Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Hi Charlie,

The only advantage of using the Scotch yoke design I can think of is that it makes a shorter more compact engine because no connecting rod is required. I think the full size engines were mostly used as pumps, the ram of the pump being on the opposite side of the yoke to the piston rod, a Weir type pump with Stephenson valve gear, if that makes sense?

Take care Tony.