The rectilinear crank consists of two sliders, one vertical, the other horizontal, running inside a cruciform guide.  The sliders cross each other's path, moving across the gap at the centre where the guide bars intersect. The piston end is connected, via a bearing, to the vertical slider. The sliders are joined by link arms which co-ordinate their movement. The geometry is such that as the vertical slider is pushed up and down by the piston, the horizontal slider is pulled from side to side. At the same time, the centre point of each link arm proscribes a circular path, and it is here that the main crank pin is attached, and the crankshaft is driven round.

The action is fascinating to watch. Strictly speaking, it is not crankless, but the crank pins' throw is only half the piston stroke length. The engine has two rectilinear crank assemblies in tandem.