Search found 131 matches

by Bumpkin
Mon Mar 23, 2015 8:11 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Stirling engine with rhombic drive 75 ccm
Replies: 28
Views: 16252

Re: Stirling engine with rhombic drive 75 ccm

Ian, your numbers are absolutely correct - in outer space. Sometimes that matters. On earth at sea level, one 14.7 psi atmosphere = a flat tire and zero psi on a gauge. And 2.7 atmospheres = 25 psi on the same gauge. Sometimes that matters. :smile:

Bumpkin
by Bumpkin
Sun Mar 22, 2015 1:36 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Stirling engine with rhombic drive 75 ccm
Replies: 28
Views: 16252

Re: Stirling engine with rhombic drive 75 ccm

Hi guys. I think you saw this already, but to clarify for other readers because this could be important: 2.7 atmospheres is indeed 25 psi, as the first atmosphere is neutral and isn't normally counted in psi.

Bumpkin
by Bumpkin
Sun Mar 22, 2015 8:55 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: can a gamma stirling engine have cylinders at 90 degree angl
Replies: 5
Views: 4495

Re: can a gamma stirling engine have cylinders at 90 degree

Certainly. And another advantage you didn't mention is that a 90 degree V can be almost perfectly balanced if you get the displacer and power-piston weights the same and then adjust the crank counterweights until it smooths out.

Bumpkin
by Bumpkin
Wed Mar 11, 2015 2:47 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: "Hi...We are new here!" First posts here (or anywhere is OK)
Replies: 442
Views: 180683

Re: "Hi" We are new here!

"I'm a long time Stirling fan..." I always heard Stirling fans last a long time :laugh: welcome to the forum Dev.
Bumpkin
by Bumpkin
Tue Feb 10, 2015 12:25 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Low temp difference beta help
Replies: 15
Views: 6116

Re: Low temp difference beta help

Joe, for a Beta, I'm assuming where you say "expansion piston" you mean "displacer?" Anyway, for a low temperature difference engine I think you'll need a lot more displacer than your approximate 1.5/1 ratio. I don't know if I've ever seen an L.T.D. Beta.
Bumpkin
by Bumpkin
Thu Sep 04, 2014 9:24 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Dual Acting Cylinders
Replies: 27
Views: 22377

Re: Dual Acting Cylinders

The hot cylinder rod seal might be a problem, but I guess you could shroud it, sorta the same effect as an Alpha-type insulating piston crown. You've brought to mind this though: There is a type of double acting four cylinder Alpha where each cylinder bottom connects to the next cylinder's top at 90...
by Bumpkin
Tue Aug 05, 2014 1:12 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Would like some feed back on my simple Gamma design.
Replies: 5
Views: 3359

Re: Would like some feed back on my simple Gamma design.

Atli S, your ratio is probably fine. I was thinking more about melting things if you used too much burner. The aluminum melting point is around 900 Kelvin. A faint red steel heater would be about 760 degrees K, and a cooler just a bit warmer than room temperature would be about 300 K. So there's qui...
by Bumpkin
Tue Aug 05, 2014 7:21 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Would like some feed back on my simple Gamma design.
Replies: 5
Views: 3359

Re: Would like some feed back on my simple Gamma design.

Atli S, if the drawing is to scale you might lengthen the crank rods as far as possible towards the piston and displacer bushing, to limit side thrust. Your 1/1.5 displacement ratio is for relatively high temperature engines where your aluminum displacer might be a problem. But aluminum could handle...
by Bumpkin
Tue Apr 15, 2014 10:29 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Making it airtight
Replies: 3
Views: 3007

Re: Making it airtight

tomostre, thanks for the inspiration. The bicycle cable housing might be just the thing for something I'm doing.
Bumpkin
by Bumpkin
Mon Apr 07, 2014 1:32 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: High powered Stirling going into production
Replies: 72
Views: 54833

Re: High powered Stirling going into production

What distresses me about high-performance Stirlings is that the design goals always undermine the only real Stirling advantage of not needing store-bought fuel. I don't have a pellet mill to fuel a special burner, but the woodstove in my house is going almost constantly for over half of the year and...
by Bumpkin
Sat Feb 01, 2014 7:45 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: 2-cylinder Gamma - project
Replies: 69
Views: 27654

Re: 2-cylinder Gamma - project

I don't know where I saw it, but someone used wax paper to make custom silicone gaskets that would release on one side. Might be worth trying.

Bumpkin
by Bumpkin
Sat Jan 11, 2014 11:40 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Here's why we NEED a 10W Stirling generator!
Replies: 8
Views: 9677

Re: Here's why we NEED a 10W Stirling generator!

Business-wise, I think it's a mismatch. Unfortunately for all of us tinkerers, but fortunately for the world, a cheaper and more user-friendly solution to most of those challenges already exists in photovoltaics. I agree that Stirlings have a place in moderate-temperature applications where they can...
by Bumpkin
Sat Dec 07, 2013 8:15 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: 2-cylinder Gamma - project
Replies: 69
Views: 27654

Re: 2-cylinder Gamma - project

I can see how predicting exact diaphragm displacement could be difficult. Anyway, I don't think having a higher ratio of displacer volume would necessarily be a bad thing unless you're running very high temperatures. You could give it a try before changing it.

Bumpkin
by Bumpkin
Tue Nov 05, 2013 10:27 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: DIY rubber bellow as power piston
Replies: 17
Views: 13746

Re: DIY rubber bellow as power piston

Some silicone cook-pans have tapered sides, but the ones I've seen have reinforcing corrugations that defeat the purpose. You can make a roll-sock from an inflatable ball. Some are very pliable but don’t stretch too badly, so the movement stays where you want instead of adding dead space. They could...
by Bumpkin
Thu Oct 10, 2013 8:08 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: microwave induction stirling
Replies: 12
Views: 5188

Re: microwave induction stirling

Fullofhotair, by mentioning novelty I meant to be positive. Fun and science are often more important than efficiency and I was only saying that's one direction electrically timed and heated engines could take. It was just a random thought; my own interest is still wood-fired power. Ian, I think mayb...