LTD Stirling engine

[mklotz]

While SS is a suitably lousy conductor, I would opt for a nylon bolt if you're going to do it that way.

A plastic piston may work at these low temperatures but be wary of operating the engine in sunlight.
Many plastics do not play nicely with ultraviolet.

 

[cfellows]

From a practical standpoint, wouldn't the air inside the chamber swishing back and forth between the hot and cold sides do a lot more to equalize the temperature than the thermal conductance of the bolt?

Chuck

 

[Powder keg]

On the piston I'm thinking of turning a smaller portion that will protrude out of the top and cross drilling it for my wire con rod. The graphite should be strong enough for this, right? If that wont work, I can make a small brass piece that threads in. It can be held in place with Locktite.

The width of the ring I made for the displacer cylinder varies in legnth a small bit. Does anyone have any tricks for turning this in the lathe? I think it would be a mother bear to hold?

Thanks, Wes

 

[Bogstandard]

PK,
Remember how I did my flywheels from plate. What you can do is stick your cylinder to a piece of wood, like mdf with say a hot melt gun or even double sided tape, don't use superglue, it is liable to cause a permanent bloom on the plastic. Then friction turn it, it doesn't have to be central, it will easily trim up. Choose the edge that is the squarest to the sides for sticking first.
Another way is to make a wooden blank in the lathe, do not make it totally round, just round corners will do (if you make it just a tiny bit larger than the ID of the ring, the ring will deform and grip itself onto the blank), slip the ring on and trim the ends. Doing it this way should ensure that the ends are square to the sides.

The lads on here should be able to suggest a few more methods to try as well.

John

 

[shred]

On the piston I'm thinking of turning a smaller portion that will protrude out of the top and cross drilling it for my wire con rod. The graphite should be strong enough for this, right? If that wont work, I can make a small brass piece that threads in. It can be held in place with Locktite.

The width of the ring I made for the displacer cylinder varies in legnth a small bit. Does anyone have any tricks for turning this in the lathe? I think it would be a mother bear to hold?

Thanks, Wes

3-jaw working on the ID (jaws on the inside of the ring, crank the wrench the "wrong" way, indicate carefully if both sides aren't square) won't hold it? I've done that with bits of PVC pipe for other reasons a time or two. It's a little sketchy, but on plastic can easily be gotten-away with.

 

[Powder keg]

Shred, This is pretty flimsy stuff. It's hard but there is no way you could hold it in a 3 jaw. I like John's Idea about jamming it onto some wood? Might have trouble getting hot glue off? Besides, I'd have to buy a gun.

Thanks again for any input.

Wes

 

[Powder keg]

I dug out my face plate and will get a piece of wood screwed to it and I'll see what kind of damage I can do after work today. I'm planing on using the center bolt to hold it all together. I'll ether use stainless or plastic for the bolt? depends on what I come up with.

Thanks again for all the input:O)

Wes

 

[b.lindsey]

Shread's method does work...the key is patience...and very light cuts with a sharp edge on the tool bit. It takes a few more passes but leaves a very nice smooth finish also, thus avoiding the need for sealing gaskets as someone mentioned the other day.

Bill

 

[Bogstandard]

PK,
Thinking about it, I would try Shreds method first, it is the easiest to try for the first attempt, should have thought of that myself, I most probably couldn't see the forest for all the trees. It is basically exactly the same as I am suggesting with the wood.

John

 

[Powder keg]

I've got a really sharp tool here. I'll give shreds way a try right after work.

Wes

 

[Powder keg]

You guys are awesome!! It worked great!!! Quick, easy, and cheep!!! The ring turned out being within .005 in thickness all the way around.

Wes

 

[Powder keg]

What is a good way to polish the ends of this acrylic tube? I'm thinking just finer and finer emery?

Thanks, Wes

 

[b.lindsey]

Wes, just curious as to why you feel polishing the ends is necessary?

Bill

 

[Powder keg]

It's not necessary. I just have never worked with Acrylic and wanted to mess around with it some. Just to see what can be done:O)

Wes

 

[b.lindsey]

Oh, ok. Well fine/very fine grit paper would work if done on a nice flat surface to avoid any contouring or rounding of the ends.

 

[BobWarfield]

FYI, there are several techniques to polishing acrylic. You can use abrasives of various kinds. There is also a flame polishing technique. I haven't used it personally, but I understand it works pretty well.

Cheers,

BW

 

[Powder keg]

I tried the heat method on my ice tray. It wasn't pretty. I think I need more practice and less heat:O) I'll stick to lightly sanding the edges of the cylinders to clean them up. I'll try to get some more pictures scanned and put up here tomorrow. I have the piston figured out. Still working on the base for the power cylinder and flywheel bearing tower.

Wes

 

[Powder keg]

Here are the sizes for the power piston. It is 1/2" long and the 1/8" brass rod will stick out about 3/16". I'm using .045 wire for the con rods on this engine. I'm using this size because of the Airpot cylinders that I have. I was thinking of using epoxy to glue them into the mount?

The gland piece will screw into the mount. I think the flywheel support should be fastened with a setscrew? That way it can be adjusted if needed?

How does this sound so far?

Wes

 

[Powder keg]

Looking at some of the videos and pictures I think the conrod wire might want to be a little thinner? All it has to do is push the flywheel. Maybe some .030 wire would be better? This would save on weight. Any opinions?

Wes

 

[Powder keg]

Anyone have any idea what kind of tolerance is needed on the gland for the displacer? I'm thinking of a .001" over reamer would be a easy way to do this. Would that be too loose? Should I ream it to size then polish the shaft a bit?

Thanks, Wes