Arcing Brushes??

[deandad]

ok ... so ... newbie here ... just starting out: I ultimately want to use the motor out of my wife's treadmill to power a drill press ... I know, I know ... first I have to convince her that I can't fix it. It was doing fine for quite awhile [as a treadmill, at least], then it [sort of suddenly] started to arc in the brush area, smell "electrical", lose power, and generally run real slow as well as poorly [but nothing was spilled on it or anything like that]. So I'm trying to diagnose it while it's still in the treadmill: motor controller is MC60, motor is a 2.5 HP McMillan, treadmill is a ProForm [Sears, I think ... It was given to us]. I popped off the end cap and looked at the brushes: They seem fine ... not even close to worn or too short. Springs and caps seem fine, too. Yet, when I reassemble it, it still seems like too much spark and too much smell ... I never had the covers off and looked at it while it was running OK, so I don't really have anything to compare to.

So I guess my question is [vague, I know]: Should I be looking at the MC60, or the Power Board, or the motor itself?? If I need parts, I would rather get parts for a drill press than parts for a treadmill ... nobody can help me with that battle, so, all I'm really asking for is maybe a process of elimination to sort of help me start to know where to look for the culprit ... if i have to admit defeat on fixing the treadmill: I can then start work on the drill press [but maybey not with this treadmill if it needs new boards and a new motor].

Thanks for any possible help or encouragement ...

 

[JimDawson]

Shorted armature maybe? Take a close look at the commutator segments. Are any of them shorted together, maybe with brush carbon? Are they pretty rough?

And on another note, of course you can't fix it safely for use as a treadmill, that motor should be only run in the shop where you can keep a close eye on it.

 

[deandad]

Shorted armature maybe? Take a close look at the commutator segments. Are any of them shorted together, maybe with brush carbon? Are they pretty rough?

And on another note, of course you can't fix it safely for use as a treadmill, that motor should be only run in the shop where you can keep a close eye on it.

Good thought on the shorted armature --- I did look at it when I was looking at the brushes and it didn't seem too rough --- I guess I could sort of "scrape out" the gaps in case there's anything built up in there --- the gap width is very specific is it not? I suppose I will have to be gentle and careful.

I hadn't really thought of the safety issue of having a suspect motor inside the treadmill [where it can't be carefully monitored] ... I like it, I like it! ... I may owe you for that one ... thanks!

 

[JimDawson]

I guess I could sort of "scrape out" the gaps in case there's anything built up in there --- the gap width is very specific is it not? I suppose I will have to be gentle and careful.

The old timer method of cleaning the grooves was to grind a piece of hacksaw blade to have kind of a hook on the end and drag it through the groove. Hacksaw blades are just the right width. This goes back to the days when most autoparts stores actually had machine shops in them, and they actually rebuilt stuff there like starters and generators. That's been a while ago.

I hadn't really thought of the safety issue of having a suspect motor inside the treadmill [where it can't be carefully monitored] ... I like it, I like it! ... I may owe you for that one ... thanks!

Just doing what I can to help out, wouldn't want to expose your wife to a dangerous situation.

 

[Kernbigo]

it also may be running in the wrong direction , thread mill motor brush rigging are set at a angle and are meant to run in one direction, not all but some.

 

[Alan Douglas]

It sounds like shorted windings in the armature, and unless you can see the short, it's very unlikely to be repairable. Better now than after you'd gone to the trouble of adapting it for the drill press.

A motor shop could check the armature on a growler, but it might be simpler to get another treadmill.

 

[kd4gij]

It sounds like shorted windings in the armature, and unless you can see the short, it's very unlikely to be repairable. Better now than after you'd gone to the trouble of adapting it for the drill press.

A motor shop could check the armature on a growler, but it might be simpler to get another treadmill motor.

There fixed that for you.

 

[deandad]

it also may be running in the wrong direction , thread mill motor brush rigging are set at a angle and are meant to run in one direction, not all but some.

yeah ................ hmmmmmm.................. except that the motor was never disconnected [as in: then rewired the wrong way] for any reason before it began to malfunction. If it were to suddenly start running in the other [wrong] direction, it seems that the MC60 would somehow be at fault ... not to mention that the user would definitely notice a problem if the walking belt was to suddenly start going the other way! But, then, I suppose stranger things have happened.

 

[deandad]

yes. I definitely would not want to go too far on the drill press idea, or any other idea, with a defective motor [or, actually, any distance at all] ... That's exactly why I wanted to ask you guys, as you are all more familiar with DC motors and their controls than my own old-school self ...

It sounds like shorted windings in the armature, and unless you can see the short, it's very unlikely to be repairable. Better now than after you'd gone to the trouble of adapting it for the drill press.

A motor shop could check the armature on a growler, but it might be simpler to get another treadmill.

 

[Vladymere]

As people have said, armature. Armatures wear down, diminish in diameter, the mica between poles is now equal to the diameter of the copper. The copper is burned. Armatures can be turned down to provide a clean even surface and then the mica cut to below the level of the copper.

This is a common problem with DC motors but most motors are scrapped instead of repaired.

Vlad