The basic concept of a reciprocating engine goes back about 300 years when first developed into a crude stream engine. the same basic principles are used in today's modern engine where expanding gas is used to drive a piston and a crank is used to convert the movement into rotary motion. This engine will run on the either the exhaust or vacuum of a shop vac, a vacuum sweeper, or compressed air.
The stroke of the piston is 4 inches
The movement of the cam to drive the air diverter is 2 inches
240 RPMs as shown... max is about 400 RPMs