Rudy Kouhoupt Striling engine

[Gordon]

I have built Rudy K Stirling engine and I am having a problem getting it to run. I have read the thread about getting a Stirling to run the first time and several other articles and threads. The flywheel turns easily and the piston slides freely and stays in the cylinder if I plug the end when it is held vertically. If I put 10 psi on the system there are no leaks. There is a soap bubble every 5 seconds or so around the guide on the displacer cylinder and if I make it any tighter it binds up. If I fire it up with an alcohol flame it runs for probably 10-15 revolutions and stops. More heat does not seem to make it run any better. The flywheel seems to be rather large and heavy for such a low powered engine. Before I start lightening the flywheel has anyone else had experience with this engine?

Any suggestions welcome.

Gordon

 

[AussieJimG]

It sounds as if you might be having pressure build up in the engine. For these engines to work, the pressure in the chamber needs to go above and below ambient.

If the chamber is too well made (no leaks) the pressure will build up, the piston will go to the top of its travel, and not be able to come down again.

Most of my engines are too sloppy to suffer from that problem. On the one that did, I drilled and tapped a hole in the chamber and fitted a capscrew.

Unscrewing the cap screw periodically on start up (when the pressure gets too high) gets it going again, and eventually it stabilises.

Give it a go

Jim

 

[Gordon]

I will give that a try. Actually I have two options here. when I first tried it I thought that the piston was too sloppy so I made one which fit better so I can put the old one in again. I got rid of some other friction and leak problems in the mean time. Also there is a screw plugging the cross drilled passage between the two chambers so I cn try cracking that to see what happens.

Thanks. I will try again tomorrow.

 

[mklotz]

Also there is a screw plugging the cross drilled passage between the two chambers so I cn try cracking that to see what happens.

????

If there is no easy communication between the displacer chamber and the power cylinder, it will never run. The gas expanding in the displacer chamber must be able to expand into the power chamber.

 

[Gordon]

The screw is not restricting the passage. It is to be able to drill the passage between the two chambers and plugs the side where the drill is started. It is a Rudy design and has been built many times by others who obviously have done something better than I have done.

 

[mklotz]

Ok, gotcha.

Pull the screw out and check to see that the passage isn't clogged with swarf.

 

[Gordon]

Well I tried the looser piston and tried to release pressure through the cross port and that did not make any difference. I also lightened up the fly wheel some and that did not make any difference either. I have double checked everything and it seems to be to print but still no change. Some day I will figure out why every engine I build seems to take a lot of tinkering in order to run and then runs for some reason I cannot figure out. It seems like I tried something ten times without working and suddenly doing the same thing makes it work.

 

[mklotz]

Some random things to try...

Check that the displacer motion is ninety degrees out of phase wrt to the power piston motion.

Put some heavy oil (eg, 30 wt motor oil) on the gland where the rod that drives the displacer enters the displacer chamber.

Check that the cold side of the displacer chamber is really cold (relative to the hot side). If heat is leaking from the hot to cold side, you may not have enough temperature differential to run the engine. Try putting some cool water or ice on the cold side.

With the displacer on the cold side of the chamber and the piston at TDC, heat the hot end and see if the piston begins to move as it should. This will verify that the heat is actually expanding the air and pressing on the piston.

 

[AussieJimG]

How does it stop? Does it just slow down and gradually fade away?

Does it always stop in the same position eg with the piston at the top of the cylinder?

What happens if you turn it over by hand after it has stopped? Does it go for a while or just sulk? How does it feel - hard to turn?

We have to solve this problem Gordon, it can't be that hard surely.

Jim

 

[Gordon]

It has almost no pressure against the piston. Heating the hot end with the piston past TDC does not move the piston at all. If I put 5 PSI air pressure on the system the piston moves to TBC with good power. When it stops it does not seem to stop in any particular position. With no heat the flywheel turns about 5 turns and if there is heat it turns about 15 turns before it stops. With 10+ PSI there are only minor soap bubbles.

The only thing I can find which is not per print is the copper heat chamber calls for a .030 copper end and I put in a stepped brass plug which is about 3/16 thick. This may have a heat sink effect but it would not seem like it should be that great. I am going to try getting rid of the end plug but I do not have a lot of confidence. Even with a propane torch there does not seem to be any power.

 

[AussieJimG]

Curiouser and curiouser.

Pressurising it moves the piston so the piston will move if it gets enough pressure.

It works for a while so heat will produce enough pressure for it to run.

It runs on 5 times without heat but 15 times with heat so heat is causing some pressure - it is trying to run.

So is the air getting cold enough at the cold end? Remember that we need a DIFFERENCE in temperature and pressure. Is it possible to cool the cold end - with ice perhaps?

Mind you, I am flying a bit blind here. I looked up Rudy's engines and there are a lot of them. I am not sure which one you built. Could we have a photo?

Jim

 

[Gordon]

Here is a video of one someone else built in October

"http://www.youtube.com/v/8x6S1hOGJD4&hl=en_US&feature=player_embedded&version=3" type="application/x-shockwave-flash" allowfullscreen="true" allowScriptAccess="always" width="640" height="360"></embed></object>

 

[AussieJimG]

I though it might have been that one, I built one along the same lines and it just runs on a metho burner. I will see if I can post a video of it (something I have not done before). If it fails, you might tell me how you did it.

[ame]http://www.youtube.com/watch?v=Xhq7-QQiEpw[/ame]

Jim

 

[mklotz]

Jim,

I took the liberty of editing your post and fixing the video URL so it shows up in the body of the post.

For future reference, all you need to do is put the URL of the Youtube page, shown here in code form so the video doesn't show, directly into your post.

[url]http://www.youtube.com/watch?v=Xhq7-QQiEpw[/url]

 

[AussieJimG]

Thank you Marv, I will remember that for the future.

Jim

 

[Gordon]

I think (hope) that I may have the answer here. After a lot of fooling around I can get it to run for about 5 seconds but it will not run any longer no matter how much heat I apply. I have minimized friction and tried to fix all leaks. In looking at the same engine made by others it appears that the heated end is made from either stainless or steel. In looking at the picture of the one Rudy built it appears that his also is steel. The plans call for a copper tube with a brass mounting plate but that does not appear to be what others have used. In reading other discussions, I believe that the heat is transferring to the aluminum cooing section so that there is not enough temperature differential. In looking at the picture of Rudy's it even appears that he may have an insulating gasket between the two sections. Time to get back on it and try that.

 

[mklotz]

Other than silver, I can't think of a worse material than copper for a Stirling hot cap.

All mine use plain old CRS and they run fine on an alcohol lamp. I don't use insulators between the hot cap and the aluminum cold end.

 

[b.lindsey]

Gordon, it sounds like you have a bead on the problem now...hope that fixes it....sterlings are wonderful once you get them to run. Please post a vid once you have it running.

Bill

 

[AussieJimG]

Getting closer - any time now it will burst into song.

Jim

 

[Gordon]

It runs with a lot of heat but still something is not right. I have had less problem with gasoline engines which are far more complex. I will keep trying between times of being too disgusted to try again.