The McMaster motor is based on spherical geometry and has only two moving parts – the shaft and ball assembly, and the wobble-plate assembly.

Its spherical working chamber features stationary vanes fitted into slots in two inclined cones, which contact opposite sides of the wobble-plate assembly. This creates two firing chambers, each between the vane, the wobble plate and the two opposing cones.

A glow plug is used to initiate ignition, which occurs in the narrow, triangular cavity created by the inclined cones, the wobble plate and the stationary vane.

The motor fires twice each revolution. The first firing causes the wobble plate to nutate, or oscillate, which turns the shaft 180 degrees. The second firing, in the opposing chamber, causes the wobble plate to nutate back to its original position, thus completing the rotation of the shaft and ball assembly a full 360 degrees.

Each power stroke results in very smooth, high torque, equivalent to an eight-cylinder engine.