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Hi, I just made a simple Gamma engine that I want to make and see if it works before I make a more grand design with more machined parts and ball barrings.

The basic specs are

Displacement piston, 22mm diameter/ cyl is 23mm. Made from 7075 aluminium. Weighs 32.5 grams. The left rotating assembly is about 117 grams.

Power piston, 17,96mm diameter/ cyl is 18mm. Made from 304 stainless. Weighs 32.9 grams. The right rotating assembly is about 77,3 grams.

The swing wheel is 70mm diameter and weighs in at 270 grams.

Stroke is 21mm.

There are brass bushings for the crank and for the displacement piston rod.

There will be fittings and pipe between cylenders. See holes.

Think that should just about cover the basics.
Is there anything that you would do diffrently, what and why?

Best reg
Atli S
Iceland.

https://imageshack.com/i/p30UVBx2j

https://imageshack.com/i/ewI8131Lj

Atli S, if the drawing is to scale you might lengthen the crank rods as far as possible towards the piston and displacer bushing, to limit side thrust. Your 1/1.5 displacement ratio is for relatively high temperature engines where your aluminum displacer might be a problem. But aluminum could handle your wonderful Iceland geothermal heat.

Bumpkin

Bumpkin, thanks for the input. Yes everything is to scale. So i'll shorten the rods as far as I can.
As for the displacement ratio. Nothing is set in stone. Should I make displacer piston bigger to run a little colder engine? Then aprox how much bigger. I'm not looking for a very fast running engine, just a smooth running engine :)

best reg

Atli S

Atli S, your ratio is probably fine. I was thinking more about melting things if you used too much burner. The aluminum melting point is around 900 Kelvin. A faint red steel heater would be about 760 degrees K, and a cooler just a bit warmer than room temperature would be about 300 K. So there's quite a bit of room under that 760/300 temperature ratio that could still provide a 1.5/1 expansion ratio. I think a lot of the temperature difference is lost in each step through a running engine though.

Bumpkin

Oky, but it's only the piston that is made from 7075 al, the cyl it self is made from 316 stainless. Will just give it a try and see what happens :)

Atle S, I would swap the aluminium piston for a cast iron one, The aluminium one needs lots of clearance compared to a CI one even though the heat at this point is not great, The aluminium has a high coefficient of friction, and it wears badly as a sliding surface. The pistons in your car have iron rings, and lots of oil, if the oil system breaks down you'll soon know. Ian S C