Search found 131 matches

by Bumpkin
Sun May 01, 2016 8:21 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: My first post. Advice needed.
Replies: 32
Views: 14352

Re: My first post. Advice needed.

Simple and easy are entirely different things. To return to the original premise of a useful engine to add on to a woodstove: In Stirling-engine parlance that's a moderate-to-low temperature heat source, so you need a relatively large engine to process heat in and out externally, regardless of how h...
by Bumpkin
Sat Apr 30, 2016 7:52 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: My first post. Advice needed.
Replies: 32
Views: 14352

Re: My first post. Advice needed.

Narrow street bicycle tires can inflate as high as 130 psi. That's about ten bar. (The first bar wouldn't show on a gauge.)
Bumpkin
by Bumpkin
Tue Apr 19, 2016 12:28 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: My first post. Advice needed.
Replies: 32
Views: 14352

Re: My first post. Advice needed.

Hi Wellington. . I think this form of cogeneration is one of very few truly useful areas to invest Stirling development. Check out the electronic competition of Thermal Electric Generators first though. Cheap TEGs are becoming more available and may be getting to the point of making all of this much...
by Bumpkin
Mon Mar 14, 2016 7:22 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Gamma not working
Replies: 66
Views: 29539

Re: Gamma not working

Hey burnit0017 thanks for finding the more extensive write-up I asked about. It turns out I've seen it before, but thanks again.

Bumpkin
by Bumpkin
Sat Mar 12, 2016 2:33 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Gamma not working
Replies: 66
Views: 29539

Re: Gamma not working

It looks like for an initial 25% absolute temperature difference they'd design for about a 6% expansion with a 16-1 displacement ratio. Granted, there will be drops in difference through the exchanges, but it seems that if you design more towards the theoretical potential, the engine will find its o...
by Bumpkin
Sat Feb 13, 2016 10:59 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Please Check my Calcs....
Replies: 6
Views: 4471

Re: Please Check my Calcs....

Hi Sam. --------- "i agree forums like this should easily be able to produce guide lines or at least a range of examples from working engines" ---------- Actually the only guidelines I'd like to see here are basic thermodynamics and Stirling terminology. Individual thoughts and examples can be inspi...
by Bumpkin
Sat Feb 13, 2016 9:52 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Please Check my Calcs....
Replies: 6
Views: 4471

Re: Please Check my Calcs....

OK. It was a Friday night and it looks like I ran on a bit. My main point would be that In the interest of science it'd be helpful to agree on some basic terminology. I'll accept whatever works best, but I prefer "swept volume" for the mentioned ratio. I think "displacer volume" can lead to some con...
by Bumpkin
Fri Feb 12, 2016 8:20 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Please Check my Calcs....
Replies: 6
Views: 4471

Re: Please Check my Calcs....

Hi samandress. I think you're on the right track. (I think the underlined is backwards, otherwse I basically agree with this table) 1:1.5 high temp gas burners only 1:7 coffee cup engine (candle or hot water) 5:1 to 8:1 range for a stove top fan engine - 1:16 stove top example 1:10 to 1:20 LTD -----...
by Bumpkin
Fri Jan 08, 2016 11:30 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Low Temperature Differential Stirling engine plans
Replies: 14
Views: 9566

Re: Low Temperature Differential Stirling engine plans

Hi Ben. From the picture, it looks like the wrist-pins might be higher than they need to be. This could cause a bit of extra rocking friction and/or possibly leakage. Also, if it takes longer to heat the bottom plate there's more time for the heat to migrate to the top. You might try cooling the top...
by Bumpkin
Wed Jan 06, 2016 11:51 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: removing the achilles heal of stirling motors
Replies: 21
Views: 13300

Re: removing the achilles heal of stirling motors

Auret, I like these forum exchanges for the thought-provoking aspects, whether of understanding or confusion. I reckon I see the gist of your idea now. For my own purposes I'm less concerned about getting heat through the walls than I am about the internal exchange between the walls and the air, but...
by Bumpkin
Wed Jan 06, 2016 9:18 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: removing the achilles heal of stirling motors
Replies: 21
Views: 13300

Re: removing the achilles heal of stirling motors

Hi auret. Welcome to the forum, I always welcome ideas that make me think. "I trust you can see the thin walls between the working fluid and the hot and cold sources, that you understand the pumping technique to achieve this." Actually no I can't see it, but I want to. Terminology like gate and impe...
by Bumpkin
Sat Dec 12, 2015 1:18 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: In ground engine for cold climate question
Replies: 3
Views: 2828

Re: In ground engine for cold climate question

Hi paulstef. Certainly no practical knowledge here, but I think for minimal expectations your idea is certainly possible. You'd be limited to the conductivity of the dirt, so it'd probably need a big network of contact area. A loop dropped down a well into flowing ground water might make a more sust...
by Bumpkin
Wed Dec 09, 2015 8:20 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Building a Woodstove Fan Stirling Engine
Replies: 9
Views: 6689

Re: Building a Woodstove Fan Stirling Engine

Sorry for a bit off-topic newtechnician, but Ian, is your Ringbom motor self-starting? If so, I realize it might start in the wrong direction as a fan, but it would be handy to power an alternator.

Bumpkin
by Bumpkin
Tue Dec 08, 2015 1:59 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Building a Woodstove Fan Stirling Engine
Replies: 9
Views: 6689

Re: Building a Woodstove Fan Stirling Engine

Hi newtechnician. I think you would have a tough time getting a useful temperature ratio with the VW cylinder as the displacer chamber. Unless you could somehow insert a heat-break gasket, the heat will probably migrate along the cylinder faster than you could heat and cool the ends. Displacement ra...
by Bumpkin
Thu Aug 13, 2015 9:37 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: dwell on displacer
Replies: 16
Views: 11082

Re: dwell on displacer

---------------------------------------------------------------- Hi guys. I think we got to talking cross-purposes. Ian, I totally agree that a scotch yoke can run fast and smooth. I might have misunderstood, but I believe the slotted yoke tew mentions is for a different purpose - to allow some cran...