Large LTD Diaphragm Gamma Stirling Questions

Discussion on Stirling or "hot air" engines (all types)
Bumpkin
Posts: 127
Joined: Fri Mar 02, 2012 1:42 pm

Re: Large LTD Diaphragm Gamma Stirling Questions

Post by Bumpkin » Wed Mar 21, 2018 11:27 am

Hi playludesc
Development of these engines is more important to me than the modeling, so know I mean this respectfully. You can always copy other engines, but for unique circumstances and applications you should learn the basic science behind the ratios. You could Google the Ideal gas law or Boyle's law, and the Kelvin scale for starters. Or here's a bit more involved rundown with some relevant links (It's a few years old and I haven't checked the links lately.) It's meant for wood stoves, but the science is all the same. http://spragueriver.com/index.php/bumpkin-tech

Bumpkin

playludesc
Posts: 9
Joined: Sun Mar 04, 2018 10:16 am

Re: Large LTD Diaphragm Gamma Stirling Questions

Post by playludesc » Thu Mar 22, 2018 11:48 am

Thanks for the heads up, bumpkin! Just so you know, I'm not just modeling this for the fun of it--I plan to 3D print most of the parts excluding the hot and cold caps and hardware. I also plan to try and pressurize the engine with helium if I can figure out a good seal for the connecting rods. I have an idea, but I won't know if it's a good one until it's all put together. I'll definitely do some research into the gasses in hopes to get my piston and displacer ratios right on the first try. Fortunately, the printer makes revisions rather quick and easy.

Ian S C
Posts: 2150
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: Large LTD Diaphragm Gamma Stirling Questions

Post by Ian S C » Fri Mar 23, 2018 2:05 am

Up to 80 Bar or so you are just as good with a gas like Argon, it's much cheaper, and easy to get, up to 40 Bar, stick with air, at least to start with, Philips did ok with it, and its free.
Ian S C

playludesc
Posts: 9
Joined: Sun Mar 04, 2018 10:16 am

Re: Large LTD Diaphragm Gamma Stirling Questions

Post by playludesc » Fri Mar 23, 2018 9:25 am

Yeah, I'll be pressure testing it with air for sure. Need to figure out when my 2mm thick aluminum caps are gonna start bulging/when my o-rings are going to fail. But my guess is my plan for sealing the connecting rods will be the first point of failure.

Ian S C
Posts: 2150
Joined: Thu Dec 02, 2010 5:15 am
Location: New Zealand

Re: Large LTD Diaphragm Gamma Stirling Questions

Post by Ian S C » Sat Mar 24, 2018 4:31 am

2 mm aluminium isn't going to be over good under pressure. I havn't pressurized it, but when I built my Ross Yoke ALPHA motor I built it in steel, and the thinnest part of the crank case is 1/8", originally it was 3/8", but when I decided that pressurization was unlikely I got rid of a lot of weight.
Ian S C

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