15 replies to this topic

[SlowBeas]

I bought a Challenger motor, broke it in properly where the brushes are seated nicely, then cleaned it up before putting it away for use later. It has a .520" arm and a very small air gap. I'm thinking the magnets are honed at .530". It's tight in there.

 

I just pulled it out, hooked it up to a power supply for, maybe, 10 minutes, and the thing is bubbling hot. At 5 volts, it was pulling 1.5 amps. ( I have no idea if that's common. I'm merely providing it as additional data for more knowledgeable folks.)

 

My problem is the temperature. I don't know how I could expect to get a full race out of the thing without it self-combusting!

 

Ideas or thoughts?

[Cheater]

First thing I woiuld do in this situation is swap in another set of motor brushes from a motor on hand that doesn't run hot and then put it back on the power supply to see what sort of amp draw you observe and to see if the motor still gets hot. Just a first step...

 

Bad brushes will cause this; have seen it many times.

[slotcarone]

This my sound silly but are you sure you had it running in the correct direction???

[Fast Freddie]

Is it a high timed arm 42°? If so you may have too much brush overlap.

 

Did you buy a whole motor new in the package? Most motors need attention to detail if they are new, glue end bell bushing, magnet alignment, and can straightening.

 

The gap is tight at .010", that's only .005" per side. Good for drag racing but for high bank tracks .007-.010", and flat tracks .010"+ per side is in the normal range.

 

Most of the motors I had get hot on the box was because of overlap or a loose endbell bushing.

 

That's assuming you don't have it running backwards. That would be the main reason.

[gotboostedvr6]

Does it have a Chinese comm?

[Mike Walpole]

At 5v that's about what I would expect the amp draw to be for that motor, assuming it's running in the right direction. 

Why it would get that hot with that amp draw is beyond me. My G12 motors, .518" arms, 40° timing, and .532" air gap usually pull 2.5-3.0A at 3.5v and they don't get hot.

[SlowBeas]

Thanks for the ideas,. Only time -- and more time on the power supply -- will tell if I can resolve this issue.

jb

[Gator Bob]

Was it a bag motor or did you build it up?

Did it get hot during the brake-in?

What did you use to clean it?

How was it stored and for how long?

[Michael Rigsby]

I agree with Mike on this. At 1.5 Amps at 5V, that is not a bad amp draw for that arm being a mild C-Can wind like it is. Most of my Group 12 motors when I built up a good one would run anywhere from 2.5-3.5 amps at 4V.  Like others have said, blueprint the endbell and make sure the brushes are not dragging or hanging up. Make sure the bushing is glued into the endbell and aligned properly, and change the brushes over to either Gold Dust Pro's or SBF II's, and do a complete re-breaking in starting off at 5 volts for 15 minutes, then 4 volts for 10 minutes, then 3 volts for 10 minutes, then monitor your amperage draw.  It shoud be about the same, but if the bushing is centered and the brushes aren't arcing excessively, the heat should be less.

 

I've had several of the Challenger motors made by Mura and they are pretty decent motors, both the Challenger I and Challenger II. Never had an excessive heat issue with any of them once everything is setup properly.

[idare2bdul]

I assume you checked for binding before putting in the brushes.

You may also be running more (or less, not likely) brush tension than it wants.

Is your power supply clean? Ac Ripple does tend to heat things up.

Did you make an appropriate sacrifice to the motor god before assembly?

The air gap is pretty tight. Too much ( or too little) magnet can heat up an arm.

What the package says the timing is and what it actually is can sometimes be very different.

You know the brushes are actually broken in because...?

[SlowBeas]

Quick update...

 

I made a change of brushes as initially suggested by Cheater (and a couple of additional mods below) and broke it in as I normally do (short water break-in, followed by thorough cleaning and then dry run-in on my laboratory power supply), allowing the brushes to seat well against the comm. I can tell it worked because the comm looks almost clean, only a few light streaks. The motor does not run as hot, but I noticed it seems to draw slightly more amperage than before at the same voltage. You guys who understand conductivity better than me probably know the reason. When viewing from the endbell, the arm turns ccw.

 

A few minor alterations, but not a full "blueprinting":

As mentioned before, new Gold Dust brushes

Lighter springs -- adjusted slightly for proper contact

Although I didn't re-glue the can bushings, I disassembled the motor and inspected. Bushings appeared to be very well aligned already and seated in place tightly.

I added spacers to center armature in magnetic field and reduce back and forth movement as power is applied.

 

All in all, the motor runs smoothly and much cooler. It was otherwise straight out of the bag, although I bought it sometime ago. As fast as it feels, I might have to install it on a new chassis and get it ready for weekly racing.

 

Thanks for all the insights. The responses only prove I still have much to learn.

jb

[gotboostedvr6]

Water breakin can cause the brushes to get gunk trapped between them and the hoods and causes a bunch of issues.

It should be avoided at all costs.

[Bill from NH]

Water breal-ins don't cause problems if you know how to do it. Talk to Monty Ohren.

[gotboostedvr6]

Ive built enough motors to know how it effects them. It always causes issues if you don't Tear them Down

[SlowBeas]

Duly noted. That's why I always do a thorough cleaning after the water break-in. I think I covered the bases to prevent any clogging of the gaps. I rinsed it off and dried it prior to another good run on the power supply. It sounds really sweet. Only a little time on the track will tell if I did a good job.  

[gotboostedvr6]

Gunk gets into the bushings, brushes, comm slots, arm spacers, and windings. The water resistance moves the windings, prematurely wears the brushes, arm spacers, and oilites. Water rusts the metal that holds the magnets and they rub the arm.