An induction motor can be constructed in such a way as to produce a magnetic field travelling in a straight line. Such a device can be used to propel a shuttle across a loom. A stator arrangement is described by which the shuttle can be caused to oscillate without the use of switches. With suitable design there is an inherently stable condition. Expressions are derived for the amplitude and period of this oscillation, for an unloaded motor, and for a motor operating against a constant load force. These are used to derive theoretical curves and phase-plane diagrams which are compared with those obtained in practice. Proposed practical schemes are discussed.