Trouble-shooting a new Stirling

[minh-thanh]

You connect everything and it revolves about 10 times with just a good flick.?

 

[Harry Mueller]

Yes. I’ve been getting more revolutions with every reduction in piston diameter. At first, with the 1/2” diameter piston I only got about one revolution with the air hose attached. But now I get up to about 10...hard to say exactly because the first few are so fast.

I’ve also made some improvements in friction reduction along the way.

Harry

 

[minh-thanh]

Do you feel the suction or pushing of power piston when you turn lightly the flywheel ?

 

[Harry Mueller]

I can’t feel it on my finger but can when holding the tubing against my tongue. Oddly enough, I couldn’t see any effect on a lighter flame when holding it near the tube.

But if I blow into the tubing I can turn the flywheel. I don’t think there are any leaks from around the cylinder, I put 2 o-rings between each new brass cylinder.

Harry

 

[minh-thanh]

Sorry, i'm wrong, don't feel with your finger
When you turn lightly the flywheel , and release your hand, you will see the force pulling or pushing on the flywheel .Very few, but must have

 

[minh-thanh]

But if I blow into the tubing I can turn the flywheel.
Harry

seems piston is too small

 

[Harry Mueller]

Well, I’ve tried 3 piston sizes from 8mm to 13mm and none of them worked.

Not sure if I understood you correctly, but I never saw any kick back when slowly turning the flywheel. I also tried plugging the tubing hole but no kick back there either.

Thanks for trying so hard, I really appreciate it.

Harry

 

[minh-thanh]

Thanks for trying so hard, I really appreciate it.

Harry

Don't mind about it..
here ,

 

[Harry Mueller]

No, I don’t get that. I think I did when the piston was 1/2 “ diameter but not now.

But the piston fit seems perfect, not sure how I could get it any better.

Harry

 

[Harry Mueller]

I wonder now about the larger volume of air between my displacer and power piston. It is much larger than yours and may affect the test you just demonstrated.

Harry

 

[minh-thanh]

My engine is the same of your , the diameter of the power piston is 8mm, if you don’t get that, then check the piston, maybe it's too small, or the displacer rod may be too small with displacer bearing

 

[minh-thanh]

I wonder now about the larger volume of air between my displacer and power piston. It is much larger than yours and may affect the test you just demonstrated.

Harry

I think the same result

 

[minh-thanh]

But the piston fit seems perfect, not sure how I could get it any better.

Harry

If the piston fits perfectly with the cylinder, check : the displacer rod fits perfectly with the displacer bearing ?and check the engine has gas leaks at the connections ?

 

[Harry Mueller]

The motor in your video certainly shows the effects of compression. Mine does not display that and that may be the cause of my issues.

However, as I stated before, the power piston fit seems perfect. If I plug the air hole and hold the cilinder upright, air pressure will hold the piston in the cylinder. When I let air into the cylinder, the piston immediately drops out.

The brand new tubing between the two air access points is a very tight fit and I doubt there is any leakage.

The displacer piston connecting rod was initially a tight fit into the hole at the end of the cylinder (displacer bearing). With Brasso, a mild abrasive, I worked the connection until it moved smoothly.

There are only a couple of other points where air might leak in. The bolt holding the power cylinder to the frame actually enters the top of the cylinder but I would think the bolt would effectively seal that hole. I also used two smaller brass tubes with o-rings as cylinders to reduce the power piston sizes. I guess air could leak by one of these but the fact the piston can be held up by atmospheric pressure surely negates this. Other than that I can see no places where air might leak in. But your compression test suggests it does.

I’m going to give it a rest and thoroughly disassemble the engine in the next few days to see if I can find something.

Harry

 

[Goldflash]

try a light oiling with very thin oil / crc . wd40 on any parts that open to atmosphere ie power piston . displaver guide . my stirling wont run without a bit of very thin oil on the power piston and displacer piston rod .
all joints are spigot and socket and, i use teflon plumbers tape as a seal,
i roll it into a string apply it with a crossover overlap . it will compress down to about .002"
gas tight and takes the heat
thin smear of anthing sticky like silicon sealer sealer will hold it in place. works on ic engines as well for head gaskets and exhaust gaskets.

 

[Harry Mueller]

Thanks for the tips, Goldflash. I’d already done that to all the external moving joints but was hesitant to do it the power piston or the displacer rod. I’ll try that all this morning before I do anything more drastic.

Harry

 

[Harry Mueller]

Ok, poured the WD40 to it and it *almost* kept running. Squirted the WD into the cylinder and the displacement rod bearing and flicked the flywheel.

With no heat it revolved 2 seconds pretty consistently over 3 tries.

Lit the lamp, waited a couple of minutes and tried the flick again. This time it ran between 7 and 12 seconds over a half dozen tries.

Tried adding a couple of bolts to the outer edge of the flywheel but that didn’t increase the run time.

So, I’ve got a leak somewhere and I’m going to take the engine apart to see if I can figure out where it might be bleeding air. One suspect is the displacer piston, another is a hole into the upper cylinder I plugged. This engine will run.

I’m tempted to increase the power piston size to 3/8” (9.5mm) again. Any thoughts?

Thanks,
Harry

 

[minh-thanh]

Try with higher flames .

 

[Harry Mueller]

Can’t go higher...already running with a 1/2” wick and the flame surrounds the test tube.

 

[minh-thanh]

Don't use WD40. use sewing machine oil . It ran between 7 and 12 seconds : is a good signal, find another cause before you make a bigger piston