# It will not run.....



## Jmccrack (Jul 19, 2018)

Help guys this is not rocket surgery! It will almost start but not quite. It should be simple. One side at TDC steam valve let’s steam into the top of that chamber drives the piston down . The other side BDC the steam valve let’s steam into the bottom of that chamber and drives the piston up. I even made 2 polycarbonate top covers so I can see the valve action. When I put air in the system the 2 cylinders seem to be fighting each other. Any help would be appreciated. BTW before I painted it I had it running like a charm. And each side runs well on its own.


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## XD351 (Jul 19, 2018)

Is the valve sealing ?  If you are getting admission into both ends of the cylinder at the same time i would suggest the valve is not sealing or there is a problem with the casting ? Maybe a blowhole connecting both ports ?  Maybe the valve is not long enough , you want one port  just closed as the other just opens .
Looking at the top photo  you have the crank set at  180 deg apart  but it looks like the eccentrics are not set 180 apart to each other.
Try to set one cylinder up and get that running ( it will turn the dead cylinder over no problems then once you have one working just copy what you did on the other . 
At bdc you want the port closest to the crank just opening and the the port closest to the head just closed , you change the valve timing by moving the eccentric position on the crank and you change the valve position by adjusting the valve position  on the valve rod .
Keith appleton made a video of setting the valve timing on a steam engine and you can view it on his youtube channel.
HTH ! 
Ian .


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## Jmccrack (Jul 19, 2018)

I can get one or the other running just fine. When I pipe them together no joy. I just came back from the shop and I got them to run together but very rough.m


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## rlukens (Jul 19, 2018)

I can't prove this without thinking way to hard, but I suspect if you'll change the "timing" between A and B to something less than 180, things will happen. Give it a shot.


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## XD351 (Jul 20, 2018)

I'm surprised that the crank is of 180 degree design , the few twins i have made are all 90 degree cranks so they self start .
If you can get each side running separately and smoothly ( and both in the same direction ) it should run  but to get each side running by itself you would have to disconnect the supply manifold so maybe the issue lies there ? 
If the valve timing is out by even a small amount the cylinders will fight each other and it won't run or at best will run very roughly .


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## Jasonb (Jul 20, 2018)

Looking at the top picture your cranks are 180degrees apart but the levers actuated by the valve rods are in the same position, I would expect them to be either side of vertical so steam goes into one end of first cylinder and opposite end of the second.

Are the two grub screws that can be seen in the brass either side of the flywheel hub holding the eccentrics, if so that confirms you have timing issues


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## XD351 (Jul 20, 2018)

What would be the ultimate is some video of the engine being turned over by hand and showing the valve operation .


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## spacy (Jul 20, 2018)

I agree with Jasonb looks like the eccentrics are set the same(ish) so the engines will try to run in opposite directions, best to set each engine individually at TDC with a 90 degree lag whilst rotating the flywheel the same way that way you can be sure they are both going the same way.


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## dkwflight (Jul 20, 2018)

Hi
I have to say the crank timing is a bit off.
Set the crank to 90 degrees from each other and start over
Dennis.


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## oldboatguy (Jul 20, 2018)

Jmccrack said:


> View attachment 102853
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> 
> View attachment 102854
> ...



Hello,

You have two double acting steam cylinders which are coupled at 180 degrees apart. What you should do is couple them 90 degrees apart that way you will have a power stroke every 90 degrees and no possibility of a dead center. When you couple them at 180, your timing must be absolutely perfect, the humidity must be right, and the moon must be in the right phase in order for them to actually run and not inadvertently oppose each other. I think Robert Lewis Stephenson learned this back in the 1830's in designing steam locomotives. That 90 degree offset was used from then on until steam was replaced by diesel.
Tandem marine engines were also set at 90 degrees. Triple expansion ones were at 120 degrees so that there was always a power stroke going on all the way around the circle.

Hope this helps,
Oldboatguy


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## Jmccrack (Jul 20, 2018)

Guys.THANKYOU!!  I had no idea. When you look at the drawing I have clearly the cylinders are running at 180 deg not 90. What you are all saying makes so much sense. So back to the shop. I will take the main shaft out and cut a flat at 90 deg. So I can adjust the counter weight at 90 deg to each other not 180. Again thanks. This is my first 2 cylinder.


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## Jmccrack (Jul 20, 2018)

I just have to say again this forum is great for help like that. “ It takes a village”


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## johwen (Jul 20, 2018)

Jmccrack said:


> View attachment 102853
> 
> 
> View attachment 102854
> ...


Hello,
I would think the timing of the valve eccentrics are out of phase they should be set 180 degrees apart also. Cheers. john


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## Charles Lamont (Jul 21, 2018)

It is hard to tell from the photos how you have made provision for the valves to float vertically on their spindles to allow them to seal against the port-faces.


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## karolh (Jul 21, 2018)

Even though I'm not skilled in the art of miniature machining I do enjoy seeing what you guys can make from chunks of metal....a great site to visit with wonderful pieces on show.


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## Jmccrack (Aug 2, 2018)

Hey guys still no joy. I was wondering I followed these plans to the letter. How much wider should the slide valve be than the 
2 outside edges of the power ports? Right now my slide valve is .551” wide. And outside to out side on my ports is .531”. That’s only .010” per side. Is it possible that when the slide valve moves at one point both ports are open allowing air into both side of the cylinder?


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## Jasonb (Aug 3, 2018)

It is difficult to say as the engine may have been designed with little or no lap but what I would say from looking at the photo and comparing the length of the 3 slots with the cavity in the valve is that you have the valve rotated 90degrees, or it is a lot wider than needed.  I have seen this done several times

Can you post a bit of the drawing that shows the port faces and the valve to confirm this.


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## Lofty76 (Aug 3, 2018)

Hi Jm,

Difficult to see from a photo but it looks as if the slide valve is screwed directly to the valve rod, this would make it almost impossible for the valve to seat against the vlave face.

Normally the valve is free to float and is held against the valve face by steam pressure, no matter how good your machining is, its very unlikely that the valve could seat properly as shown in the photos.

Can we see the drawing arrangement for the valve chests etc?

Best regards

Lofty


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## Jim McDonald (Aug 3, 2018)

I think your cranks need to be at 90 degrees, you have them at 180 degrees.  Just a thought


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## Jasonb (Aug 3, 2018)

Forget that I just looked on Grabcad.

The cavity in the valve is 8mm, exhaust port 3mm and 2mm of metal between giving a total of 7mm. So when the valve is in the mid position air/steam will pass straight from the inlets to the exhaust. Not what you want

Its an unusual valve port arrangement as the central exhaust port is usually double the size of the inlets or maybe a bit less so would expect 5-6mm

Also agree that there is no provision for the valve to find its own position on teh portface or lift off to avoid hydraulic lock

Drawing downloads from here
https://grabcad.com/library/dual-horizontal-steam-engine-in-factory-layout-1


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## tractor162003 (Aug 3, 2018)

If you can get one or the other running just fine but when you pipe them together no joy. I think it is all in the  valve timing. I think you need to move the eccentrics a little bit one way of the other. Looking at the one I made, I think the size of the valve and holes are ok.
What Jim said "I think your cranks need to be at 90 degrees, you have them at 180 degrees." would be better but it should run with them at 180.


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## Jmccrack (Aug 3, 2018)

Can anyone point me in the direction of a drw for a slide valve configuration. You are right at mid point both ports are open. Do you think the grab cad drw is in error?


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## Jmccrack (Aug 3, 2018)

I think I have come to same conclusion. When the slide valve is in the center position both power ports are open. I followed the drawing from grabcad to the letter could there be an error in the drawing? let me get this straight. When the slide is in the center position both power ports should be covered. I will redo the slide to a design that allows it to float up and down.


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## tractor162003 (Aug 3, 2018)

How did you read these 8mm and 3mm off the drawing the one I downloaded is to small to read


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## tractor162003 (Aug 3, 2018)

I found them 47 sheets


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## Brian Rupnow (Aug 3, 2018)

Be careful about what you download from Grabcad. The designs are not vetted in any manner, so unless you are experienced enough to tell when something is wrong you will be left very frustrated and confused.---Brian


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## Jmccrack (Aug 3, 2018)

I am finding that out now. The slide valve shaft is .240 to short as well. So I am making 2 new slide valves and 2 shafts. Again has anyone out there got a drawing or can point me in the direction of a drw that shows the relationship of slide valve to ports openings. Or do I just make sure when the slide valve is a midpoint both ports are completely covered.


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## Jasonb (Aug 4, 2018)

If you keep the valve plate as it is and reduce the cavity to 7mm with no chamfer that will cure the 3 ports being uncovered. You can then either leave it with the same 14mm O/A size which gives 0.5mm lap OR reduce O/A to 13mm and have zero LAP.

If you are remaking them then I would definately go with a separate nut and slotted valve which will give better sealing

Google "slide valve lap" or "steam slide valve" and you should get the illustrations you need.

The pdf drawings are here for those that can't see decent sized drawings?
https://grabcad.com/library/dual-ho...in-factory-layout-1/details?folder_id=1536875


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## Jmccrack (Aug 4, 2018)

Here are the drawings


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## tractor162003 (Aug 4, 2018)

JM
"When the slide valve is in the center position both power ports are open. I followed the drawing from grabcad to the letter could there be an error in the drawing? let me get this straight. When the slide is in the center position both power ports should be covered. I will redo the slide to a design that allows it to float up and down."

This is NOT True when the slide valve is in the center position the EXHAUST port is open to both ends of the cylinder. The air should be going in to the steam chest.


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## Jasonb (Aug 5, 2018)

The problem is that as the valve starts to uncover the inlet port it is not wide enough to close off the exhaust port so instead of the air flowing from valve chest through the inlet port to the cylinder (blue line) it will take the easiest route and go straight out the exhaust (red line)

The flywheel probably carries the engine over when run as a single with just some wasted air but if the timing is not right or there is tightness when the two are run together the engine will stall and just blow the air to waste.

Combine this loss of air and the 0.5mm lap and the piston won't be getting the full incomming air until 54deg past dead ctr so a lot of the power stroke is lost

I have done a quick sketch to the printed drawing, the OP has used wider 1/8" slots going by pencil notes so problem will be a bit worse.


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## Jmccrack (Aug 5, 2018)

Jasonb said:


> The problem is that as the valve starts to uncover the inlet port it is not wide enough to close off the exhaust port so instead of the air flowing from valve chest through the inlet port to the cylinder (blue line) it will take the easiest route and go straight out the exhaust (red line)
> 
> The flywheel probably carries the engine over when run as a single with just some wasted air but if the timing is not right or there is tightness when the two are run together the engine will stall and just blow the air to waste.
> 
> ...


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## Jmccrack (Aug 5, 2018)

Thank you guys for all your help. I am still a bit unclear. See the sketch below I got on line





Both power ports are covered when the slide valve is in the center and the exhaust is open. As the valve moves to allow steam in the other port is open to exhaust. I am just trying to find the right dimensions to machine the new slide valve


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## XD351 (Aug 5, 2018)

I think the dimensions on the drawing are askew , the recess would work better if it was 7mm maximum with no chamfer .
The ports are on 5mm centres  so the dimension for the outer ports centres is 10mm from that subtract the width of one port (3mm ) and this will give you dimension of the inside edge of the outer ports (7mm) . If you follow the plans the recess is 8mm  long and has a 0.5mm chamfer all around so the actual size of the recess is 9mm .  This means that not only is the exhaust open to both ports at the same time it is also getting blow by from the steam chest , ideally you want one  port just open , one just shut  and that goes for the intake and exhaust events .  If you have used a different size cutter to mill the ports i would take a set of dial or digital callipers and measure from one inside edge of the outer port to the other inside edge of the other outer port and make the recess to that dimension or a little smaller , 0.5 mm or so . You will need to measure the outer edges of the same ports to ensure the valve is long enough  as well .
I think your sketch is really only to show the general arrangement , you should be able to find something on youtube to show how the valve timing events . Also have a look at Keith  appleton  on youtube , he did make a video of setting the timing correctly .


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## Jasonb (Aug 5, 2018)

Based on your penciled in dimensions this valve should work. I have shown a loose nut so valve will seat better and be able to lift if needed. Very little lap as it is not needed for running on air.

Two Jpgs showing valve at mid point and max eccentric throw plus a pdf drawing.


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## Jmccrack (Aug 5, 2018)

Jasonb
I am going out and stating to build this right now. I will send you progress pics. Thanks for the help


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## dkwflight (Aug 6, 2018)

Interesting this drawing shows the cranks90 out and not hitting TDC at the same time.


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## Jasonb (Aug 6, 2018)

Cranks on that drawing are at 180 degrees, look at the balance weights


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## dkwflight (Aug 6, 2018)

My mistake. I doubt the author creator had much interest or experience in steam.
I doubt a full size engine would start unless in the right part of the cycle. If stopped at top or bottom the engine will not start.
The biggest engines had barring engines to move the engine off center


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## Charles Lamont (Aug 6, 2018)

Jmccrmc, the diagram you found, I-I is less than D-D. That is called 'exhaust lap'.  The design you are working from had I-I greater than D-D, which is called 'exhaust clearance'. As a rule, in model work (and mostly in full-size too) neither of these is a good idea:  In the great majority of cases I-I is made equal to D-D, in which case the exhaust is said to be 'line on line'. Nobody who knows anything would design a chamfer on any of the edges, and nor would they design a slide valve that has no means of movement perpendicular to the port face.

The cages over the crossheads are also an aberration that I have never seen anything the like of in hundreds of full size engines seen live, in drawings or in photographs. I am not saying such a thing does not exist, just that if it does, it is mighty rare. Though, of course ones imagination need not be constrained by past practice.


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## Mechanicboy (Aug 7, 2018)

See the next message..


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## Mechanicboy (Aug 7, 2018)

Jasonb said:


> Cranks on that drawing are at 180 degrees, look at the balance weights
> 
> View attachment 103233



In fact it's not good idea to use 180 degree when it's the same bore and stroke in both cylinders due the steam engine can't self start. Also a fault from designer of steam engine.

Never seen the  rounded edge inside the valve for exhaustion in the drawings. All edges around the valve that are in contact with the cylinder ports must not be rounded as to the timing shall be correct, even if the valve / cylinder must once again be grinded due to wear when the valve / cylinder is not longer tight against leakage. With rounded edges, timing is changed when the valve/cylinder is worn down and grinded at new again.

I would not use a threaded hole in the valve for the valve rod. The same design as Stuart does with the valve / valve rod as the valve is movable in a direction to hold the valve on the cylinder by the vapor pressure and keep tight without leakage. See photo.


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## Jmccrack (Aug 8, 2018)

Hey guys check out the media part of this forum.

Here she is running (sort of). I can’t get any speed. It runs very free but still takes 30 psi to run.
I can’t figure out how to post a video here but there is one in the media part.


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## Jmccrack (Aug 8, 2018)

Hey guys it’s me again. I can almost get this puppy to run (see media). I have to much play in the slide Valve linkage and if you look at the Grab Cad drw. The linkage is secured to the shaft by a small setscrew. There are to links and a setscrew in each one. After a while the set screws come loose and then the timing is off. This is a weak spot in this design. I am trying to come up with a different design from the eccentric to the slide valve. Because of the position of the steam chest in relationship to the eccentric this could be tricky. The alternative is to come up with some better way to secure each link to the shaft.


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## Jmccrack (Aug 8, 2018)

It’s ingesting to watch it run. There seems to be a knock on each stroke. And some times if I run just one side I can get the piston to move back and forth just 1/2 a stroke.


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## Charles Lamont (Aug 8, 2018)

The new valves look good. However, it sounds as though there is a constant large blow to exhaust. How are the pistons sealed and how close a fit are they? You don't seem to have much oil in the valve chests.


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## Jmccrack (Aug 8, 2018)

Thanks Charles 
The piston seals are nice and tight. And you are right I forgot to oil the steam chest.


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## Jasonb (Aug 9, 2018)

Those valves don't look to be moving far enough, with a 3/32" offset to the eccentric you should be getting 3/16" movement but the valve looks to be moving less than 1/8" judged by the thickness of the valve nut against the valve chest inlet.

The arm that goes to the eccentric rod does not need to be slotted, so if you do alter them bear that in mind. All the arms should be able to be set without needing to run the engine so set them up, mark where the grub screw touches the shaft when in the right position and mill/file a flat for the screw to bear against. Make sure you set both sides to the same angle, ideally I would have the arms at 180degrees which would mean drilling another hole in the eccentric rod. This could be where you are loosing movement.

Does sound to be blowing somewhere, make sure the valves are free enough to settle onto the port face, if the tapped hole in the nut is a little off that is enough to tilt a tight nut and stop it sealing.


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## Jmccrack (Aug 9, 2018)

I was thinking the same thing. I took the unit apart the other day to check the offset on the eccentric. It’s is .093”. But you are right when I measure the actual throw on the slide valve I am only seeing .065” the difference is in loose connections. Also I put pressure in the steam chest and tried to move the slide valve by hand and it was very hard to slide back and forth. But that was because I had NO lubrication in it. Back at it today. There is no question when you have situations like this one sure learns a lot


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## Charles Lamont (Aug 9, 2018)

Jasonb said:


> The arm that goes to the eccentric rod does not need to be slotted, so if you do alter them bear that in mind. All the arms should be able to be set without needing to run the engine so set them up, mark where the grub screw touches the shaft when in the right position and mill/file a flat for the screw to bear against. Make sure you set both sides to the same angle, ideally I would have the arms at 180degrees which would mean drilling another hole in the eccentric rod. This could be where you are loosing movement.



A technical digression, if I may. With a simple eccentric, there are errors in the valve events caused by connecting rod angularity. These can be largely, but not completely, corrected by making the valve slightly asymetrical; the lap and exhaust cavity edges are made slightly different at each end. The introduction of a rocker allows for a further correction to be introduced. By arranging the arms of the rocker at something not quite 180°, it is then possible to have admission, cut-off, release, and compression all at exactly the same percentage piston stroke at both ends of the cylinder. The valve modifications I understand, but I have to confess that getting to grips with the geometry of this rocker modification is way down my to-do list.


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## Jmccrack (Aug 9, 2018)

I was thinking the same thing. I took the unit apart the other day to check the offset on the eccentric. It’s is .093”. But you are right when I measure the actual throw on the slide valve I am only seeing .065” the difference is in loose connections. Also I put pressure in the steam chest and tried to move the slide valve by hand and it was very hard to slide back and forth. But that was because I had NO lubrication in it. Back at it today. There is no question when you have situations like this one sure learns a lot.
I am going to put a dial indicator on the slide valve itself. I will report back what the actual movement is.


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## Jasonb (Aug 10, 2018)

Just had a quick look at the renderings and think I have spotted what the problem may be. They show the arms that connect to the eccentric rods sticking up not down as you have them.

Moving them upwards will solve two issues

1. They will be in line with the arm that goes to the valve rod so no loss of movement due to the angular alignment you have at the moment
2. I said the eccentric rods would need shortening to get things in a straight line but as they need to reach a further distance with the arms at the top the length should now be OK.


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## Ken I (Aug 10, 2018)

Does this help.....




Valve timing is 90° off crank throw.
Obviously both eccentrics must be 90° in the same direction from their respective crank throws.
And the crank throws for a 2 cylinder should be 90° apart not 180° which makes it a "Twingle"
Also if the "throw" on your "D" valve is too great you might also be admitting pressure during the exhaust cycle whilst also blocking off the exhaust port.
The valve stroke has to be correct as does the cavity size in the "D" valve.
Regards,  Ken


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## Jmccrack (Aug 10, 2018)

Hey guys thanks for all the help. I have tried everything anybody has suggested and still no joy. As you can see I can get to run but not well. I have no play in the valve string. I put a dial on the slide valve itself and I should have .196 total travel and I have .131. As Jasonb sayes I will switch the eccentric lever to point up and see what happens. I am losing movement somewhere. Ken I and Jansonb thank you for your drawings. What you have drawn is exactly what is happening only over a .130” travel not .198” as it should be. As I see it the short stroke works but does not allow the cylinder to produce its full power. Does this make sense?


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## Jmccrack (Aug 10, 2018)

Here is an Interesting question. If the slide valve is positioned properly but the stroke is 30% short how would the cylinder react?


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## Charles Lamont (Aug 10, 2018)

Jmccrack said:


> Here is an Interesting question. If the slide valve is positioned properly but the stroke is 30% short how would the cylinder react?


In an engine with reversing gear you can 'notch up', to shorten the cut-off point and so make better use of the expansion of the steam. The reversing gear alters  the timing, but with conventional slide valves that inevityably results in a reduced stroke of the valve. Your valves are opening the ports far enough for perfectly satisfactory running (if properly timed), especially with no load. I think we need to start look elsewhere. Some of the things you have said so far lead me to wonder about friction.


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## Jmccrack (Aug 10, 2018)

I am not sure how to explain it but when the engine runs now it has a hard knock in it. As if part way thru the stroke air is getting to the other side of the piston. I have a lot of lube in the unit now and if I turn it over by hand there is no tight spots.


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## Jmccrack (Aug 10, 2018)

Just so everyone knows. This the unit running just after I built it. See the media section


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## Jmccrack (Aug 10, 2018)

Jasonb said:


> Just had a quick look at the renderings and think I have spotted what the problem may be. They show the arms that connect to the eccentric rods sticking up not down as you have them.
> 
> Moving them upwards will solve two issues
> 
> ...




 Wouldn’t you know that you pick the drawing I did not use. All the drawings and grab cad show the eccentric linkage up. The one I used shows the eccentric linkage down. I took the steam chest apart flipped the slide valve upside down and then hooked everything up with the cover off.  When I rotate the fly wheel by hand my total travel is .084”  it should be .198”.  Moving the lever to the upright position make no difference still .084” travel.


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## Jmccrack (Aug 10, 2018)

I am wondering. I have .098” offset. I wonder if this is enough.


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## Jmccrack (Aug 10, 2018)

Hey guys how open should each port be when it is in the open position. 100% 50% 25%?. I am sure I do not have enough offset.


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## Ken I (Aug 11, 2018)

I always design mine for 100% open but as Charles Lamont stated yours should work perfectly well if properly timed.
When you stated that each cylinder runs perfectly well on its own - that begs a really daft question :- When you run them on their own are they running in the same direction ?
If not they are "fighting" each other.
Perhaps the more efficient cylinder dominates occasionally and it runs but roughly - it would also explain the apparently frictionless knocking.
My apologies but I had to ask.

Another diagnostic you can try is to hold the engine stationary by hand - apply pressure - then turning the flywheel by hand diagnose where the pushing and pulling occurs as well as any bypass, leakage or any other inappropriate flows.

Is your "D" valve sealing against its running face - are they both perfectly flat - show us a photo of the running surfaces.

Regards,   Ken


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## Jasonb (Aug 11, 2018)

With a port width of 3mm you will never get 100% opening as the eccentric throw is less, add to that your loss of movement and that reduces the opening even more.

The loss of movement you have measured will mean that air is not getting to the cylinder until it is say 25% along it's stroke and will then be shut off at say 75% of the stroke so you are only getting power for 50% of each stroke.

One way you may gain a bit more valve movement is to adjust the position of the arms. At mid valve travel the valve are wants to be vertical and the arm that goes to the eccentric rod wants to be at 90 degrees to that rod. If you still find this does not give enough movement of teh valve then increase the offset of the eccentric to say 0.125"


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## Jmccrack (Aug 11, 2018)

Jason , Ken
I want to thank you both for your patience. I put a dial indicator on all the moving parts of the steam chest linkages and what I found was .098” everywhere except the slide valve itself. It was about .080”. I got the drawings for this unit off GrabCad. And as Brian Rupnow stated these engine are drawn but not built or tested. When I started to build this engine I ask to see if anyone had built it and not said they had. There could be slight errors. I am convinced now that .098” throw on the eccentric is not quite enough. I am going to make 2 new ones and put them on. It will only take an hour or so and with the time I have in this engine it is worth it. BTW can either of you guys point me in the direction of plans for a complicated build of a 2 cylinder horizontal with a governor and reversing.


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## Jasonb (Aug 11, 2018)

Have you made the eccentrics right, you say you have 0.098" everywhere which is basically 2.5mm. the offset of the eccentric is 2.5mm which should give you 5.0mm or 0.197" movement. Did you make it with half of the offset?

Pic shows the 22mm eccentric boss offset 2.5mm as drawing and the 5mm movement you should get as it turns .


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## Jmccrack (Aug 11, 2018)

Yes I should have said I have .098” travel from center in each direction. Total movement is .196”


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## Jasonb (Aug 11, 2018)

In that case I assume the valve rod is also only moving 0.160" total

This may well be losses due to the angle of the levers, try it like I suggested above 
_
"One way you may gain a bit more valve movement is to adjust the position of the arms. At mid valve travel the valve are wants to be vertical and the arm that goes to the eccentric rod wants to be at 90 degrees to that rod. "_


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## Jmccrack (Aug 11, 2018)

I will give that a try. by the way Jason what drawing program do you use?


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## Jasonb (Aug 11, 2018)

Alibre


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## Jmccrack (Aug 11, 2018)

When the slide vale is in the center position and air is applied to the steam chest it should seal will little or no air coming out the exhaust right?


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## Jmccrack (Aug 11, 2018)

I I just added a short video to Media. If you look at it you see the slide valve open with air in the steam chest and then when I move the slide valve to the mid position you can still hear a lot of air escaping. The slide valve has lots of lube. Then you can see the engine run. The outer edges of the slide valve do not cover the outside edges of the ports. Also you can see the slide valve in motion does not uncover much of each port. I am thinking a bit wider slide valve and 2 new eccentrics maybe .120” offset. This is my fifth engine and my first 2 cylinder. I have never had so much trouble. But one sure learns a lot. 
This is a 6 cylinder radial I am working on as well






BUT first thinks first.


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## Jasonb (Aug 12, 2018)

When in mid position it should  cover the inlets. 

Can you measure the actual inlets as the valve I drew will cover the inlets shown on the drawing but if they have been cut wider then the small amount of lap won't be enough to cover them.

Even with the full 0.098" movement you are never going to fully uncover the inlet as that is wider than the available movement, this shows the valve 0.080" to one side


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## Jmccrack (Aug 12, 2018)

.529


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## Jasonb (Aug 12, 2018)

I drew the valve at 0.532" so should still just about cover your ports

Looking at the video your nut is loose in the slot and the threaded rod also looks loose in the nut all of which will loose valve movement.


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## Jmccrack (Aug 14, 2018)

You are right it almost covers. When I measure they are close to the same. But when I shine a light behind the slide valve I can see a sliver of light on both sides. I have made 2 new slide valves that give me .012” lap and I have made 2 new eccentrics at .125” the old ones were .098. I have tightened up the connection points in the valve linkage. I will put it all back together this afternoon and report back.


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## dwulfe (Aug 16, 2018)

Why doesn't the port face show any wear from the "D" valve?


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## Jmccrack (Aug 16, 2018)

Good question. I think because I have been flipping over the copper wear plate. Since I widened the Dvalve I am getting good air retention when the valve is in mid position


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## dwulfe (Aug 16, 2018)

I had trouble with D valves not seating on the port face. Irregular wear was a symptom as well as low power for given psi and hissing out the exhaust.


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## Jmccrack (Aug 19, 2018)

Hey all.
HAPPY DAYS!!!!

I found my problem. When I first ran this engine I had no gaskets in it. I thought I will just see if it runs. It did. So I took it apart, painted it and put it back together ... with gaskets. I put a gasket under the copper wear plate that sits on top of the cylinder,and one between the steam chest cover and the steam chest. I put back together and there was no way I could get it to run. So I started posting to see if anyone could help. I got suggestions from all over and they were great but none worked. When I tried to run it and had the slide valve in mid position on the copper wear plate air would come out both ports and the exhaust port at the same time. I lapped the slide valve to the wear plate and still no joy,so I started looking elsewhere. Working on it today I put the slide valve back in center position air was hissing out and it hit me. With the gasket under the wear plate and slide valve on top of the copper wear plate there a .010” gap between the copper and the ports openings on the under side this is where all my air is escaping.




As soon as i took the gasket out she runs like a charm.


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## Jmccrack (Aug 19, 2018)

Hey Guys
I uploaded a short video in the media section of it running on one side only. To all of you who said it was hissing to much air you were all right.
Thanks again for all the help


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## Charles Lamont (Aug 19, 2018)

Pleased to hear you finally found the problem. The thing about your copper wear plate is that it will wear! Copper is not a suitable material for a bearing surface as it is too soft, particularly at the faily high bearing pressure between a slide valve and its portface. Iron, gunmetal, or bronze would be better.


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## Jmccrack (Aug 19, 2018)

Thanks again for all the help


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