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

Hi Bob,

There are two pistons at 180 degrees to one another in the same cylinder and the two cross heads share the same guides; the centre crank drives the lower cross head its piston rod going through the piston rod of the upper piston rod which is driven by the two outer cranks. The lower cross heads piston is at the top of the cylinder the higher cross heads at the bottom. The pistons start together in the middle of the cylinder which is twice the length of the stroke and they move apart.  I hope this makes sense?  The idea I think is to have a balanced engine.

Take care Tony.