Search found 18 matches

by brian hughes
Sun May 14, 2023 8:40 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Dynamometers- has anyone built or used one?
Replies: 1
Views: 2024

Dynamometers- has anyone built or used one?

Has anyone measured the power output of a small Stirling, either with a brake dump or figuring out the flywheel moment of inertia and the angular acceleration? I cobbled together a very crude setup with a tachometer, a pad rubbing against a flywheel and some kitchen scales, and derived a power outpu...
by brian hughes
Wed May 10, 2023 3:21 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Introducing... The Hippie Crack Engine
Replies: 12
Views: 3435

Re: Introducing... The Hippie Crack Engine

An interesting point that perhaps got missed in the video was the engine running on after the heat source was gone- there’s quite a lot of thermal mass in that little engine that needs to be “charged”- and my educated guess is that’s why you won’t get instant starting... and why Stirling Engines are...
by brian hughes
Mon May 08, 2023 2:31 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Introducing... The Hippie Crack Engine
Replies: 12
Views: 3435

Re: Introducing... The Hippie Crack Engine

Thanks for the replies, although I would be a little bit skeptical about having to spin engines before they start running on their own. I would have my doubts that this is anything to do with the Stirling Engine operating principle, and more to do with thermal lag and bearings warming up. If there's...
by brian hughes
Mon Apr 17, 2023 5:48 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Introducing... The Hippie Crack Engine
Replies: 12
Views: 3435

Re: Introducing... The Hippie Crack Engine

On the first test with the heat applied.... it wouldn’t keep running beyond one cycle- I would have thought that if it’s ever going to work, it should just need a quick nudge to get it out of a dead spot, after that, it’s on it’s own. I could tell *something* was happening- it was harder to crank ba...
by brian hughes
Sun Apr 16, 2023 2:25 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Introducing... The Hippie Crack Engine
Replies: 12
Views: 3435

Re: Introducing... The Hippie Crack Engine

With the first attempt with a diaphragm, and a much shorter coupling tube, it wouldn't keep running- my guess is that the force produced under that configuration wouldn't overcome the frictional losses. I think, though, that I'm onto something with the water manometer. The displacer was pretty crude...
by brian hughes
Sat Apr 15, 2023 8:15 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Introducing... The Hippie Crack Engine
Replies: 12
Views: 3435

Introducing... The Hippie Crack Engine

*** Can I/how do I embed videos in a post?*** I've made a bit of progress with a long running project, based round discarded Nitrous Oxide bottles. Basically, kids buy full bottles here in the UK for £20-£30, drive to a layby, have a party, and discard a nice chunk of thick walled tube, 70mm diamete...
by brian hughes
Wed Feb 09, 2022 3:04 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Power output- management of expectations
Replies: 11
Views: 2033

Re: Power output- management of expectations

Thanks for the reply- just to give a little bit more context, my heat source is going to be the -currently- wasted heat from my biochar making burners. I've currently got more heat than I know what to do with, by "heat", I mean hot flowing gas, and getting it transferred into the hot end i...
by brian hughes
Mon Feb 07, 2022 3:43 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Power output- management of expectations
Replies: 11
Views: 2033

Re: Power output- management of expectations

https://www.sciencedirect.com/topics/engineering/stirling-cycle I think the answer that I'm looking for is the equation: energy per cycle=(mass of air in play)*(gas constant for air)*(temperature difference)*ln(compression ratio) so, putting in values of 0.0005 kilos of air, 319.3 for the gas consta...
by brian hughes
Tue Jan 25, 2022 5:18 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Regenerators.... Have I got it straight what they do?
Replies: 5
Views: 1363

Regenerators.... Have I got it straight what they do?

I've been figuring out in my head how regenerators work, what they do, and what they don't do. Do I understand correctly, that they work by storing and releasing some of the heat energy, so that the engine takes smaller "bites" of heat per cycle? So they improve the efficiency, with a smal...
by brian hughes
Tue Jan 25, 2022 6:15 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Liquid Heating/Cooling of Hot/Cold Alpha Stirling Engine Cylinders?
Replies: 82
Views: 47669

Re: Liquid Heating/Cooling of Hot/Cold Alpha Stirling Engine Cylinders?

If you Google for "Pain Mound", that's the go-to technology for extracting heat from compost, but you really need to think in terms of large volumes- the power density of a compost heap is only about 250 Watts per cubic metre.
by brian hughes
Tue Jan 25, 2022 4:37 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Power output- management of expectations
Replies: 11
Views: 2033

Re: Power output- management of expectations

Thanks for the reply- do I understand... that there's around 2 Joules per revolution given the swept displacer volume and temperature difference? How do you calculate that? I do realise that it's a theoretical upper limit, but I can see 10 Watts to charge a phone within reach. Could you bring me up ...
by brian hughes
Tue Jan 25, 2022 4:12 am
Forum: Stirling and "Hot Air" Engine Forum
Topic: Diaphragm vs. Piston.....
Replies: 6
Views: 2170

Re: Diaphragm vs. Piston.....

Thanks for the reply- what I've got in mind is going to be fairly modular so that I can experiment. I want to see if I can incorporate a condom as the diaphragm :-)
by brian hughes
Sun Jan 23, 2022 4:41 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Rotary displacer...
Replies: 1
Views: 959

Rotary displacer...

....has anyone tried it? I'm talking about a semicircular cross section displacer rotating in a cylinder with the hot source on one side and the cold sink on the other? It won't match anything with a regenerator for efficiency, but it will eliminate a lot of the reciprocating mass.
by brian hughes
Sun Jan 23, 2022 4:34 pm
Forum: Stirling and "Hot Air" Engine Forum
Topic: Power output- management of expectations
Replies: 11
Views: 2033

Power output- management of expectations

Is there an accepted formula for what power output to hope for given the engine RPM, displacer bore and stroke, and temperature difference? The engine under construction is working between an estimated 300 and 600 Kelvin, with a displacer 65mm diameter and 120mm stroke, running on air without pressu...