# Arcing Brushes??



## deandad (Jul 15, 2015)

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 ...


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## JimDawson (Jul 15, 2015)

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.


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## deandad (Jul 15, 2015)

JimDawson said:


> 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!


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## JimDawson (Jul 15, 2015)

deandad said:


> 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.



deandad said:


> 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.


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## Kernbigo (Jul 15, 2015)

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.


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## Alan Douglas (Jul 15, 2015)

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.


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## kd4gij (Jul 15, 2015)

Alan Douglas said:


> 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.


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## deandad (Jul 16, 2015)

Kernbigo said:


> 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.


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## deandad (Jul 16, 2015)

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 ...




Alan Douglas said:


> 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.


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## Vladymere (Jul 16, 2015)

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


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## Alan Douglas (Jul 16, 2015)

I'd be surprised if the commutator wore down; treadmills don't often get used that much.  Most that I've seen, were abandoned when their owners lost enthusiasm.


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## Tony Wells (Jul 16, 2015)

What are you saying, Alan? lol


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## deandad (Jul 17, 2015)

Vladymere said:


> 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




thanks, Vlad for that thought ... it seems like, given that this may be a common problem, the use of a treadmill motor on, say, a wind generator, is not really such a good idea after all ... I would think a wind generator would _quickly_ rack up a bunch more "miles" than a treadmill with an unenthusiastic owner. However, even a high mileage treadmill motor would probably have plenty of life to live as a drill press or mill. 

Yesterday I put a VOM on the commutator segments [a rather poor excuse for a VOM] and, while none seem to be shorted to the armature or the shaft, some pairs _do_ seem to be open ... I guess that's my problem.  So, I will have to tell my wife that it's not fixable as a treadmill [that part's good], but, unfortunately, it's also not useable as a DP ... bummer.  I suppose a new motor would only be $75 or so on eBay or whatever [or a different treadmill off Craig's List for a bunch less] but, oh, I _do_ love "free" stuff.  

So ... I'm not ready to throw in the towel on the DP project just yet ... we'll see ... Has anybody tried a treadmill motor conversion to a tablesaw??  The variable speed thing seems like it would solve the biggest problem with table saws:  bogging down under load ...


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## RJSakowski (Jul 17, 2015)

deandad said:


> Has anybody tried a treadmill motor conversion to a tablesaw??  The variable speed thing seems like it would solve the biggest problem with table saws:  bogging down under load ...


  I'm not sure how a variable speed motor would solve the bogging down problem.  The problem is not enough torque to handle the load.


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## deandad (Jul 17, 2015)

RJSakowski said:


> I'm not sure how a variable speed motor would solve the bogging down problem.  The problem is not enough torque to handle the load.



yeah ... I guess you're right ... if you _had_ the torque capacity, why wouldn't you be using it all the time, rather than ripping _slowly??_


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## Alan Douglas (Jul 17, 2015)

> some pairs _do_ seem to be open


Opens will usually be at the commutator connection, and _might_ be fixable.


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## RJSakowski (Jul 17, 2015)

Open windings will definitely cause sparking .  A dead sure test is to rotate the armature to different positions.  The motor will not start if on open winding.

Regarding  fixing breaks at the commutator, I have successfully repaired open windings on drills and on a Dremel.    What I did was to first find the break, usually with a magnifier.  Then I teased the broken wire out of the varnish or epoxy it was usually embedded in.  Next, I scraped some of the insulation off so I could solder a short stub on.  Then, the commutator copper had to be cleaned to allow soldering the stub to the commutator. Finally, I checked the winding for continuity and rebedded the repair with epoxy.  

Bob


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## deandad (Jul 17, 2015)

Alan Douglas said:


> Opens will usually be at the commutator connection, and _might_ be fixable.




_Really ... Hmmmmm_


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## deandad (Jul 17, 2015)

RJSakowski said:


> Open windings will definitely cause sparking .  A dead sure test is to rotate the armature to different positions.  The motor will not start if on open winding.
> 
> Regarding  fixing breaks at the commutator, I have successfully repaired open windings on drills and on a Dremel.    What I did was to first find the break, usually with a magnifier.  Then I teased the broken wire out of the varnish or epoxy it was usually embedded in.  Next, I scraped some of the insulation off so I could solder a short stub on.  Then, the commutator copper had to be cleaned to allow soldering the stub to the commutator. Finally, I checked the winding for continuity and rebedded the repair with epoxy.
> 
> Bob




sounds tedious ... but it's _FREE!!! ... _sort of.  Definitely something to think about [and certainly take another look at ... _with that magnifier_] ... if it were to end up being something I could see, I might just be inspired to try a fix ... it will either work or it won't:  either way I'm learning something and gaining some skills ...

the motor _does_ seem to be reluctant to start at times [maybe because it's on an open winding??] ... when that happens, i can usually _make_ it start by raising the speed on the console ... I guess that could be burning the surface of the commutator somewhat ... maybe I should just try rotating the armature a little bit rather than raising the speed ... 

thanks for all the input, guys


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## Alan Douglas (Jul 18, 2015)

In the good old days, armature coil wires were soldered to the commutator bars but I expect now they're all swaged by machine and probably not visually inspected.  If you see some that don't appear to be connected, they could be your problem.  However they did it, the connections should all look alike, and the resistances between any two adjacent bars should be the same.


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## Wireaddict (Jul 19, 2015)

If you can't find a bad commutator connection get the treadmill's model & serial nos. & go to ProForm's web site [&/or Sears' if they sold it] to see if they sell the armature for it.  I suspect that it's oriental-made & so parts aren't available but good luck.


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## Wobbles (Aug 2, 2015)

deandad said:


> 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.



Can't help you with the motor, but I will point out that it might be easier to sell her on an upgrade to her exercise equipment from a treadmill to an elliptical trainer. There must be 10,000 articles she can Google on reduced joint stress, fewer ankle injuries, less floor space required, safer for kids to be around, etc, etc. Once you have an elliptical, the treadmill will be gathering dust. Then you'll be commanded to get rid of it.

Besides, if you're anything like me, women are completely immune to your "magical powers of persuasion".


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