The main advantage of this design is a compact and simple mechanical
layout. The drive is transferred from the crankshaft to the valve within
the main body of the engine, and without the need for any external
components. This is of particular interest for the model engine
application where compact size is of particular importance. The RCV "SP"
range of model engines take the power output from the top of the
rotating cylinder. This leads to a particularly compact design ideal for
scale modelling applications.