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Is There A Cure For Excessive Brush Arcing?

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  • Member since
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  • From: Collinwood, Ohio, USA
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Is There A Cure For Excessive Brush Arcing?
Posted by gmpullman on Tuesday, April 16, 2019 9:06 PM

Last night I continued on a project to upgrade some decoders in a pair of Athearn Genesis HO GP9-b units. Both these engines probably have less than five hours of run time on them.

I removed the DASR decoders I had previously installed and put a Tsunami-2 in one and a Soundtraxx MC2H104AT  mobile decoder (silent) in the other.

On the test/programming track using a Sprogg and JMRI, the engine with the silent decoder would only move at very slow speed. If I increased the (JMRI) throttle just a little the Sprogg would cut out on overload.

Back at the bench I disconnected the motor wires from the decoder and hooked up test leads from a DC power supply. At 5 volts the current draw was about 420 mA, then suddenly would jump to about 2.25 amps for a few seconds all the while the commutator was sparking, smoking and stinking up the place!

I had this happen on another Genesis motor about a year ago and the plastic base that the commutator was molded onto had actually melted.

So, for this GP9 I removed the motor and doused the brush and commutator area in some LPS electrical contact cleaner. The motor design does not allow very good, actually NO access to the commutator and the brush holders are not very easy to remove either.

I wonder why a motor would suddenly act like this and what can be done to prevent it? It almost seems like there are carbon powder traces or some conductive contaminant that causes the sparking but, why so intermittent? The motor purrs along just fine then — with no intervention from me — will go into the sparking and hi current draw spasms, then just that quickly, settle down and go back to smooth running.

Since I flushed the commutator and blasted it with some canned air it seems to be better. Tonight I'm going to run the engine on test stand rollers for a few more hours and see what happens. Genesis motors run $35-40 each! I hate to invest that when the problem is sporadic and unpredictable.

Any thoughts?

Cheers, Ed

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Posted by doctorwayne on Tuesday, April 16, 2019 10:15 PM

gmpullman
...It almost seems like there are carbon powder traces or some conductive contaminant that causes the sparking but, why so intermittent?....

Electrical stuff for model trains certainly isn't my strong point, but if you're getting carbon in places it shouldn't be, perhaps the brushes are faulty - too soft, perhaps, or of inconsistent properties, with softer material in some places.

I had a remotored Athearn SW that simply stopped running, and the culprit seemed to be a brush that had totally disappeared, even though there was relatively little time on the motor, from Mashima.
Since I didn't have replacement brushes, and doubted that they'd even be available, I used some 6H lead from a mechanical draughting pencil.  It was a little smaller in diameter than had been the original, but the loco runs well with the stand-in.

Wayne

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Posted by gmpullman on Tuesday, April 16, 2019 10:35 PM

Thanks, Wayne

That is certainly a consideration. I believe I have a handful of various carbon brushes around. I'll take a look at that option.

Here is a photo of said motor:

 GP9b_PRR_Tsunami2 by Edmund, on Flickr

You can see there isn't much room to get to the commutator and the motor is pretty much crimped together making disassembly a last-ditch option.

Some years ago I had the same kind of problems with a few Buhler can motors used in Bowser/Stewart locomotives. Again, these brush-commutator assemblies were sealed inside the motor. Replacement was the only option.

Regards, Ed

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Posted by doctorwayne on Wednesday, April 17, 2019 12:22 AM

gmpullman
...there isn't much room to get to the commutator and the motor is pretty much crimped together making disassembly a last-ditch option....

Well, if it looks like a new motor is the only solution remaining, then there's little harm in trying to get this one apart for a better look. 

The locomotive to which I referred in my previous post was one I sold to a fellow member over at Big Blue, and when he mentioned that it wouldn't run, I drove down to see him, east of Syracuse, on my way to visit a friend in Ohio.  I couldn't see anything wrong with it, but was very embarrassed to have sold something defective (it was fine when I shipped it and had been running after he got it) so I bought it back.  When I got it home, I discovered that one brush was missing, but the spring was still there in the brush-holder slot.  While it runs fine now, it's a bit too modern for my layout, so the 45 is a shelf queen for now...



I'm mostly glad that the one which went to California hasn't experienced any problems, and the other two are with a friend who lives nearby, here in southern Ontario.

Wayne

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Posted by RR_Mel on Wednesday, April 17, 2019 6:59 AM

Contact Athearn Customer Service, I found them very helpful in the past with such problems.  Once they sent me a new replacement motor that was out of warranty no charge.
 
 
Mel
 
 
My Model Railroad   
 
Bakersfield, California
 
I'm beginning to realize that aging is not for wimps.
 
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Posted by xdford on Thursday, April 18, 2019 7:11 AM

Hello Ed,

You wrote ...  

"I wonder why a motor would suddenly act like this and what can be done to prevent it? It almost seems like there are carbon powder traces or some conductive contaminant that causes the sparking but, why so intermittent? The motor purrs along just fine then — with no intervention from me — will go into the sparking and hi current draw spasms, then just that quickly, settle down and go back to smooth running."

I am not familiar with the Genesis motor but it would seem to me that you have got a fine shard of copper floating about the area of the commutator that is getting in the way of the brush causing the intermittent high current draw when it arcs over two of the slots. If you have a compressor (not one of the big industrial ones,) or a can of compressed air you could try giving it a light blow through the vacant space while the motor is running ... don't try to blow into it yourself as you could cause the motor to arc with the moisture in your breath.

Hope this helps but I think you will be doing a replacement for that motor!

Regards from Australia

 

Trevor

 

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Posted by gregc on Thursday, April 18, 2019 9:16 AM

what about a cleaning and using a conductive oil such as Excelle?

greg - Philadelphia & Reading / Reading

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Posted by mbinsewi on Thursday, April 18, 2019 10:45 AM

Nothing to do with motors in model locomotives, when a drill, or circular saw would start an unusual amount of sparking from the brushes, it meant the tool was about finished, or, a build up of stuff around the brushes, or, possibly an irregularity in the commutor, or, all of the above.

If you were "pro-active" in tool maintainence, you could get a new set of brushes, and hope the communtor was still ok, and not scratched up too bad, and continue on.

Sometimes using a blast of air would clean out any "junk" (carbon?) build up, and it would run OK, for a while.

But I digress.

Mike.

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Posted by xdford on Thursday, April 18, 2019 5:27 PM

I have reread your thread and wonder if it is a case of simple lubrication? 

I also have a few British trains that I have run on a memorial layout in honour of a friend at exhibitions past. Some of these engines have run quite well and then had high pitched  spasms  and slow downs (high current draw??), which I fixed with a very light dose of oil or teflon grease to the bearing from the outside of a similar style motor. 

If this is the case, the arcing you described would be the result of the excess current draw caused by the motor being stalled for that instant 

The bearings should be self lubricating but possibly need a little assistance. That is going to cost you virtually nothing to try anyway... hope it helps

Regards from Australia

Trevor

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Posted by gmpullman on Thursday, April 18, 2019 6:43 PM

Hello everyone. An update:

gregc
what about a cleaning and using a conductive oil such as Excelle?

xdford
I have reread your thread and wonder if it is a case of simple lubrication?

Cleaning, yes! That helped considerably. I held the motor over a pan then doused ti with a good grade of electrical contact cleaner.

In the past I HAVE used CRC 2-26 and DeOxit on the motor bearings. (Haven't tried Excelle, yet)

Now I am second guessing that move. My theory being a conductive lube seeping back into the very close insulating area of the commutator. There is a bronze thrust washer right there, too. So, I believe the dust of the carbon brushes mixes with the excessive oil and cakes up too much rather than getting slung off if it were left dry.

I remember electricians at work chewing out guys for cranking way too much grease into motor bearings. They would disassemble motors and the whole armature was packed full of grease. The nameplate says "In normal use grease every other year" or something close to that.

So after a cleaning and a blowing out with a can of Dust-Off I reinstalled the motor and ran it on test rollers for four hours. No spike in current and no visible arcingSmile Current was a steady 420 mA at six volts.

Last night I rewired the decoder and ran again in both directions for about six hours. alternating speed and direction every half-hour or so. All good! Stall current was about 470 mA at 10 volts.

So, is there a suggestion for a NON conductive lube? I agree that the sintered bronze bearings need some lube but perhaps in some cases I've over done it.

I'll post some photos later of the first Genesis motor that gave me problems and I did a necropsy on it. This puppy got so hot there was melted lead slung off the armature and stuck to the inside of the brush holder!

mbinsewi
If you were "pro-active" in tool maintainence, you could get a new set of brushes, and hope the communtor was still ok, and not scratched up too bad, and continue on.

I've done that myself, Mike. Had a twenty-year old Skillsaw that I replaced the brushed in. Got me another two years of good use. Blowing out the sawdust and gunk helps. Also reduces overheating as the air passages can get clogged.

RR_Mel
Contact Athearn Customer Service, I found them very helpful in the past with such problems.

That will be "plan B" Mel. So far it looks like this motor may have a second chance. Athearn sent me a whole F7 truck once when one of the fingers were found broken where the bearing cap holds the truck in place.

Thank you, everyone— Wayne, Mel, Trevor, Greg and Mike, for the great comments and suggestions.

Cheers! Ed

 

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Posted by xdford on Thursday, April 18, 2019 9:10 PM

Hi Ed,

You wrote

"So, is there a suggestion for a NON conductive lube? I agree that the sintered bronze bearings need some lube but perhaps in some cases I've over done it."

Kadee Teflon Lube has worked well for me for that if you can use it on the end of a metal skewer while the motor is running, it should run off onto and into the bearing. No point in using a bamboo skewer as it will simply absorb the grease under the heat (micro as it may be) generated.

Thanks for your thanks and I am sure we have all been pleased to help,

Cheers from Australia

Trevor

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Posted by gmpullman on Saturday, April 20, 2019 4:10 AM

xdford
Kadee Teflon Lube has worked well for me

Thanks, trevor. I'll give it a go Yes

WARNING

The following contains graphic images that may be upsetting to electrical engineers and model loco tinkerers.

 ATH_DC-motor2 by Edmund, on Flickr

 ATH_DC-motor1 by Edmund, on Flickr

This motor was from a Genesis F7 or F3 loco that smoked itself for no apparent reason.

 ATH_DC-motor3 by Edmund, on Flickr

Those two red plastic brush housings click together to bring the brushes in contact with the commutator.

 ATH_DC-motor-brush by Edmund, on Flickr

The brush seems to be a composite bronze material. It is a dark gold color.

 ATH_DC-motor4 by Edmund, on Flickr

Look at the lead and gunk slung around inside the bell-housing. A blob of lead and another thrust washer is still inside. The brush on the right is stuck inside the sleeve.

There could have been a "run" of certain Genesis motors that had a QC issue. As I said previously, there was a batch of Buhler motors in Bowser locos and those hi-amp Life-Like motors that got into some of the PAs. Maybe I just happened to get a pair. Hard to say exactly when these were made but the GP9 was perhaps three years ago. Maybe the Geep will be OK for now?

Thank You, Ed

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Posted by rrinker on Saturday, April 20, 2019 1:45 PM

 Second picture, is that inadvertent damage that occurred taking it apart or are those commutator segments really loose from the left side? And they are so totally caked with gunk. The brush that came out doesn't looks too overly worn down, but if the other one was jammed and not able to flot, that could cause some issues. But the strange thing about that would be it would probably get better after more run time, as the brush was worn away and the pressure reduced. Excess oil on the end bearings can do that, the oil burns witht he arcing and just turns the entire commutator black with residue, and some gets flung all over the inside. I had an old junk motor I once played around with and tried that - put a tiny drop of oil on the commutator. For about 30 seconds it actually ran better, then is all burned and the commutator turned black and it barely ran until I scrubbed it clean again.

 COuld easily be bad batches, depends on how hard they sit on the production line workers in the Chinese factories. I think all it would take is for someone to over oil a batch to end up with results like this. I've had locos that, unopened in the packaging, had pools of oil beneath the truck gearboxes (luckily it did not get on the paint), so why not motors.

                                     --Randy


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

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Posted by gmpullman on Saturday, April 20, 2019 11:05 PM

rrinker
 Second picture, is that inadvertent damage that occurred taking it apart or are those commutator segments really loose from the left side?

The heat built up so bad that the copper segments shifted. The insulating material is what the black gunk is. It melted. Motor was running when it disintegrated, slinging lead, plastic and graphite or carbon inside the housing. Burned off or melted the solder connection to the windings.

The decoder was a TCS-DASR and it held up OK.

Ultimately, I believe the lesson here is to use any lubricants sparingly.

I think what prompted me to over-lube was all the times I had 
Stewart and early Life-Like locos that would whine like crazy. Screech was more like it. So the motor and worm bearings were suspect since it was a high pitch whine. 

I have opened some brand new Genesis locos and the oil was pooled up at the bottom of the plastic wrap the loco was packed in. I think some of the hot warehouse or UPS truck atmosphere would also soften up the truck grease and make it seep out. Some Bowser locos I bought brand new had white teflon grease literally oozing out of the truck gear boxes.

The GP9 that I first wrote about has been running for a few hours now so hopefully I caught it in time and cleaned out the commutator area good enough to keep her running.

Thanks for the comments and suggestions, Ed

 

 

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