A pencil-sized motor to write home about

A motor with a similar diameter to a pencil (8mm), and a shaft as thin as a pencil lead (0.8mm), has been developed by the Swiss precision motor manufacturer, maxon. The 16mm-long DC motor (shown below) weighs less than 4g and can deliver a nominal 0.5W.

The electrical insulating properties of the ceramic shaft allows an extremely compact contactor design. Precious metal brushes are used to ensure constant low-contact resistance contact between the brushes and commutator.

At the heart of the RE8 motor is a patented, lightweight, ironless rotor which has a low inertia and allows rapid acceleration. Maxon claims that it much more efficient than rival motor designs, making the motor suitable for battery-powered applications such as insulin pumps.

Options include planetary gearheads for applications where the motor speed is too high and the inertia too low, and sensors for detecting the motor`s speed and position.