Rack-and-pinion motors: hybrid of linear and rotary machines

The field over an open-sided linear motor contains a rotating component which can be used to spin rotors of a variety of types. If the field of the linear motor is visualised as a magnetic `river¿, the motion is analogous to a mechanical rack and pinion. The paper concentrates on reluctance- and hysteresis-type rotors which can develop substantial torque in small sizes. It is shown that the possible acceleration of steel rotors increases with decrease in size. The effect of linear-motor fields on iron and steel filings is investigated and a demonstration of rack-and-pinion action using a permanent magnet is described.