Adjusting PMDC Motor Timing

The ETEK (Manta) motor I have has the timing set to neutral- that is, the magnets can be rotated a few degrees in either direction.  Supposedly, it’s set up neutral so it can be run adequately in both directions, but if you’re planning to run it on only one direction, you may be able to take full advantage of it by advancing or retarding the magnets- AKA timing the motor.

Here’s an easy to understand explanation of that procedure, from a model aircraft site:

As the motor rpm increases it requires the rotor coils to be energised sooner so that they get the full magnetic field strength in time to react with the stator’s
magnetic field. Also when the load increases, the magnetic field in the rotor coils increases, which interacts with the stator’s magnetic field, producing a rotated resultant magnetic field.

Some motors allow the brushes’ angle to be changed by the same amount as the field rotation, thereby increasing the motor’s efficiency under a given load.
That’s called for motor “timing”.

An electric motor may be timed under load by slowly changing the brush holder’s angle while measuring the current. The ideal brush angle is when the motor draws less current. There is no fixed ideal timing angle, since the best timing angle changes as the motor load and speed changes.

So, there’s the problem.  To time it properly, you have to be able to load it and spin it up to a similar speed as your riding speed – probably something best done with a dynomometer.


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