Comm Damage / Wear ??????

[TedBull]

I have a handwound Comp motor that has alot of comm wear/damage after only 4 comps. Looking for good information as to possible causes to the damage in such a short time-96 minutes runtime max. After looking over the brushes again, the brushes where chipped on the edges and broke apart easily. The opinion of my local club members is possibly too soft of brushes. Here are the picks, please let me know what you think. The black stuff you see is all carbon, no debris found in motor.

[EeePee]

What was the motor in? How many volts were going to it? How much water has it seen (knowing you PNW types )?

[Charlie-III]

Sorta hard to tell from the pictures (focus & lighting) but it only looks like normal wear with serrated brushes. A little cleaning and it wouldn't be too bad.
Has the motor run really hot (hot like, "touch it & burn yourself" hot?)

Maybe I would change my mind if the focus was better as was the lighting.

Maybe hot the comm with some electrical cleaner and take another picture?

Lets see if JRH or Eddie want to comment.

[TedBull]

Originally Posted by EeePee

What was the motor in? How many volts were going to it? How much water has it seen (knowing you PNW types )?

Motor was in my 1.9 comp rig. Ran on 2s thru Tekin FXR. This motor has not seen a rainy comp so no water or sand, no dust or dirt.

[TedBull]

Originally Posted by Charlie-III

Sorta hard to tell from the pictures (focus & lighting) but it only looks like normal wear with serrated brushes. A little cleaning and it wouldn't be too bad.
Has the motor run really hot (hot like, "touch it & burn yourself" hot?)

Maybe I would change my mind if the focus was better as was the lighting.

Maybe hot the comm with some electrical cleaner and take another picture?

Lets see if JRH or Eddie want to comment.

Never ran hot. Only ran 4 comps. Couldn't get camera to focus any better. but I can try again.

[TedBull]

Cleaned the comm with motor spray and wiped it down with paper towel. Removed washer and took some new pics. Best I could do, I realy tried to show the definition and depth of the grooving. Keep in mind, only 96 minutes max of comp time and no practice runs.

[EeePee]

More like a really hard brush scraping away on the soft copper commutator.

The depth seems pretty excessive to me for 96 minutes of runtime, but I've never worked on the smaller motors with the smaller brushes. I'm thinking a smaller contact patch of the brush face is doing more harm than a larger brush, but I guess surface area would be relative between the two different size motors. I got no idea, really.


Hard serrated brush, really high spring tension and 96 minutes... that could be about normal, maybe. Was the brush serrated to begin with?

The red tint is interesting also, indicating heat. Or is that a refection?

[Cordwood]

What color springs were on it?

[TedBull]

Originally Posted by EeePee

More like a really hard brush scraping away on the soft copper commutator.

The depth seems pretty excessive to me for 96 minutes of runtime, but I've never worked on the smaller motors with the smaller brushes. I'm thinking a smaller contact patch of the brush face is doing more harm than a larger brush, but I guess surface area would be relative between the two different size motors. I got no idea, really.


Hard serrated brush, really high spring tension and 96 minutes... that could be about normal, maybe. Was the brush serrated to begin with?

The red tint is interesting also, indicating heat. Or is that a refection?

Not sure if the brush started life as serated or not?

Red tint is just reflected light. Comm is nice golden on untouched surface and more silver on brush surface. My other dedicated 1.9 comp motor has gone a full season without any real wear on comm or brushes, and it has smaller brushes than this motor.

Originally Posted by Cordwood

What color springs were on it?

Shiny Chrome springs. They seem light compared to my other motors matt silver finish springs.

[Charlie-III]

Pictures look a bit better.
Yep, really looks like a hard serrated brush, possibly with a bit too much spring tension on the brushes.
How was the pinion mesh?
Any binding in the drivetrain?

You've been around for a while, so I will guess you have a decent idea on how to set up a rig and maintain a motor.
I agree the wear seems a bit much, but if the brushes were hard & serrated, then what you are showing does not look too far out of place.

I usually run a softer brush in crawler motors, easier to replace brushes than cut comms.

[EeePee]

Originally Posted by TEDBULL

My other dedicated 1.9 comp motor has gone a year without any real wear, and it has smaller brushes than this motor

I knew!! you were going to say that. They always do!

[Cordwood]

Just an idea but the timing wasn't retarded was it?

The chrome silver springs I have are heavy but I think the blacks are even heavier.

Have you asked the motor builder about it?

[WIDELOAD]

That's gnarly wear for only 90 off mins of run time. It doesn't have any burning/pitting that I can see, so I don't think it was a timing issue.
Just looks more like super aggressive brushes/springs or an overly soft copper on the comm.
Sure is strange....Hopefully JRH & Eddie will chime in with their opinions.

[TedBull]

Pinion spur mesh is always kept perfect. No binding in drivetrain.

I recieved the motor from the builder "Broken in". installed it and started comping it. I did not adjust or change anything with the motor. Timing set at nuetral from builder. Didint have any trouble untill the dragbrake started to suffer. Then I tore it down and found the problem. This is my third motor from the builder, differant version then first two.

My driving syle is slow and steady with some bursts of wheel speed when needed. Only ran on 2S, never hot.

Motor builder is aware and not sure what caused the problem. But he is leaning towards debris causeing the wear and doesnt belive the brushes or spring pressure to be at fault. I dont know much about motor wear, but I dont think debris under the brushes would create such even wear across the com. Again, no debris inside motor. Motor was very clean with exception to carbon.

[TedBull]

Originally Posted by WIDELOAD

That's gnarly wear for only 90 off mins of run time. It doesn't have any burning/pitting that I can see, so I don't think it was a timing issue.
Just looks more like super aggressive brushes/springs or an overly soft copper on the comm.
Sure is strange....Hopefully JRH & Eddie will chime in with their opinions.

I agree. Eddie lives close to me and is a acquaintance. Good guy, lots of knowlage. I sent him the first set of pics. He was not sure why the brushes damaged the comm. Could not be more specific without seeing it in person. He was also not sure if it could be turned down with the amount of damage without seeing it in person. Eddie WAS NOT the builder of this motor.

I will see if I can get eddie to chim in.

[Charlie-III]

I really have to find a reason to visit my Lynnwood customer site.......

[EddieO]

The comm looks red at the bottom....typically a red comm is a sign of being overgeared and/or too light of spring....but you say its reflection....sure looks red though.

My only guess at this point is that the brushes may not of been fully seated, so they they were riding along the tips, which puts a LOT of tension on a small area. So it grooved the crap out of them and then the running finally seated them, but the damage was done.

You can bring it by and I will see if I can figure it out....

I can tell you stiff springs are a must on most mini motors. The magnets in everything suck, except the cobalt.....so stiff springs are the only way to get decent braking.

Later EddieO

[rock hard]

The brushes are not serrated, the brushes are stock assotiated mini mod brushes, not alot of options there.
The springs are stock also, and soft, actually IMO all the mini springs are soft, again, not alot to choose from.

I have seen contrabands, and black markets that have exessive wear. I have never had one look like this in 1 1/2 hrs of use. But one thing they all had in common, they was all dirty. !st motor I had fail on a guy ( a well known local here)

It was a 15t at state finals, he was pissed too, but to be honest, the motor was dirty, and that dirt and grim floating inside the motor only does harm.

[TedBull]

Thanks Eddie. I am waiting to hear from the builder again, hopefully he and I can work something out. If not, then its coming to you for sure. I just hope there is enough comm left after its turned.

[rock hard]

Originally Posted by EddieO

The comm looks red at the bottom....typically a red comm is a sign of being overgeared and/or too light of spring....but you say its reflection....sure looks red though.

My only guess at this point is that the brushes may not of been fully seated, so they they were riding along the tips, which puts a LOT of tension on a small area. So it grooved the crap out of them and then the running finally seated them, but the damage was done.

You can bring it by and I will see if I can figure it out....

I can tell you stiff springs are a must on most mini motors. The magnets in everything suck, except the cobalt.....so stiff springs are the only way to get decent braking.

Later EddieO

I'll buy a couple sets of those springs