OT-Carbon brush problem

Here's my idea, may make sense, hope it's clearly stated (I seem to be writing unclearly lately). What if you made up a little sleeve of copper that just slid around your wire, and counterbored the back side of the brush so the sleeve could slide into it (but would be restrained from sliding through by the base of the counterbore). Then put the sleeve in one side, put your lead in through the other side, and solder the lead to the sleeve on the backside. Once installed, hopefully something would keep the sleeve/lead assembly from pulling out the back -- maybe the side of a slot or something.

Grant Erwin

Do the leads come out on only one side? If so, one could find a side lead brush and file it down. Or a large top lead brush, and cut a smaller side lead brush out using a small handsaw.

I recall that the leads are inserted into the brush material before it's pressed and cured, as a part of the original manufacture. I suspect that one cannot later attach the leads. I've never seen a brush that didn't have molded-in leads, although I wasn't looking.

Joe Gwinn

"Grant Erwin" Once installed, hopefully something would keep the sleeve/lead assembly from pulling out the back -- maybe the side of a slot or something. ^^^^^^^^^^^^^^ Good idea. To secure the copper sleeve, how about flaring the hole on both sides, and filling the flare spaces with the same solder used to hold the wire in the copper tube. Another idea would be to flare the copper tube with a punch (gently.) A third possibility would be to cement it in with the liquid that is used for repairing the rear window defroster grid on cars. It's kind of a "correction fluid" consisting of copper dust suspended in a varnish.

I'd try silver bearing conductive epoxy. It's saved my arse more than once when I had to make a low resistance electrical connection to something I couldn't solder because the heat would damage what it was attached to, or the metal was difficult to solder to. (Think aluminum.)

I have no idea how well it would bond to carbon though.

IIRC in the olde days stranded leads were attached to brushes by setting them into an oversized hole and then tamping fine copper powder down into the hole around the wire. They must use something like hollow punches for that operation.

Jeff

I seem to recall from A&P school brush pigtails being pressed in and cured in as Joe describes... a really specialized process I'm sure.

Starter brushes move a lot of amperage... this one might take some thought. Can't think of a much better place to ask than here though.

I bet there are company's out there specializing in making up brush assemblies... there must be.

Good Luck!

Erik

How big? I've got a bagfull of replacement brushes that came in a box of stuff from a surplus auction at the nearby Naval Air Station. The leads appear to be swaged in and they look to have a much higher ratio of carbon to copper than typical high current brushes. On a hunch I whacked one with a BFH and put a pretty big divot in it rather than smashing it. They're .343 x .375 x .690, not including the bump where the leads attach. If you want to experiment, email me your address and I'll pop a few in the mail.

Ned Simmons

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Should read, "higher ratio of copper to carbon."

Ned Simmons

Jerry Martes could certainly find you some side lead brushes, though you might have to file them down to fit. He was in the alternator repair biz for years, "has sources". I'm sure he'd be glad to help.

Here's one I used a long time ago. They say they'll make as few as ONE custom brush. (But at what price?)

Jeff

Motorcycle starter brushes are side lead and come in a number of different sizes. Go to a non dealer repair shop. He probably has a bunch of assorted sizes in his tool box. Maybe something you can cut to size. Karl