[lerman]

They claim to use standard components, pistons, rings, etc. Sure they do. You just take a standard piston and bend it so that it will fit inside a torus.

To make a standard cylinder, you just bore it and lap it. I can make a piston on my lathe. Then turn some grooves for piston rings. Or, I could cast the piston out of aluminum and then turn some slots for rings. That's not so easy with a curved piston.

Ken