Pressure is supplied to each cylinder by means of a fixed plate forming a plain thrust bearing with the back of the cylinder block. This has two openings in it which supply and exhaust steam to and from the cylinder; as the cylinder block rotates it opens and closes communication with each pipe. This method of valveless steam admission is also used on many basic oscillating cylinder engines. This arrangement results in a compact engine with a low part count, at the expense of including a large frictional surface.
