Any Stirling experts out there? This dog won't hunt.

[Dataporter]

A couple of years ago, I built the Stirling Engine below from plans in a book called "Model Stirling Engines" by Rudy Kouhoupt.

I like the looks of it, but, this dog won't hunt! It doesn't run. It comes darn close, but no cigars!

I tinkered and tinkered and as far as I can tell, everything is to specifications. I just put in on the shelf out of disgust, but now I want to re-visit it.

Anyone here in Hobby Machinist Forum Land know how to troubleshoot Stirling engines?

Any one have the video Rudy made about this engine? http://bay-com.com/pid/184/Machining_DVD.html

Thanks in advance! Dave

 

[Terrywerm]

I have not yet gotten into Stirling engines, but expect to sooner or later, so I will be watching this with great interest! I know that they can be some rather finicky little devils at times.

I have the same book by Rudy K, and find it to be rather interesting, even though there are no build details for any of the engines in the book.

 

[Walt]

I have zero experience with Stirling engines. The stuff I've read has included statements about low internal friction being crucial to correct operation.

Walt

 

[Dataporter]

I polished the piston and the displacer shaft and all the bearing surfaces in an attempt to minimize friction.

Might be the power cylinder... I used a bronze bushing. Specs call for bronze or cast iron. Where can I get piece of cast iron rod .75" diameter x 1.5" long??
The I.D. of the power cylinder is .562.
I made a couple of pistons from 303 stainless. The specs call for aluminum or cast iron. I've seen graphite is a good material for Stirling power pistons. I guess it is light and slippery!

Dave

 

[Walsheng]

I polished the piston and the displacer shaft and all the bearing surfaces in an attempt to minimize friction.

Might be the power cylinder... I used a bronze bushing. Specs call for bronze or cast iron. Where can I get piece of cast iron rod .75" diameter x 1.5" long??
The I.D. of the power cylinder is .562.
I made a couple of pistons from 303 stainless. The specs call for aluminum or cast iron. I've seen graphite is a good material for Stirling power pistons. I guess it is light and slippery!

Dave

You can get a piece of 3/4" x 12" long cast iron from McMaster-Carr for about $17. You can also get 1" x 6" long for under $10.
There are also a couple of model engine forums where there is a ton of information. I don't know if it's OK to mention them by name here so just do a search for them.

John

 

[Dataporter]

Thanks for the replies. I love this forum. Great comradery, respect, lack of commercialism, etc.

FYI I did find some every useful stuff here http://www.stirlingbuilder.com/troubleshooting-tips
I think I've done most of these suggestions, but I'll go through them again one by one.
I may try some ice on the "cool" side... and /or try to sink or better insulate the union between the hot and cold sides.

D

 

[E.Tinker]

The November/December 2005 (Volume 24, Number 6) issue of HOME SHOP MACHINIST featured an article, "Build a Horizontal Stirling Engine". Article photos show an engine which appears to be the one you made (or at least a very similar design). The author states that the engine was a machining project for high school students working with machines that don't have the best accuracy, and that most student's engines run immediately after assembly (provided they have smooth action, compression, and a little kickback when the 4-3/4" flywheel is spun). He discusses several design modifications and the reason for the changes which have improved the success of the project. If you haven't seen that article, writing for a reprint may help. I gather that larger engines are more forgiving of tolerances than miniaturized (scaled) versions. It makes sense that a .001 error on (for example a 3X larger engine would affect performance less than a .001 error on a 1/3 scale engine) The HSM engine has a displacer cylinder bore of 1-1/2", power piston bore of 1-1/4".

I'm a "wannabe" machinist, working with a wood lathe + manual cross slide. An improvised Dremel grinder gives me a lighter finish cut, improving my set-up, and helps to overcome machine wear and inaccuracies. Building the HSM engine is on my bucket list, but still a ways off. Congratulations on your build--very professional looking, certainly worthy of praise. I'll be looking forward to future reports on what tweaks got it running.

Carroll Johnson (aka E.Tinker)

 

[Timberwulf]

I built a similar small Stirling engine a couple of years back and found, apart from as little friction as possible, the most sensitive setting was the 90 degree offset of the 2 cranks. Once those two items were sorted it would reliably run at about 1500 rpm.
I hope that helps.

 

[Round in circles]

Cheap cast iron

I don't know if in the states you still have houses with the old fashioned up & down sash windows that were raised & lowered via a top pulley , sash cord and counter weight. If so perhaps a trip to a building demolition yard might be a source for some of the 16" long x 2" dia sash window counter balance weights .


Here in the UK they were still being fitted in houses built around the time of the second world war and are still fairly easy to get hold of as they replaced lead weights which were a more valuable metal .

 

[MarioM]

A couple of years ago, I built the Stirling Engine below from plans in a book called "Model Stirling Engines" by Rudy Kouhoupt.

I like the looks of it, but, this dog won't hunt! It doesn't run. It comes darn close, but no cigars!

I tinkered and tinkered and as far as I can tell, everything is to specifications. I just put in on the shelf out of disgust, but now I want to re-visit it.

Anyone here in Hobby Machinist Forum Land know how to troubleshoot Stirling engines?

Any one have the video Rudy made about this engine? http://bay-com.com/pid/184/Machining_DVD.html

Thanks in advance! Dave

View attachment 82182View attachment 82183View attachment 82184

A while ago I made the very same engine from the same book. It was the first engine I had made. It did not want to run when finished,.......and I was going crazy:banghead:.....but the trouble was friction. Also you have to look for .0005" clearance between piston and cylinder, which is not easy to achieve if you do not have experience.....I had to make two pistons. Also check the clearance between the gland and displacer rod.....the minimum possible.....also made it twice.

After working all friction points it worked nice, but it needs a lot of heat........maybe far to much......but it works. ) I might go back to it some time and make it look nicer and see if I can make it run with less heat. Hope this helps you....looking forward to see yours running.
Check the video in you tube.

http://www.youtube.com/watch?v=8x6S1hOGJD4