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How to Build a Gearless Brushless Motor

Brushless gearless motors are most commonly found in high performance wheelchairs. The heavy loads and power starts of these devices plus the mission critical nature of the component make wheelchair motors a difficult engineering problem. The brushes are the weak part in standard DC motors. The constant rubbing wears down any material. The gear train always introduces friction and power loss. This loss of efficiency is intolerable in wheelchairs, which must carry their power supply and run for hours without recharging and without failing.

Things You'll Need

Permanent magnet
Stator with three windings
Phase controller

Instructions

- 1
  Put the permanent magnet at the center of the motor instead of around the edges. This is the big difference between a brushless motor and a conventional motor. Both motors work by the interaction between a magnet and the constantly changing field of an electromagnet. In the brushless motor, the permanent magnet in the rotor -- the central rotating part -- instead of in the stator -- the fixed outer part.
- 2
  Wind the stator with three coils spaced 120 degrees apart. At any time, the poles of the rotator are being attracted by the electromagnet in front of it and repulsed by the electromagnet behind it. Getting the correct current to the correct coil of the stator at exactly the right time is the responsibility of the phase controller. These are boxes containing coils and capacitors, which shift the current 120 degrees forward and backwards. They are normally used to control three phase AC motors.
- 3
  Embed the motor in the object you will be turning, so no gearing is necessary. This is the main reason that gearless motors have not found a lot of uses outside of wheelchairs. It is easy to embed the motor in the wheel of the wheelchair. Instead of a small rotor that is entirely contained within the stator, a magnetized rail runs around the wheel of the wheelchair and the rotor runs through the brushless gearless motor. This arrangement is not feasible in many applications.

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