The longer link AB has a pivot at its mid-point to which the shorter link is connected.

Great care has been given to each item so as to provide wide experimental scope without unduly complicating or compromising the design.

Each piece of apparatus is self-contained and compact. Setting up time is minimal, and all measurements are made with the simplest possible instrumentation, so that the student involvement is purely with the engineering principles being taught.

Due to CD = BD = AD the geometry guarantees that as B moves toward C the point A must travel in a straight line. This equipment is part of a range designed to both demonstrate and experimentally confirm basic engineering principles.