminate poor fuel atomization as a cause of the problem.  The same carburetor should work well enough with propane to complete a quick test.  Or rig up some kind of temporary "spewforth" fuel system for a quick test.  Too much propane will produce a black exhaust to let you that the mixture is too rich.

Clark.  Coolspring Power Museum.


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## Cogsy (Jul 11, 2018)

Sorry, didn't realise that (I thought it was just free spinning). Maybe as a quick and dirty test, dump a charge of liquid fuel in the plug hole and try and start it. On a small engine it will initially be flooded but after spinning it over for a bit it should start and run quite well on that single charge for a second or so. If it runs more strongly than usual it's likely you have a fuel issue, if not then it's something else...


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## Gordon (Jul 11, 2018)

I think that I may have found at least part of the problem. Due to the design of the intake and exhaust valves there is a very short part of the stroke between exhaust and intake. Both valves are atmospheric operated, that is no mechanical opening, only exhaust pressure and intake vacuum opens the valve.  I just found that prior to the actual intake at the carburetor I am getting a short burst of positive pressure at the carburetor throat prior to the actual intake. This may be exhausting the fuel back through the carburetor prior to actual intake. My theory at this point is that the fuel at the jet is exhausted and by the time the actual intake takes place there is no fuel to atomize. I am getting a good suction at the the carburetor but it may be coming too late. 

Off to test my new theory.  This certainly is a unique and interesting design but that is why I am doing it in the first place. After 20+ "ordinary" engines I am just looking for things that are out of the ordinary. Last couple of projects have included Howell "V" Twin and a Snow.


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## Ramoye (Aug 19, 2018)

Gordon said:


> I think that I may have found at least part of the problem. Due to the design of the intake and exhaust valves there is a very short part of the stroke between exhaust and intake. Both valves are atmospheric operated, that is no mechanical opening, only exhaust pressure and intake vacuum opens the valve.  I just found that prior to the actual intake at the carburetor I am getting a short burst of positive pressure at the carburetor throat prior to the actual intake. This may be exhausting the fuel back through the carburetor prior to actual intake. My theory at this point is that the fuel at the jet is exhausted and by the time the actual intake takes place there is no fuel to atomize. I am getting a good suction at the the carburetor but it may be coming too late.
> 
> Off to test my new theory.  This certainly is a unique and interesting design but that is why I am doing it in the first place. After 20+ "ordinary" engines I am just looking for things that are out of the ordinary. Last couple of projects have included Howell "V" Twin and a Snow.



Gordon,
I am also building the Atkinson Differential Engine.  I have experienced the same problems you described in trying to get it to run.  I have run it at least 150 hours with very little success.  It did run for about 7 seconds on its own.  I pressurized the cylinder and the rings held 90 psi, until I moved to a different part of the cylinder, then it was leaking.  Suspect my cylinder is not good enough.  Ordered new cylinder material and will machine it completely, versus doing brazing of components (had problem with warpage from the heat).  I found that too lose of an intake spring will cause spitting out the carb.  Seems the thing was not getting enough fuel to fire consistently.  This engine has been a real challenge.  Have you had any success?
Thanks.  Ray.


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## Gordon (Aug 19, 2018)

Ray: Not having much success. I have lapped the cylinder and have tried remaking the pistons and the rings a couple of times being careful on depth and width of the ring grooves.  Just cannot get compression. Like you I can put air in the cylinder and it seems to hold but running it or turning it over by hand does not seem to generate any pressure. It seems to draw well at the carburetor but there is almost no pressure in the firing position. Strange: If I put a pressure gauge in the spark plug hole I get very low pressure turning it over in the right direction but much more pressure if I turn it over backwards. It has become one of these things that "I am going to beat this *&*%$". Not sure where to go next.


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## Ramoye (Aug 19, 2018)

Gordon said:


> Ray: Not having much success. I have lapped the cylinder and have tried remaking the pistons and the rings a couple of times being careful on depth and width of the ring grooves.  Just cannot get compression. Like you I can put air in the cylinder and it seems to hold but running it or turning it over by hand does not seem to generate any pressure. It seems to draw well at the carburetor but there is almost no pressure in the firing position. Strange: If I put a pressure gauge in the spark plug hole I get very low pressure turning it over in the right direction but much more pressure if I turn it over backwards. It has become one of these things that "I am going to beat this *&*%$". Not sure where to go next.


 Gordon,
I have made two sets of rings in trying to get this to run, the rings are sealing at certain points in the cylinder (holding 90 psi).  
I too noticed low pressure at the spark plug hole when turning clockwise, but the pressure more than doubled turning counter clockwise.  Not sure why.  I even ran it backwards with the electric motor (just for the heck of it), but no luck in it running.  To develop the power needed, seems the pressure needs to be higher on the compression stroke.  Maybe a new cylinder, rings, and pistons will do it (I have to eliminate any leaks).  
To get strong pops, I had to squirt heavy oil in the carb, which indicates bad cylinder and ring fit.  Since rings seal at certain points in the cylinder, it indicates to me that the rings are good, but the cylinder may have some waviness in it.  
Best run I had was with a 1 1/2 inch link on the right and 1 7/16 on the left (tried all kinds of different link configurations and cylinder positions).  A choke plate on the carb seem to help some with controlling the air intake.  
Hope to get new material in a few days to start on a new cylinder.  This time, I am going with air cooled instead of water cooled.  My material has an I.D. of 1.125, so no boring operation needed, just honing.  The wall thickness is enough to allow machining of the bosses.  Will not touch the cylinder with a torch (warpage caused me a lot of problems with the cylinder the first time).
Been a fun and interesting project, though frustrating at times.  I will keep in touch as I progress.
Thanks Gordon.  Ray


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## Ramoye (Aug 19, 2018)

Ramoye said:


> Gordon,
> I have made two sets of rings in trying to get this to run, the rings are sealing at certain points in the cylinder (holding 90 psi).
> I too noticed low pressure at the spark plug hole when turning clockwise, but the pressure more than doubled turning counter clockwise.  Not sure why.  I even ran it backwards with the electric motor (just for the heck of it), but no luck in it running.  To develop the power needed, seems the pressure needs to be higher on the compression stroke.  Maybe a new cylinder, rings, and pistons will do it (I have to eliminate any leaks).
> To get strong pops, I had to squirt heavy oil in the carb, which indicates bad cylinder and ring fit.  Since rings seal at certain points in the cylinder, it indicates to me that the rings are good, but the cylinder may have some waviness in it.
> ...


Correction Gordon, it was 1 1/2 inch link on the left and 1 7/16 on the right.


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## Ramoye (Aug 19, 2018)

Ramoye said:


> Correction Gordon, it was 1 1/2 inch link on the left and 1 7/16 on the right.


Gordon, 
One theory I have is that the steep angle of the piston rod, when the piston is at the end of the cylinder, may be putting a side load on the piston, causing leakage across the rings.  When it was holding pressure, the right piston was far into the cylinder.  The majority of the leakage is on the right piston in my engine.
Ray


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## Gordon (Aug 20, 2018)

How are you checking pressure at various positions? The only place to add air pressure is through the spark plug hole and there is only a short distance near the firing position where you can pressurize the chamber. Once the left piston starts the return stroke the spark plug hole is covered and there is no way to pressurize the chamber.

I also have played around with various lengths of connecting rods and linkage bars. At this time my cylinder is mounted quite low. I have made the engine from flat stock, not castings and the front plate looks like Swiss cheese from all the times I thought that I had the right location for the piston in relation to the spark, intake and exhaust ports only to find that it was not right and I ended up moving it yet again.


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## Ramoye (Aug 20, 2018)

Gordon said:


> How are you checking pressure at various positions? The only place to add air pressure is through the spark plug hole and there is only a short distance near the firing position where you can pressurize the chamber. Once the left piston starts the return stroke the spark plug hole is covered and there is no way to pressurize the chamber.
> 
> I also have played around with various lengths of connecting rods and linkage bars. At this time my cylinder is mounted quite low. I have made the engine from flat stock, not castings and the front plate looks like Swiss cheese from all the times I thought that I had the right location for the piston in relation to the spark, intake and exhaust ports only to find that it was not right and I ended up moving it yet again.


Gordon,
I pressurized the cylinder at the spark plug port (while holding the flywheel) to test ring seating on the left end of the cylinder.  For the right end of the cylinder, I used an air hose with a rubber tipped nozzle at the intake port (while holding my finger over the exhaust holes in the muffler) (note: piston ends must be open at intake port).  Saw leakage by the right piston rings to the outside. Good method to check valve seating as well.  FYI, you can also use a piece of air hose and put it to your ear to check for leakage while running (poor man's stethoscope).  
I raised the cylinder today about 1/16 of an inch to reduce piston rod angle (put slotted holes in cylinder mount plate for adjustability, have some slow water leaks but will fix that later after I get the engine running).  I used 1 1/2 link on left and 1 7/16 link on right.  Definitely improved the running of the engine with the electric motor, but still did not run on its own power.  It did kick over a few times when I shut the electric motor down, also kicked over a few times when cranking by hand.  I am going to run it in some more tomorrow in this configuration to see if it improves. I did not run a pressure test today to see if raising the cylinder improved the leakage, but I suspect it did help some by the way it was running.  Still waiting on new cylinder material in case I need to make a new one.  Ray


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## Gordon (Aug 21, 2018)

I have been checking leakage by spraying soap solution around the pistons and turning it over by hand. I get bubbles mostly on the left cylinder. Relying on my ears is not a good test. My ears do not work well in even ideal conditions. Too many years working in noisy shops without hearing protection. Even with hearing aids they are below normal range. 

In my research on piston rings it seems like it is necessary to have pressure behind the rings forcing them out. I wonder if at low or no speed the rings do not actually seal properly. I have learned a lot about piston rings recently. Mostly that some folks claim the only way to get them to seal is to make them to very close tolerances and carefully heat treat them and others seem to get satisfactory rings with very crude methods.

I assume that you have mounted the cylinder at the recommended position and then adjusted port clearances with various connecting rod lengths. I have been moving the cylinder around trying to find the magic spot.


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## Ramoye (Aug 21, 2018)

Gordon said:


> I have been checking leakage by spraying soap solution around the pistons and turning it over by hand. I get bubbles mostly on the left cylinder. Relying on my ears is not a good test. My ears do not work well in even ideal conditions. Too many years working in noisy shops without hearing protection. Even with hearing aids they are below normal range.
> 
> In my research on piston rings it seems like it is necessary to have pressure behind the rings forcing them out. I wonder if at low or no speed the rings do not actually seal properly. I have learned a lot about piston rings recently. Mostly that some folks claim the only way to get them to seal is to make them to very close tolerances and carefully heat treat them and others seem to get satisfactory rings with very crude methods.
> 
> I assume that you have mounted the cylinder at the recommended position and then adjusted port clearances with various connecting rod lengths. I have been moving the cylinder around trying to find the magic spot.


Gordon,
My piston rings could be suspect, but they do seal well in certain locations of the cylinder when applying pressure.  I can wiggle the flywheel and hear them seat.
Had a good day today, for the most part.  With the cylinder raised 1/16 of an inch (used a 9/32 drill bit as a height spacer from the base plate to the bottom of the cylinder attach plate (2x3 inch plate), changing to 1 7/16 links on both sides, and advancing the spark, I am getting consistent and strong pops (best run-in to date).  Still not enough to run on its own, but getting close.  Had an issue with the set screw coming loose (the threads in the aluminum oscillating arm wore out) on the right oscillating arm to piston rod, allowing the pin to come out and contact the cylinder.  No damage though (got lucky).  I fixed it by drilling a 1/16 hole through the piston rod ear and pin, then using safety wire to secure it (worked well and I don't ever have to worry about that pin coming out again).  Will come up with something more professional looking once I get the engine running.
Tomorrow, I plan on raising the cylinder some more to reduce the piston rod angle (hopefully it will help with piston ring sealing, and gain more power).  I will need to slot my cylinder mounting holes some more to accomplish this.  I will raise it to the point where the two pistons just about touch using the two  1 7/16 links.  Reducing the piston rod angle is really helping.
I have used the same connecting piston rods throughout the project, but used various lengths of link arms to adjust the port clearances, as well as moving the cylinder around.  For the rings, I built a fixture to put the rings in and placed them in my foundry for heat treating (heated fixture and rings to barely red hot, then allowed them to air cool).  I did a final machining (after heat treating) of the rings using a fixture similar to the one in the book.  My rings are made from cast iron.  My rings have about 1 to 2 thousandths side wall clearance in the piston groove.  I may be too deep on the groove depth (about 0.012" in addition to the ring thickness).  I hand filed the gap to just barely go into the cylinder when compressed.  The first set of rings I made was a learning curve.  The second set of rings I made was used initially, but I felt the gap was too much, so I made a third set I am currently using.  The piston rings should be tight enough to seal with hand starting.  I have tried varying the electric motor speed to see if it helped anything with the running of the engine, but did not seem to make any difference.  Ray


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## bluejets (Aug 22, 2018)

Is this the single cylinder engine i.e.* not* the opposing piston type?

I built one of these years ago and it works fine. 
Mate of mine knocked up some castings for the barrel, head, uprights and conrod, the rest is machined.
Very touchy on the fuel needle so once set I leave it be.

Also plug can get fowled up easily so I up-ed the voltage on the coil to 12v and works fine now.

Fuel is just unleaded petrol with around 5% oil. Have tried methanol as well with castor, seems much the same.

This next bit is a mystery to me....perhaps the inlet could be a poppet valve but the Exhaust????



Gordon said:


> Due to the design of the intake and exhaust valves there is a very short part of the stroke between exhaust and intake. Both valves are atmospheric operated, that is no mechanical opening, only exhaust pressure and intake vacuum opens the valve



There should be a video of my engine on youtube somewhere, see if I can find it and put in a link.


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## Ramoye (Aug 22, 2018)

bluejets said:


> Is this the single cylinder engine i.e.* not* the opposing piston type?
> 
> I built one of these years ago and it works fine.
> Mate of mine knocked up some castings for the barrel, head, uprights and conrod, the rest is machined.
> ...


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## Ramoye (Aug 22, 2018)

This is the engine with opposing pistons in one cylinder.  It has been a challenge to get it to run!  I have tried everything I can think of.  Decided to make a new cylinder from stock 1.125 inch I.D.  No boring and brazing, which I hope will make a better cylinder.  Will need to make new pistons, piston rods, and rings.


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## Ramoye (Aug 22, 2018)

Ramoye said:


> Gordon,
> My piston rings could be suspect, but they do seal well in certain locations of the cylinder when applying pressure.  I can wiggle the flywheel and hear them seat.
> Had a good day today, for the most part.  With the cylinder raised 1/16 of an inch (used a 9/32 drill bit as a height spacer from the base plate to the bottom of the cylinder attach plate (2x3 inch plate), changing to 1 7/16 links on both sides, and advancing the spark, I am getting consistent and strong pops (best run-in to date).  Still not enough to run on its own, but getting close.  Had an issue with the set screw coming loose (the threads in the aluminum oscillating arm wore out) on the right oscillating arm to piston rod, allowing the pin to come out and contact the cylinder.  No damage though (got lucky).  I fixed it by drilling a 1/16 hole through the piston rod ear and pin, then using safety wire to secure it (worked well and I don't ever have to worry about that pin coming out again).  Will come up with something more professional looking once I get the engine running.
> Tomorrow, I plan on raising the cylinder some more to reduce the piston rod angle (hopefully it will help with piston ring sealing, and gain more power).  I will need to slot my cylinder mounting holes some more to accomplish this.  I will raise it to the point where the two pistons just about touch using the two  1 7/16 links.  Reducing the piston rod angle is really helping.
> I have used the same connecting piston rods throughout the project, but used various lengths of link arms to adjust the port clearances, as well as moving the cylinder around.  For the rings, I built a fixture to put the rings in and placed them in my foundry for heat treating (heated fixture and rings to barely red hot, then allowed them to air cool).  I did a final machining (after heat treating) of the rings using a fixture similar to the one in the book.  My rings are made from cast iron.  My rings have about 1 to 2 thousandths side wall clearance in the piston groove.  I may be too deep on the groove depth (about 0.012" in addition to the ring thickness).  I hand filed the gap to just barely go into the cylinder when compressed.  The first set of rings I made was a learning curve.  The second set of rings I made was used initially, but I felt the gap was too much, so I made a third set I am currently using.  The piston rings should be tight enough to seal with hand starting.  I have tried varying the electric motor speed to see if it helped anything with the running of the engine, but did not seem to make any difference.  Ray



Gordon,  I raised the cylinder today from 9/32 to 11/32 from the bottom of the cylinder mounting plate to the base.  Ran worse.  Dropped to 5/16 and saw some improvement, but not as good as 9/32.  I have decided to pull the plug on this cylinder, piston, ring combo.  Got my cylinder material in yesterday, so will start on a new cylinder and pistons.  Should be able to buy 1.125 rings at a reasonable cost.  For my current cylinder I.D. (1.167), I could not find rings so had to make some rings for myself.  Having any success on your engine?  Ray


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## Gordon (Aug 22, 2018)

Still no luck. I thought that I had found the problem. There was air leaking around the spark plug boss. I smeared JB Weld on the joint to see if that fixed the problem. It fixed the leak but still would not run. It would fire occasionally but would not run. My bore is 1.128 and I made the rings and pistons accordingly. I do not understand why the rings seem to have a descent seal when I put air in the cylinder but they do not seem to generate pressure when it is rotated. I am making new linkage arms at 1 1/2 C/C which raises the whole assembly. Not sure about your theory of angular pressure on the piston. A lot of engines have a rather steep angle on piston to connecting rod. If I raise it much more I am going to have further problems with the top of the intake valve stem hitting the oscillating arm. I already have whittled out a big chunk of the arm.

I have turned over the engine about 3 hours on the latest set of rings and the rings are not polished all the way around the circumference.  The latest rings have about .0015 side clearance and about .002 gap. Any self respecting engine should be showing some cooperation with those characteristics. 

I have run into two problems with the design which I find strange because so many others have made this engine and no one else has remarked about it. The hole where the pivot pin goes through the oscillating arm is not really clearly specified. It is not at the center of the radius and I think that I guessed wrong. Also as stated above the intake valve stem interferes with the oscillating arm. 

Gordon


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## Ramoye (Aug 22, 2018)

Gordon said:


> Still no luck. I thought that I had found the problem. There was air leaking around the spark plug boss. I smeared JB Weld on the joint to see if that fixed the problem. It fixed the leak but still would not run. It would fire occasionally but would not run. My bore is 1.128 and I made the rings and pistons accordingly. I do not understand why the rings seem to have a descent seal when I put air in the cylinder but they do not seem to generate pressure when it is rotated. I am making new linkage arms at 1 1/2 C/C which raises the whole assembly. Not sure about your theory of angular pressure on the piston. A lot of engines have a rather steep angle on piston to connecting rod. If I raise it much more I am going to have further problems with the top of the intake valve stem hitting the oscillating arm. I already have whittled out a big chunk of the arm.
> 
> I have turned over the engine about 3 hours on the latest set of rings and the rings are not polished all the way around the circumference.  The latest rings have about .0015 side clearance and about .002 gap. Any self respecting engine should be showing some cooperation with those characteristics.
> 
> ...


Gordon,
Seems like your bore and ring fit is spot on.  I had to grind my oscillating arm as well to get the intake valve stem to fit, as well as chamfer the piston rod edges to clear the cylinder.  I thought my piston rod angle theory might be correct after I raised the cylinder to 9/32 and it was running better, but raising it more made it worse, so maybe my theory is not correct.  I still have leakage past the piston rings at the far ends of the cylinder (could just be the cylinder is a bit banana shaped from brazing heat warpage).  My rings are shiney all the way around, but there is a small area (1/4 inch) on the circumference where it is shiney across part of the width (rings could be a tad out of round).  I bet I have put close to 200 hours on this engine in trying to get it to run.

I know what you mean about the oscillating arm/piston rod pivot hole.  The drawing was not clear.  I noticed the pivot bar hole location in the frame assembly (for the oscillating arms) was triple dimensioned, leaving me guessing on which dimension to use (note: I have cast the front and back panel twice now).

On your engine, have you tried squirting some heavy oil in the carb. to see if the rings seat better?  To keep my engine firing I have to occasionally squirt some oil in the carb. (downside is a fouled plug, requiring frequent cleaning).  With my cylinder/pistons/rings combo I cannot get it to produce enough power to run on its own, but it does fire with the electric motor (I think the increased speed of the electric motor overcomes the ring leakage enough for it to fire).  The weird thing is that occasionally the engine will fire loudly (like a gun going off).

Tomorrow I will start on a new cylinder.  I plan on making this one air cooled with fins.  First, I need to spend some time tuning up my milling machine (cheap mini-mill which I do not care for much, but it gets me by).  Ray


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## mic (Aug 22, 2018)

hi
i made this engine a few years ago and had the same problems, finally worked out that the bore length was to long for the hone length. which made the bore not dead true and bypass of the rings, decided to find longer hones and gave up as cost to high for commercial, its sitting under the bench waiting
mic


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## Ramoye (Aug 22, 2018)

mic said:


> hi
> i made this engine a few years ago and had the same problems, finally worked out that the bore length was to long for the hone length. which made the bore not dead true and bypass of the rings, decided to find longer hones and gave up as cost to high for commercial, its sitting under the bench waiting
> mic


I am starting to make a new cylinder with 1.125 I.D. DOM steel.  I should not have to bore it, but just hone it.  No brazing, fully machined (making it air-cooled with fins).  On the cylinder I have been using, it warped on me during brazing (about .070 banana shaped).  I pressed a slug through it while heating and was able to straighten it to .010 banana shaped.  It was then bored, which came out to an I.D. of 1.167 (some clean-up from the slug being pressed through).  I have wondered if maybe the boring bar tried to follow the banana shaped hole somewhat.  Took measurements of the cylinder and measured no more than .002 over the 1.167 at any one spot the total length (before honing).  I have also wondered if the hone stayed on the ends longer than the middle as it went back and forth.  It was a fine stone brake cylinder hone you buy at the auto parts store.  I am measuring a slightly bigger I.D. on the ends than the middle (after honing).  Thanks for responding.  Ray


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## Gordon (Aug 23, 2018)

I have actually lapped the cylinder and I can not find any spots where the bore varies. I do not have any way to accurately check if the bore is parallel throughout the length. I actually used a piece of copper tube about a foot long and chucked it in the lathe. I then added lapping compound the that and ran it through the bore so I am pretty sure that the bore is a consistent diameter and straight. I do not have the precision equipment to check everything. I am using a snap gauge to check the bore but the readings are coming out consistent. It would seem like the bore would have to be quite a bit out of parallel to affect the compression as long as the bore was consistent diameter. 

I am beginning to think that I am getting air leakage around where the various mounting bosses are brazed to the main cylinder tube. Yesterday I discovered that I had an air leak around the spark plug boss which was actually coming out around the cooling tube which indicated that I may actually be leaking into the cooling tube. I am thinking that the solution may be to make the whole cylinder assembly out of a solid piece of square stock so that no welding or brazing is required. I thought that by doing a rough bore about .010 under size , brazing, bore to about .001 under size, hone and then final lap would solve the fit problem. By doing a final bore to size after the brazing should solve any size or parallel problem.

I am going have one more try at making new linkage today. If that does not work the next step is to make one piece cylinder with integral mounting boss for intake, exhaust and spark plug. 

Gordon


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## mic (Aug 23, 2018)

we have the same problems, using a brake hone was the cause of my problems. the hone is to short for length of bore.if you used lapping compound on a long tube after using the brake hone it would take a fair bit of time to get all the bore dead true again, try using coarse then changing down to fine. use liquid soapy water around rear of pistons when try compression if bubbling, its rings or not true, rings will quickly get better if not its out of true. 
mic


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## Ramoye (Aug 23, 2018)

Gordon said:


> I have actually lapped the cylinder and I can not find any spots where the bore varies. I do not have any way to accurately check if the bore is parallel throughout the length. I actually used a piece of copper tube about a foot long and chucked it in the lathe. I then added lapping compound the that and ran it through the bore so I am pretty sure that the bore is a consistent diameter and straight. I do not have the precision equipment to check everything. I am using a snap gauge to check the bore but the readings are coming out consistent. It would seem like the bore would have to be quite a bit out of parallel to affect the compression as long as the bore was consistent diameter.
> 
> I am beginning to think that I am getting air leakage around where the various mounting bosses are brazed to the main cylinder tube. Yesterday I discovered that I had an air leak around the spark plug boss which was actually coming out around the cooling tube which indicated that I may actually be leaking into the cooling tube. I am thinking that the solution may be to make the whole cylinder assembly out of a solid piece of square stock so that no welding or brazing is required. I thought that by doing a rough bore about .010 under size , brazing, bore to about .001 under size, hone and then final lap would solve the fit problem. By doing a final bore to size after the brazing should solve any size or parallel problem.
> 
> ...


Gordon,
I had a cracked braze joint around the intake boss, I put J.B Weld around it, but it could still have a leak.  Also, there seems to be a leak path on the bottom of the boss to the screw holes.  Could be leaking around the valve body mount screw holes.  I have decided to make a cylinder from one piece of metal.  Bought a five inch long 1.375 OD 1.125 ID DOM steel tube.  I plan on cutting flats (slots) in it for the valve assemblies to mount, tapping for the spark plug boss, and machining cooling fins.  I will mount the cylinder by machining 1/2 inch flats (slots) on top and bottom of the cylinder and bolting 1/2 square bars to it (top and bottom).  I will then weld the other end of the 1/2 square bars to a 2x3 (1/4 inch thick) flat plate that will be bolted to the front panel.  I agree Gordon, brazing is not the way to go with this, too many chances for leakage via cracks and warpage.  If cooling fins are not enough, can always connect a small DC electric motor to the battery to blow air over it (might have to make a cooling shroud out of sheet metal.  We will get there eventually!  Thanks Gordon.  Ray


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## Gordon (Aug 24, 2018)

Mic: I used a brake hone just to remove tool marks. Just for a short period of time. Then I lapped. A piece of copper tube just fit in the bore so I used lapping compound until the whole length of the bore turned freely and was polished the entire length.

Ray: I just ordered a piece of square cast iron to remake the cylinder. That will eliminate the air leakage around the various bosses which I feel is probably where I am loosing compression. There are other plans by Brooks Pendergrast which use that setup. I am quite sure that my cylinder bore is adequate and is straight. Are you sure that you have enough material on the tube to mill flats to mount the intake, exhaust and spark plug without encroaching on the bore especially at the mounting screws? 

It is interesting how little the cylinder assembly moves to completely change the piston position at exhaust, intake and firing ports. About 1/32  seems to completely change the relationship.

Gordon


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## Ramoye (Aug 24, 2018)

Gordon said:


> Mic: I used a brake hone just to remove tool marks. Just for a short period of time. Then I lapped. A piece of copper tube just fit in the bore so I used lapping compound until the whole length of the bore turned freely and was polished the entire length.
> 
> Ray: I just ordered a piece of square cast iron to remake the cylinder. That will eliminate the air leakage around the various bosses which I feel is probably where I am loosing compression. There are other plans by Brooks Pendergrast which use that setup. I am quite sure that my cylinder bore is adequate and is straight. Are you sure that you have enough material on the tube to mill flats to mount the intake, exhaust and spark plug without encroaching on the bore especially at the mounting screws?
> 
> ...


Gordon,
I like how you lapped the cylinder with lapping compound and copper tubing.  I think I will try that versus the brake hone with my new cylinder.  My I.D. on the stock DOM material is measuring 1.118.  I hope to lap an additional 0.003 to .oo4 off on the radius to give me a final I.D. of 1.125.  I noticed in the book a design for a lapping tool.  Does the copper tube work just as well?  How long would it take to lap three to four thousandths off the radius?

Started machining my new cylinder today.  My wall thickness is 0.375 inches.  This allowed me enough material to cut a slot for the valve bodies.  Gives me 0.231 thickness left to tap 6-32 (bottom tap) before encroaching the cylinder bore.  Being steel, should give me enough threads to mount the valve body (I hope).  I cut a 1/2 inch wide slot to attach a 1/2 square bar.  I will weld the other end of the square bar to the 2x3 inch mounting plate.  There will be a square bar on top and bottom of cylinder for mounting.  

For the spark plug boss, I will machine male threads on the outside of the boss, female threads for the cylinder, then screw the boss into the cylinder.  I will coat the threads with J.B. weld before screwing into the cylinder.  Inside of the boss will be tapped for the 10mm spark plug.

Thanks Gordon.  Ray


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## Gordon (Aug 25, 2018)

Ray:
If you have 3/8 wall thickness then it probably will be OK. You said previously that you had tube which was 1 1/8 ID x 1 3/8 OD which would only give you 1/8" wall thickness.

If you are going to take .003 to .004 by lapping I would estimate that you would have 1 to 2 hours but I am not sure. It would depend on how coarse the compound would be. Some folks seem to use diamond compound which cuts much faster. Others advise against diamond compound because diamonds are forever and would get embedded in the cylinder wall.

Gordon


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## Ramoye (Aug 25, 2018)

Gordon said:


> Ray:
> If you have 3/8 wall thickness then it probably will be OK. You said previously that you had tube which was 1 1/8 ID x 1 3/8 OD which would only give you 1/8" wall thickness.
> 
> If you are going to take .003 to .004 by lapping I would estimate that you would have 1 to 2 hours but I am not sure. It would depend on how coarse the compound would be. Some folks seem to use diamond compound which cuts much faster. Others advise against diamond compound because diamonds are forever and would get embedded in the cylinder wall.
> ...


Gordon,
My mistake, the O.D. of my tube is 1.875 (0.375 wall thickness).  I drilled a mounting hole for the intake valve body this morning, 0.170 deep (still have 0.051 before encroaching on the cylinder bore.  Waiting on a 6-32 bottoming tap I ordered.  The valve body fits nicely in the 1.0 inch wide slot.  Dimensionally, the valve bodies should fit the new tube at the same position as when it was mounted on the brazed boss of the old cylinder.  Only difference is that the valve bodies are mounted in a recess vs. on top of a boss that was brazed to the top of the cylinder.

I assume your cooper tube was not expandable for lapping?  If not, did you have problems first turning the tube with the lapping compound on it?  I have both a course and fine lapping compound.

Ray


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## Gordon (Aug 25, 2018)

Ray:
I had two pieces of copper tube. The standard thin wall copper was a couple of thousands undersize and the heavier wall was right on 1.125 so I started with the thin wall tube and then went to the thicker wall piece. I guess go visit a plumbing supply with your micrometer. I got the thin stuff from Lowes and the heavier stuff from a plumber friend who had it in his scrap pile. I started with the bore about .001 to .002 oversize and lapped it to about .003 oversize. I started by trying to make the lap as shown in the book and found that the thin wall stuff was not working well so I went to my friend and got a heavier piece and discovered that I could just insert the whole 12" length in the cylinder.

Gordon


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## Ramoye (Aug 25, 2018)

Gordon said:


> Ray:
> I had two pieces of copper tube. The standard thin wall copper was a couple of thousands undersize and the heavier wall was right on 1.125 so I started with the thin wall tube and then went to the thicker wall piece. I guess go visit a plumbing supply with your micrometer. I got the thin stuff from Lowes and the heavier stuff from a plumber friend who had it in his scrap pile. I started with the bore about .001 to .002 oversize and lapped it to about .003 oversize. I started by trying to make the lap as shown in the book and found that the thin wall stuff was not working well so I went to my friend and got a heavier piece and discovered that I could just insert the whole 12" length in the cylinder.
> 
> Gordon


Thanks Gordon.  Talking about copper wall thickness from Lowes, I had to replace a valve in my house and bought a copper coupling to solder the pipes together, but the Lowes coupling would not fit my thicker older copper house plumbing.  I had to sand and sand the I.D. to get it to fit.  What should of been a minute job turned out to be 30 or 40 minutes because of that coupling.  Ray


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## Gordon (Aug 25, 2018)

The different thickness of tube is supposed to be in the ID. The OD is supposed to be the same. Needless to say commercial copper tube is not precision stuff. You may have to measure them to get the right size to fit your bore. Your bore is quite a bit under size so you may have to split a piece to get down to your initial diameter then change to a stock piece. I just purchased an Acro lap from KBC for $22 so you cannot do a lot of playing around with the home brew stuff. 
Gordon


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## Ramoye (Aug 25, 2018)

Gordon said:


> The different thickness of tube is supposed to be in the ID. The OD is supposed to be the same. Needless to say commercial copper tube is not precision stuff. You may have to measure them to get the right size to fit your bore. Your bore is quite a bit under size so you may have to split a piece to get down to your initial diameter then change to a stock piece. I just purchased an Acro lap from KBC for $22 so you cannot do a lot of playing around with the home brew stuff.
> Gordon


Not sure what the deal was with the Lowes coupling, but I had to do a lot of hand work to make it fit.  Maybe my housing tubing was out of round where I cut it.  Soldered up nicely without any leaks though.  That was a couple of years ago.

Sounds like $22 well spent.  I will check it out.

Thanks Gordon.

Ray


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## Ramoye (Aug 25, 2018)

Gordon said:


> The different thickness of tube is supposed to be in the ID. The OD is supposed to be the same. Needless to say commercial copper tube is not precision stuff. You may have to measure them to get the right size to fit your bore. Your bore is quite a bit under size so you may have to split a piece to get down to your initial diameter then change to a stock piece. I just purchased an Acro lap from KBC for $22 so you cannot do a lot of playing around with the home brew stuff.
> Gordon


Gordon,
I looked up the Acro lap on the KBC site.  It states the lap will expand 15%.  When they say a barrel lap is a 1 1/8, does that mean it expands from 1 1/8, or do they mean max expansion is 1 1/8?  Not sure if I need a 1 1/16 or 1 1/8?


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## Gordon (Aug 25, 2018)

Gordon,
I looked up the Acro lap on the KBC site. It states the lap will expand 15%. When they say a barrel lap is a 1 1/8, does that mean it expands from 1 1/8, or do they mean max expansion is 1 1/8? Not sure if I need a 1 1/16 or 1 1/8?

It is the nominal size so you need 1 1/8. One problem is that they have a minimum order. 

I ordered cast iron on eBay to make a new cylinder and USPS just brought me an empty box with a hole in the side. I have some 2" square HRS so I will probably try to use that. I filed a claim but that is going to take a while.


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## Ramoye (Aug 25, 2018)

Gordon said:


> Gordon,
> I looked up the Acro lap on the KBC site. It states the lap will expand 15%. When they say a barrel lap is a 1 1/8, does that mean it expands from 1 1/8, or do they mean max expansion is 1 1/8? Not sure if I need a 1 1/16 or 1 1/8?
> 
> It is the nominal size so you need 1 1/8. One problem is that they have a minimum order.
> ...


Thanks Gordon. 
Sorry about your cast iron order.  Sounds like you have my luck.
Ray


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## Chiptosser (Aug 27, 2018)

Guy's 
 A barrel lap will not expand at the end of the lap, it expands thru the center like a barrel shape.
Why not make your own laps to fit your bores?
Use brass, aluminum, copper or steel.   Drill and tap for a tapered pipe plug, allen type works best.
Drill and tap deep enough to let it expand. Then cut, lengthwise an inch or more, you will have to experiment.
Now you have an adjustable lap that expands on the end.  This is how injection mold laps work for ejector pins.
I have made many different sizes,over the years.   You can start a little big and size it, to the grit of the lapping compound that you are using.
As different types of compounds act differently. Also, are you under cutting or recessing, at the end of the bore in a blind hole situation ?
You can resize these laps later for other projects. 
Good Luck


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## doc1955 (Aug 27, 2018)

Chiptosser said:


> Guy's
> 
> Use brass, aluminum, copper or steel.   Drill and tap for a tapered pipe plug, allen type works best.




I use wooden dowels or old broom handels turned to size then split end with band saw split into four sections then turn a wood screw into end to expand. When you make a lap you want to use a soft material you want the lapping compound to embed itself into the lap and not what you are lapping. I have used this method many times and works just fine.


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## Chiptosser (Aug 28, 2018)

Yes,  wood is good,  hard maple, hickory  something hard and straight grain.  I like using phenolic   material too, very durable.


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## Gordon (Sep 5, 2018)

Still not having much luck with this thing. I made a new one piece cylinder from steel. Lapped it and made sure that the piston and rings were to correct size. Slightly better compression but when I turn it over with the electric motor it fires but will not run on it's own. 

When it fires it fires with a loud explosion. I am thinking that I still am not getting a good fuel mix and the engine is flooding and the explosion is burning off the excess fuel. The needle valve is extremely fussy. 
A very slight adjustment makes the difference between explosion and nothing.  I tried making a new manifold to take a commercial aircraft carburetor but due to poor planning on my part the carburetor interferes with the exhaust valve. I am going to work on the carburetor and fuel mix. I may try propane even though I have not had any luck with propane in the past.


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## Cogsy (Sep 6, 2018)

To test if it is fuel you could shut the fuel supply off, but make sure it can still get air, then tip a small amount of fuel into the spark plug hole, reinsert the plug and try and start it. It will definitely be flooded but as it clears the excess, if all else is correct, it will start up and run for a couple of seconds. I've seen motorcycle engines test run in this fashion without having a carb attached. I'm not sure how enough fuel is retained in the cylinder for long enough to keep the engine running so long but it does work. You want to make sure it can't get more fuel through the carb or it could stay in a flooded state and not fire at all, which won't help your diagnosis.
Remembering that old saying "90% of carburettor problems are electrical" it is a good way to rule out an electrical/timing problem.


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## Gordon (Sep 6, 2018)

I am pretty sure that the ignition is OK. I started with an electronic ignition (S&S) and switched to my old faithful automotive known box of 6 volt battery, automotive coil and condenser and points. If I accidentally touch the plug it give me a good jolt and it has a good spark both with the plug removed and ignition wire to ground. I still think that the problem is compression but I will try your suggestion of fuel in the spark plug hole again.


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## doc1955 (Sep 6, 2018)

To me it sounds like your timing is either way to early or to late. Usually ends up with an extra loud report. I would guess to early. Have you changed the timing around a little and see. I haven't built this engine but I would guess you want it to fire a few degrees before top dead center.


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## Gordon (Sep 6, 2018)

I have tried playing around with the timing. One big problem is that there is a very short time when the combustion chamber is actually open to ignition. The left hand piston goes over to the left and uncovers the 3/16 dia hole between the spark plug and the combustion chamber and just a few degrees of rotation later the right hand piston completes it cycle and both pistons begin the return exhaust stroke to the right. There is only about 15 to 20 degrees of rotation where the combustion chamber is actually open to the spark plug. Too advanced and the left hand piston is still blocking the chamber and too late and the left hand piston is on the exhaust stroke and again covering the 3/16 dia hole.


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## Ramoye (Sep 7, 2018)

Gordon said:


> I have tried playing around with the timing. One big problem is that there is a very short time when the combustion chamber is actually open to ignition. The left hand piston goes over to the left and uncovers the 3/16 dia hole between the spark plug and the combustion chamber and just a few degrees of rotation later the right hand piston completes it cycle and both pistons begin the return exhaust stroke to the right. There is only about 15 to 20 degrees of rotation where the combustion chamber is actually open to the spark plug. Too advanced and the left hand piston is still blocking the chamber and too late and the left hand piston is on the exhaust stroke and again covering the 3/16 dia hole.


Gordon,
Any luck with your engine?  I am almost finished with my new cylinder, just need to machine some cooling fins.  The ARCO lap tool worked great.  Measuring 1.125/1.124 at every point I checked.  Still have not drilled the 3/16 holes into the bore yet.  I do not trust the hole location as stated in the book.  

Was looking at my old cylinder this morning.  When turning counterclockwise, seems like everything is good (alignment wise).  Got good compression at the spark plug.  Ran it some backwards and got faint firing.  This engine is a puzzle!  

Sorry to hear your new cylinder did not help much, I may have the same experience when I try my new cylinder.  I will need to make new pistons and get new rings (I can buy 1.125 instead of having to make them like I did before).  Ray


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## Gordon (Sep 7, 2018)

Ray:Not much more progress. I have been kind of sidetracked with a funeral and some fall yard maintenance etc. For some reason the engine only seems to fire when it is flooded. I think that it is only firing maybe every other cycle and when it fires it does so quite violently.  It drains the gas tank (1 1/2" dia x 3" long) in 15 to 20 minutes so it is going through a lot of fuel. When it fires it is actually spraying a gasoline mist back through the carburetor throat. I will have to do some more playing around with stronger and weaker springs and also relap the valve seat. If I close off the needle valve so I get less fuel it does not fire at all. It seems to come closer to running with the timing set after TDC. Before TDC does not seem to work as well. I am quite sure  that the problem is in carburation. It is not vaporizing properly.In have been using my proven automotive type ignition with 6 volt battery, auto coil, auto condenser and auto points which I have used successfully on other engines.

Hopefully I can do some more playing around with it tomorrow. 

Gordon


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## Ramoye (Sep 7, 2018)

Gordon said:


> Ray:Not much more progress. I have been kind of sidetracked with a funeral and some fall yard maintenance etc. For some reason the engine only seems to fire when it is flooded. I think that it is only firing maybe every other cycle and when it fires it does so quite violently.  It drains the gas tank (1 1/2" dia x 3" long) in 15 to 20 minutes so it is going through a lot of fuel. When it fires it is actually spraying a gasoline mist back through the carburetor throat. I will have to do some more playing around with stronger and weaker springs and also relap the valve seat. If I close off the needle valve so I get less fuel it does not fire at all. It seems to come closer to running with the timing set after TDC. Before TDC does not seem to work as well. I am quite sure  that the problem is in carburation. It is not vaporizing properly.In have been using my proven automotive type ignition with 6 volt battery, auto coil, auto condenser and auto points which I have used successfully on other engines.
> 
> Hopefully I can do some more playing around with it tomorrow.
> 
> Gordon


Could be carb problems.  Always bothered me that the carb spits gas (weak spring force on the valve seemed to make it spit vs. a stronger spring, but too strong a spring could impact fuel getting in the cylinder).  Makes me wonder if it is not getting enough gas until it cycles several revolutions?  Seems spring tension is super sensitive (might make an adjustable spring by using thin washers under the spring).  

I had to take a few days off to rebuild part of my deck, and yard work.  Hope to get some more time to work on the engine.  About ready to order rings and make new pistons.  Ray


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## bluejets (Sep 8, 2018)

Ramoye said:


> This is the engine with opposing pistons in one cylinder.  It has been a challenge to get it to run!  I have tried everything I can think of.  Decided to make a new cylinder from stock 1.125 inch I.D.  No boring and brazing, which I hope will make a better cylinder.  Will need to make new pistons, piston rods, and rings.



Machinist friend of mine, George Punter,  took a look at this particular engine here a couple of years back. 
Someone here had the same problems as you are having.
He suspected a design flaw and what he did was redraw the plans into (at the time) Pro Desktop where one can interlock parts and "see" a skeleton view of everything working, revolving etc. etc.
His final conclusion was, as drawn, the engine could never work as the location of the spark plug was completely wrong for correct operation.
He was starting to redesign but other more important stuff cropped up.

I don't think he went any further after that but I will ask him and post back his exact results or if he intends to finish the remake.
We have both built the other type Atkinson engine with good results.

cheers Jorgo


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## Gordon (Sep 8, 2018)

Jorgo
I would certainly be interested in your friends take on the design. I am also convinced that the actual firing area is just too limited. I have built over twenty engines and I have never had as much problem as I am having with this engine. I have not really figured out why this engine will not at least run even intermittently. I have remade the cylinder three times. I have made three sets of pistons and at least five sets of rings. The last set of parts was made with careful attention to correct tolerances. The cylinder was carefully lapped. The pistons were made to closely fit in the cylinder. The rings were made for a close fit. I have tried to find any leakage points. I have tried at least four different carburetors. 

I am almost to the point of just setting the engine on the shelf and working on something else at least for a while but I hate to just give up. Also there are more of these engines made by others which seem to work. 

Gordon


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## WOB (Sep 8, 2018)

I suspect your rings as well.  The variable sealing you describe is not right.

.002" is really too much side clearance for the rings.   You should be shooting for .0005 to .001" max.  The upper and lower outside corners of the rings have to be burr free and preferably have a tiny 45 deg. bevel maybe .001"-.002" wide.  Looking at them under 10X magnification will surprise you.  The ring surface against the cylinder wall should be finished very smoothly.  I finish up with 600 grit SC paper before slicing them off the parent tube and end up with a near mirror finish. The top and bottom surfaces that face the ring groove walls should likewise be very smooth. I cut mine off about .002" wider than the ring groove and finish them to size by hand on a 600 grit diamond bench stone after heat treating.   Then I bevel the outside corners as described above.  This method give precise control of ring thickness and gives very smooth surfaces to support the oil seal between groove and ring.    Your existing groove depth is not a problem IMHO.    A good way to judge ring fit is to put a finished ring into a clean cylinder ( no piston)  squarely and  hold the cylinder up to a bright light.   The ring circumference should be light tight.  If light shows anywhere over the length of the piston stroke, the bore is not uniform and you need to make a new cylinder.

WOB


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## Ramoye (Sep 8, 2018)

bluejets said:


> Machinist friend of mine, George Punter,  took a look at this particular engine here a couple of years back.
> Someone here had the same problems as you are having.
> He suspected a design flaw and what he did was redraw the plans into (at the time) Pro Desktop where one can interlock parts and "see" a skeleton view of everything working, revolving etc. etc.
> His final conclusion was, as drawn, the engine could never work as the location of the spark plug was completely wrong for correct operation.
> ...


I have suspected the hole location for the bore penetrations are off.  On the last cylinder, I had to slot the exhaust hole because the pistons did not align with the hole.  I also slotted the intake hole because I read that another builder had to do that to get it to run (he stated that the intake hole needs to be open 90 degrees of rotation).  By slotting my intake hole, it did improve things, but not enough for the engine to run on its on power more than kicking over a few times (had no more room to slot before infringing on the intake valve body mount hole, but thought about opening up the hole larger than the 3/16).  I am making a new one piece cylinder (no brazing or boring required).  This is an intriguing engine, but a real mystery to me.

I am thinking of building a model on a flat board to better understand what is going on.

Gordon, I think I figured out why the compression is higher on the spark plug side when turning the engine backwards.  The right piston is stationary while the left piston starts moving to the right, thus compressing the gas.  Ray


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## Gordon (Sep 9, 2018)

Ramoye said:


> I have suspected the hole location for the bore penetrations are off.  On the last cylinder, I had to slot the exhaust hole because the pistons did not align with the hole.  I also slotted the intake hole because I read that another builder had to do that to get it to run (he stated that the intake hole needs to be open 90 degrees of rotation).  By slotting my intake hole, it did improve things, but not enough for the engine to run on its on power more than kicking over a few times (had no more room to slot before infringing on the intake valve body mount hole, but thought about opening up the hole larger than the 3/16).  I am making a new one piece cylinder (no brazing or boring required).  This is an intriguing engine, but a real mystery to me.
> 
> I am thinking of building a model on a flat board to better understand what is going on.
> 
> Gordon, I think I figured out why the compression is higher on the spark plug side when turning the engine backwards.  The right piston is stationary while the left piston starts moving to the right, thus compressing the gas.  Ray



On the original patent drawings the upper links were adjustable and I have seen other models built with the adjustable links. I may give that a try. At this point I think that the rings are sealing quite well but the compression stroke is short and actually begins while the left piston is still retracting so it is not compressing the chamber at the beginning of the stroke.

I have thought about lengthening the holes into the bore but have been hesitant to do so since once it is done there is no going back. Without knowing what is causing the non running condition it is hard to make adjustments.

I find it strange the there are so few build logs on the various forums. There are several where a build was started but when it gets near the end the entries stop. I suspect that they are having the same problem we are having. There are several youtube videos where others have an engine running. On one video the poster said that he had 500 hours building and 500 hours getting it to run. Another said that it only would start after it was hot. I don't know how you get it hot without running it. Quite a few others have attempted this engine and some apparently have succeeded but I am reasonably sure that the ones who were successful have made some modifications. I wish we could find others who have completed it and find out what if anything they did to make it run. Running in with an electric motor may be part of the answer but I do not think that is the entire answer.


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## dsage (Sep 9, 2018)

I started reading this thread today. I hope you guys figure it out. As with all my engine plans I redraw them in Alibre design before making chips. It helps me find errors and doing the drawings helps me understand the operation. I also get to animate it to be sure it "works" and makes sense.
  I redrew these plans a couple of years ago and the animation showed some issues with piston timing. I ran into all the issues you have mentioned including the dimension that were either missing or did not jive with how it is supposed to go together.  In CAD I also tried a lot of the changes you have mentioned and I couldn't get it to make any sense. So I put the plans aside.  Having said that I have seen a few of the engines running at NAMES and Cabin Fever. I asked one gentleman if he had any issues. He said there were problems but he didn't recall what they were. Apparently he got it working.
EDIT:
I had a quick look at my book and I made a note on page 36 where it shows the layout of the left oscillating arm. I noted that the location of the hole at the tip if the arm (where it connects to the piston rod) is wrong based on the final machining on page 81. I'm not sure exactly what I meant by that. Perhaps there are incorrect dimensions called out or my the CAD model showed it did not go together properly as it was specified. That's the only notes I made but I seem to remember something else. Perhaps with the hole layout on the main plate??
  Does this ring any bells??

Good luck.


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## dsage (Sep 9, 2018)

BTW. I did a theoretical compression calculation from the operating volumes  in my CAD drawing and I figure the compression of the engine is only 3.2:1
I might be wrong on that. But if I'm right it's going to be pretty iffy for the engine to run. Also it doesn't leave any room for leaks anywhere.
Let me know if I made a mistake.
You should be able to measure that with a pressure gauge in the spark plug hole while cranking it. Theoretically it should measure about 45lbs. Too low to be reliable IMHO.


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## Gordon (Sep 9, 2018)

dsage said:


> BTW. I did a theoretical compression calculation from the operating volumes  in my CAD drawing and I figure the compression of the engine is only 3.2:1
> I might be wrong on that. But if I'm right it's going to be pretty iffy for the engine to run. Also it doesn't leave any room for leaks anywhere.
> Let me know if I made a mistake.
> You should be able to measure that with a pressure gauge in the spark plug hole while cranking it. Theoretically it should measure about 45lbs. Too low to be reliable IMHO.



Thank you for your input. I found at least two places where the drawings are at least incomplete. On page 81 it shows the connecting rod hole on a 2 7/16 radius line which is pretty much worthless without a location on that radius. I think that I guessed wrong and have been trying to compensate ever since with different connecting rod c/c and different link arm c/c. As I built it the pistons hit each other. Also the intake valve stem interferes with the RH pivot arm and the arm must be reworked to provide clearance.

I redrew the engine also except that I only do 2D which does not show running interference.  I may have to bite the bullet and learn 3D but I am comfortable in 2D after using it for about 20 years.

I think that your take on low compression ratio and the engine only runs if everything is exactly right. That would explain the extended run in times most folks experience. 

At this point I am torn between just setting it on the shelf at least for a while and keep on trying after spending all this time on it.

Gordon


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## Gordon (Sep 13, 2018)

Latest results. Maybe getting closer. I lowered the fuel tank so that the carburetor has to suck the fuel from the tank. On the drawing it shows the tank up about level with the carburetor so it can actually siphon fuel once it starts flowing. I think that was flooding the chamber. I also made another upper link so that now it is 1 1/2 C/C on the right and 1 7/16 C/C on the left. This gives a little longer exhaust time and a little longer intake time. At this point it fires pretty constantly when it is turning over with the electric motor. One strange thing is that it will fire pretty regularly for a couple of minutes and the kind of fire erratically for a short period of time. If I put my finger over the carburetor intake to choke it it then runs again for a couple of minutes. This indicates that I am not getting proper vaporization in the combustion chamber which is probably due to marginal compression. I will try playing around with stronger and weaker springs.


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## dsage (Sep 13, 2018)

Gordon:
I presume you have a one way clutch on your starter motor or some way of disconnecting the starter once it starts to fire? Once the engine fires you need to get the starter off the engine otherwise the starter will hold it back.
  Sounds like your getting close. I did notice on the CAD animation that as-specified the time the intake port is uncovered is only about 20 deg of flywheel rotation (exceedingly short). So your efforts to extend that are probably worthwhile. Part of the problem is the intake hole into the cylinder is pretty small and the one piston covers it up very soon after the other piston starts to move to create suction. I guess your link changes will help with that?? But I guess you'd have to be careful the change does not throw off clearances at the other end??
I wonder if an oval port extending farther down the cylinder would help to extend the intake duration. A big change I know. But port timing is everything in a (sort of) two stroke engine.
The whole engine timing is pretty sketchy.
Keep us posted.
Thanks


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## dsage (Sep 13, 2018)

Gordon:
I found a few minutes to play around with my 3D CAD drawing and I entered your dimensions for the two links and you are correct the right piston moves to give more intake stroke (about 90 deg) BUT  I see a severe loss of compression with those dimensions. i.e. the two pistons are considerably farther apart on the compression end. (about double the gap from what I had before).
 Now you must take this info with a heavy dose of salt because I could have made a mistake or mis-interpretation of the drawings.
 For some reason I had both links at 1.688 C/C even though the drawings showed 1.562 (1-9/16). So I might have fiddled the values when I first drew it and saw problems to give optimal compression. But I will admit these dimensions may be why I now show a very short intake time.
  This is only FWIW info. But I think your going to find changing the links might fix one problem and cause another. It only makes sense.
I'm thinking re-positioning / sizing the intake port might be the answer rather than adjusting the motion works. Certainly there is lots of possibility to extend the intake port because there is quite a long intake stroke to take advantage of. BUT there is another problem with the motion of the pistons (as I see it). On the intake motion both pistons are moving at about the same speed (together) from right to left. So in effect there is really very little vacuum created. It's not until the very end when the pistons are both near the left side that the right pistons suddenly moves more than the other causing compression.
It's all very wacky.
  I'm sorry I don't have more time to fiddle with it to come up with a solution.


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## Gordon (Sep 13, 2018)

dsage said:


> Gordon:
> I found a few minutes to play around with my 3D CAD drawing and I entered your dimensions for the two links and you are correct the right piston moves to give more intake stroke (about 90 deg) BUT  I see a severe loss of compression with those dimensions. i.e. the two pistons are considerably farther apart on the compression end. (about double the gap from what I had before).
> Now you must take this info with a heavy dose of salt because I could have made a mistake or mis-interpretation of the drawings.
> For some reason I had both links at 1.688 C/C even though the drawings showed 1.562 (1-9/16). So I might have fiddled the values when I first drew it and saw problems to give optimal compression. But I will admit these dimensions may be why I now show a very short intake time.
> ...



This thing is  super fussy. It was firing consistently first thing thing this morning and would almost run unassisted. Suddenly it just quit firing . I played around with some adjustments and finally found that the mounting plate which mounts the cylinder to the main body had loosed up and was moving in the holes. The holes are only about 1/32 oversize but it was enough to throw things off. When mounting the cylinder assembly Gingery shows where the pistons should be while looking through the 3/16 dia holes. This is very difficult to achieve. You think that you have it and just tapping the assembly and moving up/down/left/right 1/32 throws everything off. My mounting plate looks like Swiss cheese from all of the times I thought I had it and drilled and tapped the holes only to have it off when I put it back together. I suspect that the folks who have this running just happened to find the sweet spot with everything just right and if they disassembled it and put it back together it would not run. It seems to run best with the ignition timing retarded to a few degrees past TDC.


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## Ramoye (Sep 13, 2018)

Gordon said:


> This thing is  super fussy. It was firing consistently first thing thing this morning and would almost run unassisted. Suddenly it just quit firing . I played around with some adjustments and finally found that the mounting plate which mounts the cylinder to the main body had loosed up and was moving in the holes. The holes are only about 1/32 oversize but it was enough to throw things off. When mounting the cylinder assembly Gingery shows where the pistons should be while looking through the 3/16 dia holes. This is very difficult to achieve. You think that you have it and just tapping the assembly and moving up/down/left/right 1/32 throws everything off. My mounting plate looks like Swiss cheese from all of the times I thought I had it and drilled and tapped the holes only to have it off when I put it back together. I suspect that the folks who have this running just happened to find the sweet spot with everything just right and if they disassembled it and put it back together it would not run. It seems to run best with the ignition timing retarded to a few degrees past TDC.


Hi Gordon,
Glad you are making some progress.  What dsage said about the intake hole seems to jive with what the guy on youtube said about slotting the intake 3/16 hole to allow 90 degree rotation of the flywheel.  I slotted mine until it was bumping up against the intake valve body mounting hole (about 45 degrees).  Saw some improvement when I did this.  Height of cylinder seemed best at 9/32 between base and bottom of 2x3 cylinder mounting plate.  Have not had a chance to work on my new cylinder in a few days (been working on my house, plus had to order more 1/8 end mills for making the cooling fins).  I may look into making an adjustable cylinder (to let it move left or right).  Thanks Gordon, and thanks to dsage for looking into this.  Maybe we will figure this thing out eventually!


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## Gordon (Sep 13, 2018)

Ramoye said:


> Hi Gordon,
> Glad you are making some progress.  What dsage said about the intake hole seems to jive with what the guy on youtube said about slotting the intake 3/16 hole to allow 90 degree rotation of the flywheel.  I slotted mine until it was bumping up against the intake valve body mounting hole (about 45 degrees).  Saw some improvement when I did this.  Height of cylinder seemed best at 9/32 between base and bottom of 2x3 cylinder mounting plate.  Have not had a chance to work on my new cylinder in a few days (been working on my house, plus had to order more 1/8 end mills for making the cooling fins).  I may look into making an adjustable cylinder (to let it move left or right).  Thanks Gordon, and thanks to dsage for looking into this.  Maybe we will figure this thing out eventually!


I am not doing well today. Performance seems to be worse. I think the position of the cylinder is a big part of the problem. I am thinking about slotting the mounting plate to allow adjustment left and right.

I am not worrying about cooling fins at this point. If I get it running I will go back and put cooling fins on the assembly. I am not sure if they are necessary. I ran it for over an hour yesterday with the electric motor and the engine firing and it did not get excessively warm.


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## Ramoye (Sep 13, 2018)

Gordon said:


> I am not doing well today. Performance seems to be worse. I think the position of the cylinder is a big part of the problem. I am thinking about slotting the mounting plate to allow adjustment left and right.
> 
> I am not worrying about cooling fins at this point. If I get it running I will go back and put cooling fins on the assembly. I am not sure if they are necessary. I ran it for over an hour yesterday with the electric motor and the engine firing and it did not get excessively warm.


I slotted my holes and tried different positions with different links.  Thinking of making the cylinder slide on a block by using adjustment bolts.  Since I went air cooled, it opens up more possibilities for design changes without worrying about messy water leaks.


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## Gordon (Sep 19, 2018)

The more I look at this engine the more I am convinced that it marginal at best. Obviously some folks have the engine running but there are also a lot of attempts setting on a shelf or under the bench because the builder could not get the exact right combination. I am convinced that the problem is in the compression stroke. As the RH piston is advancing to compress the fuel mix the LH piston is retreating at a slightly faster rate and only for the last few degrees of rotation is the LH piston stopped while the RH piston is still advancing so there is a very short time when the fuel mix is actually being compressed into a combustible mixture. Any slight variation of the ideal state makes ignition marginal at best. 

The engine concept is intriguing but it certainly is a reason why it never was a commercial success. 

Gordon


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## Gordon (Sep 21, 2018)

I presently am trying to learn Fusion 360 cad to try to visualize the operation and to determine what various modifications do to change the operation. Hopefully I do not just give up before I even make the initial drawings. Lots of things to learn before I can become comfortable with 3D cad. I have discovered that I can import my 2d parts into the program and make 3D parts from that. The manipulation, assembly and animation of the parts is going to be the problem.

Gordon


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## Cogsy (Sep 21, 2018)

Given the amount of trouble this engine has given you I'm definitely keeping it off my 'to build' list. I'm not sure I'd have the patience to go as far as you have but I'm sure you'll work it out eventually. Good luck!


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## Gordon (Sep 22, 2018)

I played around with Fusion 360 yesterday and that is probably going to be as frustrating as trying to get the engine to run. I imported the oscillating arm drawing from my 2D drawing and tried to convert it to 3D. After trying everything I could think of and looking at videos and forums I still have not figured it out. I am not sure that it is worth the frustration to learn the 3D cad. I thought that at least I would be able to take advantage of the work I had already done without starting from scratch. Obviously others have produced 3D drawings so it is possible.

Gordon


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## bluejets (Sep 23, 2018)

This Lars Christensen is really good at describing how to use Fusion 360.



One thing is he originally forgot to show everyone the easy way to get around inside the drawing screen but he rectifys this in a later video.


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## Gordon (Sep 27, 2018)

Looks like it is time to just put this engine on the shelf. Learning Fusion 360 is just another frustration. I do not have enough use for 3D cad to spend the hours learning it. I was hoping that I could learn enough to put together at least a rough assembly so that I could see what happens when I move parts around or make some dimensional changes but that is going to take many hours.

I tried making a temporary eccentric pivot shaft to adjust the location to see if there was a point where the compression stroke could be improved. Not enough difference to affect the operation. No matter what is done the left hand piston and the right hand piston are moving to the left at a similar rate and unless the left hand piston stops before the right hand piston reaches the end of its stroke there is not enough difference in the stroke to actually compress the fuel mix to make it combustible.   

I am sure that there is a magic point where the existing design will allow a marginal running condition. I have had the engine firing while driven by an electric motor but the moon moves or the wind shifts or the engine gods frown and suddenly it will not fire at all. Something changes again and it will fire again for a few minutes.

Gordon


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## johnmcc69 (Sep 27, 2018)

Hi Gordon, I'm sorry to hear about all the frustrations you've been having in both the construction of the engine & learning 3D CAD.

 In my years of experience with 3D CAD (Pro-Engineer), I have never had very good luck in importing 2D sketches into it. I've found it easier to start from scratch, the problem lies within the complexity of the imported 2D geometry. As you have seen, endpoints don't match up & tangent points on arcs are no longer tangent. One of the first things I learned was to keep your sketches simple, leave fillets, arc's, cuts, & holes out of your "first" sketch. Do these AFTER your first extrude/feature. The reason being, it will be SO much easier modifying the additional features in the long run. If I had a nickel for every time a complex sketch failed after modifying it...
 When these features are separate features in your "tree", modifying them is as easy as a right click on the model tree.

 Your first models don't need to be highly detailed for what you want them to do, leave the cosmetic stuff (rounds, fillets, etc.) Off. Make an assembly with them & see how they go together. When you get that far, you can go back at anytime & change & add features to the individual parts that make up that assembly. It's actually pretty cool. 

 I hope some of this helps & encourages you,

 John


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## Ramoye (Sep 28, 2018)

Gordon said:


> Looks like it is time to just put this engine on the shelf. Learning Fusion 360 is just another frustration. I do not have enough use for 3D cad to spend the hours learning it. I was hoping that I could learn enough to put together at least a rough assembly so that I could see what happens when I move parts around or make some dimensional changes but that is going to take many hours.
> 
> I tried making a temporary eccentric pivot shaft to adjust the location to see if there was a point where the compression stroke could be improved. Not enough difference to affect the operation. No matter what is done the left hand piston and the right hand piston are moving to the left at a similar rate and unless the left hand piston stops before the right hand piston reaches the end of its stroke there is not enough difference in the stroke to actually compress the fuel mix to make it combustible.
> 
> ...


Hi Gordon,
I know exactly what you have gone through with this engine (very frustrating, and this is my first engine build).  I am still trying to finish my new cylinder, but the USPS lost my package of end mills (what a mess working with the USPS).  I will keep working to get it running, but thinking the design is very marginal in working.  Ray


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## Motorteb (Sep 30, 2018)

Hello Gordon I am not a very active member as far as posting on this forum but I have been following your frustrations with your Atkinson differential engine with some interest as this is the engine I am building at the moment and today was the day that I actually got the engine running for two half hour runs.(a bit touchy very smooth running) more work to be done yet.

I did not use my plans from the Gingery book the plans I got I’m not sure where they originated from as there is no name or information on how to build with the copied pages I have although, I did buy the Gingery book to use as a reference there are considerable differences in the two engines regarding the pivot points as I drew both of these engines in the CAD program to compare the reference points.

So I can give you no advice regarding the Gingery design I have had similar problems to you but all my problems were man-made which is a long story as I converted the plans from Imperial to metric and sometimes I read numbers back to front which resulted in me having to make eccentric’s sleeves to correct the mistakes that I had made and I must say this has worked beautifully.

It would be a shame not to finish your engine it has taken me about 2 ½ years To get to the stage I am at now, not full-time of course only spare time when available.

I will try to put some photos up of my engine I made patterns for most parts and cast them in cast-iron by local foundry.

Keep trying

Leith


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## Gordon (Sep 30, 2018)

Motorteb said:


> Hello Gordon I am not a very active member as far as posting on this forum but I have been following your frustrations with your Atkinson differential engine with some interest as this is the engine I am building at the moment and today was the day that I actually got the engine running for two half hour runs.(a bit touchy very smooth running) more work to be done yet.
> 
> I did not use my plans from the Gingery book the plans I got I’m not sure where they originated from as there is no name or information on how to build with the copied pages I have although, I did buy the Gingery book to use as a reference there are considerable differences in the two engines regarding the pivot points as I drew both of these engines in the CAD program to compare the reference points.
> 
> ...


I am convinced that the pivot points are the problem. Unfortunately I am not familiar enough with 3D cad to be able to do an animation to actually see what is happening. I spent a lot of time last week trying to learn Fusion 360 so that I could determine what would correct the situation. I even tried making some wooden pieces and tried moving stuff around but that effort did not prove to be successful. 

Is there any way you could share the other design with me without violating copyright law? I really do hate to just abandon my work to this point but it is just getting too frustrating.  I am starting to do some improvements on the Howell V2 I made last year. I have a tendency to get an engine running and then move on to the next project without doing the final fine tuning.

I will send you a private message with my email address and would appreciate it if you could at least share the pivot points. I can read DXF cad files.

Gordon


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## Motorteb (Sep 30, 2018)

Yes Gordon I will respond to your request just might have to wait a couple of days for me to put that together for you

Leith


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## Gordon (Sep 30, 2018)

Motorteb said:


> Yes Gordon I will respond to your request just might have to wait a couple of days for me to put that together for you
> 
> Leith


Thanks. Maybe I can get this figured our yet.


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## Ramoye (Sep 30, 2018)

Gordon said:


> Thanks. Maybe I can get this figured our yet.


I ordered some material to make an adjustable piston rods for both left and right pistons.  Seems that may do the same thing as moving pivot points.


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## Motorteb (Oct 5, 2018)

Hello Gordon I have left some information on your email you may have overlooked the importance
of the actual movements of these arms as the differential ratios of travel for the pistons are extremely important and I'm not sure you will fix it by just adjusting the position of the pistons. My engine is a long way from being perfect although I have had running for about three hours run time. I have found that the fuel mixture is critical this seems to be a very small difference between running rich and lean I must say the engine is extremely efficient would have not used any more
than approximately 80 mil for three hours run time.

Leith


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## Gordon (Oct 5, 2018)

Motorteb said:


> Hello Gordon I have left some information on your email you may have overlooked the importance
> of the actual movements of these arms as the differential ratios of travel for the pistons are extremely important and I'm not sure you will fix it by just adjusting the position of the pistons. My engine is a long way from being perfect although I have had running for about three hours run time. I have found that the fuel mixture is critical this seems to be a very small difference between running rich and lean I must say the engine is extremely efficient would have not used any more
> than approximately 80 mil for three hours run time.
> 
> Leith


Thank you. I will do some work on that. It is interesting because the left arm and the right arm are different. They are both the same on the Gingery plans. That may make the difference.

Gordon


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## Ramoye (Oct 5, 2018)

Gordon said:


> Thank you. I will do some work on that. It is interesting because the left arm and the right arm are different. They are both the same on the Gingery plans. That may make the difference.
> 
> Gordon


I can see how different length pivot arms could make a difference.  I have finished my new 100% machined cylinder.  I have also finished making adjustable piston rods (not sure it will make a big difference, but does give me some more adjustability.  Was so close to running before).  Still need to machine new pistons (ordered some 1.125 rings that should be here in a few days).  How things going on your end Gordon?  Thanks to Mr. Leith for sharing his experience with this engine.  Ray.


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## Gordon (Oct 5, 2018)

Ramoye said:


> I can see how different length pivot arms could make a difference.  I have finished my new 100% machined cylinder.  I have also finished making adjustable piston rods (not sure it will make a big difference, but does give me some more adjustability.  Was so close to running before).  Still need to machine new pistons (ordered some 1.125 rings that should be here in a few days).  How things going on your end Gordon?  Thanks to Mr. Leith for sharing his experience with this engine.  Ray.


I just finished CAD drawings on this design. It looks good. I think that it could work. It will involve making new front and back panels and new arms. Right and left. If interested I can email you my rather crude CAD layout. I still have not mastered 3D so it is 2D.


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## Ramoye (Oct 6, 2018)

Gordon,

Looks like it will work.  Did you use the Gingery cylinder port locations for your CAD model?  I assume the link arms and piston rods are the same length?  In the bottom of the drawing, are the oscillating arms and panel a comparison to the Gingery parts?

Seems from your operation views (in the upper part of the drawing) that the compression would increase on the spark plug side of the cylinder.  On the Gingery version, the pistons were hitting at the exhaust port and had a wider gap at the spark plug port.  This may explain the higher compression on the valve side of the cylinder.

Thanks Gordon.

Ray


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## Gordon (Oct 6, 2018)

Ramoye said:


> Gordon,
> 
> Looks like it will work.  Did you use the Gingery cylinder port locations for your CAD model?  I assume the link arms and piston rods are the same length?  In the bottom of the drawing, are the oscillating arms and panel a comparison to the Gingery parts?
> 
> ...


The linkages are from the Gingery plans. It looks like the left piston completes the travel to the end faster so that the right piston can compress the fuel mix. The original design has both pistons traveling in tandem at about the same speed so that the mix did not get compressed.
Gordon


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## Ramoye (Oct 7, 2018)

Gordon said:


> The linkages are from the Gingery plans. It looks like the left piston completes the travel to the end faster so that the right piston can compress the fuel mix. The original design has both pistons traveling in tandem at about the same speed so that the mix did not get compressed.
> Gordon


Thanks Gordon.  I assume your CAD model used the Gingery port locations?
Are you planning on making new front and back panels, as well as new oscillating arms?
Ray


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## Gordon (Oct 7, 2018)

Ramoye said:


> Thanks Gordon.  I assume your CAD model used the Gingery port locations?
> Are you planning on making new front and back panels, as well as new oscillating arms?
> Ray


It looks like the Gingery port locations will work if the cylinder assembly is moved about 1/16 to the right. I will probably make new panels and new arms. I have so much time in this thing at this point a few more hours is not a big deal. Hopefully the cylinder can be reused. I have done some more playing around with CAD to try to check things out. I have not checked the stroke length on the two designs and will check that tomorrow when I am back in the shop.

Obviously there are other designs out there. 

Gordon


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## Ramoye (Oct 7, 2018)

Thanks Gordon.  I plan on drilling the 3/16 port holes in the new cylinder tomorrow.  Like you, I have put a lot of hours into this project.  Enjoyed it though.

Ray


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## Gordon (Oct 8, 2018)

For others who may be interested, this shows the difference with alternate  arms and pivot points. In the top sequence the left piston is retracting faster than the right piston so that there is more time for a compression stroke. 
Gordon


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## Ramoye (Oct 8, 2018)

Thanks Gordon.  This is awesome.  Shows what is going on.

Ray


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## Gordon (Oct 8, 2018)

Ray:
If you would like I can send you all of my drawings showing all of the parts for making a bar stock engine. I can send them in PDF or DXF or DWG if you can read them in that format. This forum will only permit PDF so if you want send me your email and I can send them direct.


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## Brian Rupnow (Oct 8, 2018)

Have a look thru my build. You might see something that would help you out.---Brian
Apparently I can not post a link to my build here, so Google Brian Rupnow Atkinson engine and it will let you in thru the back door.---Brian


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## Ramoye (Oct 8, 2018)

Brian Rupnow said:


> Have a look thru my build. You might see something that would help you out.---Brian
> Apparently I can not post a link to my build here, so Google Brian Rupnow Atkinson engine and it will let you in thru the back door.---Brian


Thanks Brian.  Really nice job on your engine!  The engine Gordon and I are building is the Atkinson Differential Engine.  I believe your engine is the Atkinson Cycle Engine.  Ray


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## Ramoye (Oct 8, 2018)

Gordon said:


> Ray:
> If you would like I can send you all of my drawings showing all of the parts for making a bar stock engine. I can send them in PDF or DXF or DWG if you can read them in that format. This forum will only permit PDF so if you want send me your email and I can send them direct.
> 
> [email protected]


Thanks Gordon.  Just sent you my email address.  Ray


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## mohavegun (Oct 9, 2018)

Gordon said:


> This post is to vent my frustration but if someone has some insight it is certainly welcome. I am building the Atkinson Differential engine from the Gingery plans and I am not having any luck in getting to run. Gingery said that he had to turn the engine over with an electric motor and a belt to the flywheel for up to 40 hours to seat the rings before it would start dependably. I have been doing that for quite a few hours (25-30) but I am not seeing any improvement. I am sure that the problem is compression but a solution escapes me. Due to the unique design you can only feel the compression on the last portion of the compression stroke because the spark plug hole is covered until the last part of the stroke. There seems to be good suction at the spark plug hole on what would be the exhaust stroke.
> 
> 
> At this point it kind of fires about 1/3 of the time and even that is intermittent. If fires for a while and then quits firing until something like carburetor adjustment or cool off occurs. I have tried different spark timing and different carburetors and carburetor adjustments but nothing seems to change. I am using the S&S ignition and there seems to be a good spark.
> ...





Gordon,

The problem with most hard starting home builds is not the piston and rings, it is the finish of the cylinder bore.  I have found in the last few years of playing with model engines that this is the most often mis understood factor.  

The remedy here is to finish the bore of the cylinder dead straight and perfectly round.  This is only possible to achieve with a lap or hone.  When I say hone I am NOT referring to the spring hones often used by model engine builders, I am talking about a precision hone like used in automotive machine shops.  These generally use a single stone mounted on a mandrel with precision cut radius supports opposite it in the cylinder bore.  This type of hone will routinely hold a +/-  .0001" tolerance on roundness, straightness and diameter in the hands of a skilled operator.  

I see two options for solving your problem...

First would be to read up on copper laps, perhaps you could build a simple copper lap on your lathe and then lap your cylinder straight and true.  It takes a lot of time and you will learn something on the way.

Second option, take your cylinder to an auto repair shop that has a Sunnen rod hone and tell the machinist there to make the hole straight, round and true and finish as fine as possible.  He will probably charge you $15.00 or so to do the job and then you can build new pistons and rings.  Once you have the engine back together it should be running in no time, it will be necessary to seat the rings.

TIP!...  get some super fine lapping compound and dope up the cylinder bore with a small amount of it mixed with light oil (3 in 1 works here)  and dry run the engine for a few minutes with your electric motor.  dismantle and clean out the abrasive compound, put the motor back together and it should be fairly easy to start.  I use this method on my engines and if bore and piston fit is good the start very easy after lapping in.  

In my shop, I have a Sunnen MBB hone and mandrels, most home shops do not have such a luxury.  (my shop is a working machine shop and has been for almost 30 years).

Rod


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## Ramoye (Oct 21, 2018)

Gordon said:


> Ray:
> If you would like I can send you all of my drawings showing all of the parts for making a bar stock engine. I can send them in PDF or DXF or DWG if you can read them in that format. This forum will only permit PDF so if you want send me your email and I can send them direct.


Gordon,
Had any luck with your engine?  I finished my new cylinder and pistons with new rings from Otto (everything fit nicely).  Ran it a couple of hours with electric motor assist, but disappointed that I did not get any strong pops.  Will run it some more to see if additional break-in makes it run.  Beginning to think I will need to make new oscillating arms and panels.  Ray


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## Gordon (Oct 21, 2018)

Ramoye said:


> Gordon,
> Had any luck with your engine?  I finished my new cylinder and pistons with new rings from Otto (everything fit nicely).  Ran it a couple of hours with electric motor assist, but disappointed that I did not get any strong pops.  Will run it some more to see if additional break-in makes it run.  Beginning to think I will need to make new oscillating arms and panels.  Ray


I made new arms and panels. It has much better compression but I still cannot get it to run on it's own. It fires every stroke but not enough to keep it going. Then the braze on the crank broke and I just got that back together yesterday and decided to try moving the cylinder to get  a longer compression stroke and a shorter intake stroke. It is closer to running but there is still something not quite right. I slotted the hole on the intake port and that may be my problem. So far I have remade just about every part but the base and the side panels.

If you decide to remake the arms and front panel let me know and  I will send you my revised as built drawings. 

Gordon


----------



## Ramoye (Oct 22, 2018)

Gordon said:


> I made new arms and panels. It has much better compression but I still cannot get it to run on it's own. It fires every stroke but not enough to keep it going. Then the braze on the crank broke and I just got that back together yesterday and decided to try moving the cylinder to get  a longer compression stroke and a shorter intake stroke. It is closer to running but there is still something not quite right. I slotted the hole on the intake port and that may be my problem. So far I have remade just about every part but the base and the side panels.
> 
> If you decide to remake the arms and front panel let me know and I will send you my revised as built drawings.
> 
> Gordon


Looks like you are getting close.  I slotted the intake hole in my old cylinder and it helped, maybe it will help you (puts more fuel in the cylinder, I believe).  I have not done that on my new cylinder, YET.  I had a much better day today.  I was getting strong pops and the cylinder was getting very hot.  Seems to be burning more fuel with the new cylinder (may indicate better suction).  I plan on running it some more tomorrow with the electric motor.  Total of 6 hours so far with the new cylinder.  I now have the option to adjust the piston rod length if I have no success with additional break-in.  If all fails, I will make new oscillating arms and plates.  Good luck Gordon.  Maybe we will beat this thing!  Ray.


----------



## Ramoye (Oct 24, 2018)

Gordon said:


> I made new arms and panels. It has much better compression but I still cannot get it to run on it's own. It fires every stroke but not enough to keep it going. Then the braze on the crank broke and I just got that back together yesterday and decided to try moving the cylinder to get  a longer compression stroke and a shorter intake stroke. It is closer to running but there is still something not quite right. I slotted the hole on the intake port and that may be my problem. So far I have remade just about every part but the base and the side panels.
> 
> If you decide to remake the arms and front panel let me know and I will send you my revised as built drawings.
> 
> Gordon


Gordon, 
Had a good day today.  The engine kicked over a few times on its own.  It ran, with electric motor assist, more consistent than ever before.  Cylinder got very hot.  Switched to 1 7/16 links on both ends, and adjusted the piston rod lengths so that both pistons are nearly even with the ends of the cylinder.  I had to play around some with the timing.  I now have 15 hours on the new cylinder.  I will run it some more tomorrow and see if it develops more power.  How things going on your end?  Ray


----------



## Gordon (Oct 26, 2018)

Ramoye said:


> Gordon,
> Had a good day today.  The engine kicked over a few times on its own.  It ran, with electric motor assist, more consistent than ever before.  Cylinder got very hot.  Switched to 1 7/16 links on both ends, and adjusted the piston rod lengths so that both pistons are nearly even with the ends of the cylinder.  I had to play around some with the timing.  I now have 15 hours on the new cylinder.  I will run it some more tomorrow and see if it develops more power.  How things going on your end?  Ray


I am not making much progress. The engine fires but still not enough power to run on it's own. I am sure that the problem is that I now have a mix of two different designs so the position of the ports is wrong. I am making a new cylinder. I should not have slotted the intake port. That makes the intake stroke too long and the compression stroke too short.
You said that you have made adjustable piston rod. I am curious as to how you did that. I have seen engines made with adjustable top linkage rods but not the connecting rods.
Gordon


----------



## Ramoye (Oct 26, 2018)

Gordon said:


> I am not making much progress. The engine fires but still not enough power to run on it's own. I am sure that the problem is that I now have a mix of two different designs so the position of the ports is wrong. I am making a new cylinder. I should not have slotted the intake port. That makes the intake stroke too long and the compression stroke too short.
> You said that you have made adjustable piston rod. I am curious as to how you did that. I have seen engines made with adjustable top linkage rods but not the connecting rods.
> Gordon


Gordon, 
The last couple of days saw no improvement from the other day.  The cylinder gets very hot and the engine can kick over 3 0r 4 times on its own.  I now have 21 hours on the new cylinder.  I have adjusted the pistons to various positions, adjusted the  timing and carb., and achieved the same results.  I am beginning to think the Gingery design has some flaws.  Seems the compression needs to be higher for complete combustion.  Still measuring about 8 psi at the spark port.  Still got some leakage by the pistons at 90 psi (measured 1.125/1.124 diameter at all points along the cylinder, and could not get a .002 feeler gage (smallest size I have) between the ring and groove wall).  Maybe it still needs more break-in? 

I made the variable piston rod by drilling a hole for a 10-28 thread between the fork toward the piston end (rod aligned vertical in the mill) to a certain depth for a bolt (depends on how much adjustment you want).  I then cut the rod into two pieces, plus took a little material out for adjustment clearance (I choose 1/4 inch adjustment capability).  I then tapped the two parts for a 10-28 thread (could use 10-24, but 10-28 gives a little finer adjustment).  I cut the head off a 10-28 aircraft bolt I had (had to use a die to cut additional threads on the shank) and screwed it into the piston half of the rod, applying some epoxy on the threads to secure it.  To use, just screw the fork end of the rod onto the bolt/stud and pin to oscillating arm.  I used a small check nut to make the assembly a little stiffer, but I do not believe you really need it.  I hope my description makes sense?

Ray


----------



## Gordon (Oct 26, 2018)

Ramoye said:


> Gordon,
> The last couple of days saw no improvement from the other day.  The cylinder gets very hot and the engine can kick over 3 0r 4 times on its own.  I now have 21 hours on the new cylinder.  I have adjusted the pistons to various positions, adjusted the  timing and carb., and achieved the same results.  I am beginning to think the Gingery design has some flaws.  Seems the compression needs to be higher for complete combustion.  Still measuring about 8 psi at the spark port.  Still got some leakage by the pistons at 90 psi (measured 1.125/1.124 diameter at all points along the cylinder, and could not get a .002 feeler gage (smallest size I have) between the ring and groove wall).  Maybe it still needs more break-in?
> 
> I made the variable piston rod by drilling a hole for a 10-28 thread between the fork toward the piston end (rod aligned vertical in the mill) to a certain depth for a bolt (depends on how much adjustment you want).  I then cut the rod into two pieces, plus took a little material out for adjustment clearance (I choose 1/4 inch adjustment capability).  I then tapped the two parts for a 10-28 thread (could use 10-24, but 10-28 gives a little finer adjustment).  I cut the head off a 10-28 aircraft bolt I had (had to use a die to cut additional threads on the shank) and screwed it into the piston half of the rod, applying some epoxy on the threads to secure it.  To use, just screw the fork end of the rod onto the bolt/stud and pin to oscillating arm.  I used a small check nut to make the assembly a little stiffer, but I do not believe you really need it.  I hope my description makes sense?
> ...


That makes sense. I understand. I have also pretty much come to the conclusion that the Gingery design is marginal at best. I am still working on the new cylinder. I have at least enough extra parts to make most of another engine. I have built about 20+ engines in the last several years and I have never had one which gave me this much trouble. I have usually found that I have as much time in getting an engine to run as I have in making the engine in the first place. I see these other folks posting videos of a completed engine and showing it running the first try with just a few minor adjustments. I have never had that happen. 

Gordon


----------



## Ramoye (Oct 26, 2018)

Gordon said:


> That makes sense. I understand. I have also pretty much come to the conclusion that the Gingery design is marginal at best. I am still working on the new cylinder. I have at least enough extra parts to make most of another engine. I have built about 20+ engines in the last several years and I have never had one which gave me this much trouble. I have usually found that I have as much time in getting an engine to run as I have in making the engine in the first place. I see these other folks posting videos of a completed engine and showing it running the first try with just a few minor adjustments. I have never had that happen.
> 
> Gordon


If you look close on the videos, looks like some engines have been modified from the original.  Starting to understand why.  This is a tough engine to make run.  I will run it some more (another 30 hours), but growing doubtful it will work.  May have to redesign it by making new panels, oscillating arms, and links.  I would like to see higher compression on the spark plug side.  I believe mine is just burning gas vs. combustion.


----------



## Ramoye (Nov 2, 2018)

Gordon said:


> That makes sense. I understand. I have also pretty much come to the conclusion that the Gingery design is marginal at best. I am still working on the new cylinder. I have at least enough extra parts to make most of another engine. I have built about 20+ engines in the last several years and I have never had one which gave me this much trouble. I have usually found that I have as much time in getting an engine to run as I have in making the engine in the first place. I see these other folks posting videos of a completed engine and showing it running the first try with just a few minor adjustments. I have never had that happen.
> 
> Gordon


Gordon,
How things going on your end?  

I have concluded that a design change is in order to make this engine run.  Compression is very low on the spark side, but compression much higher on the valve side.  This is due to the two pistons almost hitting on the valve side, but a piston gap on the spark side.  This is also causing spitting through the carb., which I believe is causing some fuel starvation into the cylinder.  Just can't produce enough power.  I pressurized the cylinder with 90 psi through the spark plug port and it held, indicating to me that the pistons, rings and cylinder are good.

I have an idea.  What if an offset crank pin is used for the two oscillating arms.  This would move the compression from the valve side to the spark side (pistons almost touching on spark side, but wider gap on valve side), which should greatly reduce carb. spitting (allowing better intake of the fuel charge).  The offset crank pin could be made with a taper on the end to lock it into the crankshaft (the 3 inch plate on the end), allowing adjustability of the oscillating arms.  Would require the four jaw chuck to make the offset crank pin.  I am thinking a 1/8 inch offset, that could be adjusted to less if need be.  May need a cup washer over the end of the crank pin to lock the taper end of the offset crank pin down with a bolt.  What do you think about this?  I ran this idea by a friend of mine and he thinks it might work and worth a try.

Ray


----------



## Gordon (Nov 2, 2018)

Ramoye said:


> Gordon,
> How things going on your end?
> 
> I have concluded that a design change is in order to make this engine run.  Compression is very low on the spark side, but compression much higher on the valve side.  This is due to the two pistons almost hitting on the valve side, but a piston gap on the spark side.  This is also causing spitting through the carb., which I believe is causing some fuel starvation into the cylinder.  Just can't produce enough power.  I pressurized the cylinder with 90 psi through the spark plug port and it held, indicating to me that the pistons, rings and cylinder are good.
> ...


Making an eccentric crank pin would indeed change the relative stroke distances. You could do the same by modifying the upper link length. If you look at some of the other videos and images some of them have an adjustable link with a threaded adjustable connection between  the crank and the top of the crank arm. The original patent drawing had that. That should be fairly easy to make.  

So far I am not having much luck on my remake. I screwed up the cylinder by misreading the relief distance on the top of the cylinder so that I cannot move the cylinder to the right as far as it should go without getting leakage because the rings are actually coming out of the bore into the now too long relief area. 

So far no matter what I do on the original or the rework ends up pretty much the same result where I get a firing but not enough to actually power the engine.  I am not sure what is happening but I get a loud firing when it fires and not a controlled firing.

Gordon


----------



## Ramoye (Nov 2, 2018)

Gordon said:


> Making an eccentric crank pin would indeed change the relative stroke distances. You could do the same by modifying the upper link length. If you look at some of the other videos and images some of them have an adjustable link with a threaded adjustable connection between  the crank and the top of the crank arm. The original patent drawing had that. That should be fairly easy to make.
> 
> So far I am not having much luck on my remake. I screwed up the cylinder by misreading the relief distance on the top of the cylinder so that I cannot move the cylinder to the right as far as it should go without getting leakage because the rings are actually coming out of the bore into the now too long relief area.
> 
> ...


Gordon,

Unless I am missing something, it looks like to me the eccentric pin has a different effect on the oscillating arms than changing link arm lengths.  For example, a shorter link arm on the power stroke would put the right piston farther to the right of the spark plug hole, whereas an eccentric would put the right piston farther to the left (thus closing the gap, creating more compression).  The left hand link arm length would remain the same via the eccentric pin.  Could you look closer at this to see if I am missing something?  Thanks.  Ray


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## Gordon (Nov 3, 2018)

Ramoye said:


> Gordon,
> 
> Unless I am missing something, it looks like to me the eccentric pin has a different effect on the oscillating arms than changing link arm lengths.  For example, a shorter link arm on the power stroke would put the right piston farther to the right of the spark plug hole, whereas an eccentric would put the right piston farther to the left (thus closing the gap, creating more compression).  The left hand link arm length would remain the same via the eccentric pin.  Could you look closer at this to see if I am missing something?  Thanks.  Ray


Perhaps I am not thinking right. I am wrong as often as I am right but if you put in an eccentric pin and added say 1/16 to the radius the c/c from the crank C/L to the pin C/L is now 1 3/16 (1 1/8 + 1/16). Picture the crank at 3 o'clock which would move the pivot point to the right by 1/16. Now picture the same thing with the C/C still at 1 1/8 but make the right link 1/16 longer and the left link 1/16 shorter. One link 1 9/16 + 1/16=1 5/8 and the other link 1 9/16-1/16=1 1/2.  The result is the same. Also true at 9 o'clock. By making adjustable link or new links you could move one piston without affecting the other. For example keep one link at 1 9/16 and make the other 1 1/2 or 1 5/8. You would have to play around with it to determine which link or links to change to move the move one piston right or left. The advantage of adjustable or changing links C/C is that you can change one with out changing the other.

As I said, I may be completely wrong.

Gordon


----------



## Ramoye (Nov 3, 2018)

Gordon said:


> Perhaps I am not thinking right. I am wrong as often as I am right but if you put in an eccentric pin and added say 1/16 to the radius the c/c from the crank C/L to the pin C/L is now 1 3/16 (1 1/8 + 1/16). Picture the crank at 3 o'clock which would move the pivot point to the right by 1/16. Now picture the same thing with the C/C still at 1 1/8 but make the right link 1/16 longer and the left link 1/16 shorter. One link 1 9/16 + 1/16=1 5/8 and the other link 1 9/16-1/16=1 1/2.  The result is the same. Also true at 9 o'clock. By making adjustable link or new links you could move one piston without affecting the other. For example keep one link at 1 9/16 and make the other 1 1/2 or 1 5/8. You would have to play around with it to determine which link or links to change to move the move one piston right or left. The advantage of adjustable or changing links C/C is that you can change one with out changing the other.
> 
> As I said, I may be completely wrong.
> 
> Gordon


Gordon,

Thanks for looking at this again.  I may be wrong, but what I am seeing with an eccentric pin would produce the same results as swapping longer and shorter link arms on the right oscillating arm as it is running.  Of course swapping longer and shorter arms as it is running would be impossible, but achieving the same results would be possible with the eccentric pin.  I have tried every combination of link arm lengths and still end up with a gap at the spark plug port and pistons nearly hitting at the exhaust valve port (my pressure gage indicates this, 8 psi at the spark plug port, 30 psi at the exhaust port).  I believe why the eccentric pin works is because the effect on the right piston is different as it rotates 180 degrees.  At 3 o'clock the offset pushes the right piston further to the left (closing the gap between the two pistons at the spark plug port, creating greater compression).  At the 9 o'clock position, the offset pulls the right piston further to the right (producing a greater gap between the pistons at the exhaust port).  The net effect should be greater compression at the spark plug port and less compression at the exhaust port (which is what we want for better combustion and increased fuel charge (reduces carb. spitting)).  I might be wrong, but I am going to try it (need the practice anyway on using the four jaw chuck to make an eccentric pin).  I will let you know what the results are.  Thanks Gordon.  Ray


----------



## Gordon (Nov 3, 2018)

Ramoye said:


> Gordon,
> 
> Thanks for looking at this again.  I may be wrong, but what I am seeing with an eccentric pin would produce the same results as swapping longer and shorter link arms on the right oscillating arm as it is running.  Of course swapping longer and shorter arms as it is running would be impossible, but achieving the same results would be possible with the eccentric pin.  I have tried every combination of link arm lengths and still end up with a gap at the spark plug port and pistons nearly hitting at the exhaust valve port (my pressure gage indicates this, 8 psi at the spark plug port, 30 psi at the exhaust port).  I believe why the eccentric pin works is because the effect on the right piston is different as it rotates 180 degrees.  At 3 o'clock the offset pushes the right piston further to the left (closing the gap between the two pistons at the spark plug port, creating greater compression).  At the 9 o'clock position, the offset pulls the right piston further to the right (producing a greater gap between the pistons at the exhaust port).  The net effect should be greater compression at the spark plug port and less compression at the exhaust port (which is what we want for better combustion and increased fuel charge (reduces carb. spitting)).  I might be wrong, but I am going to try it (need the practice anyway on using the four jaw chuck to make an eccentric pin).  I will let you know what the results are.  Thanks Gordon.  Ray


The more I look at this thing the more confused I get. Give it a try and see what happens. I am curious to see what the results will be.

FYI: Using the three jaw chuck you get an offset of 2/3 of thickness of a shim on one jaw. In other words putting a 1/4" thick shim on one jaw creates a 3/16" offset. 

Another thought is that since you will have to make a new 3" dia cam disk you could just drill a series of holes around the disk in say 1/16" increments to get +/- 1/8" from center. Properly spaced at 45° it would look like it was planned.

Good luck.

Gordon


----------



## Ramoye (Nov 3, 2018)

Gordon said:


> The more I look at this thing the more confused I get. Give it a try and see what happens. I am curious to see what the results will be.
> 
> FYI: Using the three jaw chuck you get an offset of 2/3 of thickness of a shim on one jaw. In other words putting a 1/4" thick shim on one jaw creates a 3/16" offset.
> 
> ...


Thanks Gordon for the tip on using the three jaw chuck for an offset.  I will try it.  On the 3 inch disk, I will need to cut the crank pin off (clean it up on the lathe) and drill a new hole.  I would like to make a tapered hole (also a taper on the end of the eccentric pin) to make the eccentric crank pin adjustable by rotating it (also need to make it removable to install the oscillating arms).  Good idea on drilling extra holes to make it look better.


----------



## Ramoye (Nov 4, 2018)

Gordon said:


> The more I look at this thing the more confused I get. Give it a try and see what happens. I am curious to see what the results will be.
> 
> FYI: Using the three jaw chuck you get an offset of 2/3 of thickness of a shim on one jaw. In other words putting a 1/4" thick shim on one jaw creates a 3/16" offset.
> 
> ...


Gordon,

I made a prototype eccentric pin from aluminum to prove the concept and to develop a manufacturing process.  The concept worked as I envisioned.  I was able to close the gap between the pistons at the spark plug port and widen the gap at the exhaust valve port (no more pistons hitting) by rotating the eccentric pin.  This should flip the compression over to the spark plug side of the cylinder instead of the valve side, with the flywheel rotating clockwise (hopefully resulting in better combustion and fuel intake).  I now feel comfortable in going ahead with modifying the crankshaft.  Below is my plan: 

1)  Cut the existing crankshaft pin back for installation of the eccentric crank pin.  Drill a thru hole through the remaining length of the crankshaft pin and 3" disk for installation of the eccentric pin with a #10 bolt.
2)  Machine a eccentric pin that will fit over the existing remaining cut-off portion of the crankshaft pin (the eccentric pin will have a 1/2 " counterbore (1/4 " deep)) with a thru hole for mounting with a #10 bolt.  I will use a 3/16 " shim in the three jaw chuck for creating the eccentric pin (your tip on this worked great when I made the prototype).  The eccentric pin will also be machined as to replace the 1/2 " crankshaft spacer  (called out in Gingery's book) between the oscillating arms.
3)  Mount the eccentric pin to the existing remaining cut-off portion of the crankshaft pin using a #10 bolt, washer, and nylon lock nut.  Adjustment can be made by loosening the nut and rotating the eccentric pin, then retighten.
4)  Make two new piston rods per Gingery's book (will replace the adjustable piston rods I previously made, no longer need them).

When I finish all this, I will try to run the engine again.  Very curious as to how these modifications will change the engine performance.

Ray


----------



## Gordon (Nov 4, 2018)

Ramoye said:


> Gordon,
> 
> I made a prototype eccentric pin from aluminum to prove the concept and to develop a manufacturing process.  The concept worked as I envisioned.  I was able to close the gap between the pistons at the spark plug port and widen the gap at the exhaust valve port (no more pistons hitting) by rotating the eccentric pin.  This should flip the compression over to the spark plug side of the cylinder instead of the valve side, with the flywheel rotating clockwise (hopefully resulting in better combustion and fuel intake).  I now feel comfortable in going ahead with modifying the crankshaft.  Below is my plan:
> 
> ...


I am not too sure that I understand your process. Apparently you brazed the pin in the 3" disk. I made it 1/2" dia with a 3/8" dia shoulder to fit into a 3/8" hole reamed in the disk and held in place with a #10 machine screw. With that it would simply be a matter of making a new pin by offsetting the 3/8" shoulder and rotating it into the proper position. One of the drawings which  I sent you shows how I did it. I do not have the book here now but I thought that was how Gingery made the pin as a shouldered piece. Not offset of course. 

Two thoughts: Could you determine the proper offset with your temporary set up, cut off the existing pin and just drill a new hole in the 3' disk at the new distance. ie: 1.125 +/- the offset? Would't it be easier to just make a pin with the offset shoulder?

Carry on. Good luck.

Gordon


----------



## Ramoye (Nov 4, 2018)

Gordon said:


> I am not too sure that I understand your process. Apparently you brazed the pin in the 3" disk. I made it 1/2" dia with a 3/8" dia shoulder to fit into a 3/8" hole reamed in the disk and held in place with a #10 machine screw. With that it would simply be a matter of making a new pin by offsetting the 3/8" shoulder and rotating it into the proper position. One of the drawings which  I sent you shows how I did it. I do not have the book here now but I thought that was how Gingery made the pin as a shouldered piece. Not offset of course.
> 
> Two thoughts: Could you determine the proper offset with your temporary set up, cut off the existing pin and just drill a new hole in the 3' disk at the new distance. ie: 1.125 +/- the offset? Would't it be easier to just make a pin with the offset shoulder?
> 
> ...


Gordon,
Originally, I made the crank pin per the Gingery book (it was a press fit).  But after much running, the pin started spinning in the hole.  I repaired it by brazing it to the 3" disk.  

I thought about doing what you are describing, drilling a new hole in the 3" disk.  With a press fit though (per Gingery's book), it would be difficult in removing the pin should I need to take the left oscillating arm off (with an offset shoulder in the pin, would not be able to slide the left oscillating arm onto the crank pin from the front).  I thought about putting a taper on the pin and drilling a tapered hole in the crankshaft disk (would tighten a bolt to lock it down), but it would require me to set up the 4 jaw chuck to put the tapered hole into the crankshaft disk.  The way I was planning on doing it is easier/faster, but maybe not as robust as a single pin with a tapered end (without the taper, it might start spinning in the hole).  I may take the time to make the more robust design.  I will give it some thought tonight.  Just anxious to get it running to see how this concept works.  I am moderately confident about the engine running using this concept (hopefully not another letdown though).

Ray


----------



## Ramoye (Nov 4, 2018)

Ramoye said:


> Gordon,
> Originally, I made the crank pin per the Gingery book (it was a press fit).  But after much running, the pin started spinning in the hole.  I repaired it by brazing it to the 3" disk.
> 
> I thought about doing what you are describing, drilling a new hole in the 3" disk.  With a press fit though (per Gingery's book), it would be difficult in removing the pin should I need to take the left oscillating arm off (with an offset shoulder in the pin, would not be able to slide the left oscillating arm onto the crank pin from the front).  I thought about putting a taper on the pin and drilling a tapered hole in the crankshaft disk (would tighten a bolt to lock it down), but it would require me to set up the 4 jaw chuck to put the tapered hole into the crankshaft disk.  The way I was planning on doing it is easier/faster, but maybe not as robust as a single pin with a tapered end (without the taper, it might start spinning in the hole).  I may take the time to make the more robust design.  I will give it some thought tonight.  Just anxious to get it running to see how this concept works.  I am moderately confident about the engine running using this concept (hopefully not another letdown though).
> ...


Gordon,
I re-read your message.  My concept would keep the left oscillating arm on the pin as originally designed, but the right oscillating arm would ride on an offset.  If I did what you were describing about an offset shoulder in the disk (assuming I am understanding it as you described), it would move both pistons, which is not what we want.


----------



## Ramoye (Nov 10, 2018)

Gordon said:


> I am not too sure that I understand your process. Apparently you brazed the pin in the 3" disk. I made it 1/2" dia with a 3/8" dia shoulder to fit into a 3/8" hole reamed in the disk and held in place with a #10 machine screw. With that it would simply be a matter of making a new pin by offsetting the 3/8" shoulder and rotating it into the proper position. One of the drawings which  I sent you shows how I did it. I do not have the book here now but I thought that was how Gingery made the pin as a shouldered piece. Not offset of course.
> 
> Two thoughts: Could you determine the proper offset with your temporary set up, cut off the existing pin and just drill a new hole in the 3' disk at the new distance. ie: 1.125 +/- the offset? Would't it be easier to just make a pin with the offset shoulder?
> 
> ...


Hi Gordon,
I made a test eccentric crank pin (that fit over the shortened crank pin) and spun the engine with the electric motor.  The pressure at the spark plug went up from 8 psi to 12 psi, with only closing the gap between the pistons a little.  I needed more of an offset to close the piston gap even further.  I used an 1/8 inch shim on the lathe chuck jaw to make the test eccentric crank pin.  

I determined I needed a 1/4 inch shim on the lathe chuck jaw to make the eccentric crank pin.  So I made another test eccentric crank pin and was able to close the gap between the pistons completely, but the thru bolt hole broke through the edge of the eccentric pin diameter.  As a result, I made a full length crank pin with a shoulder that goes into the 3 inch disk, as you mentioned.  

I have now completed a full length crank pin.  I still need to cut off the old shortened crank pin from the 3 inch disk, clean it up on the lathe, then move over and drill a new mount hole 1.125 inch from the center.  I hope to attempt another run of the engine on Monday.

One thing for sure, the eccentric crank pin is raising the compression on the spark plug side.  It is also creating a greater gap between the pistons on the valve side.  Will the engine run after these modifications, time will tell?  I will let you know what the results are.

How things going on your end?

Thanks.

Ray


----------



## Gordon (Nov 11, 2018)

Ramoye said:


> Hi Gordon,
> I made a test eccentric crank pin (that fit over the shortened crank pin) and spun the engine with the electric motor.  The pressure at the spark plug went up from 8 psi to 12 psi, with only closing the gap between the pistons a little.  I needed more of an offset to close the piston gap even further.  I used an 1/8 inch shim on the lathe chuck jaw to make the test eccentric crank pin.
> 
> I determined I needed a 1/4 inch shim on the lathe chuck jaw to make the eccentric crank pin.  So I made another test eccentric crank pin and was able to close the gap between the pistons completely, but the thru bolt hole broke through the edge of the eccentric pin diameter.  As a result, I made a full length crank pin with a shoulder that goes into the 3 inch disk, as you mentioned.
> ...


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## Ramoye (Nov 11, 2018)

Hi Gordon,

Sorry to hear about your broken oscillating arm.  I have broken parts too and have remade most of the parts two or three times.  Encouraging that you are getting 30 psi compression.

I finished all the new parts for the eccentric crank pin, and new piston rods, and started to put everything together.  I had to sand the oscillating arms some on a belt sander to take care of some interference issues.  I installed the 1 1/2 inch links and adjusted the eccentric crank pin.  Pistons are almost touching at the spark plug and exhaust valve ports.  I can actually rotate the flywheel by hand and make the intake valve open some (seems to have better suction), and getting much greater pressure at the spark plug port (just held my thumb over the spark plug boss).  I may try to first run the engine at this setting.  I may have to go to the 1 7/16 inch link on the right side if carb. spitting and fuel intake is still an issue.  I will try to run it tomorrow.  I need to go to the hardware store first thing in the morning to get a shorter 6-32 set screw for the right oscillating arm (the set screw I have is hitting the bottom of the cylinder when I adjust the eccentric crank arm).  Excited to see what happens tomorrow.

Best of luck Gordon.

Ray


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## Ramoye (Nov 12, 2018)

Gordon, 

I ran the engine today with the eccentric crank pin.  No real success.  At one point, the engine did turn over a few times under its own power.  I was not able to adjust it like I wanted, because at a certain point the right oscillating arm went over center (causing the two oscillating arms to hit when rotated).  Seems like the right oscillating arm pivot point needs to move to a different location to give me the adjustment I need.  This is becoming a science project.  I will play with it some more tomorrow.  Disappointing.

Ray


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## Ramoye (Nov 13, 2018)

Gordon,

Had some luck today.  I adjusted as much as I could with the eccentric crank pin and used the 1 7/16 link arms.  The engine actually ran on its own power.   I had one 3 minute run and a couple of 2 minute runs, and several runs between 30 seconds and 1 minute.  It was awesome to see it run!  Still needs more break-in time for longer runs.  

After a couple of cylinders, three different lengths of link arms, three sets of rings, two different front and back panels, steel prosthetic tips for broken oscillating arm ends, an eccentric crank pin, two different spark plugs, various fuel/oil mixtures, and a modified crankshaft, it finally ran.

Ray


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## dsage (Nov 14, 2018)

Gordon / Ray:
   I appreciate all of the research you guys are going through to figure out the problem with this engine. As I mentioned before, after I finished the 3D CAD model and found something "not right" about it I put it aside and never started the build. I've been playing around with the drawings while following your threads here. Even manipulating the drawings has been frustrating (although much less work I'm sure) and I've had no luck being satisfied that it looks like it would run. 
    It has been difficult to follow all of the changes you have made to the original design. When you finally get it running to your satisfaction would you be so kind as to detail only what changes need to be made to the drawings in the book to make it work? I'd appreciate it. Then I'll add it back into my "to be built" list. I've always liked this engine.


Thanks


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## Gordon (Nov 14, 2018)

Ramoye said:


> Gordon,
> 
> Had some luck today.  I adjusted as much as I could with the eccentric crank pin and used the 1 7/16 link arms.  The engine actually ran on its own power.   I had one 3 minute run and a couple of 2 minute runs, and several runs between 30 seconds and 1 minute.  It was awesome to see it run!  Still needs more break-in time for longer runs.
> 
> ...


That is great. I got sidetracked on a couple of other projects so it will be a few days before I get back to the engine.


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## Ramoye (Nov 14, 2018)

dsage said:


> Gordon / Ray:
> I appreciate all of the research you guys are going through to figure out the problem with this engine. As I mentioned before, after I finished the 3D CAD model and found something "not right" about it I put it aside and never started the build. I've been playing around with the drawings while following your threads here. Even manipulating the drawings has been frustrating (although much less work I'm sure) and I've had no luck being satisfied that it looks like it would run.
> It has been difficult to follow all of the changes you have made to the original design. When you finally get it running to your satisfaction would you be so kind as to detail only what changes need to be made to the drawings in the book to make it work? I'd appreciate it. Then I'll add it back into my "to be built" list. I've always liked this engine.
> 
> ...


Dsage,
I think we are making progress, but still more to do.  I will be happy to share what I have learned with others once I get it working consistently.   This thing has been a challenge.
Ray


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## Ramoye (Nov 14, 2018)

Gordon said:


> That is great. I got sidetracked on a couple of other projects so it will be a few days before I get back to the engine.


Gordon,

I ran the engine with assistance from the electric motor for about 1 1/2 hours, hoping to get a longer run under its own power.  It did not run as well today as yesterday.  The max run time (on its own power) I got out of it was 1 1/2 minutes, just barely turning.  Some (more than usual) oil was dripping out the back of the left end of the cylinder.  I suspect the top piston ring may be sticking.  I had an issue with the sticking ring before and honed it some on a stone.  May still need some more honing.  I will pull it out and check it tomorrow.  

I wish I could have gotten more adjustment from the eccentric crank pin, but was limited by the right oscillating arm going over center.  I may make an eccentric pivot shaft for the right oscillating arm.  This would allow me to adjust the pivot point of the right oscillating arm, thus giving me more adjustment with the eccentric crank pin for piston position.  Before I go to this trouble, I will do some more break-in to see if I can get additional time running on its own power.

One problem I have is some misalignment with the right oscillating arm top brass bushing, causing some binding at a certain point during rotation.  I may press the old bushing out and replace it with a new bushing.  This misalignment could be just enough to limit the run time (marginal power to overcome the misalignment).

Thanks.

Ray


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## Gordon (Nov 14, 2018)

Ramoye said:


> Gordon,
> 
> I ran the engine with assistance from the electric motor for about 1 1/2 hours, hoping to get a longer run under its own power.  It did not run as well today as yesterday.  The max run time (on its own power) I got out of it was 1 1/2 minutes, just barely turning.  Some (more than usual) oil was dripping out the back of the left end of the cylinder.  I suspect the top piston ring may be sticking.  I had an issue with the sticking ring before and honed it some on a stone.  May still need some more honing.  I will pull it out and check it tomorrow.
> 
> ...


Ray
Make sure that the oscillating arm or the connecting rod is not hitting on the bottom of the cylinder. I have had that problem. There is not much clearance.


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## Ramoye (Nov 14, 2018)

Gordon said:


> Ray
> Make sure that the oscillating arm or the connecting rod is not hitting on the bottom of the cylinder. I have had that problem. There is not much clearance.


Gordon,
I ran into that problem.  I had to chamfer the piston rods for cylinder clearance, and had to use a shorter set screw on the right oscillating arm.  Had problems with the set screws working lose, so applied some Locktite threadlocker (blue).
Thanks for the information.
Ray


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## dsage (Nov 15, 2018)

Ray:
I don't want to state the obvious but the way you wrote it, it sounds like you were forcing the engine to run with a solidly connected electric starter motor. The electric motor must be connected with something like a one way clutch (or manually applied) so the engine can run at it's own speed (faster than the starter) once it decides to run.  Basically I'm saying the starter motor and the engine cannot be solidly connected. It will never run that way. I questioned this before when you reported that the engine would not run but that it got very hot. Sounds to me like it was actually firing but being held back by the starter.
Excuse me if I've mis-interpreted your post(s).


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## Ramoye (Nov 15, 2018)

dsage said:


> Ray:
> I don't want to state the obvious but the way you wrote it, it sounds like you were forcing the engine to run with a solidly connected electric starter motor. The electric motor must be connected with something like a one way clutch (or manually applied) so the engine can run at it's own speed (faster than the starter) once it decides to run.  Basically I'm saying the starter motor and the engine cannot be solidly connected. It will never run that way. I questioned this before when you reported that the engine would not run but that it got very hot. Sounds to me like it was actually firing but being held back by the starter.
> Excuse me if I've mis-interpreted your post(s).


Dsage,
I have wondered about that.  I have a belt from the electric motor to the flywheel of the engine.  Gingery did it this way in his book, but I know what you are saying about the coupling effect.  I occasionally remove the belt and try cranking the engine by turning the flywheel.  A clutch would be nice.  I could make something and save my arm from trying to crank the motor.  Today was a repeat of yesterday.  The engine would run some on its own power (really get with it), then I would hear what sounded like a faint backfire or two, then the engine would wind down until it stopped.  Not sure why.  I tried playing with the ignition timing some.  I will try again tomorrow.
Thanks.
Ray


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## Gordon (Nov 19, 2018)

Ramoye said:


> Gordon,
> I ran into that problem.  I had to chamfer the piston rods for cylinder clearance, and had to use a shorter set screw on the right oscillating arm.  Had problems with the set screws working lose, so applied some Locktite threadlocker (blue).
> Thanks for the information.
> Ray


I added set screws on the top of each side of the connecting rod instead of at the bottom of the arm. That works much better. 

I played around with the engine again a little bit on Saturday and I tried another RC carburetor which seemed to work much better. I actually got firing instead of backfiring. I am convinced that the problem is proper atomizing of the fuel mixture. It is constantly flooding. It seem to fire when you first start and then it quits and if you take out the spark plug the chamber is completely flooded.  Clear it and it runs again for a short period until it floods again. I also have the problem with spitting back through the carburetor. I think that the problem may be that the intake valve is not seating properly. I am thinking a stronger spring on the intake and a weaker spring on the exhaust. It is always going to put pressure on the intake valve before the exhaust valve because it reaches the intake valve port on the power/exhaust stroke before the exhaust port is open. I will try some playing around with the springs. 

I also tried a Jan Ridder vapor carburetor but that just spit fuel back through the vent hole because of the pressure at the intake port before it got to the exhaust port. 

When I put the engine back together with the new cylinder and new rings I had good compression. After some running the compression is back down to about 15#.

Gordon


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## dsage (Nov 19, 2018)

Gordon said:


> I also tried a Jan Ridder vapor carburetor but that just spit fuel back through the vent hole because of the pressure at the intake port before it got to the exhaust port.



If Sounds like your intake valve is defective. PRESSURE in the cylinder should be holding the intake valve closed and sealing it - spring or no spring. Also you'll want a fairly LIGHT intake spring so vacuum in the cylinder (on the intake stroke) can pull it open.


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## Gordon (Nov 19, 2018)

dsage said:


> If Sounds like your intake valve is defective. PRESSURE in the cylinder should be holding the intake valve closed and sealing it - spring or no spring. Also you'll want a fairly LIGHT intake spring so vacuum in the cylinder (on the intake stroke) can pull it open.


Due to the design the valve would be held open without a spring due to gravity. It is vertical head down. Perhaps it should have been mounted head up but it is too late for that. I have tried lapping it and it seals but apparently not well enough.


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## dsage (Nov 19, 2018)

Understood. What I was trying to emphasize is that ANY intake valve should be held closed sufficiently to seal by air pressure. Only minimal spring pressure is required especially on an atmospheric intake engine. (in this case enough to overcome gravity plus a bit to seal).
Maybe try a bit of air pressure on the exhaust port. You'll need to make some sort of  good sealing hose adapter to the exhaust port. Hold the exhaust valve open (it should be forced open by pressure anyway). Remove the spark plug. Apply pressure then see where you have leaks. If you hear air from the carb you have intake valve leak. If you hear it from the cylinder (open end and spark plug end) you have ring leak.

Keep at it. Thanks


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## Ramoye (Nov 19, 2018)

Gordon said:


> I added set screws on the top of each side of the connecting rod instead of at the bottom of the arm. That works much better.
> 
> I played around with the engine again a little bit on Saturday and I tried another RC carburetor which seemed to work much better. I actually got firing instead of backfiring. I am convinced that the problem is proper atomizing of the fuel mixture. It is constantly flooding. It seem to fire when you first start and then it quits and if you take out the spark plug the chamber is completely flooded.  Clear it and it runs again for a short period until it floods again. I also have the problem with spitting back through the carburetor. I think that the problem may be that the intake valve is not seating properly. I am thinking a stronger spring on the intake and a weaker spring on the exhaust. It is always going to put pressure on the intake valve before the exhaust valve because it reaches the intake valve port on the power/exhaust stroke before the exhaust port is open. I will try some playing around with the springs.
> 
> ...


Hi Gordon,
I believe you are right about the intake.  I also have problems with plug fouling with too rich a mixture.  Constantly cleaning the spark plug.  Have not had much luck like I did the other day.  It will turn over and occasionally run for a few seconds.

I have been experimenting today with an eccentric oscillating arm shaft on the right side to change the pivot point, but no real change in performance yet.  Seems to be getting good firing when running with the electric motor, but only runs a little under its own power.  Frequent plug fowling.  When it does run a little, it acts like fuel starvation then quits.  My carb. is really crude and that may be part of the problem.  I need to take some time to correct my linkage misalignment, it is causing friction at certain points of the rotation.  If the engine had enough power, the little friction should not be an issue, but this thing is very marginal on the power.  My compression is running close to what you are measuring, maybe a couple of pounds less.


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## Ramoye (Nov 23, 2018)

Gordon said:


> I added set screws on the top of each side of the connecting rod instead of at the bottom of the arm. That works much better.
> 
> I played around with the engine again a little bit on Saturday and I tried another RC carburetor which seemed to work much better. I actually got firing instead of backfiring. I am convinced that the problem is proper atomizing of the fuel mixture. It is constantly flooding. It seem to fire when you first start and then it quits and if you take out the spark plug the chamber is completely flooded.  Clear it and it runs again for a short period until it floods again. I also have the problem with spitting back through the carburetor. I think that the problem may be that the intake valve is not seating properly. I am thinking a stronger spring on the intake and a weaker spring on the exhaust. It is always going to put pressure on the intake valve before the exhaust valve because it reaches the intake valve port on the power/exhaust stroke before the exhaust port is open. I will try some playing around with the springs.
> 
> ...


Hi Gordon,

Hope you had a great Thanksgiving.  

I was able to get four 10 minute runs on the engine today on its own power.  Seems to be getting better every day.  Still getting plug fouling, and when it does quit it, is after hearing what sounds like some backfiring.  To start the engine, it requires a squirt of heavy oil into the carb. and choking it until it starts running.  I lengthened the venturi on the carb, which seemed to help some.  I ordered a Poulan chainsaw carb. to try out.  I will have to make an adapter to go from the Poulan carb to the engine intake.  It will be several weeks before I get the new carb. (coming from Hong Kong, cost 6 bucks).  Meanwhile, I will keep running the engine to see if I get even more improvement.  

I fixed my misalignment issue with the right oscillating arm by replacing the bronze bushing.  Unfortunately, the oscillating arm casting cracked when I pressed the new bushing in, requiring me to braze the crack (never performed aluminum brazing before, so I learned something).

How things going on your end?

Ray


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## Gordon (Nov 24, 2018)

Ramoye said:


> Hi Gordon,
> 
> Hope you had a great Thanksgiving.
> 
> ...


Ray: Still not much progress but I have been mostly sidetracked the last week or so. I find it interesting that you refer to backfiring because that seems to be what I get most of the time, Only once did I have a run with the electric motor where I thought that the engine was firing instead of backfiring. After running a few minutes with the electric motor if I remove the spark plug it is completely soaked in fuel or oil and not too likely to run. I have been using Coleman fuel with just a little Marvel Mystery oil. I think that the carburetor is a big part of the problem. It is interesting because the Gingery plans show a very simple carburetor. I have been using a carburetor I had. Perhaps I should take another look at the Gingery carburetor. 

I do not know about the Poulan carb but I would thing that it is probably too big. The problem seems to be too much fuel, not too little.

Gordon


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## Ramoye (Nov 24, 2018)

Gordon said:


> Ray: Still not much progress but I have been mostly sidetracked the last week or so. I find it interesting that you refer to backfiring because that seems to be what I get most of the time, Only once did I have a run with the electric motor where I thought that the engine was firing instead of backfiring. After running a few minutes with the electric motor if I remove the spark plug it is completely soaked in fuel or oil and not too likely to run. I have been using Coleman fuel with just a little Marvel Mystery oil. I think that the carburetor is a big part of the problem. It is interesting because the Gingery plans show a very simple carburetor. I have been using a carburetor I had. Perhaps I should take another look at the Gingery carburetor.
> 
> I do not know about the Poulan carb but I would thing that it is probably too big. The problem seems to be too much fuel, not too little.
> 
> Gordon


Hi Gordon,

I agree that the carb is a big part of the problem, too much liquid fuel getting into the cylinder (not getting enough atomization).  It helped some by extending the venturi to get the jet and needle closer to the low pressure area.  The jet and needle really should align with the choke area of the venturi for lowest pressure point.  I think the backfiring is coming when the plug gets saturated in liquid gas, delaying the combustion.

I don't know if the Walbro chainsaw carb. is too big, it may be.  The carb is self regulating, so it may just take what fuel it needs based on the engine vacuum.  It has both a low speed and high speed adjustment, so may be able to control the fuel intake some.  For six bucks, worth a try.  Not sure how the combination of pressure pulse and vacuum will affect the carb. performance, guess I will find out?

I had a 29 minute run today with the engine running on its own power.  Then I had a 6 minute run.  Plug was fouling, but cylinder temp. may have been affecting it some too (was getting hot).  I have a small 12V fan I plan on incorporating at some point to help keep the cylinder cool.  I am using two 1 1/2 link arms and the Gingery carb. with an extended venturi.  I am having to squirt some heavy oil in the carb. to get the engine to start running.  I am using aviation gas with some 2 cycle oil mixed in.

Good luck Gordon.

Ray


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## dsage (Nov 25, 2018)

Have you guys considered propane? Sometimes (that's Sometimes with a BIG S) you can just hook  propane up to the carb where the gasoline normally connects. BUT of course you'll need a regulator. I've used a barbeque regulator thus:  (Plumbing torch tank with shutoff -  brass fittings to the barbecue regulator input -  hose from regulator output to engine). The barbecue regulator only puts out ounces (or less) of pressure so your carb needle will control it. The caveat is whether your needle is large enough because normally you need much more propane than gasoline. But it sounds like you are getting too much gasoline now so it might be ok as is.   My Parcell and Weed engine does not have a carb or needle valve. Propane flows directly into the intake valve. It was meant to run on lamp gas back in 1902. So for this engine I added an additional homemade needle valve between the regulator and the engine to control the free flow. As mentioned your needle valve might be ok as is.
Parcell and Weed engine here:
http://davesage.ca/parcell and weed.html


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## Ramoye (Nov 25, 2018)

Gordon said:


> Ray: Still not much progress but I have been mostly sidetracked the last week or so. I find it interesting that you refer to backfiring because that seems to be what I get most of the time, Only once did I have a run with the electric motor where I thought that the engine was firing instead of backfiring. After running a few minutes with the electric motor if I remove the spark plug it is completely soaked in fuel or oil and not too likely to run. I have been using Coleman fuel with just a little Marvel Mystery oil. I think that the carburetor is a big part of the problem. It is interesting because the Gingery plans show a very simple carburetor. I have been using a carburetor I had. Perhaps I should take another look at the Gingery carburetor.
> 
> I do not know about the Poulan carb but I would thing that it is probably too big. The problem seems to be too much fuel, not too little.
> 
> Gordon


Gordon,

The engine is starting to run consistent for a few minutes if I squirt heavy oil into the carb.  My theory is that the oil is doing two things.  1) There is some leakage on the left piston when the piston is all the way back on the left side.  The oil is helping to seal it.  When the piston moves to the right just a little, it completely seals and holds 90 psi.  I attribute this to a side load on the piston at the far left position.  I believe the left oscillating arm to piston rod connection needs to go down a little to eliminate the piston side load (move oscillating pivot point down may be the solution).  Also, moving the cylinder to the left may help, but changes port location relative to the cylinders.  2) The oil is helping to regulate the fuel intake, until the gas washes it away, allowing gas flooding of the engine.  A new carb. might eliminate this problem (has better gas regulation).  Could be the fuel jet diameter is too big in the Gingery carb., and the oil compensates for it by partially blocking some of the fuel.  It seems carb. settings change on any given day (may be due to atmospheric changes).

I got a 13 minute run on the engine.  Mostly though, I got a lot of 3 to 5 minute runs, repeatable with a squirt of heavy oil into the carb.  Plug fouls often, but looks like gas fouling, not seeing much heavy oil in the plug (I believe the heavy oil is burning off, because I see smoke exiting the exhaust muffler).

Ray


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## dsage (Nov 25, 2018)

Another thought on the propane. If you find it works and your happy with it you will need to build a "demand" regulator because, as I think more about it, propane will free flow out of your carb air intake when the engine is not running. A demand regulator will supply propane only when the engine "sucks" air in (like it does for gasoline from a tank below the carb).
   So to test the engine on propane initially you should probably turn the engine over and then slowly supply the propane with the needle until it runs and shut the propane off at the tank to stop the engine.


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## Gordon (Nov 25, 2018)

dsage said:


> Another thought on the propane. If you find it works and your happy with it you will need to build a "demand" regulator because, as I think more about it, propane will free flow out of your carb air intake when the engine is not running. A demand regulator will supply propane only when the engine "sucks" air in (like it does for gasoline from a tank below the carb).
> So to test the engine on propane initially you should probably turn the engine over and then slowly supply the propane with the needle until it runs and shut the propane off at the tank to stop the engine.


I have tried propane in the past but never got good results. I even built a demand regulator but still could not get it to work. It may be time to give it another try. Nothing else seems to work.


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## Gordon (Nov 25, 2018)

Ray
You may have something. I have not really tried pressure after moving back to the right but it seems like that may be true. It would also explain why I am only able to get it to fire with the timing retarded so that it fires after the piston is beyond TDC. I will have to play around with that.
Gordon


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## Ramoye (Nov 25, 2018)

dsage said:


> Another thought on the propane. If you find it works and your happy with it you will need to build a "demand" regulator because, as I think more about it, propane will free flow out of your carb air intake when the engine is not running. A demand regulator will supply propane only when the engine "sucks" air in (like it does for gasoline from a tank below the carb).
> So to test the engine on propane initially you should probably turn the engine over and then slowly supply the propane with the needle until it runs and shut the propane off at the tank to stop the engine.


Hi Dave,

I have thought some about using propane, but not quite ready to give up on using gasoline.  

Wow Dave, that Parcell and Weed engine you built is beautiful!  Great job on it!  My engine is starting to look like it has been through WW2. 

Thanks for the ideas.

Ray


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## Ramoye (Nov 25, 2018)

Gordon said:


> Ray
> You may have something. I have not really tried pressure after moving back to the right but it seems like that may be true. It would also explain why I am only able to get it to fire with the timing retarded so that it fires after the piston is beyond TDC. I will have to play around with that.
> Gordon


Hi Gordon,

Another thing that might cause some leakage on the far left, is when it was lapped the edges got a little more material taken off, but I do not recall measurements being that different, plus, it seems the rings are springy enough to compensate for it.  I still suspect a side load on the piston at that far left location.  I may make another eccentric shaft for the left oscillating arm to move the pivot point down some to test my theory.  My engine is really starting to have a lot of adjustments. 

Let me know what you find?

Thanks Gordon.

Ray


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## Ramoye (Dec 10, 2018)

Gordon said:


> Ray
> You may have something. I have not really tried pressure after moving back to the right but it seems like that may be true. It would also explain why I am only able to get it to fire with the timing retarded so that it fires after the piston is beyond TDC. I will have to play around with that.
> Gordon


Hi Gordon,

How are things progressing?

I changed things up some on my end.  I went with a 1 1/2 link arm on the left, and a 1 7/16 link arm on the right.  I am still using the eccentric crank pin to adjust the right piston location relative to the left piston (have a gap of around 1/16 inch when the pistons come together).  

I took some time to build a stand for the motor.  I also changed to a 12V ignition system, as well as adding a 4 1/2 fan and duct to cool the cylinder.  I got two great runs today of 9 minutes each.  Not sure why it quit, but it could be due to thermal issues and/or carb.  I have no throttle, so the engine was running really hard and fast uncontrolled (increasing the heat output).  I am still waiting to receive the new chainsaw carb.  The chainsaw carb. has an idle and fast needle for adjustment, as well as a butterfly valve for throttle control.  I hope the new carb. will give me better fuel management.

Ray


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## Gordon (Dec 11, 2018)

I have not made much progress. I have been doing some other things, mostly to get a break from this source of frustration. I have made a new intake manifold which provides more support for the valve. I think that the intake valve is hanging up and not closing properly. I have only had a few very short runs where the engine ran on its own. Not sure if a stronger spring would make a difference. I will be getting back to the engine again in a couple of days. I have been working on VFD drives on my lathe, mill and drill press. Another set of frustrations but at least different.


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## Ramoye (Dec 11, 2018)

Gordon said:


> I have not made much progress. I have been doing some other things, mostly to get a break from this source of frustration. I have made a new intake manifold which provides more support for the valve. I think that the intake valve is hanging up and not closing properly. I have only had a few very short runs where the engine ran on its own. Not sure if a stronger spring would make a difference. I will be getting back to the engine again in a couple of days. I have been working on VFD drives on my lathe, mill and drill press. Another set of frustrations but at least different.


Hi Gordon,

I know what you mean about the frustration.  Been a challenge.  

I had a four and five minute run today, then no luck.  Backfiring keeping it from running longer, it seems, not sure why.  I think it may be carb. issue.  Still waiting for the new carb.  At least when it runs it runs hard, too hard, which may be causing a heating problem too.

You may want to make an eccentric crank link so you can adjust the gap between the cylinders.  That seemed to be the key for getting my engine to run.  I have a 1/16 gap between cylinders, 1 1/2 left link arm, 1 7/16 right link arm.  Left piston sticks out of left end of cylinder about 1/32 (when all the way to the left) and right piston is inside the right end of the cylinder about 1/16 (when all the way to the right).  Port locations, pistons, and piston rods are per Gingery's book.

Ray


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## Gordon (Dec 12, 2018)

Ramoye said:


> Hi Gordon,
> 
> I know what you mean about the frustration.  Been a challenge.
> 
> ...


Ray: I am sure that the problem is poor vaporization of the fuel. I am not sure if it is a result of compression or carburation. I think it is some of both. The fact that you get it running by squirting oil in the cylinder points to a compression problem. The engine seems to be firing way too hard. When it is firing it is burning off fuel in excess of what it can use. Therefore it runs for short periods of time until there is just more fuel in the cylinder than it can burn off in one cycle and once it is flooded it stops running. I have played around with both a vapor carburetor and propane but I have not had much luck with either of them. I have also done some experimenting with different carbs with smaller jets and other throat size. I will be getting back on the engine in a few days.


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## Ramoye (Dec 12, 2018)

Gordon said:


> Ray: I am sure that the problem is poor vaporization of the fuel. I am not sure if it is a result of compression or carburation. I think it is some of both. The fact that you get it running by squirting oil in the cylinder points to a compression problem. The engine seems to be firing way too hard. When it is firing it is burning off fuel in excess of what it can use. Therefore it runs for short periods of time until there is just more fuel in the cylinder than it can burn off in one cycle and once it is flooded it stops running. I have played around with both a vapor carburetor and propane but I have not had much luck with either of them. I have also done some experimenting with different carbs with smaller jets and other throat size. I will be getting back on the engine in a few days.



Gordon,

I agree with you on poor vaporization of the fuel.  Today I adjusted the gap between the pistons wider.  It resulted in a 7 minute run at a slower rpm (and richer carb. setting).  This rpm seems about right, it was running way too fast before.  It still quit after the 7 minute run, which may be attributed to fuel build up (causing flooding).  Seems to be a correlation between piston gap and rpm.   I may have some piston/cylinder leakage, but it seems to have enough compression to run.

I will be glad to get the chainsaw carb. in.  Curious to see how it will work.

I ran out of time to experiment with it more today.  Will try playing with the piston gap some more tomorrow.

Thanks Gordon.

Ray


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## Gordon (Dec 16, 2018)

Got around to doing a little more experimenting on the engine yesterday. Still not much progress but I did discover that if I held the intake valve open while turning over with the electric motor the engine fires or backfires every stroke. There seems to be a fine line between a strong enough valve spring and too weak. Too strong and it will not fire and too weak and it spits back through the carburetor. It looks like there may be an ideal match between intake and exhaust valve spring match. I have tried several different carburetors and they all work some times. They seem to be close and then they will not run at all. Then suddenly they seem to work again for a short time.


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## Ramoye (Dec 16, 2018)

Gordon said:


> Got around to doing a little more experimenting on the engine yesterday. Still not much progress but I did discover that if I held the intake valve open while turning over with the electric motor the engine fires or backfires every stroke. There seems to be a fine line between a strong enough valve spring and too weak. Too strong and it will not fire and too weak and it spits back through the carburetor. It looks like there may be an ideal match between intake and exhaust valve spring match. I have tried several different carburetors and they all work some times. They seem to be close and then they will not run at all. Then suddenly they seem to work again for a short time.



Gordon,

Might can try to put shim washers under the spring to incrementally increase the spring force?  I also have noticed too weak of a spring causes carb. spitting.  Maybe temperature is affecting the spring force (I would hope it is not that sensitive).

Still waiting on the carb. to come from China.  It was only six dollars, but beginning to wish I had spent a little more to get one sooner.  I have about done all I can do for now until I get the new carb.

Thanks Gordon.
Ray


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## Gordon (May 28, 2019)

See my post at:

https://www.homemodelenginemachinist.com/threads/compression.31308/page-2


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## dsage (Jan 31, 2020)

Hi guys. Have you had any luck yet getting the engine running?
I stumbled on this video today on Youtube. He explains the motion. I haven't analyzed it yet. Maybe you can see some changes from what you built (and the book)?


There is another video here that has some good snap shots of the motion works as well.
As far as I got was to 3D modelling  it and, like you have discovered,  I can't see how it achieves any compression. I'd really like to build this engine.


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## dsage (Jan 31, 2020)

I'm pretty sure I can see some issues with the motions.
I've had some discussion with one of the builders on You tube.
Sorry I have to link to the video again. But you can read the comments by me (Dave Sage) below the video.
Any thoughts??


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## Gordon (Jan 31, 2020)

Never really got the engine running consistently for any length of time. If everything is perfect it will run but the next time it will not run even though nothing has changed. I finally decided that the design is just too marginal and I have too many other things to work on which are not as frustrating. That being said I am now working on my Snow Tandem to "improve" it and I am having similar problems. I get the engine running for a few minutes and then the next time I try it will not run. Maybe I need a less frustrating hobby.


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## dsage (Jan 31, 2020)

Sticking with the Atkinson. May I suggest you look at the videos I linked and see if  the motions are different from yours? Not withstanding that (I believe) you changed some of the linkage or positions. I'd really like to get to the bottom of the issues before I build it. Following along in the comments on the video may give you some clues. Thanks

As for the Snow. I suppose that should be a different thread but since you have similar problems perhaps there are common issues with the way you have constructed both engines. You mentioned compression issues for the Atkinson  - possibly ring or valve related? Are those items up to snuff on the Snow?
I couldn't imagine improving that design. It's complicated enough as it is


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## bluejets (Jan 31, 2020)

I gave some insight to at least one problem in the design of this engine back in #54 along with the fact that the compression ratio is very small to begin with so any machining imperfections will be a major impact on the final outcome.


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## Bruce R. (Jan 31, 2020)

I’ve learned that coleman fuel doesn’t have a whole lot of octane, I put about a 3/4 tank of gas in my engines and using the little red straw, I fill them the rest of the way with 2+2 gumcutter, that stuff is kinda like race car fuel.


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## Cogsy (Feb 1, 2020)

Bruce R. said:


> I’ve learned that coleman fuel doesn’t have a whole lot of octane, I put about a 3/4 tank of gas in my engines and using the little red straw, I fill them the rest of the way with 2+2 gumcutter, that stuff is kinda like race car fuel.



I've never heard of 2+2 gumcutter so I'm not sure what it is, but unless your engines are super high compression then octane is not likely to be your issue with the coleman fuel. Higher octane numbers simply mean the fuel can withstand higher compression before spontaneous combustion. As long as you're not getting pre-ignition ('pinging' or 'knocking') then you don't need a higher octane fuel and won't get any benefit (power, mileage, less emissions, cleaner burn, etc) from using higher rated fuel, it's just marketing from the fuel companies. This goes for any engine, so even with your car, if the owners manual says it will run on 91 then there's no point paying extra for 95 or 98 or whatever.


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## dsage (Feb 1, 2020)

bluejets said:


> I gave some insight to at least one problem in the design of this engine back in #54 along with the fact that the compression ratio is very small to begin with so any machining imperfections will be a major impact on the final outcome.



I re-read your comments in #54  I have also drawn the engine as a 3D model. I haven't built it yet because I agree that from what I can see the design is very marginal. But the design is VERY critical as to positioning and dimensions of the components. A very SMALL change can make a HUGE difference in the motion. That's why I'm wondering if those that got it running (as per Youtube) unknowingly made minor changes OR they built it perfectly (i.e. didn't inadvertently make mistakes and throw it off).
I have rotated the crank in my 3D model exactly as shown in the one video and observed the positions and motions in between positions and from what I can see there is a big difference in motions that could result in much better compression and better intake strokes. I made those comments to the builder in the Youtube video. He admits that he made a wooden model first and played around with it to get it right (not his words). He says the book is correct but..... who knows.
Manipulating the 3D model is very tedious but that's what I might have to do to see what results in the "proper motion" or improves it.
It's one of those engines I'd really like to build but I don't want to waste my time.


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## Peter Twissell (Feb 1, 2020)

Rather than manipulating a 3d model, it may be easier to create a spreadsheet to calculate the positions of each link at each degree of rotation of the crank. This is not as hard as it may seem, it's just a series of triangles.
The spreadsheet can then calculate the space between the pistons and the compression or expansion of that space.
Once the spreadsheet is written, it is relatively simple to alter the positions of fulcrums and lengths of links to observe the effect on compression and expansion.


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## dsage (Feb 1, 2020)

Peter Twissell said:


> Rather than manipulating a 3d model, it may be easier to create a spreadsheet to calculate the positions of each link at each degree of rotation of the crank. This is not as hard as it may seem, it's just a series of triangles.
> The spreadsheet can then calculate the space between the pistons and the compression or expansion of that space.
> Once the spreadsheet is written, it is relatively simple to alter the positions of fulcrums and lengths of links to observe the effect on compression and expansion.



Easy for you maybe. I have no idea how to attack the problem that way. A spreadsheet I could handle maybe but....past that I'm lost on a methematical approach. You'd still have to make changes to the bits and pieces and re-calculate. I'm not sure what I'd be looking at in a spreadsheet full of numbers. Seems to me watching the parts physically move after a change would be more productive. There's a lot of stuff going on.
I can easily animate the 3D model. You just rotate the flywheel and watch it move. Then make a change in the drawing for a piece or spacing to see the effects of changes and to observe the results. It's easy to stop and measure any aspect of the model at any time. The trick is keeping all the connections in tact. Sometimes the 3D model can fall apart.
I think I mentioned I did a bit of this and found that very minor changes can send the motion works into some very wacky gyrations that are obviously wrong. I wouldn't know what the numbers on a spreadsheet were telling me. I'm more of a "try it" kind of guy anyway. Mathematical analysis is not my wheelhouse.
Feel free to have a go though.


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## bluejets (Feb 1, 2020)

dsage said:


> I re-read your comments in #54  I have also drawn the engine as a 3D model. I haven't built it yet because I agree that from what I can see the design is very marginal. But the design is VERY critical as to positioning and dimensions of the components. A very SMALL change can make a HUGE difference in the motion. That's why I'm wondering if those that got it running (as per Youtube) unknowingly made minor changes OR they built it perfectly (i.e. didn't inadvertently make mistakes and throw it off).



I would say the former as George drew it using Prodesktop 3d at the time with dimensions from the drawing.
As you say, time waster if not going to work as is, so any drawing development with improvement would be essential I'd imagine.
In George's instance, the time element was primary reason not to go any further, too many other things to do.

Not that it would make any difference in this instance but, any low compression engine can have performance increase but using methanol as a primary fuel with castor as lube and nitro methane added in varying amounts to the methanol volume. Readily available at model aircraft shops.
The nitro introduces oxygen as it burns and adds to the compression. Reason for aircraft use is it tends to widen the needle setting quite considerably, it lowers the idle speed and  it improves the transition from idle to increased revs.
Most instances we would add an extra shim under the head to actually lower the compression a small amount for the nitro use on some 4 strokes.
OS were usually ok as primarily designed to run on 10 to 20%.

Usually amounts in 10% increments are the most noticeable.
Byproduct of the nitro is acid which, if left for long periods can attack internal parts so best to give a good wash out later.


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## dsage (Feb 1, 2020)

bluejets said:


> I would say the former as George drew it using Prodesktop 3d at the time with dimensions from the drawing.
> As you say, time waster if not going to work as is, so any drawing development with improvement would be essential I'd imagine.
> In George's instance, the time element was primary reason not to go any further, too many other things to do.
> 
> ...


 An interesting treatise on Nitro. Thanks. I'll try to keep that in mind.
But if I'm to build it It'll have to run on Naptha like the rest of my engines or maybe propane. Since I'm between projects right now I'll do a bit of work to see what can be done if anything to improve the motion works.
What would be nice would be if someone that has one running could make some measurements of all the important pieces and spacings. Of course there is the possibility that the book dimensions are fine (likely) as stated by the one Youtube builder and it's just an exceedingly finicky engine (very likely).
Thanks
http://davesage.ca/


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## bluejets (Feb 1, 2020)

No..... I just spoke to George on this an he even quoted an original builder who had one running at an engineering show in the UK as saying plans were wrong.

Builder had to re-do the drawings.


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## dsage (Feb 1, 2020)

bluejets said:


> No..... I just spoke to George on this an he even quoted an original builder who had one running at an engineering show in the UK as saying plans were wrong.
> 
> Builder had to re-do the drawings.



Interesting. I talked to someone at Cabin Fever one year and he also recalled something he had to change but he didn't (wouldn't ??) say what. Perhaps there is some conspiracy going on here  LOL


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## bluejets (Feb 1, 2020)

dsage said:


> Interesting. I talked to someone at Cabin Fever one year and he also recalled something he had to change but he didn't (wouldn't ??) say what. Perhaps there is some conspiracy going on here  LOL


Well I doubt the people at the UK engineering competition would be full of crap.
They are highly respected both for their work and their expertise.
They don't get to where they are by telling or making up stories.


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## dsage (Feb 2, 2020)

bluejets said:


> Well I doubt the people at the UK engineering competition would be full of crap.
> They are highly respected both for their work and their expertise.
> They don't get to where they are by telling or making up stories.


Agreed.
But as mentioned it would be nice to have some clues as to what was changed. Either way I'll play around and see what I come up with. Unless I stumble on it, it won't be any time soon.


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## bluejets (Feb 2, 2020)

Position of the plug was just one of many.


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## dsage (Feb 3, 2020)

bluejets said:


> Position of the plug was just one of many.


I'm sure the plug position will fall out of the analysis. The first thing will be to get the compression up by changing the motion works to get the pistons closer together at the left end. Once that's achieved it's easy enough to move the plug over the piston ends.
I looked at the problem almost all day yesterday. Fiddling around with the 3D model and making sure I had drawn everything as per the book.
As I once discovered when reading the book there is a big discrepancy between the form of the oscillating arm casting  on page 36 and where you are supposed to machine the holes on page 81. They show the connecting rod joining hole placed on a particular radius from the pivot hole and it seems to me you wouldn't be able to achieve that with the castings produced from page 36.
Anyway I made sure my drawing was as per page 81 (because that's what they said to machine). I originally had it more like the casting shape and dimensions on page 36. Changing it didn't make any major difference.
Analysis showed that there is almost zero compression. I looked simply at the distance between the pistons when the intake air is finally trapped in the cylinder and where the pistons come together at the left compression end. I didn't bother with volumetric calculations.
In fact there is expansion of the distance between  the pistons in the travel between the two ends so there is a bit of vacuum going on while it's traveling.  The spacings at each end were almost the same - so zero compression.
I then went trough various changes in part positions and link lengths and I could get up to 3:1 ratio but it required MAJOR changes that I doubt were undertaken by any builder purposely or by accident.
One major change included making the intake port in the cylinder  a slot to take more advantage of the intake stroke and moving the pivot point of the left oscillating arm. That's where I got the 3:1 compression.
As suspected all along changes of only a fraction of an inch shifted positions at both ends basically improving one end and removing the benefits from the other and and generally destroyed the whole geometry.
 I assume something quite simple must be at the root of the fix. There are a LOT of things to change. All of them affect the motion significantly.
I'll work on it some more today (maybe).


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## Gordon (Feb 3, 2020)

dsage said:


> I'm sure the plug position will fall out of the analysis. The first thing will be to get the compression up by changing the motion works to get the pistons closer together at the left end. Once that's achieved it's easy enough to move the plug over the piston ends.
> I looked at the problem almost all day yesterday. Fiddling around with the 3D model and making sure I had drawn everything as per the book.
> As I once discovered when reading the book there is a big discrepancy between the form of the oscillating arm casting  on page 36 and where you are supposed to machine the holes on page 81. They show the connecting rod joining hole placed on a particular radius from the pivot hole and it seems to me you wouldn't be able to achieve that with the castings produced from page 36.
> Anyway I made sure my drawing was as per page 81 (because that's what they said to machine). I originally had it more like the casting shape and dimensions on page 36. Changing it didn't make any major difference.
> ...


I did a lot of playing around with drawings. I only have 2D CAD so I had to just move parts around. There is a similar design by Brooks Pendergast which gives a slightly better compression. The parts are quite a bit different but it still does not make a dependable engine. As you have discovered the compression is generated by one piston moving slightly faster than the other so there is very little compression. Also when the engine fires the pistons are not in a good position to provide power to the crank. The linkage arms are almost horizontal when it fires so not much power is transmitted to the crank. If you want I can give you my CAD drawings and you can play around with them. If interested send me your email address in a message and I will send them to you.


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## awake (Feb 3, 2020)

Just a thought - would it be helpful to print up some models using a 3d printer? 3d CAD is marvelous, but there are times when I find it easier to look at an actual something rather than the visualized object on the screen, and even more so when moving the parts around.


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## dsage (Feb 3, 2020)

awake said:


> Just a thought - would it be helpful to print up some models using a 3d printer? 3d CAD is marvelous, but there are times when I find it easier to look at an actual something rather than the visualized object on the screen, and even more so when moving the parts around.


Gordon / awake:
I think I'm ok with the 3D model / drawings I have. Thanks
The advantage of the 3D computer model is priceless in the ability to manually rotate the flywheel very slowly and watch the pistons move, stop them in a precise position at both ends of the travel and make measurements and look for interferences. I can get through several changes to see the effects in an hour or so.
3D printing is far too slow to make multiple trial changes but it might be useful to get something "in hand" when I'm satisfied I've gone as far as I can.

As an update I found another error in MY DRAWINGS. I was thrown off again by the discrepancy between page 36 and 81 on the oscillating arms. When you set out to re-draw a part from a book you look for something that gives the most information especially when there are defined curves. Page 36 was great because it laid everything out with measurements radii of curves so that's what I used.
Page 81 threw a lot of that away because the spacing between the holes is defined as to be machined.
So I changed my drawing to be as per page 81 dimensions. That made the shape of the arms slightly different that those defined on page 36  (Because the curves no longer fit with the dimensions, but not a significant difference. Now I'm pretty sure  I'm working with "the book" dimensions. (however vague and scattered they may be).
All that done unfortunately it made only a bit of difference in the compression (which was previously zero) I though it would have made more.
Currently I'm playing with making the left conrod a bit longer and making the intake port a slot (instead of a hole).
Of course there are the usual "change this and it changes that" problems but lengthening only the left conrod affects the compression directly. The slotted intake port allows more intake charge while the left piston moves left - a good thing because there is quite a bit of movement in that piston alone before the right piston starts to follow - so more useful intake time.
I have the compression ratio (actually the ratio of the pistons gaps at each end of travel) to about 2.5:1. I have not done the volumetric calculations to get the actual compression. It might be higher than 2.5:1  (I doubt less) but it is certainly more than the zero I was getting. The ratio of 2.5:1 is barely enough but it will probably run if everything else supports it. It won't be winning any tractor pulling competitions for sure.
The changes so far are some that can be made easily to an existing engine and are also minor changes if building a new engine. I hope all the required changes follow that idea.
I'm not done yet. I might come across some more simple changes.


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## bluejets (Feb 3, 2020)

dsage said:


> I assume something quite simple must be at the root of the fix.



I would not assume anything with this particular engine.

One thing to remember here is this was originally all done with a slide rule, no computers, no digital calculators, just grey matter, pencil and paper.

There is of course the other Atkinson engine which, although does present some setting up problems, does work pretty much from the drawings.
I have one here as does George.


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## dsage (Feb 3, 2020)

bluejets said:


> I would not assume anything with this particular engine.
> 
> One thing to remember here is this was originally all done with a slide rule, no computers, no digital calculators, just grey matter, pencil and paper.
> 
> ...



I have one of those engines as well which is somewhat why I want to build this one.
http://davesage.ca/
I'm not assuming anything but I am trying to stick to simple changes so that an existing engine can be modified and a new one won't be much different than the original.

End of the day news is that I have the compression up to 4.3  with sort of minor changes. But I have to check carefully because as I said before sometimes when you make a change in a part it comes disconnected from the rest of the engine and it isn't telling the truth about it's motion. But I'm hopeful.
Possibly more tomorrow.


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## Gordon (Feb 3, 2020)

I can tell you that both Ray and I tried different length connecting rods, different linkage, different pivot points, different crank center and everything else we could think of and never got anything which gave us a good running engine. Never got anything but marginal compression. It will kind of run if the moon and the stars are in correct alignment.


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## dsage (Feb 3, 2020)

I think this is where the 3D modelling is helping. I can try a several different "Pieces" in a couple of hours and don't have to make any chips. Rest assured I've had LOTS of failed attempts because what seems like it may be a good idea turns out to be crap for one reason or another. The motion works are vary finicky - as you know. I'm really glad I have this tool because I can imagine your frustration having tried so many real parts. I'll have more to report tomorrow (I hope).


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## propclock (Feb 4, 2020)

Thanks Dave I find this very interesting.  Design it and then make it.
The proof is in the pops. 4-1 sounds like most old reliable engines.
I think 4-1 CR will definitely work. Make chips! oh yea it's cold in 
Canada. Well then, think about it,h until it is warm enough. 
Later Dave.


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## dsage (Feb 4, 2020)

Thanks Paul:
I think that building the engine (according to what I've found) is what I'm going to have to do. The best compression I'm able to achieve is about 4.3 but it requires a few modifications that although could be made to an existing engine are probably best applied to a new build. I wouldn't want to tell anyone to go ahead and modify an existing engine that might have other parameters already modified. As mentioned everything seems to affect the result (mostly for the worse) and combining these modifications with pre-existing mods might result in trashing the engine.
Like medical insurance, preexisting conditions make your policy null and void 
For what it's worth the changes to a perfectly "by the book" engine require making the left conrod longer, moving the cylinder center line up a bit,  adding a slight bit to the top of the left piston and because of those changes the intake port needs to be made into a slot instead of a hole starting where it is and extending it toward the water jacket.
If one might be satisfied with only about 3.7:1 compression then simply adding some to the top of the piston and making the intake port a slot would probably do.
The intake port slotting seems to be the most effective change. The left piston moves quickly to the left during intake while the right piston moves slowly following it. This is what gives the intake suction. There is quite a bit of rotation where the pistons movement are creating suction but it appears because of the size of the original intake hole in the cylinder the suction is cut off prematurely when the right piston covers it up. With the port slotted by the correct amount full advantage is taken of the vacuum available. After a certain point the pistons move together to the left with a large gap between them so no more vacuum is created. That distance forms one value in the compression ratio because that much gas is trapped between the pistons.
After that the right piston starts to move faster and creates compression on the left end of the cylinder. The gap between the pistons at the left side forms the other value in the ratio. (only a gap ratio but it's pretty close to the actual compression ratio).
I've measured about 0.500 at intake end and .116 gap under compression (4.3:1).
And yes the spark plug hole needs to be moved to the right a bit. But if you are satisfied with the original designs misalignment of the 10mm sparkplug with the hole then it won't bother you. I decided it would be better to use a 1/4" spark plug and make a new boss for it to screw into. Then there is just enough space up against the water jacket to get the sparkplug electrode right down to the hole.
That's enough (vague) info for now. Vague because I don't want anyone to risk their existing engine.
BUT if any of the info has tweaked you interest I can be more specific.
The first caveat would be that you need an engine built exactly by the book. I hope I have it drawn it that way and that I'm starting from the proper place otherwise all bets are off. 
That's why it might be better to start a new build with the dimensions I have for the whole engine. I'm confident it will work. I have found CAD to be dead accurate in the past (assuming it's drawn that way).


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## Gordon (Feb 5, 2020)

dsage said:


> Thanks Paul:
> I think that building the engine (according to what I've found) is what I'm going to have to do. The best compression I'm able to achieve is about 4.3 but it requires a few modifications that although could be made to an existing engine are probably best applied to a new build. I wouldn't want to tell anyone to go ahead and modify an existing engine that might have other parameters already modified. As mentioned everything seems to affect the result (mostly for the worse) and combining these modifications with pre-existing mods might result in trashing the engine.
> Like medical insurance, preexisting conditions make your policy null and void
> For what it's worth the changes to a perfectly "by the book" engine require making the left conrod longer, moving the cylinder center line up a bit,  adding a slight bit to the top of the left piston and because of those changes the intake port needs to be made into a slot instead of a hole starting where it is and extending it toward the water jacket.
> ...


As far as adding to the top of the left piston and changing the connecting rod I think the same thing could be accomplished by just making a longer LH connecting rod. The goal is to move the LH piston to the right and just making the connecting rod longer does that unless that causes some interference some other place. As far as slotting the intake I think that you may have something there. You are starting the compression stroke with a smaller initial volume so that you are able to compress the smaller volume with a shorter stroke. What you are doing is creating a shorter stroke. Getting fuel into the chamber is not the problem. Getting the fuel to a state where it is compressed enough to create a combustible mix is the goal. I have played around a little bit with my drawings but I still have not found the sweet spot. As you have found a relatively small change makes a big difference. I found that just the amount of play in the various connecting points can change things.


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## dsage (Feb 5, 2020)

Gordon said:


> As far as adding to the top of the left piston and changing the connecting rod I think the same thing could be accomplished by just making a longer LH connecting rod. The goal is to move the LH piston to the right and just making the connecting rod longer does that unless that causes some interference some other place. As far as slotting the intake I think that you may have something there. You are starting the compression stroke with a smaller initial volume so that you are able to compress the smaller volume with a shorter stroke. What you are doing is creating a shorter stroke. Getting fuel into the chamber is not the problem. Getting the fuel to a state where it is compressed enough to create a combustible mix is the goal. I have played around a little bit with my drawings but I still have not found the sweet spot. As you have found a relatively small change makes a big difference. I found that just the amount of play in the various connecting points can change things.



You are correct and that particular solution to do both (add to the piston and to the connecting rod) was just one of the many places I ended up with good compression. Noticing that effect, I actually tried transferring all of what I added to the piston to the conrod instead and vise versa in increments.
The whole thing is a repetitive trial and error and that's just were I ended up with one of dozens of trials.
Then I started thinking about someone modifying an existing engine and decided that just adding to the piston would be a simple(er) fix. BUT it appears from my experimentation the best solution is not to add just to the conrod because the piston movement is not linear so the effect of adding to the rod isn't linear either (even though it pretty linear as the piston gets to the center of it's travel). So I did end up with a balance. But there was very little added to the piston top. (note I again haven't given values).  Of course either of those changes can cause piston clash at the right end so..... Over and over you go.
I think we might be on the same page with the intake port. Although I don't understand your explanation we're probably saying the same thing. From watching the model I can see that there is a point in the movement of the pistons together to the left where the gap between them is maximum - therefore trapping the maximum mixture. Slotting the intake port to the proper point allows the mixture to "flow" onto that gap before it is trapped. The more you trap and compress into a fixed volume on the left end is by definition better compression.

I have been intentionally vague with any dimensions because the more I read the book the more IMHO I've concluded it's a piece of crap. Many confusing dimensions and dimension s that don't jive from one place in the book to another and very poor and vague descriptions of assembly.
Case in point is pages 83 through 87 where they basically suggest just slapping the cylinder assembly onto the front of the engine and fiddling with it's position until the movements just "work properly" giving several thing to look for. Anyone that knows how finicky the movement is knows that is not a proper suggestion. They even suggest that new connecting links might be required to make the movement work properly.
IMHO this is completely un-acceptable as any other set of drawings I've used ASSUME you have made everything as per the plans and that it WILL work if they give the the proper dimension for assembly and they do so.
SO it's for this reason I've concluded that anyone with an existing engine should NOT take any of my advice because I can't guarantee how your particular engine is currently assembled. Moving almost anything a few thou changes the whole operation.
So I think I've decided to build it according to my drawings but that will take some time. Don't expect results any time soon.
I might consider a build log here when I start.
But who knows I might fail too. 

BTW have you tried propane or a vapor carb?? I ask because watching the movement with respect to the intake slot some of the movement is just shuttling of the pistons with very little relative movement and so the actual vacuum produced may be very low. So low that the intake valve may not work.  I'm thinking propane under a very slight pressure - just enough to be cut off by the valve spring and no more, may go in better under low vacuum. Also a carb generally does not work well with low vacuum so the liquid fuel will not be vaporized. A vapor carb might be better.
Food for thought.


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## Gordon (Feb 5, 2020)

dsage said:


> You are correct and that particular solution to do both (add to the piston and to the connecting rod) was just one of the many places I ended up with good compression. Noticing that effect, I actually tried transferring all of what I added to the piston to the conrod instead and vise versa in increments.
> The whole thing is a repetitive trial and error and that's just were I ended up with one of dozens of trials.
> Then I started thinking about someone modifying an existing engine and decided that just adding to the piston would be a simple(er) fix. BUT it appears from my experimentation the best solution is not to add just to the conrod because the piston movement is not linear so the effect of adding to the rod isn't linear either (even though it pretty linear as the piston gets to the center of it's travel). So I did end up with a balance. But there was very little added to the piston top. (note I again haven't given values).  Of course either of those changes can cause piston clash at the right end so..... Over and over you go.
> I think we might be on the same page with the intake port. Although I don't understand your explanation we're probably saying the same thing. From watching the model I can see that there is a point in the movement of the pistons together to the left where the gap between them is maximum - therefore trapping the maximum mixture. Slotting the intake port to the proper point allows the mixture to "flow" onto that gap before it is trapped. The more you trap and compress into a fixed volume on the left end is by definition better compression.
> ...


I am at a little disadvantage here because I actually ended up building the engine using the Pendergast plans. I started with the Gingery plans and had very poor results so I ended up using the other plans. That may or may not have been a good decision. I did a lot of playing around with drawings with various linkages and various connecting rods. I also did a lot of making experimental parts with just different centers w/o actual bearing points. That is something like making the upper linkage from 1/4 x 1/2 steel bar with centers slightly longer and slightly shorter just to see what cheapened. I soon discovered that actual parts did not give the same results as the drawing would suggest. 

As far as carburation. I did try both a vapor carb and a propane carb but i did not have very good luck. Getting fuel into the cylinder is not a problem. It is easy to get fuel dripping out of the exhaust because it is not vaporizing and burning properly.

I have been using 2 D cad for a long time and I can do things with that. I even started to play around with Fusion 360 but I was not sure that I wanted to spend the time that it would require to learn it properly. As someone said folks who are familiar with 2 D are at a disadvantage because 3 D is an entirely different concept.


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## dsage (Feb 5, 2020)

Gordon said:


> As far as carburation. I did try both a vapor carb and a propane carb but i did not have very good luck. Getting fuel into the cylinder is not a problem. It is easy to get fuel dripping out of the exhaust because it is not vaporizing and burning properly.
> 
> I have been using 2 D cad for a long time and I can do things with that. I even started to play around with Fusion 360 but I was not sure that I wanted to spend the time that it would require to learn it properly. As someone said folks who are familiar with 2 D are at a disadvantage because 3 D is an entirely different concept.



Your example is why I don't recommend changing anything unless you are at wits end and just want to try something that sounds like it might help.
I'm sure I'll run into issues as well if / when I build it. I've used the 3D modelling enough to trust it completely as long as I have the parts modeled correctly. I've found many mistakes in drawings I've received. That's why I always re-do flat drawing in 3D CAD before I make chips. You can instantly tell when things don't fit and the program can point out interference's. 
SO I'm pretty sure if I build it according to what I have now I'll be off to a good start.
Yes I used ACAD to do flat drawings for years and almost nothing transferred to the 3D process. It was very frustrating to learn but after about a year I gained enough ability be dangerous now  I'm by no means "good" at it and just follow what processes I've figured out even if they might not be the best methods.
You also have to do it frequently to remember (at least I do) and so I model a lot of things - even simple blocks with holes in them to keep fresh.
We'll see what happens I guess.


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## Gordon (Feb 6, 2020)

I am sure that given the motivation I could learn 3 D cad. The problem is that 95% of my drawing is for the model engines I am building. At 80 I probably am not going to be using a new cad program long enough to make it worth the effort to learn it. As you say it is also a use it or loose it thing. If I build two engines a year that is not enough to become proficient at using the program.  I usually do redraw the plans which gives me a better understanding of the design and frequently catches mistakes in the original drawing. Frequently the original designer does not make the drawings in a way which I find easy to use. I don't care about the dimensioning  rules I learned way back in high school. I want the dimensions to be how I am going to use them. If I have to get my calculator out to find out where I want to cut it is not done properly. A+B-C/2 may get me there but why not just put on the dimension I am going to use. Also as you have stated frequently the information is in a couple of different places and the different places do not agree. Another gripe I have with many drawings is the precision implied. This is especially true in cad where dimensions can be shown to four decimal places. .640625 implies a precision which may not be necessary. 5/8 +/- 1/16 may have been perfectly OK. I think that in many cases the original builder just started building and figured it out as he went along and made some rough sketches and calculations on the back of the envelope and when he was done someone else came along and made a drawing by measuring the final parts and may not have understood why and how things were done.

Enough soap box for one day. Sorry.


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## dsage (Feb 6, 2020)

Gordon said:


> I am sure that given the motivation I could learn 3 D cad. The problem is that 95% of my drawing is for the model engines I am building. At 80 I probably am not going to be using a new cad program long enough to make it worth the effort to learn it. As you say it is also a use it or loose it thing. If I build two engines a year that is not enough to become proficient at using the program.  I usually do redraw the plans which gives me a better ....



No problem with the soapbox. I agree with everything you said. I usually try to make everything to within a thou of the drawings (even if the dimensions are exaggerated from what's necessary). That way I don't have to worry about errors adding up (or thinking about where they may be adding up). I know the CAD package has it all fitting with what dimensions are there. I might as well build it to what it says. I generally do NOT have a 'good enough" attitude when making parts. Unless I've made a mistake and then I figure out if it's good enough to leave it like it is 
I picked up some materials today.


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## Gordon (Feb 6, 2020)

dsage said:


> No problem with the soapbox. I agree with everything you said. I usually try to make everything to within a thou of the drawings (even if the dimensions are exaggerated from what's necessary). That way I don't have to worry about errors adding up (or thinking about where they may be adding up). I know the CAD package has it all fitting with what dimensions are there. I might as well build it to what it says. I generally do NOT have a 'good enough" attitude when making parts. Unless I've made a mistake and then I figure out if it's good enough to leave it like it is
> I picked up some materials today.


I assume that you are using bar stock instead of making patterns and castings. I am really interested in seeing your build. Against my better judgment I spent a couple of hours playing around with Fusion 360. I may wise up by tomorrow and go back to my cave.


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## dsage (Feb 6, 2020)

Gordon said:


> I assume that you are using bar stock instead of making patterns and castings. I am really interested in seeing your build. Against my better judgment I spent a couple of hours playing around with Fusion 360. I may wise up by tomorrow and go back to my cave.



Yes I use bar stock for the most part. I think I have one engine built from castings.
BUT I did build the other Atkinson. My friend has a small foundry and we cast a flywheel for it. There was another one that was a bit of a reject. Good thing I kept it because I think it's the same as the one required for this engine (Or at least the dimensions are close enough at first glance). With a bit of aluminum TIG welding I think I can fix it up and make it work.
I might start a build log here when I get to building it. I don't have a good camera. I could use my phone but getting the photos off of it is an extra step.
We'll see.


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## propclock (Feb 7, 2020)

Dave the shop is calling you , too bad you will have to find an ignition
system for the new engine.
 It is a nice and moderate temperature here.
just my 1.414 cents of motivation.


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## dsage (Feb 7, 2020)

propclock said:


> Dave the shop is calling you , too bad you will have to find an ignition
> system for the new engine.
> It is a nice and moderate temperature here.
> just my 1.414 cents of motivation.


Yes. An ignition is going to be hard to find 
It's a nice moderate temp here too (in the basement shop). A good place to be with a bit of occasional exercise shoveling snow. 
It's all good.


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