An Aspin valve
consists of a cone
part fitted to the cylinder head
. Aspin valves were first patented by Frank Metcalf Aspin in 1937 although the idea was probably devised before this time. It has a large opening in one side which reveals the gases
in its internal combustion
chamber to the spark plug
, inlet port and outlet port accordingly. It is attached to the engine
via a shaft at its top, allowing it to rotate horizontally above the cylinder.