Useful resource for motor brushes

[9fingers]

I had a motor in for repair the other day. A nasty horrid brush motor but it was for a mate so I accepted the request with good grace.

All it needed was a good clean up and new brushes as one had worn to almost nothing.
However this was an old motor and spares are rare and even refurbished motrs sell for silly money on ebay.
After a bit of a search I came across
http://www.mrcarbonbrush.com
who not only had what I needed but also do a huge range of brushes for the more obscure brands of power tools that tend to have poor spares support.

Well worth a look and a possible tool life saver.

Bob

 

[kirkpoore1]

A website like this should also have replacements for motors that use brushes just to start, such as repulsion-induction motors. While rare now, they were once pretty common (like, back in the 1930's and 40's) and are good motors. I have not yet had to replace brushes on one of these, but I've seen some that were getting pretty short.

Kirk

 

[9fingers]

A website like this should also have replacements for motors that use brushes just to start, such as repulsion-induction motors. While rare now, they were once pretty common (like, back in the 1930's and 40's) and are good motors. I have not yet had to replace brushes on one of these, but I've seen some that were getting pretty short.

Kirk

Somewhere on the site I saw a comment that if your could not find what you needed, they will make brushes to order.
I've got an old Zenith variac that needs brushes suitable for about 8 amps so I might test their capabilities.

Bob

 

[TomTrees]

I have a few questions about motor brushes, but never asked...

I've often wondered if anyone has made their own brushes?
I bought a pack of twenty for buttons off of eBay some time ago, for my dad's mitre saw.

Could one just pop' em off the springs, and stick them on something else?..
Can you shave them down or even glue them together?

And is there any reduction in noise, or power gained from having a new brush?

Thanks folks
Tom

 

[9fingers]

I have a few questions about motor brushes, but never asked...

I've often wondered if anyone has made their own brushes?
I bought a pack of twenty for buttons off of eBay some time ago, for my dad's mitre saw.

Could one just pop' em off the springs, and stick them on something else?..
Can you shave them down or even glue them together?

And is there any reduction in noise, or power gained from having a new brush?

Thanks folks
Tom

Motor brushes are a complex subject.
My preference would always be to use the correct brushes or perhaps use that supplier who will make brushes to suit your application.
However, many time I have filed down other brushes to fit tools that I can't get ones to fit. Take equal amounts of each opposing face. Always ensure good sliding fit with no excess clearance that might allow it to twist and jam.

The brush material should be the correct type for the application so choose a donor brush from a similar power application.
Usually springs are higher resistance than the copper braid that is normally used to carry the current to the brush. Relying on the spring alone is risky as the power disipated in the spring can cause it to loose pressure.

Gluing brushes together I would class as an absolute last resort and normal glues are of course insulating. Silver loaded epoxy might help but usually needing bigger brushes implies higher current and the material is not likely to be correct. Ideally if you cant get the correct type or are too mean then start with a larger brush and cut it down.

Some brushes are specialist such as for automotive starter motors and off axis type found in washing machine motors and similar for high speed high power unidirectional use. I would never mess with these. Use the correct approved parts.

Finally I don't think you will improve performance of brush motors over using the correct part specified by the manufacturer.

hth
Bob

 

[TomTrees]

Wow, it is certainly a complicated subject then !

I thought it might have been lot simpler than that, boy was I being a bit optimistic, to say the least. :lol:
I did feel a little like I was being a little lazy, so did a minute of random keyword youtubing before posting.
I'm glad I hadn't trawled through many videos, as it would have been a pointless endeavour for the kind of thing I was looking to find.

I have a wee three wheeled bandsaw, that I was thinking of making into a strip sander, but the thing is soo loud, that makes me not want to bother with, plus I don't really like sanders,
as I have no dust collection in the workshop.
I try and find a way of cutting things, as a workshop rule, rather than abrade them.


I was thinking that the brushes could be worn on this thing, due to the noise,
Never checked them though.
I must have a look at them sometime, to see if,
A: If they're the correct fit,
B: if they're worn down,
and C: if the springs and the copper braid are equal.

Thanks Bob, for another motor learning experience

Cheers
Tom

 

[9fingers]

Brush motors are always noisy, not due to brushes but related to the the obscene armature speed, the amount of air required to cool them and their open frame construction. I can guarantee that you wont hear brush noise over the rest of the racket from them.
Their big advantage is power to size ratio compared to an induction motor and cheapness for portable tools but for aural sanity stick to induction motors.

Bob

 

[TomTrees]

Thanks Bob
Good to know this stuff, albeit disappointing to read.

Maybe there's some chance I will turn the machine into a sander, but it's definitely not on the...
"to do someday" list now.
I might hold onto the idea, if I ever need to do something with it, that might fit the bill, but an angle grinder is so much more compact, and probably just as capable for most applications that I foresee.

Once again, many thanks for schooling me on motors of all kinds.
I guess I have gotten a taste for induction motors, and might look for a wee induction motor if the need arises.

Regards
Tom