Search found 131 matches

by Bumpkin
Fri Aug 07, 2015 9:34 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: directional air flow
Replies: 5
Views: 4944

Re: directional air flow

Directional flow might have some advantage, but it loses the Stirling advantage of simple regeneration that comes from the air passing forth and back through the same route. Ericsson incorporated regeneration with his directional flow design, but it was more complicated. It might be worth looking up...
by Bumpkin
Sun Aug 02, 2015 1:34 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: dwell on displacer
Replies: 16
Views: 11097

Re: dwell on displacer

Hi. The thing that always bothers me about these whang-bang systems of longer dwell, is that it takes energy to accelerate the displacer each time it moves instead of the normal crankshaft connection where deceleration returns the energy to the flywheel. An eccentric gear drive or roller cam or othe...
by Bumpkin
Fri Jul 31, 2015 9:21 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Hi Temp Bellows
Replies: 6
Views: 5948

Re: Hi Temp Bellows

Hi mastrovetraio. The linkage could be quite simple; a normal crank with three throws, the center driving one end and the other two far enough outboard that the rods bypass outside the bellows to drive the other end. There may be good reasons to do it another way though. There are a few opposed Alph...
by Bumpkin
Tue Jul 28, 2015 11:36 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Hi Temp Bellows
Replies: 6
Views: 5948

Re: Hi Temp Bellows

I just saw the picture in your introduction post. Beautiful glass work. To my mind, artistic expression is one of the Stirling engine's strong points. Magic and beauty. A lot of potential there.
Bumpkin
by Bumpkin
Tue Jul 28, 2015 11:16 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Hi Temp Bellows
Replies: 6
Views: 5948

Re: Hi Temp Bellows

Hi mastrovetraio. I wouldn't expect much power or speed, but those could sure make a bright demonstration engine. I made a model {not an Alpha} from a car shock-absorber bellows, and some observations: You don't need a wrist-pin joint, but if the bellows extends very far, the top will flop around un...
by Bumpkin
Mon Jul 27, 2015 10:39 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Gamma not working
Replies: 66
Views: 29612

Re: Gamma not working

The pictures and text are frustratingly puzzling, but It looks like a toilet plunger; purpose-built to induce more pressure on one side than the other. I think the mentioned 5 psi would be possible before the s hits the fan. Certainly other diaphragm designs and materials like truck air brakes commo...
by Bumpkin
Sun Jul 26, 2015 10:28 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Gamma not working
Replies: 66
Views: 29612

Re: Gamma not working

Hi burnit. Just some random thoughts. Some sort of adjustable balance spring might serve better than a balance weight to overcome the diaphragm tension and/or varying levels of pressurization. The spring could hook to the rod so as to balance the forces before they add to friction loads at the rod a...
by Bumpkin
Thu May 28, 2015 8:40 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Large LTD Stirling for CHP
Replies: 7
Views: 6407

Re: Large LTD Stirling for CHP

No worries of being off-putting. If we can't be genuinely thankful for genuine criticism, we can't evolve. I've already changed part of the mentioned page, so again thanks. We're of like mind about getting power from wood with large displacement and off-the-shelf parts, but we need to consider "who'...
by Bumpkin
Wed May 27, 2015 5:48 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Large LTD Stirling for CHP
Replies: 7
Views: 6407

Re: Large LTD Stirling for CHP

I have far less money than sunshine, and my p.v.s are certainly more than 20 years old, but if we have different priorities for efficiency that's fine. Thanks for looking at my thoughts on heat transfer, I can see I'll have to work on being more clear.

Bumpkin
by Bumpkin
Sun May 24, 2015 11:31 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Large LTD Stirling for CHP
Replies: 7
Views: 6407

Re: Large LTD Stirling for CHP

Hi MisterQED. I think sometimes people follow technology away from their goals. I can't see much point in Stirling engines trying to compete with modern photovoltaics or internal combustion, but when burning alternative fuels for heat in cool climates, a CHP Stirling makes a lot of sense. Unfortunat...
by Bumpkin
Tue Apr 21, 2015 12:27 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Eliminate the displacer?
Replies: 1
Views: 8021

Eliminate the displacer?

Hi folks. Some recent down-time left me with too much thinking and too little doing. Here's part of the residue, in case it could be useful to someone. For possible critique or discussion there's more stuff and a contact address at my page on wood stove co-generation: http://spragueriver.com/index.p...
by Bumpkin
Wed Apr 15, 2015 6:57 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Beta Stirling Project
Replies: 27
Views: 11491

Re: Beta Stirling Project

Hi Akya. Sorry to bring this up a week late, and you probably already accounted for it, but I just remembered something regarding the question of finding the point where the displacer and piston are closest. Make sure you account for the rod deflection angle: for instance, unless the rods are infini...
by Bumpkin
Sun Apr 05, 2015 12:45 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: calculating relative dimensions
Replies: 11
Views: 5535

Re: calculating relative dimensions

In numerous prior posts Ian has explained traditional ratios far better than the illustration above. For modeling, history, and art, staying reasonably close to those recommendations should serve well for high-temperature engines. Other goals might need other ratios, derived from understanding a bit...
by Bumpkin
Thu Apr 02, 2015 8:10 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: calculating relative dimensions
Replies: 11
Views: 5535

Re: calculating relative dimensions

Wow. Sorry for the confusion. But honestly, if you were really going to go that way, triangles might be more fun. Bill, "relative" was meant to reference the equation where it looked like you wanted to work out the displacment to match the famous, or infamous, 1.5/1 ratio. Comparing squares to circl...
by Bumpkin
Wed Apr 01, 2015 8:02 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: calculating relative dimensions
Replies: 11
Views: 5535

Re: calculating relative dimensions

For relative displacement, pi doesn't matter. You could have square pistons and the answer would still be the same. So all you need to do is compare bore x bore x stroke. And if there's just one crank pin as is likely in the example picture, you don't even need to know the stroke - just bore x bore ...