This mechanism is similar to that in model S-27, but uses a rack and sector of a pinion gear to replace the thin wrapping band of S-27. The unwrapping of a tension band wound around a fixed cylinder produces an involute curve found in gear teeth profiles. The involute is related to the cycloid curve produced when a circular cylinder rolls on a fixed straight-line. In this motion, both the cylinder sector and the straight-line sector (the rack) are moving. The Voigt catalog attributes this mechanism to Reuleaux himself along with models S-27 and S-29.

Francis Moon 2004-07-00