Request Advice - LTD Tin Can Stirling

[Hawke]

Im in the process of a good attempt at the LTD Stirling, however its not working still.

Pro's would be a nicely balanced flywheel, little friction with a sealed bearing. Lightweight nylon fishing line thru tube removed from a paper clip, slick and smooth operation. Good alignment of crank to all connections.

However I wonder about the Styrofoam displacer with aprox 1/8" side gap to the chamber. I suspect the bottom seal may be too low below the stopping point of the displacer. Could the power diaphragm latex be an issue here as well?

[Ian S C]

Hawke, just a few casual observations, the tube for the displacer connection seems to be a bit loose, you want minimal clearance here. It's proberbly got a bit much of a gap under the displacer, 1/8" clearance top and bottom would be better.
How free are the sealed bearings on the crankshaft, for these engines it's common to remove the seal, wash out the grease, and lightly oil with something like sewing machine oil, better than 3 in 1 oil which can get a bit gummy, as does WD 40.
You may need to put a balance weight on the flywheel (a washer, or coin)attached with blu tac or similar, to counter balance the displacer.
These motors can be most frustrating, sometimes taking hours to get going, then like my latest one, a free piston motor with a linear alternator, a type that can be more frustrating than any , it went first time. Ihave not put an electrical load on it yet, might try later today. BEST WISHES, KEEP IN CONTACT. Ian S C

[Hawke]

Thank you for the info Ian! I can increase the size of the fishing line easy enough. This is a real insight as to the extremely tight yet smooth flowing tolerances these engines require. I had some future ideas on tweaks like cooling fins and a plan to make the underside vented for a small flame and even the next version to include a water pump cooling system, but I need to get past the issues here first. Frustrating a bit.
The bearing did initially concern me with the sluggish characteristics these commonly have. It has gotten fairly warm in the building and lost most of the grease but not as free as it could be. I may have to abandon it. I did suspect the clearance of the displacer at the bottom.

What about the power diaphragm, any concerns you see there? Im thinking I should I move to a tighter, more stretched movement there.

[Ian S C]

Hawke, I was wondering how are you heating the motor? I don't think hot water will do it. One of the main reasons the low temp motors have plastic, or glass between the top and bottom plate, is to insulate the hot from the cold ends.
The diaphragm should show signs of swelling with the pressure. The rubber from surgical gloves would be good, or a party balloon.
For the next motor (getting ahead of things a bit)with the displacer cylinder, instead of putting a disc up the can, use the bottom of he can in this position, you'll be able to put a small candle under it without melting the seal. Too much heat , and the displacer might collapse. Ian S C

[Hawke]

Gotcha on the bottom disc. Thx Ian. It is sealed with an epoxy that I tested before and does begin to melt under direct heat but pretty high temps. Heating btw way on this one has been a small tea candle getting it only slightly warmer than what you can touch. I have seen some signs of swelling in the diaphragm as you said but not what I think should be happening. I suspect leaks maybe at the diaphragm held on only by 2 rubber bands and the stretch of the latex glove.Also I never tested the seal of the disc so thats a suspect. The biggest gap would be the nylon string and tube coming from the displacer. Im doing the 4/10 work grind right now which zaps a 57 yr old pretty hard.

For the next motor (getting ahead of things a bit)

Haha, in fact Ive already started on a beam walker. I set the LTD on the shelf for a "time out". I think it will act better when I give it some more attention later. I have been know to recycle I told it! Hehe

I'll make a new thread for the Beam-Walker to keep comments and suggestions for it separated from the LTD Tin Can Stirling here.