[Matej]

Hello,
Are there any places online where one may purchase 'universal' brush holder rings in various sizes?

I have a nice small motor that would be perfect for a motorcycle, but it only has two brushes. I would like to convert it to four brushes if possible.
Also, instead of re-drilling the end bell or housing to advance the motor, I would rather advance it by drilling new holes in the brush holder, assuming it is not more expensive than the motor itself.

Thank you.

 

[major]

Hello,
Are there any places online where one may purchase 'universal' brush holder rings in various sizes?

I have a nice small motor that would be perfect for a motorcycle, but it only has two brushes. I would like to convert it to four brushes if possible.
Also, instead of re-drilling the end bell or housing to advance the motor, I would rather advance it by drilling new holes in the brush holder, assuming it is not more expensive than the motor itself.

Thank you.

Typically there is no "universal" brush holder assembly. Such assemblies are custome designed for each motor or series of motor designs/manufacturers. If you can find sufficient information, it may be that a motor maker has service replacement parts which will fit different designs.

If you're talking about going from 2 brushes at 180° to 4 at 90° apart, that won't work as the motor would need to change from 2 to 4 poles.

By-in-large, the brush count and size in a particular design is suitable for its rating along with the rest of the components used in that design. For a particular duty cycle, the brush may be the limiting factor thermally, but doubling the brush would likely mean another feature will become the new limit, like the armature wire, or even the commutator. I don't see a circumstance where doubling the brush is a reasonable or even a workable improvement unless the motor design was deficient in the first place.

Regards,

major

 

[Matej]

Thank you for the reply major.
The brushes are actually next to each other, at 90 degrees. Does that mean it should be possible to convert it to four brushes?

After searching online today I actually found the exact brush holder as is in the motor. It seems that it is shared with various golf cart motors.

It looks exactly like this, minus two brush brackets.

 

[major]

Thank you for the reply major.
The brushes are actually next to each other, at 90 degrees. Does that mean it should be possible to convert it to four brushes?

After searching online today I actually found the exact brush holder as is in the motor. It seems that it is shared with various golf cart motors.

It looks exactly like this, minus two brush brackets.

Something is fishy. I need to see what you have. Please post photos inside and out along with specs. What you propose is possible but so unlikely I'd give it like 0.01% chance.

 

[Matej]

It is the same motor as this one. Made by ADC for Caterpillar.
You can see the one brush on the side, and there is another brush under the steel cover plate. No brush on the bottom or on the other side.
Initially I thought that someone must have removed the other two brushes for some reason, but this motor appears to only have two as well.

 

[Matej]

Here are pictures of the inside.

 

[Matej]

P.S.
To go off-topic a bit, would it be alright to advance a small motor like this the standard 12 degrees?

I wanted to try to run it at 96-120V. Is that too much? The current would be limited, of course.

I have only ever advanced large motors and I am not sure how it would affect a small motor.

 

[major]

Hi Mat,

Looks like those motors are in that small percentage. They are 4 pole and armature is wave wound (2 circuit) so can utilize only 2 brushes at 90° on comm. So going to 4 brush ring is doable, BUT, as I mentioned, the armature coil wire gauge is insufficient to tolerate the increase in current capability of double brush conduction area. From the photos it is obvious the armature uses round wire ( maybe AWG#14) with multiple turns vs the single turn rectangular copper ribbon hairpin armature coils typically found in forklift traction motors.

Using increased brush area with that armature will be counterproductive. If you run currents at levels the armature can tolerate, the brush current density will be too low and comm filming/brush wear will suffer. That is the reason the original designer used only 2 brushes. And those comms appear to be nicely filmed.

As far as advance goes, in degrees, daimeter should not matter. I have always felt 10° or more was too much. I like 5-7°.

Thanks for the pics,

major

PS fyi. Lap vs wave armature. http://www.electricaleasy.com/2012/12/armature-winding-of-dc-machine.html?m=1

 

[Matej]

Thank you for the replies and sharing your knowledge.

I was only going off the simplistic assumption that more brushes = better performance.
But if I can use only the two brushes that the motor came with to the same end goal, then even better as I will not have spent extra money for nothing.

Thanks again!