Piston Cylinder Connection for Alpha Stirling

Discussion on Stirling or "hot air" engines (all types)
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robwallbank
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Joined: Sun Nov 13, 2016 4:26 pm

Piston Cylinder Connection for Alpha Stirling

Post by robwallbank » Sun Nov 13, 2016 4:46 pm

Hi, I am building a model Alpha Stirling engine for a university project and am having an issue with the connecting tube between the two piston cylinders. The two cylinders have a bore of 24 mm and come with a removable plastic end (which I think can act as a seal?) which in turn has a bore of 17.7mm (its from Airpot, model 2KS240 for reference). The tubing connecting the two should ideally be removable, as I am hoping to test it with and without a regenerator to see the effects on efficiency.
Any tips or advice on how to achieve this, and retain a good seal, would be greatly appreciated!

Ian S C
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Re: Piston Cylinder Connection for Alpha Stirling

Post by Ian S C » Tue Nov 15, 2016 3:21 am

Is the motor to be a GAMMA, or ALPHA, and what lay out, V , or parallel, Ross Yoke , or ordinary crankshaft. How are you going to incorporate the glass cylinder into the hot cylinder.
Ian S C

robwallbank
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Joined: Sun Nov 13, 2016 4:26 pm

Re: Piston Cylinder Connection for Alpha Stirling

Post by robwallbank » Wed Nov 16, 2016 10:14 am

Thanks for your response! It is Alpha, V layout (pistons at 90 degrees to each other) with an ordinary crankshaft. Both of the hot and cold cylinders are made of glass due to the fact that we have very limited workshop time and so are buying them in, as this saves time and they have a lower coefficient of friction than what we could make ourselves.

Ian S C
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Location: New Zealand

Re: Piston Cylinder Connection for Alpha Stirling

Post by Ian S C » Thu Nov 17, 2016 2:10 am

I think I made the Heylandt Crown on the hot piston of my ALPHA motor about two and a half times the diameter high, this allows the hot cap to be fairly long, thus keeping the heated area as far as possible from the fitted piston end, so that the hot piston is not too hot while the top of the hot cap runs at red heat.
The transfer tube for the V engine would go from the joint between the glass cylinder, and the hot cap, to the top of the cold cylinder, this could incorporate the regenerator, but if made a bolt on fitting the tube could easily be changed to a plain tube or a different regenerator.
Ian S C

robwallbank
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Re: Piston Cylinder Connection for Alpha Stirling

Post by robwallbank » Fri Nov 18, 2016 8:15 am

I hadn't thought about a Heylandt Crown - honestly I haven't heard of it before! How would I incorporate that into the bought in cylinders, sorry?
How would the bolt fitting be attached? Just because the cylinder is made of glass I would be worried about cracking it or deforming it and blocking the piston movement?
I have since been advised by uni technicians that using o rings/rubber seals would be alright due to the low pressures involved (as it is only going to be powered by a small candle) and basically just pushing the tube in. My only question with regards to this is if the inner bore of the seal is 17mm would an outer diameter for the tubing of also 17mm be alright? Or would it need to be slightly smaller to hold it in properly?

Ian S C
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Location: New Zealand

Re: Piston Cylinder Connection for Alpha Stirling

Post by Ian S C » Sun Nov 20, 2016 1:54 am

For the hot cylinder the glass part would be the same size as the cold cylinder, but the cold cylinder would have a flat cylinder head, where as the hot one needs an extension made of (preferably) stainless steel, this is the area that gets heated. This is my Ross Yoke ALPHA motor as it was when first built, the water jackets have been removed, and replaced with aluminium fins, next thing to fit is a fan for cooling. The hot cap is the tall part with the gas burner near the top.
Ian S C
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Test 008 (640x480).jpg (185.55 KiB) Viewed 3316 times

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