Piston valve engine purchased in Switzerland. Need help.

[CalypsoParticipant @calypso]

[CalypsoParticipant @calypso]

Greetings to all.

I am a 68-year old model/toy steam collector living near Geneva in Switzerland.

I have acquired a piston-valve static engine through a local auction site and although the engine is complete, I am having problems running it and am beginning to doubt if construction had been completed before it was put up for sale.

I have uploaded a video which is self explanatory, although I am sure that I am indeed using the exhaust outlet connector as my air / steam inlet.

The only way I can get the engine to work is to slightly release the back of the main (piston) cylinder. If I tighten the back completely, the engine will stop working

I think this "leak" releases air when working which should be released as the exhaust air.

I would be grateful for any help with solving this issue as I would really like to have this engine running as it should.

John

[JasonBModerator @jasonb]

Welcome to the Forum Calipso.

One thing that I would check is that the spigot on the end cover is not blocking the steam passage in the side of the cylinder bore. On some models you have to remove a small amount of metal from the cover in this area so the steam has enough room to flow as shown in this picture

Also check that the piston is not hitting the end cover.

I wonder if those two lower pipes are some form of cylinder drains but can't see how they ar eopened and closed

J

 

Edited By JasonB on 09/12/2014 17:46:52

[John OlsenParticipant @johnolsen79199]

Piston valves are commonly inside admission, since that way the gland does not have inlet pressure steam on it. That would suggest that you are in fact putting the steam in the right place, and that the other two pipes that join together are supposed to be the exhaust. It is possible that Jasons suggestion is right, I have done this to myself at least once. The timing must be about right for it to go at all. It is also turning the correct direction…conventionally on a horizontal engine when the piston is coming out the crank is going over the top. (I'm sure there were exceptions…)

Of course, being a piston valve, it would try to run even if you were putting the steam in the exhaust connection…a slide valve would not seal if you did that. So some simple piston valve designs have been reversed by just swapping the connections. (Not ideal if the valve has lap and lead.)

It does look like quite a competent job, possibly based on commercial castings. Whoever did the machining has made both the rods with a nice belly on them, which is a bit of trouble to go to. Getting that style of crosshead to align well is also not trivial. I see you also have the makings of a governor for it. They tend not to work all that well in small sizes but look nice going around.

One suggestion would be to take the top cover off and check what happens when you turn the engine over. You can connect the air to the other connection so that you can tell by the hiss when it is open to the cylinder. I've checked the timing on engines by doing this…you can just use a rubber hose and blow air through by mouth to detect when ports are opening and closing.

John

[CalypsoParticipant @calypso]

Thank you both very much.

The most frustrating thing for me is that I am not able to take anything apart.

Now this sort of thing is not new to me and I do have the tools to do it.

The engine is bolted and pinned to the metal base and the cylinders are soldered in place.

I did try using a 100W soldering iron as well as a torch, but the solder refuses to budge (silver solder?).

I would love to see the inside of the piston valve, but I just can't get to it.

It's just about running on air at about 2 bar (15psi) and I am beginning to be tempted to just leave it at that.

[CalypsoParticipant @calypso]

Er.. I think that should read 30psi.

[Ian S CParticipant @iansc]

If it was me, I'd probably remove the cylinder cover (if that were the problem) by machining it off, and making a new one to bolt on. Isn't it annoying when someone does this to a model.

Ian S C

[CalypsoParticipant @calypso]

Yesterday, I spent a couple of hours trying to figure out what was wrong. I am determined to run it on steam.

Well, I think i finally worked out what was wrong.

I removed the screws on the back of the main cylinder (again) and checked to make sure that the piston was not fouling the back at TDC. It wasn't.

I then put it under air pressure (2 bar) and tried again. Yes, the piston was pushing the back out at TDC!

So it looks like JasonB was right. The piston must be moving further back under pressure.

I'll be making a couple of thicker gaskets, and I am hoping that this was the problem.

I'll let you know the result.

[JasonBModerator @jasonb]

Quite possible, when you turn the engine over by the flywheel any play in the various joints will be in compression so the piston does not get pushed as far. When under steam or air all the slop in the pivots is stretched out and the piston moves that little bit further.

Keep us posted

[Author]

Posts