For brushed or brushless, there is apparently a method that can be done to adjust efficiency slightly. When I built my electric boat, I had some conversations with the motor designer of the Etek. I was doing dyno testing and had noticed that FWD and REV currents were different, I was curious so I asked why. In his response, he gave this tidbit:
"The motor control's software was developed to give the best efficiency at the load points when it is used as an outboard motor (propeller loading).
Usually, the no-load current is the same in forward and reverse. This is normally set on the assembly line.
You can experiment with the efficiency under full load. Simply mark the two halves of the case with a scribe or paint marker, then you can loosen the bolt that holds the two halves together. A "tap" of a hammer and you can rotate the two case halves to effect the timing. This will give you the same current in forward and reverse, but may slow the motor in the forward direction.
I have done this on a running motor. You can try this out on the water to see if you can get the loaded current to decrease."
--- In electricboats@yahoogroups.com, "John Green" <v_2jgree@...> wrote:
>
>
> Hi,
> I was just wondering if there is any advantage to having the brushes in
> a DC motor able to rotate slightly as a unit around the axis of the
> commutator.
> Seeing as it must take time, albeit small, to create a magnetic field,
> then just like with spark timing on a gas engine, which advances as the
> speed increases, maybe the torque, in particular, of a DC motor could be
> changed by changing the timing of the contact with specific commutator
> segments?
>
> John
>
>
> --
> http://www.fastmail.fm - Send your email first class
>
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