Dc motor spinning faster in one direction than the other

[OPM881]

The title says it all, but basically I have a 24volt dc 150watt motor that is hooked up to 2 12V9AH sealed lead batteries that is spinning faster in reverse than forward. I cannot for the life of me figure out what is wrong. I opened the motor up and it looked alright inside. Any ideas?

Alternatively, if anyone knows where I can get a dc motor with a gear drive fit for an electric skateboard/scooter that doesn't cost more for shipping than te motor, that would also be helpful

[RussellK]

I think that's not uncommon for a brushed motor - from what I understand, you can adjust that behaviour by rotating the brushes.

[paulvk]

Something like this do http://secure.oatleyelectronics.com/...7bbc7b7bb8cebd

[OPM881]

Ive looked at Oatley before, but he never responded to any of the 3 emails I sent. I found a guy out of paramatta that has ended up having one(every other time I googled my current models number it only came up with stuff from china where a minimum purchase was 50 of them), so have ordered from him. Still would like to know why the hell it is doing this though

Russel, when you say rotating the brushes, are you talking about turning the brushes around inside their casing, or moving the whole thing around?

[RussellK]

Originally Posted by OPM881

Russel, when you say rotating the brushes, are you talking about turning the brushes around inside their casing, or moving the whole thing around?

I think the whole arse-end of the motor gets rotated which has the effect of changing when the coils are energised with respect to their position relative to the magnets. By adjusting this timing, you can optimise the performance of the motor, but for one direction only, thus it runs slower in the other direction.

[TRG.dOinK]

lol I also emailed Oatley a question a week ago, never got a reply. Poor service.

[mtma]

It's due to the timing of the commutator (which on a DC motor affects the timing of the magnetic field generated on the rotor).

It's usually advanced on one side by a certain angle to cause the motor output to be higher for a certain rotation direction. That's most likely what you're seeing here.

The motor in reverse would see a retarded timing - which translates to lower output.

In RC car racing back when brush motors were the common motor racers would adjust the timing on some of the motors to get even higher output than previously possible without changing anything else. (and in some racing classes this was considered cheating)

You will also notice this on some (most?) drills - usually unscrewing is slower by a reasonably noticeable amount - although the difference in the noise is usually the big give away.

ED- I also don't see why this is a problem given how normal electric skateboards are (with one driven wheel). Would possibly be an issue if you had individually driven motors though.

[paulvk]

I have always rung Oatley to ask questions and place orders but I think they are suffering as all others with a lot less sales and I think now only have a few staff but have always received what I ordered.

[OPM881]

Originally Posted by mtma

It's due to the timing of the commutator (which on a DC motor affects the timing of the magnetic field generated on the rotor).

It's usually advanced on one side by a certain angle to cause the motor output to be higher for a certain rotation direction. That's most likely what you're seeing here.

The motor in reverse would see a retarded timing - which translates to lower output.

In RC car racing back when brush motors were the common motor racers would adjust the timing on some of the motors to get even higher output than previously possible without changing anything else. (and in some racing classes this was considered cheating)

You will also notice this on some (most?) drills - usually unscrewing is slower by a reasonably noticeable amount - although the difference in the noise is usually the big give away.

ED- I also don't see why this is a problem given how normal electric skateboards are (with one driven wheel). Would possibly be an issue if you had individually driven motors though.

The issue is that the output going forward is so low that it is unable to use it to go forwards, and as the setup is only for going forward, that is sorta useless. I will try adjusting the motor when I get home, is always good to have a spare, might even try setting up an electric longboard with the spare if I can get the original to work fine.

[oculi]

Originally Posted by OPM881

The issue is that the output going forward is so low that it is unable to use it to go forwards, and as the setup is only for going forward, that is sorta useless. I will try adjusting the motor when I get home, is always good to have a spare, might even try setting up an electric longboard with the spare if I can get the original to work fine.

Flip the whole motor/ whatever around then?

[OPM881]

Originally Posted by oculi

Flip the whole motor/ whatever around then?

Cant do that due to the way the mounts work on this board. The board itself isnt a normal skateboard, it is a pure metal frame that has individual legs for each wheel that allows for tighter turning and nice handling. Because of how the legs are constructed, it isnt just a matter of swapping what wheel it is hooked up to.