Generator Brushes

cnrtool · Mar 31, 2016

Wondering how difficult it is to replace the generator brushes on a 10EE? I already have the replacements from Monarch. Mine are worn very thin. The DC motor will surge, A few taps on the generator frame stop the surging for a little while. Before I call in a repair tech's, I thought it may be wise to change out the brushes...
Anyone have any tips for this?

johninwi · Mar 31, 2016

I've not changed the brushes in mine yet, the m/g isn't even installed but i have replaced many a brush in other dc motors and generators.
My 10ee is a 1942 so yours may be different, i have 4 brushes, 2 each side, a simple wound spring holds the brush agienst the comm. The hard part is going to be the screws that the brush pig tails are connected to the brush rigging with. they look to be about a #10, small but not tiny and are sloted or straight blade. I'm guessing the new brush has forked terminals on the pigtail leads not ring terminals, an advanatage since you only need to loosen the screw and not remove it.
New brushes won't match the shape of your comm, you'll need to seat them. Easily done with silicon carbide sand paper, avoid aluminum oxide it can short the comm, (i've used aluminum oxide in the past without ever shorting anything but it was a gamble and i may have just gotten lucky. The choice is yours).
DO NOT SCRATCH YOUR NOSE OR RUB YOUR FOREHEAD. carbon dust gets every where, and stick to you really well.
You'll need something corse, like an 80 or 120 grit to start then a finer 320 or simillare to finish. The paper is slid between the comm and the new brush and the springs installed. The paper is then pulled thru the brush holding each end of the paper taunt so it forms around the comm. Repeate until you have >75% of the brush formed to the comm shape. You can lift out the brush after a few strokes and look, you'll see the form taking shape. When you've reached the 75% switch to the finer paper and finish with a few more strokes, check them again and you'll see the heavy sanding marks going away.

A small shop vac to clean up the extra dust and abrasive's, a good washing of your hands

Done.

Proper techniques for generators is to only sand in the direction of rotation, dc motors can be sanded pullibng the paper back and forth, a genny should only be sanded the one way. That said i've sanded many a genny brush by pulling back and forth with no ill effects, this was done on comm's of a larger diameter than the 10ee's comm so i really can't comment if the small diameter comm will care or not.

Browse this site, you'll find plenty of info about brushes.
The First Name in Carbon Brush Technology - Helwig Carbon

I've tried attaching a pic, it may give you a view you don't have.

johninwi · Mar 31, 2016

Also, when your brushes get short the pigtail inside the brush may become exposed and groove the comm. Short brushes should be avoided.

The new brush, when you all done. Look at the pigtail, it should make a nice loop out of the brush holder so in the future when the brush wears the pigtail doesn't hang up on the rigging.

On occasion you can also pull the pigtails to see if the brush snaps back onto the comm, if it's tight in the rig it'll drag when you pull it back, this will cause arcing and destroy the comm.

The carbon dust isn't near as bad as dykem high spot but acts the same as far as spreading out and getting everywhere. It's worse if your sweating.

9100 · Mar 31, 2016

johninwi said:
I've not changed the brushes in mine yet, the m/g isn't even installed but i have replaced many a brush in other dc motors and generators.
My 10ee is a 1942 so yours may be different, i have 4 brushes, 2 each side, a simple wound spring holds the brush agienst the comm. The hard part is going to be the screws that the brush pig tails are connected to the brush rigging with. they look to be about a #10, small but not tiny and are sloted or straight blade. I'm guessing the new brush has forked terminals on the pigtail leads not ring terminals, an advanatage since you only need to loosen the screw and not remove it.
New brushes won't match the shape of your comm, you'll need to seat them. Easily done with silicon carbide sand paper, avoid aluminum oxide it can short the comm, (i've used aluminum oxide in the past without ever shorting anything but it was a gamble and i may have just gotten lucky. The choice is yours).
DO NOT SCRATCH YOUR NOSE OR RUB YOUR FOREHEAD. carbon dust gets every where, and stick to you really well.
You'll need something corse, like an 80 or 120 grit to start then a finer 320 or simillare to finish. The paper is slid between the comm and the new brush and the springs installed. The paper is then pulled thru the brush holding each end of the paper taunt so it forms around the comm. Repeate until you have >75% of the brush formed to the comm shape. You can lift out the brush after a few strokes and look, you'll see the form taking shape. When you've reached the 75% switch to the finer paper and finish with a few more strokes, check them again and you'll see the heavy sanding marks going away.

A small shop vac to clean up the extra dust and abrasive's, a good washing of your hands

Done.

Proper techniques for generators is to only sand in the direction of rotation, dc motors can be sanded pullibng the paper back and forth, a genny should only be sanded the one way. That said i've sanded many a genny brush by pulling back and forth with no ill effects, this was done on comm's of a larger diameter than the 10ee's comm so i really can't comment if the small diameter comm will care or not.

Browse this site, you'll find plenty of info about brushes.
The First Name in Carbon Brush Technology - Helwig Carbon

I've tried attaching a pic, it may give you a view you don't have.

I agree with the technique but you have the conductivity issue backwards. Aluminum oxide is a very good electrical insulator and is the insulating film in electrolytic capacitors. Silicon carbide is a semiconductor, see

Silicon carbide - Wikipedia, the free encyclopedia

Nevertheless, I have been seating brushes with wet or dry sandpaper since 1958 and have never had a problem as long as I blew the dust away.

I used to get a lot of tachometer generators that had good brushes but were giving erratic results. It turned out that someone had moved the generator to an different printing press and running in the opposite direction shifted the brush enough to make it only contact on a sharp edge. Taping a strip of 400 grit wet or dry to the commutator and rocking back and forth with the brushes in place fixed it. I also got a lot of generators that had been run into wrecks. I asked the shop that was forwarding them to me what application was running them that hard. It turned out that it was one of the major porn printers. I guess business was good.

Bill

j.carlson · Mar 31, 2016

1943 10EE MG generator brush seating

Very timely thread ! I installed new brushes in the generator today but did not seat them in. Generator runs fine but sounds like it is turbocharged - high pitch whine !! Other than the noise, what is the down side of not seating the brushes ?

Jim C.

hitandmiss · Mar 31, 2016

You will have only a very small contact area. Under load such as acceleration you may have undesirable sparking. It does not take a lot of sparking to leave the commutator rough and shorten brush life.

9100 · Apr 1, 2016

The brushes will eventually seat as they wear, but you do not want to risk commutator damage in the meantime. Lift each brush and slide a strip of 320-400 grit wet or dry paper under it and rock the armature or "shoeshine" it holding each end of the paper around the commutator. You don't need to get complete conformity, just enough to make a reasonable sized, stable contact surface.

Bill

johninwi · Apr 1, 2016

9100 said:
I agree with the technique but you have the conductivity issue backwards. Aluminum oxide is a very good electrical insulator and is the insulating film in electrolytic capacitors. Silicon carbide is a semiconductor, see

Bill

Appreciate the correction, and appoligise for bad info, Thankyou.

j.carlson · Apr 1, 2016

Seating in 10EE generator brushes

Thanks Bill and Bill for your comments.

Have not put on a working load since changing out the brushes but did note instability at about 2000 RPM when slowly increasing speed. Guess that is load enough!! Went to 4000 RPM with the old brushes which were 'well seated' down to 1/4 " length and springs at end of travel.

Will seat them before working the lathe.

Jim C.

j.carlson · Apr 1, 2016

Replacing 10EE generator brushes

cnctool:

To answer your initial question, here is my experience:

The brush holders on my 1943 10EE are at the 2 0'clock and 8 o'clock positions as you face commutator end of the generator.

At the 2 o'clock position,easy access to the pigtail fastening screw, springs (2)and pair of brushes in the holder. Important ! Note the position of the slot in the knurled brass sleeve that holds the fixed tail of the spring closest to you. That indicates the degree of wind up of the spring coil tensioning. The inside end of that brass sleeve has a face ratchet that engages a small pin on the holder. As you lift the brush end of the spring to clear the brush slot and set it to the side, you might disengage the ratchet and loose the spring tension. If it does disengage, you will have a reference point to reset the tension.

I did not have an issue on the 2 o'clock brush change out but did on the 8 o'clock where access is more awkward being upside down. On lifting the near side spring off the brush ,clearing the holder and setting it aside, the spring went limp and I thought OS !! the spring broke. The brush holder assembly is clamped using a pinch bolt on a ~ 1/2 " stud so I removed the ass'y for a closer look. That is when I learned the details of the ratchet. Ingeneous design and no broken spring !!

Loaded the holder with the new brushes and set the tension / position of the sleeve to match the 2 o'clock and the refit the loaded holder to the same clearance as 2 o'clock. I positioned the brushes so the the pigtail came out under the spring allowing the spring to have full contact with the brush.

Now to seat the brushes to the commutator as noted in prior posts in this thread.

I ordered brushes direct from Monarch. Terrie Schwaiger - 937 492 4111

Jim C.

DaveE907 · Apr 2, 2016

Tearing up the commutator with extremely high current/area loads which heat it beyond further service. Don't do that. It's abusive and ignorant. It's a major FU to not bed in high amperage brush/commutator interfaces, physics doesn't give us any breaks.

cnrtool · Apr 2, 2016

Wow, great information, many thanks to those who replied. When I slow down a little (or when I get tired of doing small stuff on my 24 x 80 webb lathe), I take a crack at the brush installation.

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