# A different opposed piston engine---



## Brian Rupnow (Dec 17, 2013)

I have been fascinated with a post on another forum about an opposed piston engine. I do not want to plagiarize someone else's post, so I have been surfing around the internet looking at "other" types of opposed piston engines. I found one today, and spent some time doing some preliminary modelling in Solidworks to see what would be involved. I'm not totally sure that this is "do-able" as a model engine, but I thought it was well worth having a look at. This is what I come up with---a 3/4" bore x approximately 1" stroke air cooled single crankshaft engine. I'm not sure if I will go farther with this or not, but it IS interesting.---Brian


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## Art K (Dec 17, 2013)

Brian,
Isn't this similar in concept to the Atkinson Differential engine?
Art


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## compspecial (Dec 18, 2013)

Brian, this is the principle of operation of the "rootes" diesel used in the "commer" truck and known as the TS3 engine, it was watercooled and had a blower to scavenge the spent gases when both inlet and exhaust ports were open, there are one or two examples of survivors on "U tube"
                                                     best regards Stew.


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## Brian Rupnow (Dec 18, 2013)

Art--the action of the Atkinson differential engine was different than the action of this engine I am proposing. You have to see an animation of the Atkinson differential to see what I mean.---Brian


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## Cogsy (Dec 18, 2013)

I see where this is heading... Can't wait to see the build pics Brian!


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## Brian Rupnow (Dec 18, 2013)

Okay--I wasn't 100% sure that this would work with a conventional crankshaft, but it will. My 3D models are not correct in all cosmetic aspects, but the parts which count, i.e. widths and center distances, etcetera are spot on. I can animate this in Solidworks and everything goes round and round without crashing, just as it should. The big ugly looking part, grey in color, has an offset in it which means that the blue "connecting links" are far enough apart not to hit each other and to allow a bit of space between them for a center crankshaft bearing if I decide that I need it.


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## Till (Dec 18, 2013)

Brian, there was an engine of that kind in Germany 80 years ago called "Balance-Motor" by OTTO GRAF. 
The balancer ("ugly grey part") was seated with an excenter to automatically change the stroke during operation, which was controlled by the vaccum in the induction manifold.
 Thus the engine had the same effective compression ratio over a wide range of throttle angle and rpm, resulting in good fuel economy over a wide range of rpm even with smaller loads. 
If you're interested in this topic, you might do some research on the "Balance-Motor" by OTTO GRAF. Search for EUDELIN, too.

Edit: You want to have a look at Patent DE 476625 C


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## crueby (Dec 18, 2013)

Think I see how it would work but not sure - assume there is an inlet/exhaust of some kind for steam/air/fuel in the center between the pistons? Looks like it should be interesting to watch it run.


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## Brian Rupnow (Dec 18, 2013)

Interestingly enough, everything seems to go together amazingly well. That being said, as you can see I haven't modelled in the valves, cams, nor timing gears yet, nor the flywheels. I think I may make the intake valve an "atmospheric" type, same as I have used on many hit and miss engines, so it won't need a cam.--And yes, you are correct, the sparkplug and both valves fit in the center between the two cylinders. I couldn't see any good way to mount everything with one long double ended cylinder, so that has morphed into two cylinders and a center plate which will have the sparkplug and valves mounted in it, and also give me a way to support the cylinders. I may go with only one flywheel, out on the back side of the main vertical support plate. I will probably spend another $100 and buy a complete ignition package with batteries, etc. from Roy Sholl to provide my spark. Of course, if I do go ahead with this engine, I will provide the blueprints to anyone who is interested. I will probably post drawings as I go along, but its much safer to wait until I have a running engine and have made any required updates or changes to the drawings. Then I will post a download link to all of the drawings as pdf files so you won't need any specialized software to open them.


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## Brian Rupnow (Dec 18, 2013)

Here we have a couple of cross sections through the center of the cylinders. One shows the pistons almost at "Top Dead Center"--they will actually be flush with the inner ends of the cylinders when they are at top dead center. The other shows the pistons at "Bottom Dead Center".--And yes, there is a slot in the outer ends of the cylinders to provide clearance for the linkages. The slot is less than 3/4" wide, so the piston will be fully supported even in this extreme position. The piston rings (which I have not modelled yet, nor grooved the cylinders for) will not go back far enough to catch the rings on this slot. Each piston will have one Viton o-ring.


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## Brian Rupnow (Dec 18, 2013)

Well there!! That's enough silliness for one day. I managed to squeeze in a set of timing gears, a camshaft, and 95% of the exhaust valve train. I have hidden the one standoff that would normally obscure the timing gears, just so you can see better how things are mounted.---Brian


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## johnmcc69 (Dec 18, 2013)

Very similar to the Atkinson "Differential" engine.

 Nice design.

John


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## Brian Rupnow (Dec 18, 2013)

Just did a final volume check, and without taking any valve lead, lag, etc. into consideration, the compression ratio will be 5.4:1


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## petertha (Dec 18, 2013)

Brian Rupnow said:


> the compression ratio will be 5.4:1



Silly question, but in a configuration like that with 2 cylinders sharing 1 common TDC combustion volume, does the standard compression ratio calculation still apply?


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## Mike N (Dec 19, 2013)

The Kansas City Hay Press Engine has 2 pistons that meet in the middle of the cylinder.
[ame]http://www.youtube.com/watch?v=LGlIXKG5ttY[/ame]


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## deverett (Dec 19, 2013)

Brian

I'm amazed at your ingenuity, not only on this engine but all your previous designs.

Dave
The Emerald Isle


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## Brian Rupnow (Dec 19, 2013)

petertha said:


> Silly question, but in a configuration like that with 2 cylinders sharing 1 common TDC combustion volume, does the standard compression ratio calculation still apply?


 Petertha--I am assuming that it does.


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## Brian Rupnow (Dec 19, 2013)

Aha!!!--Seems that we do have room for two valves and a sparkplug in there!! It just took a bit of wiggling. The exhaust valve is cam operated, the intake valve is atmospheric.


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## Brian Rupnow (Dec 19, 2013)

This is a section taken through the center of the cylinders, and coincidentally through the center of the exhaust valve and valve cage. I have added the groove in the pistons for the Viton o-ring. The pistons never get any closer together than what is shown in this section view, and when they are fully at the other end of the stroke, the rings never get close to the slot in the rear of the cylinders. You can see where the exhaust exits through the right hand side of the green 3/4" block which holds the cylinders. I have not shown the exhaust pipe yet. The intake valve would be pretty well identical in a section view, except for the fact that it is an "atmospheric" valve, needing no cam to energize it, and the port which leads to the carburetor faces out the opposite side of the green 3/4" block from the exhaust port.


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## Brian Rupnow (Dec 19, 2013)

As luck would have it----I was just getting warmed up with this new engine design because I don't have any "real" engineering work at the moment. This morning I got a panic stricken call from an inventor I do business with, who is "Just going to die!!!" if he doesn't get a new thing patented before the end of the year. (I don't know why.) At any rate, he needs a bunch of drawings to submit with his patent request----And he needs then RIGHT NOW!!!  Ah well, I never could turn down money!!--Engine development may slow down a little bit for a while.


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## Brian Rupnow (Dec 19, 2013)

Wowsers!!!


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## Brian Rupnow (Dec 19, 2013)

I don't see a great deal of sense in spending a lot of time machining a fancy flywheel for an engine like this. All of the "monkey motion" and neat stuff to see working will be on the "front" side of the engine. What I have shown here is simply a 4" diameter disc of mild steel or possibly cast iron, with a boss on each side. The boss on the side towards the main vertical plate is 7/16" long x 1" diameter, long enough to stand the main body of the flywheel out clear of the 3/8" bolt heads which are holding the stand-offs in place. The boss on the exposed side is 1" diameter x 1/8" long, and serves no purpose other than a cosmetic one.


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## Charles Lamont (Dec 19, 2013)

I suggest this engine configuration is most advantageous as a 2-stroke, such as the Deltic & T3 already mentioned, where ports at opposite ends provide excellent scavenging, especially with a blower. 

The arrangement is is also useful for research, as an eccentric mounting of the rocker shaft allows simple adjustment of the compression ratio.

As a 4-stroke I don't see anything much to recommend it, other than it is slightly oddball. But hey, you're doing it, not me.

BTW if you are not familliar with them, Deltics in particular have a wonderfully distinctive sound:
   [ame]http://www.youtube.com/watch?v=ggm1YVith44[/ame]
the Commer is distinctive too:
   [ame]http://www.youtube.com/watch?v=e0sLp7wvq60[/ame]


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## gus (Dec 19, 2013)

Looks simpler and less parts to build than the Nemett-Lynx IC Engine. I am keen but will have to wait after I finish up the H&M.


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## Davewild (Dec 20, 2013)

Hope you get to build this Brian, looks very interesting, I am following along.

Dave


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## Brian Rupnow (Dec 20, 2013)

Due to the physical shape of this engine, I won't be able to screw the exhaust pipe nor the carburetor into the center block, because they will hit on the cylinders and not be able to turn. Consequently, they will both have to be attached with bolt on flanges and some of gasket. I like to run a bit of two cycle oil with my Coleman fuel to lubricate the cylinder and piston, so the exhaust is always messy--so---I ran the exhaust pipe out towards the back side of the engine. If I need to, I can add an auxiliary bracket from the exhaust pipe to the main vertical backing plate. The "intake manifold" for the carburetor will be an unusual shape, but it serves to move the carburetor away from both the cylinder and the sparkplug.


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## Brian Rupnow (Dec 20, 2013)

Today I made a little time to add the snap ring grooves to the end of the cam shaft and "stand-off" pivot shafts, and downloaded some snap ring models from McMaster Carr's website. This pretty well completes the design of this engine, except for the ignition. I really wish I could just embed a magnet in the flywheel to trigger the hall effect switch for my ignition spark, but my understanding is that the magnet must be embedded in some material that is non magnetic, to work properly. I don't want to add anything more to the front side of the engine. I could use brass for the flywheel, but that would cost about a zillion dollars. Aluminum is too light to make a flywheel from. What do you think of this idea---Make the 5/8" thick flywheel from steel or cast iron, but drill a 1/2" hole 1.5" deep and Loctite in a 1/2" diameter x 1.5" long plug of round brass into the hole (close to the same relative density/weight) and Loctite the magnet in a pocket drilled in the outer end of the brass plug. I don't know if that would work or not.


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## Davewild (Dec 20, 2013)

Hi Brian

 Have have read somewhere that your idea of embedding the magnet into a none magnetic plug is totally acceptable, sorry cannot remember where I read it but I suspect it was on Jan Ridders website, I am building Jan's opposed piston two stroke and will by embedding the magnet in a plug into the steel flywheel. I would love to build this engine!!!

Dave


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## Brian Rupnow (Dec 20, 2013)

Hi Dave---I have looked at Jan Ridders opposed piston engine, and its very impressive. Of course, being a design maniac, I wanted to design my own version. The "Rupnow Engine" was the first engine that I have fully designed, and it works quite well, but I learned a few things, and will apply them to this new engine. I do hope I can get confirmation that my "brass insert with magnet" will work, because it would keep the design very clean and simple.---Brian


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## Brian Rupnow (Dec 20, 2013)

Okay--Here's what I did for my ignition, and why I did it. Having the magnet embedded in the flywheel sounds like a great idea. Trouble is, the flywheel will be keyed to the crankshaft, so there is no real handy way to adjust the ignition timing. To keep things simple, the green disc on the front of the engine is aluminum with the magnet Loctited into a pocket in the face of the disc. The disc is located rotationally on the crankshaft with a single flat ended socket head set screw. The hall effect sensor , mounted in the D-tube (the red thing) is supported by one bracket mounted to the face of the front bearing support. I have chosen to not make the bracket adjustable so consequently I can't change the engine timing while the engine is running. If I want to adjust the timing, I stop the engine, loosen the set screw, and turn the disc one way or the other, then retighten the set screw. This has no effect on the valve timing, because the relationship between the crankshaft gear and the timing gear is not affected by doing this. On the previous engine I built last summer, I had the bracket adjustable, but I found that once you get the engine running the first time, you never adjust the timing anyways.


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## Swifty (Dec 20, 2013)

A really great design Brian, can't wait until you start building this one.

Paul.


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## vederstein (Dec 21, 2013)

Here's a Youtube link on a similar design of engine:

[ame]http://youtu.be/pGaISFg_ZIw[/ame]


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## Brian Rupnow (Dec 21, 2013)

vederstein---That engine is the one which was the basis for my design. You will see that the one in the video is a diesel with a roots style blower. Mine will be a 4 cycle with spark ignition.


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## Brian Rupnow (Dec 21, 2013)

As always, I find that the hardest part for me to build is the crankshaft.--So---That is where I tend to go first. If I can build the hardest part, then everything else is (or should be) downhill from there. The crankshaft is 3/8" diameter. The outer "webs" are 3/16" thick, and the center web is .469". The space between the webs is 9/32", and the actual "throw" of the crankshaft, from the centerline out to either of the con rod journals is 0.5". The con-rod journals are also 3/8" diameter. The webs are all 1/2" wide. All I have to do now is decide whether to machine this all from one piece of hot-rolled steel, or to do a built up and silver soldered crankshaft. Both have their own unique difficulties, and each represent a lot of work if I screw it up----


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## Brian Rupnow (Dec 22, 2013)

This is the crankshaft, and if I was feeling really bold, I would machine it completely from one piece of steel. I lay in bed last night, and decided to take the cowards way out and build it up from pieces, in a rather unorthodox fashion. I have the material on hand, and if it works, it will be one of the easier crankshafts I have made.---If it works!!!


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## Brian Rupnow (Dec 22, 2013)

Center section of crankshaft


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## Brian Rupnow (Dec 22, 2013)

Then if I was to make the two outside ends of the crankshaft, press fitted together as shown-----


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## Brian Rupnow (Dec 22, 2013)

Then, in a perfect world, if I could make a good fixture to align the two ends of the crankshaft, I should be able to silver solder the last two joints to end up with a perfectly aligned crankshaft. A point to note, is that the last two joints to be assembled would not be a press fit.--I do want the silver solder to "wick" into the joint. When mig weld solidifies, it has a tendency to pull the welded components out of alignment. Silver solder doesn't do that, because the entire joint has to be heated to a uniform temperature for the silver solder to melt and flow around, so there are no thermal stresses trying to pull the metal to one side or the other. I have never tried to build a crankshaft like this before, but it certainly has an appeal to me. I will build one and take a few pictures to let you know how it goes.---Almost makes me wish I had an old lathe so I could grip one end in the 3 jaw chuck and the other end in the tailstock chuck before doing the final silver soldering!!!


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## Niels Abildgaard (Dec 22, 2013)

Hello Brian

There is a lot of forces on the rocking arms and I suggest that You unite the cantilevered rocking shaft free ends with a tie rod of some kind.


Kind regards


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## Brian Rupnow (Dec 22, 2013)

So---We've made a start. That is a piece of 1018 hotrolled steel, 1/2" square. The two very outside holes are drilled and reamed to 0.375". All of the other holes are reamed to 0.3735" diameter. All done in one set-up.


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## Brian Rupnow (Dec 22, 2013)

Now we have a step #2. After recoating the side of the drilled part with layout dye, I take a piece of 1/2" dia. cold rolled steel, and turn one end for a "good fit" into the .3725" reamed holes, set it in place, then scribe around the outside of it with my scriber. This gives me my "reference" lines for trimming to length and radiusing the ends of the 3 crank webs. Why didn't I make the end webs out of thinner material?---Because I figure the thicker material is less apt to move when I weld it, and it can be turned to finished size in the lathe after welding, by turning from the non welded side.


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## Brian Rupnow (Dec 22, 2013)

So----Nothing is welded yet, but it sure do look good!!! The hurting time will come tomorrow after the welding, so I can see how much it pretzels. Actually, the initial mig welding shouldn't move anything. Then I will have to build an alignment fixture before I do the final silver soldered joints.


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## canadianhorsepower (Dec 22, 2013)

Hi Brian............I did my last chemo treatment last week and I should start feeling better soon
 I think that only plug welding would be good enought for this and causing you less work also 
 drill your counter weight and crank pin "smalle for the crank pin and then fill the hole with the tig
 one side would be good enought


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## Brian Rupnow (Dec 22, 2013)

Hi Luc--Good to hear from you. Hope you feel better soon!! ! All of the joints only get mig welded on one side. (I don't have tig). The last two "welds" made with silver solder will be done with the 3 "part cranks" in a jig t0 keep everything straight.


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## Brian Rupnow (Dec 22, 2013)

Tomorrow morning I will build a crankshaft jig, to align the 3 sections of mig welded crankshaft for final silver soldering to join the 3 mig welded sections together. The pale green blocks will be drilled and reamed to 0.375", and bolted to a piece of cold rolled steel flatbar 3/4" x 1.5". I will use an 8" length of 3/8" cold rolled round rod to align the two green blocks before bolting them down to the steel flatbar, then after the bolts are tightened  will slide the alignment bar out and fit the 3 pieces of crankshaft in place. I have drilled and tapped the green blocks for a single #10-24 set screws to hold things in place. Then I can turn the jig on end and set it in my vice for the final silver soldering of the remaining two joints. I will let it cool in the jig, then unbolt the green blocks from the steel flatbar and slide them off over the ends of the crankshaft. If I have lived a good clean life, I should end up with a perfectly straight and very strong crankshaft.


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## Brian Rupnow (Dec 23, 2013)

Alright--That part went well. I love my mig welder!!! Now I'm working on my jig.


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## Philjoe5 (Dec 23, 2013)

Geez Brian.  Last time I looked in on this thread a week ago you were "toying" with this idea.  Now you're already into it.  Looks interesting to me and should be quite a neat engine when completed.

Cheers,
Phil


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## Brian Rupnow (Dec 23, 2013)

This is the jig with a 3/8" diameter cold rolled rod in it for "set-up".


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## Brian Rupnow (Dec 23, 2013)

And now its all over but the shouting!! The silver soldering is finished. The journals were painted with "Wite-Out" correction fluid to keep any unwanted silver solder away. The spacers are in there to guarantee that I end up with the desired 0.28" between the webs. I'm going upstairs now for a drink of rum and egg nog while I wait for everything to cool off. Cross your fingers for me!!!


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## Brian Rupnow (Dec 23, 2013)

TA-DA!!!!---We have a crankshaft!! Is it straight?--Well, that depends a great deal on where you measure it. When I first took it out of the jig and put one end in the 3 jaw chuck on my lathe, the far end was out by about .030" total indicated runout, as per my dial indicator. That's .015" "out of center". I gave it a couple of light taps with my dead blow hammer, and it moved around amazingly easily, to almost no runout.  This thing seems to be amazingly flexible. The good news is that no silver solder migrated onto my con rod journals. Will I be able to use it?--Yes, I expect I will. I doubt very much that I could have had greater success if I had tried to machine the crank from solid.--In fact, given how flexible it seems to be, it would have been a nightmare to machine from solid. I think this will be one of those "Suck it and see" situations where I won't know how successful I was until I have built the rest of the engine.


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## Brian Rupnow (Dec 23, 2013)

If you liked the crankshaft, you'll LOVE  this!!!!


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## Brian Rupnow (Dec 23, 2013)

I wonder what it would cost to have the profile water jet cut. There is nothing critical about the profile. I could save it out as a .dxf file.


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## jwcnc1911 (Dec 24, 2013)

Brian, what material do you want this made out of?  I can CNC you a couple rods if you would like.

I was wondering what you were going to do next.  I enjoy seeing your engines come together, and ultimately run.

Let me know if your interested.


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## Brian Rupnow (Dec 24, 2013)

jwcnc1911 --The material would be 6061 aluminum. Where abouts in the world are you? Do you work from a dxf file or do you take the code directly from a solid model of the part.--Brian


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## jwcnc1911 (Dec 24, 2013)

I'm in N. Alabama.  Your SW solid file will be good.  I'll generate toolpaths directly from the solid file.


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## Brian Rupnow (Dec 25, 2013)

Okay JW--I'll take you up on that. Will send you files today or maybe tomorrow. Thank you. Send me your "real" email address.---Brian


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## Brian Rupnow (Dec 25, 2013)

A gentleman from Alabama "jwcnc1911" has just stepped foreword and kindly offered to make the two rather complicated links which you see coming out of the ends of the cylinders on his CNC equipment. What a wonderful thing for him to do. A Christmas present I wasn't expecting. I have cleaned up and added some detail to the actual connecting rods that go from the links he is making to the crankshaft.


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## Brian Rupnow (Dec 27, 2013)

One of the issues that you get into with an engine like this is 'Where the heck do I run the gasline"??--I have floated an idea here that looks like it will work, not foul any of the moving linkages, and not hide any of the moving linkages. I'm not sure about that vertical gas tank though.---I may have to rethink that!!!


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## Brian Rupnow (Dec 27, 2013)

Tomorrow I will go to my metal supplier and buy some material. I'm going to build all of the big stuff first, so I will have something to bolt the little stuff to as I build it.


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## Brian Rupnow (Dec 27, 2013)

And the other two "big" parts--


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## Brian Rupnow (Dec 28, 2013)

This is what $50 buys this morning!! A piece of 5/8" aluminum 5" x 5/8" x 16", a piece of cast iron 4" diameter x 1 3/8" long, and a piece of 1/2" square cold rolled x 19" long. The plate will give enough material to build the complete plate frame (I will have to mill part of it down to 1/2" thick for the front bearing support plate.)--Also, the cast iron will build my flywheel. The plate was $30 The cast iron was $20 (would have been $15 if I had chosen hotrolled 4" dia. steel instead.) The 1/2" square cold rolled was thrown in as a free-bee. I got it because, if that welded crankshaft I made is hinky, I will make up a second one with 1/2" square webs instead of 3/16" thick, and Loctite/dowel it together instead of welding it.


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## johnmcc69 (Dec 28, 2013)

Nice start! Why didn't you choose the cheaper hot rolled?

John


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## Brian Rupnow (Dec 28, 2013)

John--I don't have a good answer for that. I asked for a price on hotrolled steel, stress-proof steel, and cast iron. They didn't have any stress proof, (which I've been wanting to try, because everyone says it machines so nicely.) I picked the cast iron, and I don't have a good reason why!!!---Brian


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## Brian Rupnow (Dec 28, 2013)

Well---It's a start. It seems like I spend a lot of time getting parts READY to start machining them!!!


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## jwcnc1911 (Dec 28, 2013)

Brian, had a little time to look at the solid tonight.  Generated toolpaths and designed a fixture for the flipside.

Hopefully I can get out in the shop soon.

Another great design, and most of all, thanks for sharing with the community!  I look forward to seeing it run.


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## Brian Rupnow (Dec 29, 2013)

Well JW, you and I were working together today---just a thousand miles apart!!! I finished the flywheel today and 95% of the frame plates, but had to stop about 4:00 because my legs were killing me from standing at the machines all day. Damn, I hate getting old. Tomorrow I will assemble all of my finished parts and post a picture.---Brian


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## Philjoe5 (Dec 29, 2013)

This what I love about bar stock engines.  It all starts when you go to the metal store, buy a few chunks of metal.  Then the story unfolds or unravels as the case may be.

Good luck on this one Brian

Cheers,
Phil


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## Brian Rupnow (Dec 30, 2013)

Its early in the morning here, and my good wife is still sleeping, so its time to spend some quiet time on the computer. I can use this time to catch up on a whole bunch of detailing. I will post these now so you can see the direction I am moving in, but don't bother to copy them, as I will post an updated download file to all of the drawings at the end of this job. Many of these drawings undergo minor revisions when I actually come to build the part, for one reason or another. I will correct any drawing that changes, so that the final download file will have all corrected drawings in it.


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## Brian Rupnow (Dec 30, 2013)

And a few more details--


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## Brian Rupnow (Dec 30, 2013)

As promised yesterday, here is the first assembly, consisting of the crankshaft, flywheel, and all but one of the frame components (the plate the cylinders attach to). I set my glasses in the foreground to give a sense of scale on this engine. Its not very big!!! So far, so good. The parts all fit together. (I don't have the crankshaft bushings in place because I haven't made them yet!!!)-----Brian


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## Brian Rupnow (Dec 30, 2013)

Okay jwcnc--I have a place to mount the two bits you are making for me!!! I haven't put the snap ring grooves in yet.---Its safer to wait and get everything mounted BEFORE cutting the snap ring grooves. I have also mounted the camshaft. That's enough for me for today.---Brian


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## Brian Rupnow (Dec 30, 2013)

There will definitely be some head scratching involved with making this part!!!


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## gus (Dec 30, 2013)

Brian Rupnow said:


> Well JW, you and I were working together today---just a thousand miles apart!!! I finished the flywheel today and 95% of the frame plates, but had to stop about 4:00 because my legs were killing me from standing at the machines all day. Damn, I hate getting old. Tomorrow I will assemble all of my finished parts and post a picture.---Brian



Getting old is a part of life ,we cannot avoid. After two engines,Gus was burnt-out after building the Webster and the Rupnow Engines.This explains for "The do nothing for last four weeks". 

Spring cleaning in ten mins from now and back to "work" on the second. New Year Day tomorrow will be hooking up the big slimy fish with friends.

Happy New Year.


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## Brian Rupnow (Dec 31, 2013)

Today I had to go down to my "nut and bolt" store to pick up the 3/8" socket head capscrews that hold the cantilevered pivot shafts and camshaft into the main vertical support plate. While I was there I asked the sales guy if they carried any of the "low head" style of capscrews. He did, and the head on them is roughly 0.180" shorter than the head height on a standard 3/8" shcs. He didn't have any 5/16" shcs in that style, but he did have some 5/16" flat head capscrews.  So---I bought them and installed them this afternoon. This allows me to move the flywheel in 0.185" closer to the main support plate. I will have to cut that much off the long hub on the flywheel, but that will still leave me room for a couple of set screws. I like this much better, allowing me to keep the flywheel tucked in tighter to the main vertical support plate.


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## Swifty (Dec 31, 2013)

I'm enjoying following this latest build, will be very interesting to see it working.

Paul.


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## Brian Rupnow (Dec 31, 2013)

Swifty--I'm venturing where "Angels fear to tread" here. I will be pretty excited if/when it runs.--Brian


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## Philjoe5 (Dec 31, 2013)

Brian,
This engine design is really neat.  I have been studying the part you're going to have CNC'd trying to figure out how I'd make it on manual machines.

I'm enjoying this thread also

Cheers,
Phil


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## dave-in-england (Dec 31, 2013)

Brian,

Why don't you use Stainless Steel Countersunk set-screws ?

No need to mess about setting up tooling for making the counter-bores for the cap-heads,

when a countersunk tool will do, and the screw heads will fit perfectly flush with the alloy plate.


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## Brian Rupnow (Jan 1, 2014)

Dave--I don't understand your post. Flathead capscrews (which you are calling countersunk cap screws) are available in in plain steel, and the tooling for them is readily available. Why would I want to use stainless steel? I did use that style of flathead capscrew on the center hole where my camshaft sets, but used the lo-head capscrews on the larger 3/8" bolts which hold my pivot shafts. I had to maintain SOME space between the back of the flywheel and the vertical main body plate so I would have room for a hub and set screws on it.


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## dave-in-england (Jan 1, 2014)

Sorry about the confusion Brian,
You mentioned the need for more space behind the flywheel, where the cap heads are sticking out.

These countersunk screws would fit right flat with the body.

I prefer the bright and shiny stainless screws, they don't cost much more than the dull steel variety.  ;D


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## Brian Rupnow (Jan 1, 2014)

Lord, Lord Molly--It must be an engine!!!-There's a sparkplug in it!!! I have spent all day working on that center part with the sparkplug in it.--Man, there is a lot of work in that little devil. Great way to spend New Years day!!


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## Philjoe5 (Jan 1, 2014)

Seems to be coming together nicely.  Do you have the ignition part figured out yet?

Cheers,
Phil


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## Brian Rupnow (Jan 1, 2014)

For the ignition I'm just going to use exactly the same CDI set up from Roy Sholl that I used on the "Rupnow engine". It works fine. it's costly, at about $100 a pop, but it seems to be maintenance free, and I still do enough "real" engineering work that the cost doesn't alarm me too much.


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## Brian Rupnow (Jan 1, 2014)

I decided that I wanted to use one of the small router guide bearings on the end of my valve pushrod similar to the way I did on the "Rupnow Engine". This meant a couple of simple changes, one being that the pushrod had to increase in diameter from 1/4" to 9/32", so that with the 1/4" diameter bearing mounted on the end of it, it could still be inserted from the top of the engine. The other change involved milling a .094" wide x 0.2" long slot in it and putting a 3/32" pin through the plate it rides in to keep it from rotating. I also drilled and tapped the rocker arm for a #5-40 bolt with a rounded contact end so that I could adjust the valve lash.


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## Brian Rupnow (Jan 1, 2014)

I have found a much better place for the gas tank. It will be made from my remaining piece of 1" o.d. brass tubing, salvaged from an old halogen floor lamp. It will be 4" long and clear the top of the flywheel by 1/16", and will bolt to the back side of the main vertical plate.  I can arrange my intake manifold so the top of the tank sets just below the fuel delivery hole in the venturi of the carburetor, which must be done to prevent gravity flooding. I haven't modelled in a filler cap or neck yet.


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## johnmcc69 (Jan 1, 2014)

Looks great Brian. I know you wanted a solid flywheel, but I think a pattern of 4 "Tear drop" cutouts would look great.

 John


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## Engineville (Jan 1, 2014)

Are there to be bearings for the crankshaft in the two support plates?  Im missing something; OD of shafts is 0.3745" and ID in support plates is 0.438".  I look at your assembly photos and I cannot tell if there are bearing-bushings or not.


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## Philjoe5 (Jan 1, 2014)

I like the cam follower/valve lifter assembly Brian.  It has an easy way to adjust valve lash without disassembling the mechanism.  I've filed that design away.

Cheers,
Phil


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## Brian Rupnow (Jan 2, 2014)

Engineville said:


> Are there to be bearings for the crankshaft in the two support plates? I&#8217;m missing something; OD of shafts is 0.3745" and ID in support plates is 0.438". I look at your assembly photos and I cannot tell if there are bearing-bushings or not.


Go back and carefully read the text in post #70.


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## Brian Rupnow (Jan 2, 2014)

Nothing is new under the sun!! Chuck Fellows found this engine on Youtube, which is very close to mine. Neat stuff!!!---Thanks, Chuck.
 [ame]http://www.youtube.com/watch?v=v38PuSrMPk4[/ame]


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## Brian Rupnow (Jan 2, 2014)

I have to go out to my metal supplier today and pick up my grey cast iron material for the cylinders. I figured that since the pistons are the same material, I might as well buy the material for them also. This of course required a detail of the piston and cylinder to get my lengths from.


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## Brian Rupnow (Jan 2, 2014)

$15 buys 12" of 1 1/2" diameter grey cast iron. Enough for both cylinders and pistons. It actually comes in at 1 5/8" so should clean up nice at the required 1.5" dimension that I need.


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## Brian Rupnow (Jan 2, 2014)

Wow!!! I'm liking this more and more as I go along. I did however, learn a valuable lesson today. I had finished the first cylinder, had it drilled, reamed, all the fins cut on it----and then proceeded to part it off from the parent stock which was still firmly gripped in the lathe chuck. As I got close to having it fully parted off, I thought "Gee--I wonder if I should stick something in the open end to catch the cylinder when it finally parts off?"--I decided not to, as I have a big fear of getting caught up in a rotating part.--So----I parted it off and let it fall into the chip tray.----Only DAMN!!! It didn't fall into the chip tray!! It sucked back under the chuck and CRACK----2 of the center fins were broken off cleanly on one side.--However, being the weasel that I am, I decided that I can mount the cylinder with the missing fin parts facing down and back, and they won't be noticeable when the cylinder is mounted. When I got to the second cylinder, I parted it off PART WAY and then walked it over to the band saw to finish cutting it completely away from the parent stock.


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## Brian Rupnow (Jan 3, 2014)

In this picture you can see what I have done for a "head gasket"--although I guess to get technical, since there isn't really a cylinder head on this engine, its the seal between the cylinder and the center block which the cylinders bolt to.--At any rate, it seals in the compression. The Viton O-rings are available in a 1/16" diameter cross section (which actually measures about 0.070") and an inside diameter of 1". The annular groove which I cut into the mating face of the cylinder is about .075" wide x .045" deep. In theory, this gives me about .025" of compression on the o-ring when the cylinder is bolted up tight against the center block. In the picture, one o-ring is fully seated in the groove, while the other o-ring is propped up so you can see the actual groove which it sets in. I have modified the cylinder drawing to reflect these new dimensions, and when I get this engine running all of the corrected drawings will be in the download link I provide.--And yes, the bolts do go through, but its a tight fit.


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## lathe nut (Jan 4, 2014)

Brian, WOW another great and different project, that one is sure above my head for now but will copy and paste someday will be able to do such, my wife has given me the storage room that is connected to the car port it has a finished inside and is 6X24 feet enough room to put some machine and me, then I can start playing, thanks for the sharing as always, Lathe Nut


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## BronxFigs (Jan 4, 2014)

Brian...

I must say that you have made very great progress with your design and have turned a lot of two-dimensional drawings into the real thing.  

It really is a wonderful to be able to watch a concept become a reality, but even better is your sharing with all us forum members.  Building an engine is difficult enough without thinking of all the endless details, lighting, set-ups, editing, etc. when the build is to be photographed.  However, tutorials like yours are a God-send.  I have been reading and posting on this forum for less than one year, and I can't tell you how much I have learned from all the experienced builders that post on this forum.

My hat is off to builders like you who give and share your designs without reservation.


Frank


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## Brian Rupnow (Jan 4, 2014)

Thank you Frank---Now I'm going to feel warm and fuzzy all day------


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## Brian Rupnow (Jan 4, 2014)

I have decided to devote my weekend to making "easy things". One or two of the drawings I am about to post may have been posted in an earlier version, but they have changed. I am not going back to change previous posts. All drawings will be updated and corrected in the download link at the end of the job.


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## Brian Rupnow (Jan 4, 2014)

And a few more "easy" parts---


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## Brian Rupnow (Jan 4, 2014)

And one last part to finish out the morning----


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## Brian Rupnow (Jan 4, 2014)

Hmmm--Not a particularly good start to the morning!! My new Powerfist brake cylinder hone which is supposed capable of fitting 3/4" to 1 1/8" brake cylinder bores---There is no way in Hell that it is going to fit into a 3/4" bore.  RATS!!! I guess these cylinders will move directly from "reamed" to "lapped"


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## Brian Rupnow (Jan 4, 2014)

Well--I didn't get quite as many parts made as I thought I would this morning (I seldom do)---But---Progress was made. Cylinders got lapped, rocker arm support and rocker arm and push rod got made and test mounted.---But DANG-- I didn't know it was this dirty before I took the picture!!!--NOTE TO SELF---Blow off with air hose BEFORE taking pictures!!


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## robcas631 (Jan 4, 2014)

Highly Impressive!


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## Brian Rupnow (Jan 5, 2014)

Today I made the exhaust pipe and bracket, the two connecting links that attach the pistons to the arms that my friend in Alabama is making, and the intake manifold. I haven't made the pistons yet because I am waiting for a piece of tooling that I had to order to finish them. There are MANY strange angles on that intake manifold, and the batteries are dead on my digital angle finder, so I did it the "Old School" way by scribing layout lines and "milling to the line" as I went along.


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## Brian Rupnow (Jan 6, 2014)

Todays offering to the machine Gods is a tiny pair of connecting rods. These are the rods that connect the crankshaft to the two pieces that JNCW in Alabama is making for me. They don't look like much, but I have spent nearly all day making them.---I tried to get a picture of them "in place" on the engine, but its just getting too crowded in there to show very much.---
 -Brian


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## Brian Rupnow (Jan 7, 2014)

When I get to the point of ordering my cdi ignition from SNS engineering, I will now have a place to mount the magnet and the D-tube which holds the Hall Effect sensor. Why is there layout dye on the intake manifold?--Because when I got it bolted into place, I seen that I had missed machining one of the weird angles when I had it in the mill. The dye just helps me to know which face the weird angle goes on when I put it back up in the mill. I have been waiting for a long 1/4" ball nosed endmill to come in so that I can go ahead and finish the pistons. It came in this morning, so I guess the pistons are the next thing I am going to work on.


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## BronxFigs (Jan 7, 2014)

Brian-

I'll ask because I don't know....could you have fired this engine by using a glow-plug, if you wanted to?  If yes, why did you choose a sparker, over the glow-plug?  

Just curious.  If I don't ask, I can't learn.  Also, at what point in the designing phase, did you decide on using the Hall ignition system?

The build becomes more interesting as it progresses to the obvious conclusion.....a video of the engine running.



Frank


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## Brian Rupnow (Jan 7, 2014)

I can't give a good answer about glow plugs, because I have never used one. I THINK they depend on the engine having a high compression ratio like a diesel, but that is only guesswork. Why did I go with a cdi ignition?--Well, I added up the price of a set of ignition points, a condenser, a 12 volt coil--and that came to about $75.00--and that doesn't take into consideration the $100 or more you would spend on a 12 volt car battery to run things. The complete cdi set up cost about $100, including 4 small rechargeable batteries about the size of small flashlight batteries and a recharger. That was my reasoning.


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## Brian Rupnow (Jan 7, 2014)

This is piston #1 in the chuck. A whole lot of hogging off material to get from the 1.6" diameter piece of grey cast iron down to .875" diameter. I did this with an indexable carbide, and cut the piston to about 3/8" longer than what the finished length was going to be. Once I got it down to .875" diameter, I switched tools to a newly sharpened HSS cutter, and took it down to the finished diameter of 0.750" using a lathe speed of 970 rpm.--Of course the last 5 or 10 cuts were done with much breath holding at .001" to .002" depth of cut.--I have ruined so many parts by turning them undersize that this is always a very scary thing for me. At this time I also put the counterbore in the end of the piston using a drill, then a 1/2" diameter 4 flute endmill, then a carbide boring tool. After reaching the diameter I wanted, I used a 0.093" cut off blade and plunge cut to a depth of .056" for the o-ring groove. This is what the o-ring book recommends, but if its not deep enough I can turn it a bit deeper later. I won't know for sure until I assemble the piston in the cylinder and see how "tight" it is with the groove at this depth. Next step was to move the cut off blade up to the finished length I want the piston to be plus about 0.030"and plunge cut about 0.060" deep. I will take the part out of the lathe now and finish the cut on my bandsaw, then put it back in the lathe and face that sawcut end off until the exact length is reached.


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## Brian Rupnow (Jan 7, 2014)

With the piston cut to length in the saw, then faced off in the lathe, the next step will be to put the slot in the bottom of the counterbore that the connecting rod fits into, and to drill the cross hole for the wrist pin. The piston will fit into the cylinder now, but if you push it through with your finger you can feel a few rough spots. The piston will be coated with 600 grit carborundum paste and worked back and forth until any roughness is gone.


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## BronxFigs (Jan 8, 2014)

Thanks, Brian for explaining your ignition choices.


Frank


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## Brian Rupnow (Jan 8, 2014)

JWCNC--What's the status of the two arms you were going to CNC for me? I'm running out of things to machine up at this end. Once I get these pistons sorted out, I only have the timing gears and valves left to tackle.---Brian


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## Brian Rupnow (Jan 8, 2014)

There are a couple of things worth talking about in this picture. The first and possibly worst, is that once I have milled the 1/4" slot in the piston for the connecting rod to fit into, there is absolutely no good way that I know of to ensure that I am drilling the wrist pin hole at exactly 90 degrees to the slot. What I resort to, is sticking the con rod into the slot (You can see the end of it sticking out of the piston) and then setting my machinist level on the bit that sticks out, then rotate the rotary table until it is right "on the bubble". This gets me "pretty damned close", but I wish I had a better way of doing it. The second point, which is pretty obvious, is that when the chuck jaws are positioned to give the drill and reamer good access from the top, the bottom jaw of the chuck is always in the way, so I can drill and ream "almost" all the way through, but have to finish it up in my machinists vice.


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## Brian Rupnow (Jan 8, 2014)

The pistons are finished. I am always somewhat amazed that parts so small could take such an immense amount of machine shop time to make. I spent a lifetime as a design engineer wondering what in the name of #[email protected]^ was taking so long for my machinist to make a few simple pieces. Now I know---My apologies go out to every machinist that I ever thought was "dogging it".  I'm starting to run out of pieces to build. I will leave the valves and cages to the very last moment. I know I can make them. I've made them a number of times before. It's just that they are such hateful damn things to make that I will make everything else that I can first. Probably work on timing gears and exhaust cam tomorrow.


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## dsage (Jan 8, 2014)

Hi Brian:

Watching your build with great interest - as usual.
With regard to your drilling the hole in the piston. Try using that nice slot in the mill table. Lay the piston along the slot, put your connecting rod inside like you have it and use shims under the rod such that when you clamp the rod down it rotates the piston so the slot is parallel to the table. Or use a very narrow clamp or piece of scrap that will go up inside the slot and wiggle the piston while you tighten it to rotate the piston.
Then clamp the piston directly to the table slot and release the rod (or clamp) on the slot.
Use an edge finder or indicator to indicate the side of the piston and from there you can move over the right distance to be over the centerline of the piston. Same way to find the position of the hole from the end of the piston.
 Using the slot will give you some space below for the drill and reamer to pass through the piston.

In the end it really makes little difference if the slot is turned slightly. It only results in the piston be being rotated slightly. Presumably you have a bit of side play in the slot so the rod can float a bit. You should.
What IS important is that the hole is right on the center line of the piston.

I've just finished making a 2.5" diameter aluminum piston for a Parcell and Weed hit-miss engine circa 1902 using this method.
I've thought about documenting the build here but that takes a lot of time. I've been taking pictures.

Thanks for your efforts in documenting your build.

Sage


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## dsage (Jan 8, 2014)

Hi Brian:

Another comment on the piston.
Why is the hole so far near the top? Do you have any clearance issues with the rod on the inside of the piston? I assume you can animate the engine to check that sort of thing. Admittedly the geometry of this particular engine is weird so I guess it works.

The hole is usually at or below center to give the rod more room to oscillate back and forth.

Nice CAD work BTW.

Sage


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## Brian Rupnow (Jan 8, 2014)

Sage--This engine has some weird geometry, plus the fact that there is a slot at the rear/bottom of each cylinder that the big rocker arm fits up into. In a perfect world, the piston only needs to be slightly longer than its own diameter (to keep it from "cocking" in the cylinder.) This piston is extra long because it needs the extra support when its at bottom dead center. The lower half of the skirt extends right out over the slot.


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## gus (Jan 8, 2014)

Brian Rupnow said:


> Sage--This engine has some weird geometry, plus the fact that there is a slot at the rear/bottom of each cylinder that the big rocker arm fits up into. In a perfect world, the piston only needs to be slightly longer than its own diameter (to keep it from "cocking" in the cylinder.) This piston is extra long because it needs the extra support when its at bottom dead center. The lower half of the skirt extends right out over the slot.




Hi Brian,

Gus trying very hard not to build this engine. Alas !!! My spirit is strong but mind n body is weak.

Trust all is well by now and winter is about over.


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## Brian Rupnow (Jan 8, 2014)

Hi Gus--Always good to hear from you. I wouldn't recommend anyone building this engine until I see if it is going to work. As for winter--Its just getting started good. Snow came and stayed in mid December, we have been having blizzards for last week. Schools closed, highways closed, police warning everyone not to travel unless its an emergency. Currently have 20" of snow, -25 C  at nights. It will stay very cold with snow thru February and March, then start to head into spring about half way thru April. The ice generally goes out of the local lakes around the 23 April.


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## Charles Lamont (Jan 8, 2014)

I don't suppose this job is intended to run very fast, but it did occur to me that the fatter push-rod now has much more inertia than the other valve-train components. You could ease the job of the valve spring quite a bit by making the push-rod hollow. Just a thought.


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## Brian Rupnow (Jan 8, 2014)

Charles--You are right. If it gives me any trouble, I will drill it out hollow and put a threaded insert in top where the valve lash adjuster bolt is.---Brian


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## Art K (Jan 8, 2014)

Brian,
So that means the ice fishermen start clearing off the ice on April 22 and the rest fall through on the 23rd.
Art


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## Brian Rupnow (Jan 8, 2014)

Art K said:


> Brian,
> So that means the ice fishermen start clearing off the ice on April 22 and the rest fall through on the 23rd.
> Art


 No---The law states that all fish huts and debris must be off the ice by the end of March (or something like that), and woe betide anybody who lets their junk fall through into the water when the ice goes out. Heavy duty environmental fines, permanent suspension of fishing license, emasculation and beheading. Its got kinda crazy here in Ontario in the last 15 years.


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## Brian Rupnow (Jan 9, 2014)

Moving along---We need gears. The last time I used this particular gearset, I didn't have an extended hub on the gear, so I had to cross dowel it to the crankshaft. This works, but its VERY permanent, and it weakens the crankshaft. This time I will take a slightly different approach.


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## Brian Rupnow (Jan 9, 2014)

I am going to try something a little different this time and go for a bolted on cam---


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## Brian Rupnow (Jan 9, 2014)

Does anybody know of a reason not to build the large timing gear out of grey cast iron? I have lots of short pieces of 1.6" diameter grey cast iron left over from making pistons and cylinders but I don't have any steel large enough in diameter (1.33").


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## Fluffy (Jan 9, 2014)

G'Day Brian,
I have made a set of back gears for my lathe from extruded grey cast iron (80, 40, 30, & 25 teeth x 1.5 module) which have been in use for some time now & have not given any problems. They create far less noise than the poorly cut original gears.
The large timing gear (56 tooth, 24 DP shown in attached image) on my Bonza hit & miss was made from the same material & it runs without problems.
I hope this is of some help.
I have been away for a while & have only just read all of the posts re your opposed piston engine. Very well done Brian, it looks great & I look forward to here it running.
Regards,
Don.


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## Brian Rupnow (Jan 9, 2014)

Thank you Fluffy. I will try the cast iron and see how it works.---Brian


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## Brian Rupnow (Jan 9, 2014)

What did I do today??--Well--Not that much really. The round piece laying down has the outer diameter of the crankshaft gear turned on the end of it, and the collar which gets silver soldered to it after the teeth are cut is setting on the end of it. The piece which is setting on end with the purple layout dye on it is going to become my "bolt on" cam. it will be going up on the rotary table tomorrow.  I think I will be bold and turn the camshaft gear from grey cast iron.


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## Brian Rupnow (Jan 10, 2014)

Today we see the simple way to make a cam. This is a cam with straight line flanks, and it works very well in any low speed i.c. engine. If you want to see an excellent video on making a cam with "rounded" flanks, search for the excellent video posted by Chuck Fellows. In yesterdays post, you seen the short piece of shaft standing on end with purple layout dye on it. If you look close you can even see the base circle of the cam scribed on the end of it. I put it in the 3 jaw chuck on my rotary table and centered it under the guill.  I decided at that point to use the dials and move things around to drill and tap the two #4-40 holes, and then recentered the part under the quill.  Then by inserting a pointer in the quill chuck, I moved the table right and then left 0.094" and scribed two lines, equally about center, 3/16" apart. I then used my scriber and a straight edge to connect the lines to the previously inscribed circle.Then I rotated the rotary table until the scribed "flank" lines were parallel to the "x" travel of the mill. Then it was simply of milling to the required depth plus a bit more on each side. Once both sides were milled, I then used the rotary table to mill away the remaining stock to final shape. Then I took the part over to the lathe and parted off the finished cam.


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## Brian Rupnow (Jan 10, 2014)

CURSE!! SWEAR!! STAMP FEET!!!--cast iron isn't going to do it for me!! It might make a good gear with a flat face on both sides. It does not work well with the 3/8" diameter protrusion on one side. After 30 minutes of machining, I was just cleaning up the o.d. of the 3/8" diameter x 1/4" long "spigot" that the cam slips over when the whole damn spigot popped off, clean as a whistle. Now I will go buy some cold rolled steel.


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## Brian Rupnow (Jan 10, 2014)

It was probably my fault. I put the .25 bore in the gear first, then was turning the tit down to 3/8" diameter as per the drawing.  I find that cast iron eats up HSS tooling very rapidly, so I was using a carbide. If you let carbide get a bit dull, it puts a lot of pressure on what you are cutting. It was more a matter of my questionable machining talent than a fault of the cast iron. I realized after my last post that this gear is turning on a stationary steel shaft, so I couldn't really make it from steel or it would gall. I dipped into the Rupnow fortune and bought 3" of 1.5" diameter brass for $15.--That will make a good gear and will turn without galling on the mild steel shaft.


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## Brian Rupnow (Jan 10, 2014)

One last pic to finish off the day. This is where I was headed this morning with my cast iron gear before it let me down. Tomorrow or Sunday if I can get some teeth on my gears and a couple of counterbored bolt holes, I'll be in business!!!


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## Brian Rupnow (Jan 11, 2014)

So---Today we have a set of timing gears, with bolt on cam. They are set up in a test block in the picture so that I can confirm to myself that they do mesh properly, and they seem to be fine. It's hard to see that the cam is bolted on, so I've included a pic of the back side of the cam gear, where the heads of the two #4-40 shcs. are visible.


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## Philjoe5 (Jan 11, 2014)

Brian,
I like the way you bolted the cam to the gear.  I'll have to try that on my next build

Cheers,
Phil


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## robcas631 (Jan 11, 2014)

That is an awesome design!


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## robcas631 (Jan 11, 2014)

Brian...So this is a new concept?


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## bmac2 (Jan 12, 2014)

Hi Brian. Im no engineer. Ive only built a few steam/air engines. And all I know about small IC engines is tuning up my lawn mower in the spring. That said. Following this thread and looking at this thing its going to sound *****in!


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## Brian Rupnow (Jan 12, 2014)

Robcas--No, its not a new concept. In fact, its been around for quite a while . Do a search for "opposed piston engines"--You'll be surprised. I just thought it would make a very interesting model.---Brian


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## Brian Rupnow (Jan 12, 2014)

This is kind of a "double duty" picture. In the foreground, laying on the book is my exhaust valve pushrod with the 1/4" diameter x 0.110 wide router bearing fitted into a slot in the end, with a 0.093" diameter axle. I made the pushrod 9/32" diameter so it could be inserted down thru the hole it rides in from the top of the engine. You can also see the .093" wide slot in the pushrod, which lets it travel up and down but not turn crosswise. There is a matching .093" diameter hole which can be seen just at the top of the center section in the background, which a .093" diameter cold rolled rod fits through to keep the pushrod from turning and getting the wheel out of alignment. In the back ground you can see the brass cam gear with the steel bolted on cam setting in place on the engine.


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## BaronJ (Jan 12, 2014)

Hi Brian,
Slightly off topic.  Are you aware that you can extract small 6mm dia or there about's, ball bearings from scrap 80mm computer fans.  The fans often seize up but its usually the sleeve bearing that fails in this way.  Also some fans have two ball bearings.  Since these fans are just thrown away they are usually free for the asking.

PS. Following your build with interest.


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## Brian Rupnow (Jan 12, 2014)

Thanks Baron---Yes, I did know that. I have a whole bin full of reclaimed bearings here. ----Brian


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## Brian Rupnow (Jan 12, 2014)

In this picture, you can see that I have Loctited the bushings into the front and rear crankshaft support plates and inserted a "guide rod" that I know is straight before tightening the bolts down that hold the plates to the base. I will let it set up like that overnight. I have also silver soldered the ring onto the small crankshaft gear and you can see it setting on the crankshaft in the foreground. The reason for the soldered ring is this---The gear in its stock form allows a hub with only about a 1/16" thick, not enough to hold set screws. I made the ring a separate piece, and drilled and tapped it for two #8 set screws. Then I silver soldered it onto the thin-walled hub of the gear, drilled and tapped a second time through the thin wall, and end up with a good solid hub to hold the set screws which position the gear rotationally on the crankshaft, without having to drill a hole for a dowel pin thru the crankshaft to hold the gear.


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## Brian Rupnow (Jan 12, 2014)

The Loctite was completely set up after about 3 hours, so I just had to drop the crankshaft into place and see if it would turn. It does!!! There are a couple of stiff spots in it as it turns, because the crank is not 100% "true".--That's not a show stopper, because none of the cranks of this style that I have built are completely true, and the engines all run fine. I will "run it in" with my electric drill to loosen up the bearings a bit, and it should (we hope) be fine.---and the timing gears mesh fine.--That is always a concern, because there is no adjustment on the hole centers for the crankshaft and timing gear shaft.


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## Brian Rupnow (Jan 13, 2014)

So---Here we are "running in" the crankshaft. I suppose that if I were a perfect machinist, I could skip this step, but you work with what you got!!! When everything is assembled, and all the bolts snugged down, the crankshaft binds like hell. That's due to a host of reasons  i.e.---stacked up tolerances, plates not being perfectly 90.0000 degrees on the bottom---a crankshaft that has a bit of "oink" in it. What this "running in" does is wear away the major binding points on the brass bushings supporting the crankshaft. I keep A LOT of oil slathered on while this is happening, and let it run for about an hour. By the time it is fully run in, a baby's breath will turn that crankshaft. I put both the timing gears on as well, figured they could run in at the same time. You will see that I have the front bearing support set up so that I can access the bolts which hold it down to the base plate. I start out with these bolts fairly loose, then every 10 minutes or so I go out into the main garage, add a bit more oil, and snug the bolts down some more. Keep repeating that until the bolts are fully tight.


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## Brian Rupnow (Jan 13, 2014)

I can hardly believe it!!! All of the mechanical parts are finished except for the valves and guides, and the carburetor. JWCNC--If you were serious when you offered to make the two arms for me, I need them now!!!  I have been messing about making gas tank parts, and hope to fab up the two ends and get everything soldered together this afternoon. I haven't been happy with the small size of filler caps and necks that I have fabricated on previous gas tanks, so with the help of a couple of commercial plumbing parts I am going to do something a bit different this time. That nice screw on lid with the knurl on it was a cast brass pipe cap before I committed a little lathe work on it.


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## Brian Rupnow (Jan 14, 2014)

I'm sure you guys have all heard reference made to "The Good, the Bad, and the Ugly"!!!--Well this is the "Ugly" stage. We have passed, or fortunately missed the "Bad" stage of things. It would only have been bad if, after all this silver soldering it had leaked somewhere. Now, with various files, sanding strips, etcetera, I hope to turn this into the "Good". --I love my new filler cap and neck. It not only gives me a bigger hole to aim for, it also lets me see so I can stop pouring before the damn thing is overfilled with fuel running everywhere!!


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## Brian Rupnow (Jan 14, 2014)

Well there!!! That's good enough for the girls I hang around with!!! Polishing is a dirty, dirty job. I look a bit like Sambo the racoon.


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## BaronJ (Jan 14, 2014)

That's a lovely bit of brasswork, very nicely fettled and polished.  It the exhaust pipe and the flywheel would look spectacular in chrome !


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## Brian Rupnow (Jan 14, 2014)

Baron J---Glad you like it. Chrome is wayyyyyy out of my price range.---Brian


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## Brian Rupnow (Jan 15, 2014)

If anyone builds this engine, then sooner or later they are going to need a gas tank. This is what the assembled tank looks like mounted on the engine.


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## Brian Rupnow (Jan 15, 2014)

We start out with the assembly of all the pieces put together, and then move on to drawings of all the pieces.


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## Brian Rupnow (Jan 15, 2014)

More gas tank pieces--


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## Brian Rupnow (Jan 15, 2014)

And last, but not least, if you have a gas tank, you will want a  screw on gas cap.


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## Brian Rupnow (Jan 15, 2014)

Before I rush out to spend $100 on a cdi ignition, I want to make sure this engine is going to run. I still have a set of points and two 12 volt coils here, and a points mounting block left over from the Rupnow Engine. For the sake of two drilled and tapped holes in my front bearing support plate, I think I will give the points a try first. I'm not quite finished with the engine yet. JWCNC has confirmed that he is indeed working on the two links for me, and I have to now make the valve guides and valves.


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## Brian Rupnow (Jan 15, 2014)

Both valve guides are finished. The steel tool in the picture is my "seating tool". I don't try and put the 45 degree angle valve seats in while the guides are in the lathe. I drill the 1/4" hole in one end, drill and ream the 1/8" thru hole, then take the guides out of the lathe and use the seating tool by hand to put in the 45 degree valve seat. The seating tool has a 1/8" diameter extended nose that fits the reamed hole in the guide, to ensure that the valve seat is concentric with the 1/8" diameter reamed hole that the valve fits into. The actual "seat" area is very small--about .015".


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## Brian Rupnow (Jan 15, 2014)

This is about the best picture I can get of the very narrow valve seat.


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## Brian Rupnow (Jan 15, 2014)

These are details of the valves and valve cages for the engine. Exhaust and intake are identical. I have to check back through the thread and see if I have posted these before, because they have changed.


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## Brian Rupnow (Jan 15, 2014)

Valve #1 is machined. It fits the guide well. That's because I must have shut the damn lathe off 300 times to "check" for size so as not to go undersize and ruin it. I machine about 3/8" of length at a time, taking it down to 0.129" diameter. I'm afraid to take it down any farther than that. After I get the full length machined, I take it down the rest of the way with #220 grit paper.--I'm surprised that I haven't worn out the on/off switch on my lathe---Yes, you can sand it undersize too--I know!!!


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## Brian Rupnow (Jan 15, 2014)

Someone on another forum has asked-"Will I press fit the valve cages into the center block, what kind of Loctite will I use, and why do the ports have to be drilled into the valve cages with the valve in place?"---This was my answer---
 --I will use #638 green Loctite. No, it won't be a press fit. My only experience with pressing valve cages into place ended in disaster--they both distorted so badly from being pressed into place that I had to remake them. As to why they have to be drilled with the valve in place---I only just discovered that today. On a conventional engine, where you can remove the head, it is no problem to remove the valve and drill thru the side of the cylinder head and the valve guide at the same time after the valve has been removed. On this engine, the valve has to be installed in the valve cage, then the valve cage Loctited into the center block. Once the valve guide is in place, there is no way to remove the valve!!! Not a really good design, and I just discovered it. Its too late to go back and change things now. It should work okay, but I want to be very sure the valve is sealing good to the valve cage before I Loctite it into place. Also, you will notice that other than the Loctite, there is nothing holding the valve cage in place. On conventional engines, I put a bit of a "head" on the valve cage and install it from the inside, so compression can't pop the whole cage assembly out. I can't do that on this engine, but I have a plan to get around that. I also have a plan for testing the "leakage" of the valve to cage seal before I install the valves and cages in the head, and I will post about that when I get to it.


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## BaronJ (Jan 15, 2014)

Brian Rupnow said:


> Baron J---Glad you like it. Chrome is wayyyyyy out of my price range.---Brian



Mmm.  There is a guy quite close to me that does chrome plating.  I asked him what it would cost to plate the parts based on a picture.  He said that it was so little that it would cost more for the time spent wiring the parts up than the actual plating.  He said bright nickle would be slightly less costly but even then the actual plating would only be pennies.  I also discovered that there is soft and hard chrome also the parts would be acid bathed first and then copper plated and then chromed.

Not a lot of help I know but at least you have some idea of what it would cost here.


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## gus (Jan 15, 2014)

Hi Brian,

Fantastic engine. Trying very hard not to get tempted to build this engine. That Gus cannot resist building this engine.
Jan 15 .Took the first cut on the milling machine. Christmas/New Year Break over and back to
work. M.I.C. Carbide milling cutters are junks. Will try out the M.I.India cutters.

Jan 17 will test run your H&M with the h&m device. Need to buy some petrol.
How is the weather??


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## Brian Rupnow (Jan 15, 2014)

Hi Gus--We have just had a week of above freezing weather--got up to +9C one day with rain. This is a pretty traditional "January thaw" and happens most winters. We still have lots of snow on the ground, but it is compacted now. Weather is starting to cool down again now, back into deep freeze for rest of winter. Most animals in the forest (except deer) depend on this thaw, because when the temps. drop back down below freezing all of the compacted snow will freeze and make it much easier for animals to get around, because they can walk on top of the snow. I am totally ignorant of what kind of winter weather you get in Singapore. I am interested t know how your hit and miss system works.--A gentleman over on "Modelenginemaker" forum, from New Mexico, USA has started to build this new opposed piston engine in 1/2 scale, based on my drawings.---Brian


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## Brian Rupnow (Jan 15, 2014)

Second valve is now finished. Second valve went much faster than first valve. Only had to shut lathe off and check size half as many times. I must get bolder as I work longer. Last week I ordered new lapping compound from McMaster Carr. I got  2 ounce jars of 350 grit, 400 grit, and 600 grit. My previous lapping compound, which some kind soul in USA sent me 5 years ago is finally all used up. I got a surprise. The stuff I have been using for 5 years was dark grey and very oily. The new stuff I got from McMaster Carr is "off white" and has more of a "paste wax" consistency. I now believe that what I previously had was carborundum compound, while this new stuff is aluminum oxide. However, I lapped both valves and valve cages with it and it seems to work just as good as what I had before.


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## Brian Rupnow (Jan 16, 2014)

As all small engine builders know, there is more than one way to skin a cat!! I didn't like the idea that I had to install the valve in the valve  cage and then Loctite the valve cage into place, leaving me unable to ever get the valve out, and making it necessary to drill the port holes into the valve cage while the valve was setting in it. Just too much bad juju there. I lay in bed thinking last night and suddenly had an epiphany!! If I set the center block up on in the mill vice and picked up on the 0.406 diameter holes which the valve cages fit into, then I could use a 5/16" drill and drill right on through the far side of the center block and tap it for a 3/8"-16 thread. The 5/16 diameter root drill hole for a 3/8" thread is about .003 oversize This gives me a hole to put the valve in through after the cages are Loctited and ported. Then I can take a couple of 3/8-16 set screws, coat them with red hi-temp Loctite and plug up the tapped holes.


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## BaronJ (Jan 16, 2014)

Brian Rupnow said:


> And last, but not least, if you have a gas tank, you will want a  screw on gas cap.



Err, Shouldn't there be a vent hole in the tank cap ?


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## Brian Rupnow (Jan 16, 2014)

No vent hole needed. I just loosen the cap 1/4 turn when I go to run the engine.


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## Brian Rupnow (Jan 16, 2014)

There is a lot going on here folks!! The valve cages are installed and Loctited into place, and you can see the 3/8"-16 set screws that I have used for plugs where I drilled completely through the other side of the main center block, which enables me to remove and/or reinstall the valves after the valve cages are Loctited in place. When I get to the final stages of setting up the engine and testing for compression, I will Loctite those 3/8" set screws into place. The springs and keepers are installed on the valves, (but just for the sake of picture taking). Those are the correct springs, but I will probably have to adjust the length of them. The 4 black pan head screws you see in the picture are #6-32 x 1/4" long, tapped into the aluminum center block to provide a physical barrier to the valve cages ever launching themselves out of the engine during a "firing" cycle. Tomorrow I will remove the valves and drill thru the main center block and into the valve cages to form the intake and exhaust ports.


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## Brian Rupnow (Jan 17, 2014)

One of the things that is EXTREMELY important on small engines like these are dowel pins. Once you have "ran in" the crankshaft, and everything is turning freely, then immediately dowel through the frame plates as you see in the picture BEFORE loosening any bolts to disassemble the frame. If you don't dowel the plates together there is enough clearance on all of the bolts holes to virtually guarantee that you will never be able to reassemble things exactly the same as it was before, and you will end up having to "run in" the engine again to have a smooth, freely turning crankshaft. I use 1/8" diameter x 1" long solid steel dowel pins, and I drill and ream the holes they fit into. I will probably put a dab of Loctite on the last exposed 1/4" of dowel before I drive them completely down flush with the bottom plate. That way, on future disassembly, they will stay with the bottom plate.


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## Brian Rupnow (Jan 17, 2014)

There now---I can't honestly say "We have ignition!!!"---But when the time comes, at least I have the points, cam, and condenser mounted.  This is all stuff I recycled from the "Rupnow Engine" when I changed it to a CDI. Why are there 4 bolts holding that tiny little points bracket on you ask?--Well, its a recycled part, and the two outboard holes would have required tapping into two bolts in the front bearing plate that just happened to be in the exact same place. So--I drilled two more holes inboard of the original two. I will probably just cut the heads of an extra pair of #8 shcs and Loctite them in to fill the two original holes.


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## Brian Rupnow (Jan 17, 2014)

This is primarily an "interest shot" to show the recess that I put in the top of both cylinders to clear the head of the exhaust valve when it opens all the way. I had initially thought that I would need the same recess to clear the end of the sparkplug and the intake valve, but I have realized that the intake valve never opens far enough to create an interference, and the sparkplug is just short enough not to cause a problem. The total lift on my cam is 0.160", and I wanted to make sure that I had clearance under the head of the exhaust valve when it is fully open. I have just finished lapping the pistons into their respective cylinders with 600 grit lapping paste, and then washed them thoroughly in a pan of varsol, then blew them off with the air hose. When I walked back into my office from the main garage, I though this would be the only time those recesses are going to be visible, so I should take a picture. When the cylinders are installed in the center block, there is 1/4" between the ends of the cylinders, and the pistons come right up to the very end at top dead center.


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## dsage (Jan 17, 2014)

Hi Brian:

 Concerning your issue with not being able to insert the valve with the valve cage in place. Without the benefit of the pieces in front of me, it would appear that perhaps the valve stem, spring, rocker arm pivot tower etc. etc, could be shortened enough to make the valve short enough to fit inside the head and able to be inserted from the inside - No?
 You seem to have an awful lot of valve stem above the head.
 (A lot of rework I know)

 Certainly the valves don't need to open more than about 30thou.
 (there is a rule of thumb how much to open a valve based on it's diameter which escapes me at the moment, but it isn't much).

 Like I said it's tough to tell without going back through all the pictures and drawings.

 Looks like you solved the issue anyway.

 Nice work !!

 Sage


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## Brian Rupnow (Jan 17, 2014)

I can't believe it!!! All of the mechanical parts are finished. I may use a small model airplane carb on this for its initial "start up" phase. I'm waiting for Chuck Fellows to come up with the "perfect" carb design before I build a carburetor. All I have left to do is to drill and ream thru the main backplate and the center plate which supports the cylinders for a couple of locating dowels and put a keyway in the crankshaft for the flywheel. JWCNC has assured me that he is working on the two arms that he volunteered to make for me, and has told me he would be shipping them to me today. I have to design/build a starter hub/pulley combination for the front of the crankshaft, but I'll do that this weekend. I just checked, and I started the design of this engine on the 18-December. Tomorrow will be the 18-January.--Its amazing how much you can get done when you don't have any other work to do!!!


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## Brian Rupnow (Jan 17, 2014)

DSage--I may have been over cautious when I drilled the thru holes. It seems to me that after having the valves in and out a few times today, they probably didn't need the thru holes. They will (just barely) go in thru the side hole where the cylinder fits on. Oh well, no harm-no foul. Some of these things only become clear after the fact. ---And if I had installed and Loctited things without the thru holes, and then couldn't get the valves out, I'd have been up that well known creek without a paddle!!!


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## Brian Rupnow (Jan 18, 2014)

I dismantled everything this morning, and cut keyways into the crankshaft. I even learned a nifty trick while doing it. I put the slots in with a two flute endmill. I plan on using 1/8" square keystock, and I knew that a 1/8" endmill always cuts a bit oversize. I hunted around in my cutter drawers and found a 3mm endmill, which is 0.118" wide. I made successive .005" deep cuts until I had reached the desired depth of cut, then offset the table .004" to each side in .002 increments, and came up with an exact .125" wide slot. The missing .001" I put down as cutter side deflection.


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## Philjoe5 (Jan 18, 2014)

The nice thing about cutting your own keys and keyways is that when you're in the first assembly for trial fits you can make keys that work but are loose enough to get out easily.  Nothing more irritating than a key that won't budge.

Cheers,
Phil


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## Brian Rupnow (Jan 18, 2014)

Well---There it sets. There is nothing more that I can do until I have the two arms which are supposedly somewhere "in shipment". I haven't cut the slots in the bottom outer end of the cylinders yet. I won't do that until I have the "arms" to fit to. I need a small break now-----but not too small I hope. I want to get those arms on and see if this thing will run.


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## dsage (Jan 18, 2014)

Hi Brian:

 I'd be interested to know how you do the (internal) keyway in the flywheel or whatever goes on the end of your crankshaft.

 Sage


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## Brian Rupnow (Jan 19, 2014)

Sage--I use a broaching kit which I purchased from Littlemachineshop.com  It will work on hubs of 1/4", 5/16", 3/8", 7/16", and 1/2" bore diameters. The hubs fit into the bore of the pulley or whatever you want to keyseat, and the broach is pressed down through the slot with a manual arbor press. Each tooth on the broach sticks out a few thou farther than the teeth ahead of it, so by the time it is pushed all the way through, the keyway is formed. If the keyway is not deep enough at that point, you can put the spring steel shim (pictured laying on the lid) in as a spacer and push the broach through again. It works on aluminum, brass, and cold rolled steel pulleys.


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## Brian Rupnow (Jan 19, 2014)

It seems I am going to have a "time window" on my hands now, until my CNC'd arms show up here. I think I'm going to get very bold and be the first to build a "Chuck Fellows Carburetor" to run on this engine. Chuck has done some outstanding research into a small carburetor which has a built in throttle on it to control the speed of the engine. My only previous success with carburetors has been on the simple "one speed" carburetors as used on hit and miss engines, where the speed was controlled by the governors. I've had a couple of bad scares when starting these small hit and miss engines without the governor hooked up, and had the engines "run away"--that is rev up uncontrollably until I could either pull the sparkplug wire or get my finger over the carb throat to "choke it to death"--sure gets the old adrenalin flowing!!!


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## BaronJ (Jan 19, 2014)

> I've had a couple of bad scares when starting these small hit and miss engines without the governor hooked up, and had the engines "run away"--that is rev up uncontrollably until I could either pull the sparkplug wire or get my finger over the carb throat to "choke it to death"--sure gets the old adrenalin flowing!!!



I'll bet it does...

Anyway nice set of broaches.  I keep threatening to treat myself to some, but I don't have any spare arms n legs.


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## dsage (Jan 19, 2014)

>>I use a broaching kit which I purchased from Littlemachineshop.com 

Ahhh. You do it the right way 

I asked because I was wondering if you had a crude but effective way of doing it. Like me hardening and sharpening a piece of square tool steel, fastening the flywheel to the mill table and progressively shaving off a bit at a time from the bore with the "tool" in the quill. Effective but tough on the quill. I guess I'd also have to invest in an arbor press to do it right (your way).

 I guess I should bite the bullet.

Thanks

Sage


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## BaronJ (Jan 19, 2014)

dsage said:


> >>I use a broaching kit which I purchased from Littlemachineshop.com
> 
> Ahhh. You do it the right way
> 
> ...



I've only ever had to cut a keyway in a bore once.  Fortunately it was an aluminum pulley. I did mine in the drill press, clamped to the middle of the drill table, just as you describe.  Tapping the table with a hammer...  Not only painfully slow but more steps than stairs.  The saving grace was the grub screw sat on top of the key.


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## Swifty (Jan 20, 2014)

Sage, I've done key ways that way plenty of times, don't know how hard it is on the quill, but it sure is hard on your arm.

Paul.


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## dave-in-england (Jan 20, 2014)

.

I don't understand why modellers struggle with all that setting up and making exact and tight fitting keys and keyway slots, especially in small model engines.

It is a lot easier just to mill a slot in the face of the gear 3 mm wide x 3 mm deep and use a length of 3 mm silver steel
rod through a simple hole in the shaft.

When the gear is pushed up against the shoulder it is all held together rigid and cannot move.
Also easy to take apart again.  :hDe:  



.


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## Brian Rupnow (Jan 20, 2014)

There we have it folks. The "Chuck Fellows Carburetor" Newly minted. I have spent about 4 1/2 hours getting to this stage, which seems like an incredibly long time for such few small parts.--I didn't have to make anything twice. I did not incorporate an "air bleed hole" because Chuck has decided that it doesn't really do anything to enhance the carburetors performance. Drilling the 0.040" holes has a high pucker factor, but it went okay. Now to put it all together----


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## BaronJ (Jan 20, 2014)

dave-in-england said:


> .
> 
> I don't understand why modellers struggle with all that setting up and making exact and tight fitting keys and keyway slots, especially in small model engines.
> 
> ...



Hi Dave,

I like this idea !  This is one that I shall put in my, not so little, black notebook.
Thanks:


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## Brian Rupnow (Jan 20, 2014)

Second half of day not nearly as fortuitous as first half of day---Have managed to fill entire carburetor with soft solder---not once, but two times!!! Now I remember why I hate soft solder worse than snakes!! Finally melted everything out, drilled everything out, tapped everything out,and used silver solder to attach needle to needle valve cap. Arrrrggghhhh!! Should have went with silver solder in the first place. Leave soft solder for plumbers!!!


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## Brian Rupnow (Jan 20, 2014)

TA-DA---Old age and treachery triumph once again!!! Beautiful carb, Chuck, but I never had one fight so hard after all the pieces were made.


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## Brian Rupnow (Jan 20, 2014)

I just went through all of the drawings to make sure they were updated, and saved them as pdf files. I still have to do up 3 or 4 assembly drawings with bills of material, and then I will be posting a download link.


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## BaronJ (Jan 21, 2014)

Hi Brian,

That dam flux gets everywhere :wall:  A dab of permanent marker in the right places may help, that is if you can get it where you need it.  I suspect that it would be difficult looking at that carb.


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## Brian Rupnow (Jan 21, 2014)

The drawings are all finished and corrected. There are over 50 detail drawings and assembly drawings. I have saved everything as .pdf files, so you won't need any special engineering software to open the drawings and you can download it from the following link, but be warned--It's a 7 meg download. If anybody discovers a mistake or missing dimension, or there are any missing drawings, let me know. Warning--This is not a project for amateurs. You should have built at least 3 or 4 i.c. engines before attempting this one. The complex shaped rocker arms may need some "fettling" on the end which enters the cylinders, but I don't know how much because  haven't got my arms yet to trial fit them. If you decide to build it, please let me know, and good luck. It is a bit unusual for me to release a drawing package before I have a running engine, but I know that everything fits except for the arms, and when  receive mine I will post about fitting them in my thread on the forum.
http://www.mediafire.com/download/l5kw3n56pexauty/RUPNOW%20OPPOSED%20PISTON%20ENGINE%20DRAWINGS.zip


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## BaronJ (Jan 21, 2014)

Brian Rupnow said:


> There we have it folks. The "Chuck Fellows Carburetor" Newly minted. I have spent about 4 1/2 hours getting to this stage, which seems like an incredibly long time for such few small parts.--I didn't have to make anything twice. I did not incorporate an "air bleed hole" because Chuck has decided that it doesn't really do anything to enhance the carburetors performance. Drilling the 0.040" holes has a high pucker factor, but it went okay. Now to put it all together----



Hi Brian,

Where can I see or get hold of the "Chuck Fellows Carburettor" ?  A google doesn't get me anything.

Thanks:


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## Brian Rupnow (Jan 21, 2014)

Our very own famous engine builder, Chuck Fellows has the plans in the download section of this forum.


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## BaronJ (Jan 21, 2014)

Thanks Brian,

I wonder why the search didn't find it ?

Anyway got it now.


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## Brian Rupnow (Jan 21, 2014)

BaronJ said:


> Thanks Brian,
> 
> I wonder why the search didn't find it ?
> 
> Anyway got it now.


 
 Perhaps because you spelled carburetor incorrectly!!--Seriously, the search engine on this forum yields so much information that it isn't all that helpful.---Brian


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## BaronJ (Jan 22, 2014)

Brian Rupnow said:


> Perhaps because you spelled carburetor incorrectly!!--Seriously, the search engine on this forum yields so much information that it isn't all that helpful.---Brian



Ouch !  Slaps wrists...  use speeling chequer in future. :hDe:


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## Brian Rupnow (Jan 22, 2014)

Lacking anything else to do, today became "gasket day". I have found a rather foolproof way to make my gaskets. I simply bring up the 3D model with the surface that my gasket has to seal, (in this case, the exhaust and intake manifolds), and arrange them "FLAT" to the screen and print them at 1:1 scale. This gives the exact size I need. I then cut them out with scissors and use a glue stick to stick them to some 0.030" thick mystery gasket material I purchased in a package of "random gasket material" I have a jar full of very simple gasket punches I have made by taking a piece of round cold rolled steel the diameter I want, chucking it in the lathe, and then running a lathe center/countersink into one end until I have a cone shaped recess with very sharp cutting edges all around. This operation "flares" the end of my punch tool a bit, so I use a bit of 220 grit paper on the o.d. while it is spinning to get rid of the "flare". I lay the gasket on a piece of wood, center my punch on the hole I want, and one light smack with a small hammer yields a perfect sized hole with clean edges. I also have a leatherworkers punch which works really great on the small 1/8" diameter holes. After all of the holes are punched, then I cut out the perimeter with a pair of scissors. Today, I used some nasty black Permatex-2 "form a gasket" on both sides of the gasket before I assembled things. This makes the gasket twice as effective, but then you spend a half hour with Q-tips and paint thinners cleaning up the immediate area and your fingers. I use a little green 638 Loctite where the carburetor screws into the intake manifold, and even a little "Seal all" on the carburetor, where the fuel jet passes through the main carb body. Compression test???--well, at this point in the engine development, I can put my thumb over the open end of one cylinder, and then blow on the other end until my eyes bug out, and not detect any air leaks. I know the piston rings will seal--the Viton rings make that a cinch. If, while I am busting a lung trying to create a air leak by blowing into the cylinder I "pop" either of the valve stems, the air blasts out, then reseals immediately when I release the vale. that is a GOOD sign!!!


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## Philjoe5 (Jan 22, 2014)

This is good information Brian.  Thus far, I have no gaskets in place on my engine and was thinking about using Permatex, but then it's a mess to disassemble.

I may try this technique out.  I have a set of similar punches I made up ages ago.

Cheers,
Phil


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## Brian Rupnow (Jan 23, 2014)

Great care has been taken to ensure that yes, the gas tank really IS lower than the carburetor. That is why the intake manifold has such a wonky shape. I couldn't put the gas tank any lower because of the flywheel, so I had to make an intake manifold that would lift the carburetor up just that teensy bit that makes such a huge difference to how the engine runs. Probably 50% of the problems encountered by first time i.c. engine builders is that they get the gas tank too high in relationship to the carburetor. Since there is no float and needle in these small carbs to shut off the gravity flow of gasoline, the engine will flood terribly and when left unattended all of the fuel in the tank will run out of the carb onto the workbench.


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## Brian Rupnow (Jan 28, 2014)

Holy Crow!!! Look what showed up at my house today. These are not the original arms that JWCNC was going to build for me. A gentleman in Kansas said he was so anxious for my build to proceed that he cranked out these two arms and sent them to me air express!!! I know that JWCNC has been working on a pair of arms for me, but has ran into some unrelated problems that are going to delay them. If he does manage to finish the arms he has started for me, I will pass them on to the next person who can show me that they are seriously building this engine. So---Thank you BIG BIG Mr Kansas!!!


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## Philjoe5 (Jan 28, 2014)

They look really good Brian.  Are you ready to fire it up?

Cheers,
Phil


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## Brian Rupnow (Jan 28, 2014)

Not yet. I have to make and mount bushings and machine the slots in the bottom of the pistons.--It's getting close--Hope everything fits up!!!


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## Brian Rupnow (Jan 28, 2014)

Well, there we go boys and girls---The arms are a perfect fit!!! I have to cut clearance slots in the bottom of the cylinders, and a bit of "fettling" here and there, but I'm very pleased with what I am seeing.


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## BaronJ (Jan 29, 2014)

Brian Rupnow said:


>



Hi Brian,

They look beautiful !  The guy that made them deserves a pat on the back...


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## bmac2 (Jan 29, 2014)

Wow. Those look sweet. 
Looks like your Birthday and Christmas both fell in January this year. Passing on the spare set? It cant hurt to have a little good Karma in the old machine shop bank account. 
This can be a frustrating hobby, trying things that I honestly dont know how to do, but the willingness of people on this site to help makes a real difference. 
WAY TO GO KANSAS ! Thm:


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## Brian Rupnow (Jan 29, 2014)

BMAC2---I've grown older and a little more cynical with the passage of time. Many times over the last 5 years people have made parts for me, just because they are very nice guys, and genuinely want to help. In the essence of "Tit for Tat" I decided I should be a good guy and do the same thing. Two people on the board were making Websters last year, and they had no way to make the gears. I cut the gears for both Websters and mailed them out to the fellows. Neither of them finished their engines.--Perhaps I shouldn't care, but this pi$$ed me off to no end. I will give the spare set to someone who needs them, but only when I see they have invested enough time to have built at least 2/3 of the engine first.---Brian


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## Brian Rupnow (Jan 29, 2014)

So--The last two cuts, opening up the slots in the cylinder bottoms for the arms had me concerned. I sat here last night thinking of making special fixtures to bolt the cylinders to while I machined them, thinking of dismounting the cylinders and holding them in the chuck on the rotary table to machine them---I didn't sleep worth a damn thinking of how to do this. This morning I got up, bolted my angle plate to the mill table, clamped the engine to the angle plate, and inserted a 4 flute 1/2" endmill in the mill. I centered the cutter in the cylinder with my electric edge finder, Sat my tool height at "0" by touching the tip of the tool to the end of the cylinder and setting my digital vernier depth gauge on the mill, and then took 0.010 depth cuts back and forth across the area I wanted to cut away. I set the stops on my x axis so I couldn't overtravel, (didn't want to cut into the far side of the cylinder) and made successive passes to the depth of .438". Then I offset the "Y' axis in .005 increments and opened out the slots .030" in each direction to get the 9/16" width I wanted.--worked like a charm!!! Now I have to lightly file all the sharp edges created by the cuts (especially on the inside so I don't cut the Viton rings when inserting the pistons) and I can start reassembling things.----and Oh yes, while I was making those cuts, I had a wad of toilet paper shoved down the cylinders to keep most of the chips and dust out of the rest of the engine.


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## Brian Rupnow (Jan 29, 2014)

Check out this movie. It is AWSOME!!! As I had expected, there is a bit of "fettling" with a hand file required around the lower corners of the "arms" that fit into the cylinders but really not much. When I look at a cross section of the assembled cylinders with my 3D software, I knew that the underside of the arms cleared the bottom inside of the cylinders at the centerline, but since the cylinders are round I expected there would be some slight interference with the bottom corners of the arms. Nothing that 5 minutes with a file doesn't fix.  I don't have the Viton rings on the pistons in the video. It will "stiffen up" a lot after the rings are installed. I still haven't made a proper check for compression, but will get to that. Now I will time the valves and then the ignition, and then, well,---we'll see!!!


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## dsage (Jan 29, 2014)

Hi Brian:
 Probably my computer but, the audio on the video is fine but the video is stop action and I only get about three frames of the engine in action. It doesn't play on line. I had to download it.
 Sort of strange.
 Not to worry. I'll wait for the final "fire up".

 Excellent work and done in record time I'd say.

 Sage


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## Brian Rupnow (Jan 29, 2014)

Very strange, Sage. Its hosted on Photobucket, and plays fine on mine when I click the picture.---Brian


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## Brian Rupnow (Jan 29, 2014)

I got the valve timing set, but then had to stop and make 4 pivot pins for the ends of those strange shaped arms. Normally, I just cut short pieces of cold rolled shaft and hold them in place with a dab of 638 Loctite, but in this case, if one of the pins ever worked out while the engine was running, it could do some real damage. Right now I'm waiting for a call back from my bolt store, to see if they have any 3/16 external e-clips.


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## Shopguy (Jan 29, 2014)

Brian
That is one phenomenal piece of work you've got going there.
Waiting with anticipation for seeing it run.
Many thanks for your continued contributions to the hobby.
Ernie Johnson


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## Brian Rupnow (Jan 29, 2014)

Thanks Shopguy--I'm getting excited myself!! The hard part will/may come tomorrow.


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## Philjoe5 (Jan 29, 2014)

Very cool engine Brian.  Can't wait to see it run under its own power.

Cheers,
Phil


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## Brian Rupnow (Jan 29, 2014)

So---I don't think I can be any readier than I am now. The valve timing is set. I do that by loosening off the grub screws in the crankshaft gear so that I can rotate it by hand without the crankshaft moving. Then I turn the crankshaft over in the direction I want the engine to rotate until the pistons are about 1/8" from being at bottom dead center. Then I rotate the crankshaft gear in the same direction with my fingers (the camshaft gear will rotate in the opposite direction) until the lobe on the cam is just at the point where if it went any farther it would start to lift the exhaust valve. Then I lock down the crankshaft gear grubscrews, and that's all there is to valve timing.--The ignition timing is set. I do that by loosening off the grub screw in the ignition cam so the cam rotates free of the crankshaft. I keep turning the crankshaft in the direction I want the engine to run until the piston is about 1/8" before top dead center. Then I rotate the ignition cam in the same direction . If you have seen the drawing of this engines ignition cam, you will see that it is perfectly round with a flat machined on one side. Whenever the rubbing block on the cam is riding up on the main diameter, the points are open. When the leading edge of the flat gets to the rubbing block on the points, they will close. The stay closed until the trailing edge of the flat spot lifts the points open again.--And that (the points opening) is what collapses the primary "field" in the coil and induces a high tension spark in the secondary windings of the coil. I set the position of the cam so the points begin to open at about 1/8" before the pistons reaches top dead center, and lock down the ignition cam grubscrew. ----I have filled my new fuel tank with a 40:1 mix of Coleman fuel and 2 cycle engine oil. This will lubricate the pistons and the cylinders and the Viton O-rings. I have the engine setting on top of 3 sheets of white printer paper, so if there are any leaks in my fuel system I will see tomorrow morning. I have opened the needle valve on Chucks carburetor 3/4 of a turn, and opened the throttle screw one full turn from the fully closed position. The valve lash is set so that when the pushrod is not riding up on the cam there is about .015" free play between the top of the valve and the rocker arm. All that remains to do is hook up my coil and battery, cross my fingers, say a short prayer to the God of small engines, and crank it up. Cross your fingers for me!!!---Brian


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## Art K (Jan 29, 2014)

Sage, I have had that problem with photobucket videos, gives me the "buffering" message. If I'm patient 15-20 minutes to watch a 1:30 minute video, you tube videos no problem.
Brian, I find myself drawn to anything you build, despite not being overly excited about "slow" engines I find your builds captivating. If I didn't have something in the works I would consider your opposed. And maybe will in the future.
Art


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## lathe nut (Jan 29, 2014)

Brian, been following the thread and not saying anything but just being a looker you sure make one there like I call it a lot going on, fellow would have to try to look at one part for a while before he could go to another one then try to take it all in, that is nice of you to share with us you know that is one of those engines that a fellow would love to have to show off to people who appreciate the finer things but I think that is out of most tinkers abilities, so its a copy past and when all done print and keep hoping someday that one would be good enough to build, thanks again for you time to photo, explain and in the end show us a real running winner, Lathe Nut


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## Herbiev (Jan 30, 2014)

Just awesome. Looking forward to seeing it run under its own power.


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## johnmcc69 (Jan 30, 2014)

WOW Brian. Awesome. Great design, great build thread. 
I can't wait to see it run. Fantastic...

 John


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## BaronJ (Jan 31, 2014)

Looking good.

I'm looking forward to seeing it running too.


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## Brian Rupnow (Jan 31, 2014)

Well--------------------The engine is moved out to the main garage and bolted down to my test bench. The power box is all hooked up. The 12 volt battery has been on the charger all afternoon.--I bought a new fire extinguisher this evening. I have to do 2 hours engineering design work for a customer tomorrow morning. I think I'll put the furnace on in the main garage while I'm doing the design work.--And then--Maybe---Gee, I hope this thing runs!!!


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## Brian Rupnow (Feb 1, 2014)

This morning we are on our way---


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## Brian Rupnow (Feb 1, 2014)

Okay--Now I have to sort out what to do next. Engine runs, but rings are awfully tight. This means that engine fires and runs like crazy with " starter drill assist" but bogs down and quits shortly after drill is removed. I can pull it apart to cut the ring grooves a little deeper, or I can make a temporary extra flywheel, in hopes that the added mass will give that extra inertia to keep the engine turning over between "hits". The rings will wear in a bit as soon as I have consistent running, and a temporary add on flywheel is probably the easiest thing to do for now.


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## Brian Rupnow (Feb 1, 2014)

The pulley is only lightweight aluminum, wouldn't do as a flywheel. If I oil all the pivots, bearings, etc. with a squirt oil can its good for 1/2 to 3/4 of an hour of running. These are low speed engines. I have tried the needle valve at many different settings to make the mixture leaner or richer. There is definitely an effect, but not enough effect. We aren't through yet. I'm going to make a 4" diameter x 1/2" thick steel second temporary flywheel. I may try my model airplane carb. I am right on the cusp of a running engine.


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## BaronJ (Feb 1, 2014)

Ooh the suspense...


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## johnmcc69 (Feb 1, 2014)

Looking good Brian!! 
 From what I've seen (& read.) on similar designs like
the Atkinson Differential engine, they use a larger flywheel
& oilers.

 John


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## Brian Rupnow (Feb 1, 2014)

I'm going to give it up for today. The frustration level is getting too high. The second flywheel helped a great deal, and I have gotten a few sustained runs of 20 to 40 seconds, but then it dies. When an engine does that, if its a weak coil, it won't start up again right away. Mine will start up again right away, so I don't think there is anything wrong with the ignition. When engines start at all and give a sustained run of 20 to 40 seconds and then die, it is generally a carburation problem. Either it is running out of gas, or it is flooding itself, getting too much gas. I have played enough for today, and of course I have advanced the timing and retarded the timing many times trying to find the "sweet spot". I did cut one coil from the intake valve spring, as I wasn't seeing any movement in the valve while turning the engine over with the drill. Removing one coil seemed to do the job, as I could see the valve "dance" after that while it was turning over.--And of course, the engine has loosened up considerably after a number of short duration runs.Tomorrow I will try it with my model airplane carb and see what happens.


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## Philjoe5 (Feb 1, 2014)

> When an engine does that, if its a weak coil



Brian,
I'm suspicious that I'm dealing with a weak coil too.  Is there any way to check it other than looking at the quality of the spark?

My spark is hard to see and yellow, not blue.   I thought I remember reading somewhere that you should be able to hear the spark, with the plug out of the engine.  True?

Cheers
Phil


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## Brian Rupnow (Feb 1, 2014)

Phil--I'll probably take flack for this, but I don't think you can tell by the colour nor by the sound of the spark. In a perfect world all sparks would fat, loud, and blue-white. That actually happens about 1/3 of the time. Lots of times the sparks are yellow, quiet, and not all that big.---and the engines run just the same!!!  If your engine fires, starts, runs for a few seconds and then won't stay running it could be the coil. But if you immediately try to restart it and get the same results, its probably not the coil. If a coil goes out, it stays out for a while until it cools off. Its more apt to be a carburation issue. If it doesn't fire at all, then its either coil or points or sparkplug.


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## Brian Rupnow (Feb 2, 2014)

I simply couldn't cope with an engine which had nothing out front to grab on to and turn by hand. Last night I pulled the starter hub off the front and bored out a piece of 2" diameter aluminum to press fit over the outer diameter. A bit of Loctite and a press fit, then let it set up overnight. This morning  was able to knurl the o.d. of the aluminum. Now I can actually grab it and turn the engine over by hand. Compression on this engine is phenomenal, but I thought it would be after all those firing "pops' yesterday.---It bounces back when you try and spin it through the compression stroke by hand. I have a couple of hours of design work to do this morning, and then maybe we'll give it a go with the model airplane carb.


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## Brian Rupnow (Feb 2, 2014)

I'm running out of tricks!! I changed carbs, and although perhaps it is marginally better with the model airplane carb, still no lasting joy. I have great compression. I have good gas. I have adjusted the timing both retarded and advanced to the point of ridiculous. Had a couple of 1 minute runs, just enough to get my heart beating real fast, but then it petered out. The only thing left to monkey with is valve timing. Now I have to pour a glass of red wine, go upstairs with my good wife, and consider things for a while!!


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## Shopguy (Feb 2, 2014)

Brian,
Is something changing when it heats up?
Valves, pistons, fuel supply? Or cylinder pressure?
Possibly would increasing the mass of the flywheel help?
I mention this because the fuel air charge is going to start expanding once it hits the somewhat hotter intake ports and other internal parts, more so than in a cold engine.  This would, theoretically  require more force to overcome hence more flywheel inertia.
Keep at it you're getting closer.
Ernie


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## canadianhorsepower (Feb 2, 2014)

Hi Brian,,
 nice pieace of work if I can give my opinion 
 your intake track is way to long. The longer the higher your RPM has to
 be for the pulse wave to work I would simply put a small 90 degree elbow
 and put the carb right over the intake valve  

 good luck


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## Brian Rupnow (Feb 2, 2014)

No, there is no thermal difference, because its not running long enough to develop that kind of heat. I have already doubled the mass of the flywheel so it now has two 1/2 " thick x 4" diameter steel flywheels, which should be lots. Luc's answer may carry part of the truth, and yet I see Chuck Fellows running his vertical engine with an intake track 5 or 6" long, so I doubt that's it.


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## tonyr (Feb 2, 2014)

Brian,

I have had similar issues with a couple of engines I have made.
Try putting a tube on the air intake of the carb, then vary the size of hole in the end.
Start by covering the end with tape or card and put a small hole in it and try the engine.
Keep making the hole a bit bigger to see if it improves the running.
I think the extra depression in the carb inlet helps draw the fuel better.
It has worked for me a couple of times. If it improves the running you can make it permanent.

Tony


Sent from my iPad using Model Engines


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## Brian Rupnow (Feb 2, 2014)

Tony--I may try that.---Brian


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## dsage (Feb 2, 2014)

Tony:

You mean like a choke?

Brian:
Along this same line of thought. When you try to start it, and just before it dies, does it help to give it a quick finger over the carb - choke trick? This will tell you if it's getting fuel. The finger trick will cause it to suck raw fuel for an instant.

I'm sure you've thought of all the stupid things but I'll throw them out there anyway. For the benefit of others if nothing else.

You have a vented cap on the fuel tank - right?

You mentioned before that you have the fuel tank at the optimal height but you can prove this and also check for the ability of the engine to PULL fuel if you temporarily lower the fuel tank down a bit such that you have a tiny bit of air in the tube right where it enters the carb. When the engine is cranked over it should have enough suction on the fuel line to lift the fuel even though it is a tiny bit lower than the carb. If not, not enough vacuum on the intake stroke or too small a fuel needle opening or too big a venturi. Also related - in terms of an atmospheric intake valve but maybe too heavy/light of a spring.

How does the sparkplug look - wet/dry, fuel or oil soaked?

Good compression requires a good spark. Does the spark look like it has a bit of reserve.

Try running it in the dark. You might be able to see a spark leak somewhere.

Sage


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## Niels Abildgaard (Feb 2, 2014)

Stupid remark removed.Excuse me


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## Walltoddj (Feb 2, 2014)

Just a thought but could you have to much compression? I ran two stroke kart engines in the 70's and we had modified the cyl head for a better flow. When we ran it we had low power after a compression test we were over 300psi. Got it back to about 125psi and it worked fine. I know you've been trying all base just my idea.

Todd


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## Brian Rupnow (Feb 2, 2014)

Luc--I hold Chuck in very high esteem. We all copy one and other to some extent here, and we all try to be friendly about it. I have posted engine builds that were totally Chucks idea, and tried very hard to explain to people that although I might have posted detail drawings of something, that Chuck Fellows was the originator of the concept. A lot of the time, the person who gets credit for something new is the person who first builds it, runs it successfully and posts a video of it running. There is no room for pettiness nor meanness on this forum.


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## Brian Rupnow (Feb 2, 2014)

This afternoon I had my first successful long duration run. The engine ran for 3 minutes, and I actually shut it off, it didn't stop on its own. A glass of red wine and an hours nap will do wonders for your thought processes. I went through the engine bit by bit in my head, and I couldn't really fault my design nor build process. It kept coming around to carburation, somehow. I an going to post two pictures---Take a good look at the assembly picture. Note that at the end of that brass tube between the carburetor and the strange shaped inlet manifold, all you see is plain tube--maybe part of one thread. I happen to know that there is almost 3/8 of an inch of thread on the end of that tube.  Think about it---the threaded end extends so far into the intake block that there is only very little room for fuel vapour to get past the end of the tube.--so---I would crank the engine until it had drawn enough fuel through the small gap to start the engine. The engine would start, run like gangbusters until it used up the small amount of fuel in the inlet block, then die from fuel starvation. Look at the picture of the carb and inlet tube by itself. I set it up in the mill and milled a 3/16' slot in the underside of the threaded area. Put is back in the engine, and almost immediately had a long duration run.---DOH!!!! The reason I shut the engine off is that the brass tube was beginning to unscrew itself from the intake. Those are not tapered pipe thread, simply 5/16"-18 unc threads. I took it apart, cleaned up both areas with some "hot" paint thinners, added a bit of 638 Loctite and put it back together, and came in the house to post this thread. MAYBE---video tomorrow. MAYBE---I've got another winner after all!!!


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## Brian Rupnow (Feb 2, 2014)

Chuck--I'm not sure just where this leaves your carburetor, in all the shuffle. I like it, and I would like to use it, but of course my first priority here is to get a running engine. Once I've got the engine tuned and running satisfactorily with the airplane carb, I may get out my old tried and true test bench, the Webster, and give your carb a whirl on it. The Webster is currently running the same model airplane carb, and it has been a very dependable little engine over the years, so I think it might be a better test bench for your carburetor. The problem with trying it on a new, never before ran engine is that I have too many "unknowns". Once the dust dies down from this opposed piston build, I will definitely fit your carb to the Webster which is more of a "known quantity" and do a thread on how satisfactory it works for me.----Brian


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## Philjoe5 (Feb 2, 2014)

Brian,
This opposed engine startup has been a great education for me.



> The problem with trying it on a new, never before ran engine is that I have too many "unknowns".



After least weeks problem with my intake valve I decided to slow down and get my engine running with your proven carby.  At the moment I have too many unknowns too.  If it runs with your carby that will prove the valves and rings are operating properly.  Then I can go from there.  

Cheers,
Phil


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## Brian Rupnow (Feb 2, 2014)

Philjoe--Start up are always the most high stress part of an engine build. Especially when the world is watching. I like to post my stuff, warts and all, so that new engine builders can see some of the tricks (and pain) involved. When I first started engine building, that was one of the hurdles that I faced.---Nobody else posted their many attempts and failures. They waited until everything was perfect and then posted and sort of gave the impression--"Heck, this is easy, anybody could do it!!!"---And I would build an engine, and it wouldn't run, and after I had tried all the tricks I knew I simply wouldn't know what to do nor who to ask. It's not that people purposely withheld information. It's just that I didn't know what questions to ask.----I learned back then that the most dangerous and harmful people on any forum are those who, though good intentioned, would suggest things they had heard about somewhere, but never actually done themselves. I try really hard to give advice only on things which I have personally had experience with. It just makes you crazy when an engine won't start, and you don't know why, and there isn't anybody else that knows more than you do that you can go and ask. Been there, done that, and have the tee shirt!!!---Brian


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## Philjoe5 (Feb 2, 2014)

> Start up are always the most high stress part of an engine build



I agree.  Up to that point you may be getting lots of comments about how "good" it looks, but in the end, if it doesn't run, it's not an engine but just a collection of parts.

IC engines bring in so many variables.  Valve timing, ignition timing, carburetor design, valve seating and piston ring performance.  Did I miss anything?  But then when you get a runner, you know you've accomplished something.

It sounds like you're getting close and have done an impressive job of isolating where your problems are.

Cheers,
Phil


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## barnesrickw (Feb 3, 2014)

The issue with too much compression is usually pre-ignition.  Pre-ignition can sometimes cause damage. 


Sent from my iPad using Model Engines


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## Walltoddj (Feb 3, 2014)

Pre-Ignition is usually under load I had no pre-ignition in that engine just no power. You have understand that the engine I ran was on straight methanol with 10 cc of nitro so if I got a pre-ignition my piston was gone in about 2 seconds because did that at one time to much nitro temp gauges go off the wall. Just I found 4 strokes have a hard time starting and running if compression is high.

Todd


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## mayhugh1 (Feb 3, 2014)

Are you sure you're venting the crankcase? I know your opposed piston design should theoretically have minimum problems with this but if you have high compression and a slight mismatch in sealing or timing between the two sides you may be building up enough crankcase pressure to present the symptoms you're seeing. -Terry


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## Brian Rupnow (Feb 3, 2014)

mayhugh1 said:


> Are you sure you're venting the crankcase? I know your opposed piston design should theoretically have minimum problems with this but if you have high compression and a slight mismatch in sealing or timing between the two sides you may be building up enough crankcase pressure to present the symptoms you're seeing. -Terry



 If you take any time at all to read through the thread and look at the pictures, you should realize that the crankcase is completely open to atmosphere.


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## Brian Rupnow (Feb 3, 2014)

Alright!!!--This is not what you would call "Ticking over like a Swiss watch", but it is definitely running under its own power. I think this is a "qualifying run". I will keep pecking away until it does just set and "tick over" gracefully but for now I am going to put this up and say "Yes, I have a running engine!!!" Thank you to everybody who followed this long thread, and if any of you out there are considering building it to the plans I posted, all of the drawings are updated and any errors that I found were corrected before I put up the download link.------Brian


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## Philjoe5 (Feb 3, 2014)

Congratulations Brian.  Nice work and it was interesting to follow along.  I learned a lot in the process

Cheers,
Phil


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## Fluffy (Feb 3, 2014)

G'Day Brian,
Very well done. 
It's been a great series of posts & I have enjoyed watching your efforts unfolded from start to finish. The plans are in my engines to do file.
Regards,
Don.


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## Brian Rupnow (Feb 3, 2014)

I've sat and watched the video a few times now.---And yes, I must admit, it runs a bit like a threshing machine in heat----However, it does run. That is always the biggest concern.--That they run at all. If they run at all, then you are pretty well 100% sure that thru playing with the timing, and dicking about with the carburetor needle valve and one or two other minor adjustments, that it can be made to run smoothly and slowly. Running at all is one Heck of a milestone. If you can't get them to run at all, then you most definitely can not tune them to be smooth and graceful. When you build to somebody else's design, you generally have the certainty that as long as you follow the blueprints, you will end up with a runner. A bit of Youtube searching will turn up half a dozen engines built to the same set of plans, all setting there ticking over nicely. When you design from scratch, there is always that bit of uncertainty in your mind--"Gee--What if I overlooked some major feature that will prevent it from running at all." The feeling I get when I design from scratch and see it draw its first breath and run on its own is the same feeling I got when I built my very first wobbler (oscillating air engine) and seen it take off and spin on its own. YAHOOOOOOOOO!!!


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## gus (Feb 3, 2014)

Hi Brian,

Great engine.
 Just got back from not too cold Tokyo,Japan and about to plunge into finishing up the H&M.Did suffer a bit of burnt-out after building two engines last year. I am OK now.
Later in the year will take good hard look at building your new engine.


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## Brian Rupnow (Feb 3, 2014)

Gus--Nice to hear from you. Burn out---Yes, I can understand that!!!


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## Swifty (Feb 3, 2014)

Great engine Brian, the work that you put in to drawings and building is to be commended.

Paul.


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## Heffalump (Feb 4, 2014)

Fantastic work Brian, as usual I suppose! But thank you for bringing this to us.. can't wait to see a slow speed run.


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## Path (Feb 4, 2014)

Brian,

Again ... thanks for the ride. 

Well done and looking forward to your next project.


Pat H


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## BaronJ (Feb 4, 2014)

Hi Brian,

Yeah its alive...  Good one, nice to see it that runs.


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## BronxFigs (Feb 4, 2014)

What a privilege to be able to follow this engine build from the concept stage to the final, running stage....and, in less than two months.  What an incredible effort it took, not to mention the dedication, all the machining, thinking, photographing, posting explanations, suffering frustrations, the joyous triumphs, the tweaking, the expense of materials..... etc.

Thank you for a wonderful tutorial.  I'm sure I, and others have learned much from following this build.  I commend you for allowing us to see all the failures, and then let us see how the multitude of unforeseen problems were solved.

Truly, a machining, and educational, tour de force.

Congratulations on your success.


Frank


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## robcas631 (Feb 5, 2014)

Brian, 

You must be in 7th heaven! When all the hard work brings metal to life. For me watching this build is inspirational and educational. Well done Sir!


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## dsage (Feb 5, 2014)

Brian:

It must be a real rush to have and engine you've only ever seen on paper actually turn into an animate object. And a really good running one at that! The fact that it runs at all is testament to your design abilities.

Good job!!

I hope you'll continue a bit on this thread so we can see what you work out with the carb.

What we all need is a good carb design that can be assured to work. There is no shortage of carb drawings out there. Certainly Strictly IC magazine had one in every other issue. But how many good ones is another story.

Thanks for sharing with us. It's a lot work and we appreciate it. 


Sage


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## Brian Rupnow (Feb 5, 2014)

The engine runs, and I am indeed happy with that fact. However, running and running well are two totally different animals. I want it to be able to run very smoothly, ticking over slowly like a finely tuned motorcycle engine, yet able to be revved up by a tweak of the throttle. I will post my attempts to get to that point from where it currently is. Currently the engine is running too fast, and it is fighting to get through two complete revolutions of the crankshaft and fire again before it stalls out and quits. Posts may be slow in coming, because it is miserably cold here, and my "test bench" is out in the main unheated garage. I have an electric furnace in the main garage, but it uses a fearsome amount of electricity to keep it heated. However, slow though the ride may be, I will post about my progress and hopefully reach the point where the engine runs the way I want it to.----Brian


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## Art K (Feb 5, 2014)

Brian,
I look forward to your sorting out the problems because I know it will be a learning experience, and I will be patiently waiting. I know how cold an unheated shop/garage is up north. I ONCE tried to run my Upshur vertical at 19 F never again will I screw up my carb settings that much. 
Art


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## Davewild (Feb 6, 2014)

Beautiful work Brian, I might have to try his one!!!


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## Brian Rupnow (Feb 8, 2014)

I just got my feeler gauges out and checked, and found that my valve lash had slipped/changed to a whopping 0.023"!!! I am changing it to .005" to see what effects that has on when the valve opens and closes without changing anything else.


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## Brian Rupnow (Feb 8, 2014)

Okay--That clinches it--There is something wrong with the machining of my cam, but not with the design of it. I set the lash at .005", and readjusted the timing so that the valve lifter just began to contact the valve at 50 degrees before bottom dead center, (which corresponds with the 1/8" of final piston travel before bottom dead center. I then rotated the crankshaft by hand until the piston began its travel up the cylinder on the exhaust stroke. The exhaust valve opened fully as it was supposed to--and then stayed open through most of what should have been the intake stroke as the piston travelled back down the cylinder. I have messed up the machining of the cam. I'm surprised that the engine ran at all. So--this weekend I will machine a new cam. I knew there was a reason I designed this engine to have a bolt on cam!!!


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## Brian Rupnow (Feb 8, 2014)

Jeez--What a nasty little piggy to take the cam off of. I almost had to dismantle the entire engine!!! I can't really see anything wrong with the cam on visual inspection, but at this level there isn't really too much that would be visible to the naked eye anyway. Maybe if I had a visual comparator it would show up.--Oh well, it gives me a chance to clean up the engine.






[/URL


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## Brian Rupnow (Feb 8, 2014)

Somehow, a Demon got into my lathe!! I just checked the outer diameter that the brass gear has for the cam to fit on against the inner diameter of the gear. There was a discrepancy of .008 total runout where there shouldn't have been any. That along with the angles on the side of the cam being out of spec, probably has a lot to do with the weirdness I am seeing in my valve opening/closing. Since I have everything apart anyways, I am setting the gear up on a mandrel and turning a bit off the o.d. off the shoulder to bring it back to concentricity. Then I will bore the new cam "to suit".


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## Brian Rupnow (Feb 8, 2014)

First step to get out of this mish-mash is to true up the "spigot" on the face of the gear to be concentric. Accomplished this by using  638 Loctite to attach gear to a 1/4" cold rolled shaft, letting it set up for two hours, then doing a skim pass on the spigot. Bore on the gear is 1/4" and its a reamed hole. Now outer diameter of spigot is perfectly concentric to bore of gear, at least within the limits of my 3 jaw chuck, which has about .003" total runout--that's about .0015 out of center, which is pretty well standard for  a 3 jaw chuck. I used my 3/32" cut off blade to do the truing cut, because I didn't want to leave any radius in the corner.


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## Brian Rupnow (Feb 8, 2014)

Next step is to find a piece of 1" cold rolled steel, turn the outer diameter down to .875" which will be the major diameter of the cam, and then bore a center hole. I had to drill and then bore the center hole to match the "spigot" on the gear, because now it is a non-standard size and I don't have a reamer that was the right size. I stepped back 5/16" from the face and used my cut off tool to make a fairly wide register about .080 deep so that when I set up in the mill I will have a good guideline on how deep to mill the flanks of the gear.


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## mu38&Bg# (Feb 8, 2014)

I might suggest that you could chuck a piece of stock and turn a spigot to fit the bore of the gear. This would eliminate chuck runout, for the cost of a small piece of stock. I did just this to rework some parts last week because I had no way to hold other than a shallow bore deep in the back of the part.


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## Brian Rupnow (Feb 8, 2014)

Too late, Dieselpilot---but I wish I had thought of that. Will try to remember for next time.---Brian


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## dsage (Feb 8, 2014)

Hi Brian:

 Fixing the cam timing issue is going to make your carb work better too. As it is (was) with the exhaust open for most of the intake stroke you probably had very little vacuum to a) open the valve and b) suck fuel through the carb.

 Intake valve spring may need some tweaking now too.

 This should be interesting. Watching with great interest.

 Thanks

 Sage


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## Brian Rupnow (Feb 8, 2014)

This is as good as it gets around my house!! The angle is correct, and I'm pretty sure the holes are in the right place for my #4-40 screws. I know it fits the "spigot" on the brass gear because I've had it on there. Lord, Lord, I wish I had read-outs for this kind of work. It is SO easy to lose track of where you are and keep having to go back to "center" things under the quill!!! Barring unforeseen disasters and broken taps, I will have the cam and gear back together tomorrow morning.--Thanks for looking.---Brian


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## Brian Rupnow (Feb 9, 2014)

Very pleased to announce that everything is back together, and this time the exhaust valve really is operating exactly as it is supposed to. Begins to open at 50 degrees before end of power stroke (which is almost exactly 1/8" before piston reaches bottom dead center). Opens fully and stays open during exhaust stroke, and closes fully about 20 degrees into the intake stroke. Even with all of the mating surfaces on the plate framework located with dowel pins the engine has stiffened up a lot after complete disassembly and re-assembly, but I expected that to a degree. It is nowhere near as stiff as it was after first assembly. Before I try to run it again I am going to make a new adapter to go between the carburetor and the intake manifold. Right now there are two adapters in there, which I will replace with one much shorter adapter. I also want to do something about the routing of my gas-line so I don't have to resort to tying it up out of the way with a string, as seen in the last video. One really good sign is now that when I turn it over slowly with the electric drill or by hand, the intake valve makes a noise. Its a strange sound, kind of a combination of a gooses honk and a pigs fart!!! That indicates that the exhaust valve is sealing well and the rings are sealing well, and that atmosphere is being sucked in through the intake valve and manifold.


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## Brian Rupnow (Feb 9, 2014)

I got rid of all the plumbers nightmare between the carb and the inlet block.-That shortened things up considerably!!


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## Brian Rupnow (Feb 10, 2014)

The best laid plans of mice and men--I really couldn't find a good way to run the gas line from where it came through the backplate to the carburetor. I was terribly afraid that the flexible gas line would get caught up in all of the flailing pivot links and connecting rods and shower me with blazing gasoline. I plugged the original exit from the tank, and drilled and tapped one of the endplates 1/4"-20. That allowed for a new rigid gas line. I had a go at bending some brass tubing, but after the third kink I gave up in disgust and used some solid brass that I had to make 1/4" diameter "lines" with a .080 hole drilled full length. It isn't really apparent in the picture but it clears the pivoting link by about 1/4". I think I will put a support on the brass tube which connects to the flexible gas line and tie it back to the base with s 3/16 rod just to prevent any vibration before I start the engine again.


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## Brian Rupnow (Feb 10, 2014)

Probably something simple like this to support the gas line, whittled from aluminum.


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## Brian Rupnow (Feb 11, 2014)

That ought to keep my gas line from bouncing around!! Now if I can just find time to get everything out to the main garage for a try-out. I'm working on a design contract right now where I have to spend 8 hours a day "on-site" so it doesn't leave much time for playing with little engines. Oh well, its supposed to warm up to 0 degrees on the weekend.


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## robcas631 (Feb 12, 2014)

Brian,

Perhaps the exhaust needs to be "tuned?"  Look at the muffler on my moped, aka now 50 MPH motorcycle. 

Perhaps this helps?


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## Brian Rupnow (Feb 12, 2014)

Well, the little mouse is ready to ROAR!!! Now it's just a matter of scraping together an hour of time to try it out. Working away from home certainly cuts into one's play time. This weekend is supposed to be a big birthday party for various grandchildren at my house, and I know I'm going to get press-ganged into a big house "slick-up" before everybody shows up.--Still an all--I think I can steal an hour to try this thing out. I soon have to finish with it because I'm starting to hear hints of disapproval about the number of hours I spend down in my workshop----which is not a good thing.


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## Swifty (Feb 13, 2014)

robcas631 said:


> Brian,
> 
> Perhaps the exhaust needs to be "tuned?"  Look at the muffler on my moped, aka now 50 MPH motorcycle.
> 
> Perhaps this helps?



Brings back memories of racing 2 strokes in my 20's, we used expansion chamber exhausts, very noisy things. The neighbours certainly knew when I was tuning it up.

Paul.


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## robcas631 (Feb 13, 2014)

Brian,

 I can relate regarding spending too much time in the shop. However, I am rehauling a steam engine for my father and must finish. I will post results at a later time.

 I look forward to seeing the engine run! Also, I hope you have lots of fun with your grandkids!


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## Brian Rupnow (Feb 13, 2014)

Tonight I took another kick at the can. The little engine is much happier with the new cam, but still refuses to settle in at a nice slow speed. It will run all day at mid range to high speeds, but it peters out and just quits at low speed. The internal friction and bearing friction has faded away to almost nothing with all of the running it has been doing, so its not dyeing out from frictional load. I'm running out of ideas here. I mix 2 cycle oil with my Coleman fuel to keep the Viton O-rings lubricated, and as I ran the engine tonight I'm getting a lot of oil dripping out of the cylinder on one side, very little out of the cylinder on the other side. I will pull the piston out of the leaky side on the weekend to see if perhaps the ring is damaged. (I do have a spare). I have good compression, but it does leak down if I turn it by hand and hold it on compression. I doubt very much that it is leaking at the valves, or I would be able to hear it hissing at the carb or exhaust pipe. There is so little that you can adjust on these engines. Basically it comes down to ignition timing or carb needle valve setting, and I have tweaked both of them in both directions with varying success, but still no nice idle. I am going to do a little research and see if I can find anything enlightening on ignition timing. I have always used about 15 to 20 degrees advanced timing on my hit and miss engines, but I'm not sure if that is right for an engine like this or not.


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## Brian Rupnow (Feb 14, 2014)

I think this is as good as it gets for now. If I do add a bit more flywheel and it smooths out any more, I will post about it, but for now I think that the engine runs, it stays running and I can consider it a successful design.---Brian


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## Brian Rupnow (Feb 14, 2014)

I discovered that my timing is far more extreme than I thought it would have to be. Turning it over by hand and stopping when the spark occurs, it is firing about 38 degrees before top dead center. I measured how far it was from the open end of the cylinder to the end of the piston skirt with my Vernier caliper/depth gauge at the point where the spark occurred, and then measured again when the piston was at top dead center, and there was exactly .125" difference. When I set up that distance on the CAD model, and measure the angle of the crankshaft, it still has to travel 38 degrees to rotate to bring the piston fully to top dead center.


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## Philjoe5 (Feb 14, 2014)

Brian,
That's fantastic.  It runs great and without a massive flywheel to smooth out the ignition cycles!

Cheers,
Phil


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## Brian Rupnow (Feb 15, 2014)

Philjoe--Looks are somewhat deceiving. There is a 4" diameter x 1.5" wide flywheel on the far end of the crankshaft---You just can't see it in the video. It sets directly below the gas tank.---Brian


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## robcas631 (Feb 15, 2014)

Brian,

 I'm sure you will "fine" tune it! What you have created IMHO is a success!


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## Brian Rupnow (Feb 15, 2014)

Thanks Robcas. Today I am doing some design work for a customer, getting a haircut, helping my wife clean house for a big grand-childrens birthday party, and in my spare time making an extra flywheel to add onto the back of the existing flywheel to see if it helps smooth things out a bit!!!


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## Brian Rupnow (Feb 15, 2014)

So, just like the army when it goes to bed, this is the last post. It's been an interesting run, and although there has been some frustration, it has went pretty smooth for a 8 week long design, build, and run cycle. The only thing I would change on the drawings is to make the flywheel 1 1/2" thick, instead of what the drawing in the download package calls for. The carb I posted which was developed by Chuck Fellows will work, although it may require more fooling with to make it work properly than it is worth. Chuck has since abandoned that design and is moving forward on newer, better designs for carburation. I know that Gail in New Mexico is building this engine from my plans, only he is doing his at half of my original scale. Gail tells me that he has found no mistakes in the drawings, and he is adding a few of his own personal touches to it as he builds it. If you decide to build this engine, please let us hear about it, and please have fun.---Brian


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## Brian Rupnow (Feb 15, 2014)

Youtube link to the final video.
 [ame]http://www.youtube.com/watch?v=X82vlFazAuU[/ame]


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## BaronJ (Feb 16, 2014)

Brian Rupnow said:


> Youtube link to the final video.
> http://www.youtube.com/watch?v=X82vlFazAuU



Nice video Brian.  Sure seems to run a little better.
I did notice that the points were sparking well.  I thought the capacitor was supposed to suppress that.


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## johnny1320 (Feb 16, 2014)

Nice job Brian, I am thinking that with the engine being  an oppossed piston engine that the compression ratio is higher than anticipated casuing you to need a heavier flywheel.


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## Fluffy (Feb 16, 2014)

A great job Brian,
Thanks for the very interesting series. I have enjoyed it from start to finish, well done.
Regards,
Don.


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## Brian Rupnow (Feb 16, 2014)

Liar Liar--Pants on fire---I did make one more video. I decided I couldn't spend the rest of my life demonstrating this engine with one hand hanging onto the throttle to keep it from running away with itself. So---This morning before all the birthday guests arrived I whittled out a brass bracket which attaches to the air intake side of my Traxxas carb (Loctite, as a matter of fact) with an idle adjusting screw and a tension spring to hold the throttle arm where I want it to be. Now I CAN make a video without my big ugly hand in the way. The engine is quite happy running at this speed, and if the gas tank wasn't so small I think it would set there and happily run all day.--The birthday party was enjoyed by all, our three kids, a daughter in law, a prospective son in law,and our three grandkids all managed to come home, much ice cream cake was eaten, candles blown out, and "Happy Birthdays" sang by all hands.


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## Philjoe5 (Feb 16, 2014)

Great job Brian.  I can smell the exhaust fumes here.  It was educational following along.  When you post the plans I'll be sure to download a set for a future project

Cheers,
Phil


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## Brian Rupnow (Feb 16, 2014)

Philjoe--You missed it--The plans are back at post #192. The only change to the posted drawings is the flywheel, which should be 3 times thicker than what is shown.


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## Brian Rupnow (Feb 16, 2014)

For any of you who may have downloaded the plans--This is the flywheel you will need to get this monster idling like the last video posted.


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## Philjoe5 (Feb 16, 2014)

Thanks Brian, I did manage to miss it.  I was looking in the downloads section.

Once again, a great job and thanks for sharing your work with us

Cheers,
Phil


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## Art K (Feb 16, 2014)

Brian,
Looking good, glad to see you sorted it out. What do you figure the compression ratio is? to need that much flywheel. Purrs like a kitten!
Art


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## Brian Rupnow (Feb 17, 2014)

Compression ratio is 5:1---I don't think it needs it because of massive compression. It has more to do with all the pivoting joints and levers. This is not an engine that coasts very well, even with no spark plug in place.


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## cfellows (Feb 17, 2014)

Brian Rupnow said:


> Compression ratio is 5:1---I don't think it needs it because of massive compression. It has more to do with all the pivoting joints and levers. This is not an engine that coasts very well, even with no spark plug in place.


 
 Nice finish to the project, Brian.  I'm beginning to learn that you just can't have too much flywheel.  I think the lower compression ratio is also key to getting the engines to idle better.  

 Chuck


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## johnny1320 (Feb 17, 2014)

Wow 5:1 that is definitely not too high, seems kind of low to me


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## gg89220 (Feb 17, 2014)

bonsoir
j'aimerais telecharger les plans ,j'ai regardé au poste 192 mais je ne vois pas de lien ?? je ne comprend pas ,comment faire


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## Brian Rupnow (Feb 17, 2014)

gg89220 said:


> bonsoir
> j'aimerais telecharger les plans ,j'ai regardé au poste 192 mais je ne vois pas de lien ?? je ne comprend pas ,comment faire


 http://www.mediafire.com/download/l5kw3n56pexauty/RUPNOW_OPPOSED_PISTON_ENGINE_DRAWINGS.zip


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## Brian Rupnow (Feb 17, 2014)

I don't speak any French.--What is this fellow asking me about in post #307? --It seems he may be having problem with the link, but the link works fine for me--I just tried it. Can someone help this fellow, please.---Brian


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## sssfox (Feb 17, 2014)

I'm not good at French either, but he says "I would love the plans, but I looked at post 192 and didn't see the link.  I don't understand.  What do I do??"

Don't have a clue what the problem is.


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## metal89 (Feb 18, 2014)

_Pour gg89220: aller à cette adresse et télécharger. Sinon MP pour metal89 sur usinages.com
http://www.mediafire.com/download/l5kw3n56pexauty/RUPNOW_OPPOSED_PISTON_ENGINE_DRAWINGS.zip_
_Le plus simple est de poster en français puis d'ajouter la traduction automatique donnée par Google translation_

--> To gg89220 go to the adress below and download. If any problem send me a PM  on usinages.com. Next time use google translation it helps a lot
Regards​


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## gg89220 (Feb 19, 2014)

brian 
I found the problem in post 192, the translation into French by the browser removes the link. 
I downloaded plans 
thank you


_metal89 affaire resolu merci


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## Niels Abildgaard (Feb 21, 2014)

Opposed piston engines seem to be a dead end,but they are fun to speculate.

I have personally done it for 30 years.

http://archive.is/zHnXJ

and a later version

http://archive.is/s7gTY

If there is interest in more pictures let me know.


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## Brian Rupnow (Feb 21, 2014)

Every night this week I have come home from the temporary "on site" engineering contract I am working and started this engine. This is the part of building a new engine that I always have mixed feelings about. Its coming down from a big "high", pleased that the engine runs as well as it does, and relieved that I don't have to spend every spare moment of my life machining something.---But a bit lost as to what to do now that the engine is finished. I get totally burned out every time I build an engine. I don't want to build anything for a while now--just live vicariously by reading everybody else's build posts. The trouble with building successful engines, is that ordinary engines become, well, commonplace. This tends to push me towards more exotic and "different" engines. All I really want right now is for this seemingly endless winter to be over and some warm weather. I know I will build something else---but hopefully not for a while now.----Brian


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## Brian Rupnow (Feb 22, 2014)

One of the things I discovered, that I must tell you about. The way I made the gas tank filler cap, by using a threaded pipe nipple for the gas tank filler spout and a modified threaded pipe cap for a screw on lid works great. It gives you a much larger opening and a much better chance of filling the tank with gas without overfilling it, but there is one caveat. On my other engines, I did not put a vent hole in the fuel filler cap. I just loosened the cap half a turn to run the engines and that worked fine. On this new style of cap, the screw on cap has an internal tapered pipe thread, to match the outer pipe thread on the pipe nipple. The cap is heavy enough that with engine vibration, it will screw itself closed to the point where the engine can no longer draw fuel from the tank because of vacuum lock.--This was driving me crazy. My engine would run good for 5 minutes, then die out for no good reason.--Each time, I would check the filler cap on the gas tank and think "Huh!!! I must have forgotten to loosen that a bit after I filled it.!! Finally I figured it out---I did loosen it each time, but it would vibrate closed. I solved the issue by drilling a 0.039" hole through the center of the cap.


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## wagnmkr (Feb 22, 2014)

Brian, you deserve a rest ... your last engine was a pretty quick finish.

Has much of your snow gone in these milder temps?

Before you know it you will be out and about in your yellow hot rod.

Cheers,

Tom


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## BaronJ (Feb 22, 2014)

Brian Rupnow said:


> One of the things I discovered, that I must tell you about. The way I made the gas tank filler cap, by using a threaded pipe nipple for the gas tank filler spout and a modified threaded pipe cap for a screw on lid works great. It gives you a much larger opening and a much better chance of filling the tank with gas without overfilling it, but there is one caveat. On my other engines, I did not put a vent hole in the fuel filler cap. I just loosened the cap half a turn to run the engines and that worked fine. On this new style of cap, the screw on cap has an internal tapered pipe thread, to match the outer pipe thread on the pipe nipple. The cap is heavy enough that with engine vibration, it will screw itself closed to the point where the engine can no longer draw fuel from the tank because of vacuum lock.--This was driving me crazy. My engine would run good for 5 minutes, then die out for no good reason.--Each time, I would check the filler cap on the gas tank and think "Huh!!! I must have forgotten to loosen that a bit after I filled it.!! Finally I figured it out---I did loosen it each time, but it would vibrate closed. I solved the issue by drilling a 0.039" hole through the center of the cap.



Brian, if you recall I did ask if you had missed putting a vent hole in the cap. :hDe:


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## Brian Rupnow (Feb 22, 2014)

BaronJ--Mea Culpa----Brian


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## Brian Rupnow (Mar 1, 2014)

I have discovered something about the engine that gives me pause for thought. On all of my other engines with Viton O-rings, when I turn them up to compression stroke by hand, there is absolute silence at the open end of the cylinder, and the compression does not fade away. On this engine, I can hear air hissing as it escapes past the rings, and the compression does gradually die away to nothing. It is definitely escaping past the rings, not the valves. Now why would that be?--I have a couple of thoughts, but they are only vague, semi formed thoughts at the moment. Firstly--Was the inner bore of the cylinder a bit rough, to the point where it "sanded away" some of the outer diameter of the current O-rings? If so, the bore should be smooth enough by now after all this running to allow a new set of O-rings to be installed and not cause any wear on their outer diameters, thus giving a much better seal.----Did I turn the grooves in the pistons a bit too deep?---I don't think so. if they aren't turned to the depth given, it makes the engine so stiff that it won't "turn over". Do I perhaps need two rings on each piston? --Well, yes, that is possible, but it seems unlikely, as my other engines have only one ring, and they seal 100%. The engine runs good now, and I may not spend any more time on it, but still, that escaping air bothers me. I guess the cheapest potential fix is to try a new set of rings on it and see what that does. I see the plans I posted for this engine have been downloaded 157 times, so I really hope someone else steps forward and builds this engine and posts about their progress.----Brian


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## BaronJ (Mar 1, 2014)

Hi Brian,

Has it occurred to you that the pistons may not actually be running exactly parallel to the bore.  If you draw an arc from the centre of the pivot pin you will see that it follows a curve.  This will cause the piston to want to rock up and down across its length.  I suspect that this is where you are getting leakage.


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## Brian Rupnow (Mar 1, 2014)

BaronJ said:


> Hi Brian,
> 
> Has it occurred to you that the pistons may not actually be running exactly parallel to the bore. If you draw an arc from the centre of the pivot pin you will see that it follows a curve. This will cause the piston to want to rock up and down across its length. I suspect that this is where you are getting leakage.


Not so Baron.--Although the pivot arm swings in an arc, there is a connecting rod between the piston and the end of the pivot arm which is connected at each end with a round pivot pin.--This allows the piston to ride perfectly parallel to the bore of the cylinder.


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## BaronJ (Mar 1, 2014)

Brian Rupnow said:


> Not so Baron.--Although the pivot arm swings in an arc, there is a connecting rod between the piston and the end of the pivot arm which is connected at each end with a round pivot pin.--This allows the piston to ride perfectly parallel to the bore of the cylinder.



Ah yes I see the short connecting rod. :wall:

Just a wild thought.
By the way, where are the drawings ?  I probably missed if you said.

Sorry I should learn to read...  Found the link.


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## Brian Rupnow (Mar 1, 2014)

Baron--The download link is on post #192 of this thread.---Brian


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## sssfox (Mar 1, 2014)

Brian,

With a Viton ring, if it is sized correctly, there is a seal completely around the piston, both behind and in front of the ring.

With a cast iron ring, there is a gap behind the ring and there is the gap between the ends of the ring.  All of these places allow a little leakage.  Your making the gap a little large doesn't help either.  You may have fixed the last one when you made a two-piece piston.

Also, I don't know how much time you have on it, but the piston may not be completely seated in the cylinder.

While all of these issues may seem like problems, my experience has been that none of this matters when an engine is running. Everything happens too fast.

One other thought, did you seal the joint between the two halves of the piston?
I'm not sure of your design, but air could be leaking around the screw that holds the pieces together.

Steve Fox


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## Brian Rupnow (Mar 1, 2014)

sssfox--I think you are mixing my post up with Chuck Fellows post. I am using a Viton ring, on both pistons. Both pistons are one piece construction. The joint between the cylinders and the center block is also sealed with a Viton o-ring, and there is no leakage there.--Brian


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## sssfox (Mar 1, 2014)

Brian,

You are correct.

Too many posts, too little time.

Steve Fox


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## Brian Rupnow (Mar 3, 2014)

For any of you who enjoyed this thread, make your way over to the website in this link and you can see this engine built to 1/2 scale by an excellent craftsman in New Mexico.
http://www.modelenginemaker.com/index.php/topic,3035.0.html


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## Brian Rupnow (Mar 5, 2014)

I am setting here in the middle of a construction zone, while the home renovation guys work around me. They finished the new laminate floor in my office yesterday, so I was able to get my computer and all of its associated bits hooked back up in my office. The office and main basement are all newly painted and all of the flooring has now been installed. They have done a very impressive job. While snooping around yesterday through all of my boxes of engine parts and strange objects, I see that when I got the original two Viton O-rings for the opposed piston engine, I actually purchased four, in case I destroyed one while installing the pistons into the cylinders. That's a good thing, because once the construction moves on and leaves me in peace, I will put the two new rings onto the pistons and see if that cuts down on any of the compression leakage. This is a fairly major job, because like the cam gear, the whole engine must be disassembled to get the pistons out of the cylinders. I have no desire to do any more engine building at the moment, but would like to move back onto my "marble automation" and finish it up so I can have a video of it running, being powered by the opposed piston engine. I have to finish the return ball tracks on it and mount  few more "gadgets" before I consider it finished. I also want to try a new condenser on the engine, because as many people pointed out, there is a lot of arcing going on at the ignition points. --Brian


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## Brian Rupnow (Mar 20, 2014)

Since I had my video stuff all out, and was testing carburetors this morning, I thought I would try my George Britnell clone carburetor on the opposed piston engine to see how it works there,. Works a treat!!!---Brian


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## dsage (Mar 21, 2014)

Hi Brian:

 Yes, it seems to run really well on that carb. I 'm glad you found one that works. The engine is a realy nice piece of work.
 Did George post the plans for that carb on the forum or did you make it from some of his plans that you had previously?

 Good stuff

 Sage


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## Brian Rupnow (Mar 21, 2014)

George has posted the plans on this forum. Its a one page sheet, titled (I think) Air Bleed Carburetor. I Found it rather difficult to get my head around until I modelled the parts and assembled them, because there is no assembly drawing on the one page sheet. I had to resort to doing an internet search for videos of George's 4 cylinder engine running with that carb on it to see how it went together. Then George found out what I was doing and sent me four or five pictures of it installed on his engine, which was very kind of him. The problem for me was that George's original carb plans had a .260" bore to feed four cylinders. I had to dick around with the plans and reduce it to a .156 bore to suit small one cylinder engines. In doing so, I found that it was more suitable to have the air bleed screw accessible from the top side of the carb than from the bottom. Over on my very recent thread on building the carb, I posted a download link to all of the modified drawings as pdf files.----Brian--This is George's drawing.
http://www.homemodelenginemachinist.com/downloads/files/4_CYL_OHV_SHT_J.pdf


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## dsage (Mar 21, 2014)

Thanks Brian:

 You're a hard guy to keep track of having multiple threads on the go. I'm going to have to check on you more often 

 Nice work on the Carb. Looking forward to following your next adventure. Your reporting style makes it interesting to follow along.
 Good work.

 Thanks

 Sage


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## robcas631 (Mar 23, 2014)

Brian Rupnow said:


> Every night this week I have come home from the temporary "on site" engineering contract I am working and started this engine. This is the part of building a new engine that I always have mixed feelings about. Its coming down from a big "high", pleased that the engine runs as well as it does, and relieved that I don't have to spend every spare moment of my life machining something.---But a bit lost as to what to do now that the engine is finished. I get totally burned out every time I build an engine. I don't want to build anything for a while now--just live vicariously by reading everybody else's build posts. The trouble with building successful engines, is that ordinary engines become, well, commonplace. This tends to push me towards more exotic and "different" engines. All I really want right now is for this seemingly endless winter to be over and some warm weather. I know I will build something else---but hopefully not for a while now.----Brian


 

Well said about getting burned out. I carve, paint and am designing a new boat for the summer.


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## Brian Rupnow (Mar 23, 2014)

I am thinking of making some modifications to this engine. I would like it to idle down as slowly and run as consistently as the Webster does. I think part of the problem (possibly a large part) is the small diameter mega thick flywheel. The current flywheel is 3.875" diameter x 1.625 thick. This adds up to a weight of 5.42 pounds. I am considering adding a 3/4" thick x 6" diameter ring to the outer diameter of the original 5/8" thick flywheel, which will give a total weight of about 5.5 pounds, without the two 1/2" thick pieces that were added when I was trying to get the engine to run. This weight will be positioned much closer to the crankshaft bearing and the good part is that the weight will be spread over a larger diameter, which will make the inertial effect of the flywheel much greater than it currently is. Of course this means that I will have to move the gas tank, cut the extension off the back side of the baseplate, and add a couple of "risers" under the baseplate so the flywheel will clear the table.


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## dsage (Mar 24, 2014)

Hi Brian:

 I've forgotten what's on the flywheel side of the vertical plate but just to give it a try first, why not place the engine along side the edge of the table and put a temporary large diameter flywheel on it hanging below the table top and see what difference it makes. 
  Adding only and extra .1 pounds or 2% (your calculations) doesn't sound like it would make much difference. I'd hate for you to cut and hack it only to find it make little difference.
 Once you know how much weight you need maybe you can hollow out some of the one you have and pour some lead into it.

 Sage


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## Brian Rupnow (Mar 24, 2014)

Dsage--The largest flywheel I could use was 3 7/8" diameter, because the baseplate extended out beyond the main backplate. Today I have removed the flywheel and trimmed the extended baseplate flush with the back side of the main backplate. Now I can put a larger flywheel on it, but the flywheel will extend down lower than the baseplate. That is why the pinkish color skids are bolted to the bottom of the baseplate---To get the flywheel up high enough to not hit the table. I think increasing the flywheel diameter from 3 7/8" to 6" is going to make a big difference, even though the overall weight will be the same. Later this week I will know.


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## Brian Rupnow (Mar 24, 2014)

Poor little guy---Kinda looks like a bulldog pup with its tail docked!! I removed all the flywheels and trimmed the baseplate off with my bandsaw, then set the whole engine up on an angle plate in the mill and milled the remaining bit of plate off flush with the main backplate. The two plain flywheels will be discarded. The flywheel with the center boss on it will receive a ring of mild steel 6" diameter x 3/4" thick added to its outer diameter. I managed to trade a bit of mechanical design for a laser cut ring of 1018 mild steel, but I won't have it until Wednesday. Tomorrow I will make up the two new pieces which fit under the baseplate.


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## Brian Rupnow (Mar 25, 2014)

Now I have room for a REAL flywheel!!! (That's the original flywheel shown on there). At the very last minute I decided not to but a taper on the end of the "bunks" under the baseplate. It might have looked a bit nicer, but I wouldn't have been able to use a C-clamp on it to hold it in place on my reference desk, and now that I have cleaned the desk up and put a new top on it, I didn't want to drill any holes in it.


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## gus (Mar 26, 2014)

Please post video. With a bigger flywheel slow speed iding would possible?? 

Pulling out the last few lazy bones.


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## Brian Rupnow (Mar 27, 2014)

Gus, the effectiveness of a flywheel is very much tied in to the diameter. According to what I have read 90% of the flywheels effectiveness is concentrated in the outer rim of the flywheel. The larger that rim is in diameter, the more effective the flywheel will be. All single cylinder four stroke engines have an inherent "flaw" in their design. Namely, once the cylinder has fired and the piston has reached the bottom of the stroke, there is absolutely no outside forces to bring the piston back up to top on the exhaust stroke, down again on the intake stroke and up again on the compression stroke. For that a flywheel is necessary. If the flywheel is too light or too small in diameter to carry out this work, then the engine will stall before it can go through all of the necessary moves to let it fire again.--And this ties in directly to how low a speed the engine can run at. A small diameter but very thick flywheel like I originally had on this engine is nowhere near as effective as  a flywheel of the same weight, but thinner with a larger diameter.--Brian


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## Brian Rupnow (Mar 27, 2014)

This morning I decided to pull the pistons out of the engine and check the condition of the rings. You may remember that on an earlier post I said I could hear air escaping from the open end of the cylinders when turning the engine by hand on the compression stroke. I surmised that perhaps the inside of my cast iron cylinders might not have been a "mirror finish" and consequently worn some material off the outer diameter of the Viton O-rings during the "break in" phase of running the engine. I pulled the old rings out, and although I couldn't see any specific damaged areas, the whole ring looked slightly smaller than one of the new "spares". It is not much difference. The ring on the right side of the picture is brand new, the ring on the left is one of the worn ones I removed form the engine. HOWEVER--When I reassembled the engine, it is much stiffer to turn over by hand, and there doesn't appear to be any air escaping past the open end of the cylinder on the compression stroke. Since I didn't remove the crankshaft nor bearing supports, this new "stiffness" can only be attributed to the fit of the rings into the cylinder.


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## gus (Mar 27, 2014)

Brian Rupnow said:


> Gus, the effectiveness of a flywheel is very much tied in to the diameter. According to what I have read 90% of the flywheels effectiveness is concentrated in the outer rim of the flywheel. The larger that rim is in diameter, the more effective the flywheel will be. All single cylinder four stroke engines have an inherent "flaw" in their design. Namely, once the cylinder has fired and the piston has reached the bottom of the stroke, there is absolutely no outside forces to bring the piston back up to top on the exhaust stroke, down again on the intake stroke and up again on the compression stroke. For that a flywheel is necessary. If the flywheel is too light or too small in diameter to carry out this work, then the engine will stall before it can go through all of the necessary moves to let it fire again.--And this ties in directly to how low a speed the engine can run at. A small diameter but very thick flywheel like I originally had on this engine is nowhere near as effective as  a flywheel of the same weight, but thinner with a larger diameter.--Brian



Hi Brian,
You are right.
I lost all my notes on Ingersoll-Rand flywheel designs and counterbalancing .
My China Boss called. While cutting cost ,they reduce compressor f/wheel size and weight and got into electric motor overloads with compressor running at same rpm. Gave them this simple formula -------w x r. That is to calculate and compare both old and new f/w wrs. New wheel redone and motor full load current back to normal. 
Plan to read up on locomotive balancing.Just to see where we are in flywheel
selection for our i.c. engines.


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## Brian Rupnow (Mar 28, 2014)

The larger diameter flywheel made quite a big difference, just as I thought it would. Perhaps it isn't running as slowly as the Webster can, but there are a lot more moving parts to this engine. My total flywheel weight is about the same as it was before when it was 3 7/8" diameter x 1 5/8" thick, only now it is 3/4" thick x 6" diameter. I will not be posting any more about this engine until I find something for it to actually power.---Brian


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## Path (Mar 28, 2014)

And thanks for the update .. it has been a real education following your progress.

Keep-um coming! 


Pat H.


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## Brian Rupnow (Mar 29, 2014)

Since I am having a very boring morning, and its still to cold to play outside, I have arranged a spectacle for your amusement. I have added the engine, the clutch, and the much beloved marble machine into a mechanical daisy chain, just to see what would happen. The marble machine is not in top form, as I seen it drop a couple of balls and because I have never completed the ball return track, but it runs quite well enough for a fun demonstration.--Enjoy!!!


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## cfellows (Mar 29, 2014)

That extra weight on the flywheel made a huge difference.  I could sit and listen to that engine idle all day long, such a sweet sound!

 Chuck


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## wagnmkr (Mar 29, 2014)

Well Done Brian!! I agree with chuck ... asweet sounding engine for sure.

Cheers,

Tom


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## gus (Mar 30, 2014)

Your engine ran smoothly with the bigger/heavier flywheel. 
Bought " Mechanical Engineering Design'' by Shigley from Amazon to read up
on flywheel designs.Hopefully all my future flywheels will have the best weight and diameter to run engines smoother.
May also emailed ex-IR colleaques on the formula used for air compressor flywheels.


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## Brian Rupnow (Apr 21, 2014)

Just a final post to end off this thread in case someone finds it in the future, The engine ran well, but the crankshaft was not straight, and consequently the aluminum wheel on the front of the engine danced around in a very unsightly manner. I have removed the crankshaft and replaced the "bad end" and now it runs true.


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## BronxFigs (Apr 22, 2014)

Loved the whole thread and documented engine build.  I especially liked the frustrating, "fails".  When somebody who is brilliant, fails, and then solves the problems....we all benefit.  We learn what not to do.

I will never know what Mr. Rupnow knows.  But he, along with some others ( G. Britnell, S. Huck, C. Fellows, etc. etc.) on this forum have set the high-water mark.  Their goal is, and will always be....excellence without compromise.

Good teachers to have in this 'school'.  I wish I had these kind of guys around me when I was growing up.


Frank


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## ShopShoe (Apr 22, 2014)

So,

Foot-in-mouth disease. I asked about this under load (in the "wonky crankshaft" thread) and you did it and I missed it.

I still think you get double thanks for keeping after this project to make it better and better with each tweak.
--
ShopShoe


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## wagnmkr (Apr 22, 2014)

Very Well Done Brian. The whole engine seems to be smoother now so the bearings must have made a difference as well.

After all the mods and trials and tribulations you went through, you deserve a break.

Again, I really enjoyed this thread and appreciate all your efforts.

Cheers,

Tom


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## Brian Rupnow (Feb 26, 2015)

To revive an old thread and cry "mea culpa" to all who suggested an outboard support for the cantilevered stub shafts. I haven't really ran the engine much at all since I built it and straightened the crankshaft. Last week when I was searching for an engine to run the model buzz saw I built, I noticed a strange phenomenon. Although the cantilevered stub-shafts didn't visually deflect when the engine was running, they must have at some level, because the bolts through the main backplate which anchored the stub shafts in their pockets in the main engine backplate would loosen off after about 10 minutes running, no matter how much they were tightened.Then the cantilevered stub shafts would indeed move all over the place. This presented a major pain in the butt, because I had to remove the large diameter flywheel on the back side of the engine to get at the bolt heads and re-tighten them. After removing the flywheel twice to tighten the bolts, I decided that yes, everyone who suggested an outboard support for the cantilevered shafts was right and I was wrong. So--I redesigned the removable front plate and added a couple of "extensions" with pockets to hold the extended end of the no longer cantilevered stub shafts. I made new, longer stub shafts and drilled the extended ends for #8-32 bolts. This actually entailed a couple of days work and almost total disassembly of the engine, however the engine is now solid as a rock when it runs, and I filled up a couple of horribly cold winter days with something to do.


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## Brian Rupnow (Jan 2, 2020)

I see that Barnbikes has sent me an article about opposed piston engines. I designed this one in 2008 and posted about it here. It is a sweet running engine, and has a lot of very interesting parts.---Brian


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