Stirling engine project help

Discussion on Stirling or "hot air" engines (all types)
Post Reply
Posts: 3
Joined: Thu Jan 12, 2017 3:04 pm

Stirling engine project help

Post by Poorbuilder » Thu Jan 12, 2017 3:37 pm


My goal is to make stirling engine that produces atleast 50w (and + pressuration). My idea is to make generator which is able to use camp fire, cottage firplace or "kiuas".I have acces to lathe in school but only few months so i dont have much time experimenting with design. I have read Andy ross book of making engine online, but it didnt have any dimensions for parts.

I like the design of the engine in this video (below).

It is alpha with yoke drive, but im not sure will i make it with yoke or normal. if i have understood right, there is regenerator in longer cylinder but im not sure how to calculate design for it or how long it should be (how close to hot end).

I will post someday my visions in pictures here.

so my questions are.

1) is there any plans for that engine?

2) if i try to design this by myself how i make regenerator?

3) is yoke best way to drive pistons?

4) will v positioning in cylinders matter?

This is my first post here and i have pretty bad english.

If i achieve my goal i planned to post some kind of documentaion so anyone else could build same. i havent yet found any only tin can toys.

Posts: 164
Joined: Tue Sep 06, 2016 8:09 am
Location: Việt Nam

Re: Stirling engine project help

Post by thanh-cuibap » Thu Jan 12, 2017 10:22 pm

basic information for stirling engine !
( I only know through google and learn in this forum !)
1. length of displacer chamber L = 3 times its diameter.
2. length of heater chamber = 2/3L
3. length of cooler = 1/3L
4. swept volume of displacer = 1.5 times swept volume of piston cylinder. (****)
5. length of displacer = 2/3L and stroke = 1/3L.
6. diameter displacer = diameter of the displacer cylinder displacement - 1 to 2 mm.
4-****. for a low temperature motor, the ratio might be anywhere from 10:1, to 20:1. A high temperature motor should be around 1.5:1, unless it's an ALPHA motor, in which case the ratio is 1:1.

Posts: 3
Joined: Thu Jan 12, 2017 3:04 pm

Re: Stirling engine project help

Post by Poorbuilder » Fri Jan 13, 2017 6:47 am

And one question more wich design gives best power at small size (under 10kg) aplha, beta or gamma. It seems gamma or beta would be easier to make becoase hot side doesnt need any precision between piston and sylinder (under millimeter).

Posts: 308
Joined: Tue Feb 08, 2011 2:29 pm
Location: Brokeville, NY. USA

Re: Stirling engine project help

Post by Aviator168 » Fri Jan 13, 2017 7:21 am

If you are making a portable, you might have to consider the size of the engine and stirling engines are not known for its compactness.

Ian S C
Posts: 2221
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: Stirling engine project help

Post by Ian S C » Sat Jan 14, 2017 3:39 am

I think you'll find an ALPHA motor will have the best power to weight ratio, both pistons are power pistons.
If this is your first motor, don't expect too much from it. The simplest motor is probably the GAMMA type, in a V shape, this way you only have one pin on the crankshaft.
I would recommend stainless foil for the regenerator, but if the motor is of moderate size, and unpressurised I would forget about it as if you build ALPHA, or GAMMA type the displacer works as a regenerator.
Ian S C

Posts: 3
Joined: Thu Jan 12, 2017 3:04 pm

Re: Stirling engine project help

Post by Poorbuilder » Sat Jan 14, 2017 5:46 am

Thanks for replies.
D-90 plans in Andy's book looks interesting, but i think i must change many parts. For example that water cooling. I dont know how to even saw inside aluminium pipe that precisely, so i will replace that part with pipe from regenerator and making some kind of flat cooler(2 aluminium plates with fins). Of course i try to calculate same cooling capacity.

And i don't understand how these pistons work in his plans. My guess is there is teflon sealing but i'm going to use oil.

That yoke drive looks interesting. both pistons are shortly full open and almost closed. I dont know what are the difference in performance to normal crankshaft.

35c plans looks simplier, but it is just under my target. Of course i could scale it bigger. In results there reads 1 bar? My guess is it would get more if i just pump more air there.

Post Reply