My first stirling engine

[eliotRosewater]

Hey guys,

I thought I would share my first stirling engine that I got working on the weekend.

http://www.youtube.com/watch?v=ZaGFWCyi5-Q

My goal was just to get something that worked. It barely made it. Now I got a lot of improvements to make.

Cheers,
-Derek

[jimlarsen]

Good work! Just a few adjustments and you will have it humming along in not time.

[eliotRosewater]

Thank ye.

I think I'm going to abandon this one and build a new one. I'm thinking about going to the hobby store to get some roller bearings. I got some ideas on how to improve this.

Also I'm thinking about swtiching from a diaphragm to a normal piston. I was thinking about mixing up some graphite powder and use the west epoxy system that I've used for fiberglass work in the past. It hardens to a nice smooth finish. I can also use aluminum for the cylinder and polish it to a nice mirror finish.

Gah! I'm becoming OCD on these things.

[PKM]

Wanting a nice smooth cylinder and piston for low friction isn't OCD, it's attention to detail :) When you are machining parts to half a thou' and making your own crankshaft balancers we can talk about OCD. Remember to post pictures of that mirror-finish cylinder!

[eliotRosewater]

Haha, very true. I'm staying awake at night trying to figure these engines out. I wish I had a mill or a lathe, building these would be sooo much easier. Last night I found a great resource at the hobby store for bearings and brass tubes that fit snugly within each other and threaded rod to go down the center of the rod. They are going to work great for the main motor shaft.

I'll post photos of the mirror finish cylinder. I took up polishing alluminum as a hobby (hot rodding) so I'm sure I can get that part to work. I'm thinking of making the piston using graphite powder and west epoxy. Pouring it in a temp cylinder and just working the liquid around to form the cylinder shape until it gels.

[jimlarsen]

You don't need a machine shop. You just need a good book! :-)

[eliotRosewater]

A good book? Or THE good book? Please fill me in.

[jimlarsen]

Well, you said you wished you had a mill or a lathe. I wish for those too because those machined engines are beautiful. A couple years ago an engineer friend challenged me to design a heat of the hand Stirling engine that can be built without a machine shop. It worked so well that I published the plans in a book called "Three LTD Engines You Can Build Without a Machine Shop." So yes, a machine shop would be a big boost, but with a little creativity it can be done. You can see the book on Amazon or on my website.

As far as THE good book, yah, we need that one too!

[eliotRosewater]

Hahaha. Woosh, it went right over me in my previous post. I got my parts and just did a bunch of tests. I'm ready to start designing my next engine. I think I can do this without any machining. The part I was worried about the most was getting the bearings to stick into alluminum. My uni-bit was just enough to get a nice friction fit. I've somehow become extremely lucky with parts.

Also I did some measurments today. I was trying to see what had the lowest density of 4 types of foam that I have. Packing foam (polystrene pellets?) was the lowest at a measured density of 0.00121017 g / cm^3. But I think I'm going to use Depron from the hobby store which came in at 0.00316950. The Depron seems easier to cut and I'm not really in the mood to build/purchase a hot wire to cut packing foam.

Anyway, I did see your engines and I'm very impressed by them. I never thought about using magnets to remove the connecting rod, I think that's a stroke of genius. And the same thing goes for the vertical displacer. Do they ever ramp up to a higher rpm?

[jimlarsen]

Thanks.

They will probably never run very fast, but they have quite a bit of torque for their size. I have experimented with adding weight to the flywheel and they do well with that type of load. I am going to scale one up a bit and use copper for the conductive surfaces. I hope to make it powerful enough to run some small toys, perhaps a marble machine. The vertical axle saves a lot of friction, but it makes power take-off a real challenge.

Is that foam for your displacer? Closed cell foam will work better if you can get it. It reduces the amount of dead air space in your pressure chamber. You also have to watch to make sure it won't melt, if your engine will be getting hot.