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Miller Welder (Trailblazer NT 251 with Onan)

B

Billy NY

Well-known Member
I've had this welder for over 15 years now, and it has not gotten a lot of use since its former life as a rental unit. 1583 hours now show on the meter, and its sat for years, but I have kept it running after sitting with a cover over the top, open underneath to keep moisture accumulation from happening. I've had to evict a few mice from it over the years as well.

The Onan performer 20 seems to run fine, it welds fine and all the outlets show correct voltage.

Aside from maintenance items on the engine, what does one need to do with the brushes on the generator part of it ? I see one has a bright blue arc under one brush when its running, (the black carbon looking thing that rides over the copper ring, there are 3 on this one, but only one is making an arc.)

Anyone want to elaborate on servicing/maintaining the generator part of this ? My concern is a groove from the arc or causing damage to the copper ring and or what should be done if necessary.
 
You need to pull on each brush. Make sure it is making full contact with the slip rings. You can clean the rings with a stone or a scotchbrite pad.Just rub the pad over the rings to remove the dust. Arching is a sign of a bad contact. It can burn the ring which can run into money to repair.A motor rewind shop will have the cleaning stones.Just crank up the engine and lay the stone on the rings.Just be carteful with any moving parts.
 
I figured it could gouge the slip rings, but to the touch, I do not feel any ridge or similar. They do look like they need to be cleaned or polished. I'll try the scotch brite and see if I can find a way to use same with it running, probably won't take much. I can see lines that show cleaner brass like color adjacent to the tarnished areas, I guess those would eventually become grooves from the arc.

Thank you for the advice.
 
Hello Billy NY,

You should clean the CONTACT PART OF the brushes as well. Also take the edges off the brushes. They get very sharp ON BOTH the leading and the trailing adges. That sharpness can make them chatter as the sharp edges catch the comm segments. I can make and post a sketch if you need it,

Guido.
 
Guido, that would be very helpful showing a detail of this in a sketchy posted here. At least then anyone else dealing with something like this can see it as well. Glad I saw this arc, the other 2 brushes make no arc when the generator is spinning.
 
Hello Billy. NY,


Here is the before and after picture of the brushes.You can use a knife or razor blade to take the edges off the brushes like you see in the sketch. Clean the contoured part as well. The motor Will draw less power and the brushes will stop bouncing. Make sure that tbe spring tension is good and tbe motor will be happy. Let me knkw how you make out,

Guido.
a239804.jpg
 
Thanks Guido.

I'll see if I can get a photo or two as well. I'm now wondering if I should just replace the brushes and polish the slip rings.
 
I agree with Guido. The brush surface should be smooth all the way across. They should also be free in the guides. A stuck one can burn the rings. Most brushes have a wear mark on them. No need to change them unless the surface can't be cleaned up.
 
Hello Billy NY,

If the brushes look worn or just for peace of mind, just replace them I guess. But do the same thing with the new ones. Giving the edges that clearance, will increase their service life. By the way that trick works on any brush motor AC or DC. reducing commutator contact also decreases amp draw, and encreses R.P.M.'s.......Try it! PS I may not catch up with you on this thread. Either post a new one or you can e-mail me.......Later

Guido.
 
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