Carbon brushes, how do they attach the wire?

I was taking to another poster via irc and I wondered how the copper leads are attached to carbon brushes for motors. There isn't any way I'm trying to google that one.
Can anyone here explain the process?
Thanks,
Wes
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A lot of them are in molded Wes. Go ahead and smash a bad one with a hammer sometime.
JC
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volley in

Well... sintered.
The copper wire may be just embedded in the matrix, with some length of it compressed in the finished form, or there may be a ferrule on the end of the wire, or they may dip the end of the braid in some copper/carbon/flux goo, and sinter that at the same time they're doing the body of the brush.
In any case, after baking out in a kiln at several tens of tons per square inch on the material, it becomes a near-homogenous solid, with the wire, ferrule, or metal mix embedment firmly incorporated as part of the structure.
LLoyd
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Wes wrote:

All of the ones I've ever seen had a copper "cup" that the carbon brush sat in.
The copper thingie has a spring attached to the back side to apply pressure so the brushes stay in contact with the rotor (stator?) in the motor.
Richard
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Others have said how "they" do it, as in production. It is also easy to plate copper onto carbon, and then solder (or ultrasonically weld) a lead to the copper. I've electroplated carbon rods for a carbon-arc torch in a coke bottle using copper tube for an anode and copper sulfate solution as juice.
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I assume you've done this. Does the copper carbon bond have good mechanical strength? most <servo> motor brushes have a very small area on the end of the brush.
Karl
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On Sat, 24 Jan 2009 09:14:34 -0500, Karl Townsend

I never tried brushes. I think it would work if one plated a "cap" on, probably not if one just plated on a spot or pad. I think the latter would peel fairly easily.
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In many cases, contact is only by pressure against the spring inside the brush holder. This seems to suffice for small motors in the sub-HP range.
Bob Swinney
wrote:>

I never tried brushes. I think it would work if one plated a "cap" on, probably not if one just plated on a spot or pad. I think the latter would peel fairly easily.
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Because carbon is conductive you can plate it with copper and then tin the copper or solder to it. Not the only method as little metal boxes and springs also can be used for a mechanical connection, so- it varies.
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Many patents describe alternative ways of bonding the braid or shunt: http://www.google.com/patents?q=carbon+brush+shunt This one uses powder mixture with hot isostatic pressing (HIP): http://www.google.com/patents?id=3-odAAAAEBAJ&dq=5168620
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wrote:

Many patents describe alternative ways of bonding the braid or shunt: http://www.google.com/patents?q rbon+brush+shunt This one uses powder mixture with hot isostatic pressing (HIP): http://www.google.com/patents?id=3-odAAAAEBAJ&dqQ68620
Yeah, That's what we called "molded".
JC
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