# Kostov Motor Brush Issue



## PeterH (Mar 20, 2009)

Hi there,

I have a 10 inch Kostov in my 1991 Geo Tracker conversion. Just turned 10,000 miles last month. I continue to have an intermitent problem with the brushes.

Before I go further let me explain why I think the problem is with the brushes. When the problem occurs, it is as if the motor is cutting out intermittently or running at half power. To fix the problem for a few days, all I have to do is pull the front dust/gravel shield from around the outside of the motor and just push on the spring for each set of brushes.

The problem got real bad last year and I even pulled the motor out and removed the brushes to examine them. Nothing obvious, but I'm far from a brush expert and this is still my first set of brushes. I blew out brush dust while the motor was out, put it back in, and didn't have the problem for another thousand miles or so... but it was also much colder than summer driving (when the probem seems to happen more frequently).

Could this be a case of the brushes expanding in warmer weather and experiencing a greater degree of friction between the brush and the holder and therefore preventing the brush from making full contact with the commutator? When I had the brushes out last summer, I tried to add another turn to the spring to increase the pressure, but wasn't able to do so... just physically couldn't make it happen. I got that idea from the second EV convention and the Helwig Brush expert said he does that on all of his motors.

I don't seem to have the problem in the cooler weather, but as soon as we get a couple of warm days, it happens again.

Thoughts anyone?

Thanks,
Pete


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## major (Apr 4, 2008)

It doesn't sound like a brush problem to me with cutting out or half power symptoms. More like a controller problem. Stuck brushes or weak springs would cause arcing and burning on the commutator.


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## Tesseract (Sep 27, 2008)

I agree with major that the controller (which is a Soliton, IIRC) is likely limiting output for some reason. Post your settings page and, as I usually advise, collect a log file.


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## damirromanik (Oct 28, 2012)

I have a 10 inch Kostov motor, Soliton 1 controller that has also developed a similar problem, to test the motor I hooked up a 12v battery and this proved the motor was the problem as the motor was runing radically, it did not run smoothly as normal my Soliton had no Error lights flashing normally it will warn you if it is faulty or does not like some condition, I haven't had a chance to check the brushes which should be reasonably new, but I beliveve it is a brush problem as the commutator seems good condition, this problem occurred suddenly as I was in second gear pushing the motor to maximum revs around 5000rpm as I was changing gears I must have kept on accelerating to soon before I got in to third gear so motor went high revs with no load I am hoping some brushes have gone, it is hard for me to access motor so I can check all brushes, any motor experts out there to confirm this, symptom is, no power and jerking motor which is not spinning smoothly. This could be Peters issue except he has slowly stuffed his brushes while I did it in one bad gear change?


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## major (Apr 4, 2008)

damirromanik said:


> .... this problem occurred suddenly as I was in second gear pushing the motor to maximum revs around 5000rpm as I was changing gears I must have kept on accelerating to soon before I got in to third gear so motor went high revs with no load .....


That's bad news. You have most likely distorted the armature and/or commutator. As you say the motor does not rotate smoothly at 12V, you need to extract the motor and examine it.

Frankly I am surprised we don't see more cases of overspeed damage caused this way. 

Sorry for your loss.


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## dougingraham (Jul 26, 2011)

The Soliton has an input for RPM and does a pretty good job of preventing over speed. I am assuming you don't have a tach sensor on the motor connected to the Soliton. Making sure this worked was high priority as it is so easy to overspeed a motor in neutral without it.

It does sound like damage to the comm or brushes.

As Major says, you are going to have to pull the motor and look at the brushes and comm. An overspeed situation can also throw windings if they are not wedged and glued in place properly. One advantage of these motors is that there are motor shops in many smaller cities that can repair stuff like this. Don't assume the motor has to go back to Kostov for repair.

Best Wishes!


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## damirromanik (Oct 28, 2012)

The Kostov 10 inch has max rev of 5400rpm in specification, I have installed a Rev counter on the shaft and set the Soliton1 to limit the revs @5400rpm this has been working at time of destruction, when I say the motor runs roughly I mean it doesn't spin smoothly when voltage is applied if I move the shaft by hand it feels smooth and normal so I am assuming this could be caused by one brush not making contact properly to get to all brushes is very hard but I will attempt this in a few days time I will be surprised if commutator or windings are affected as I only drove the car for few minutes and the high reving was a very momentary thing like a second or two but this is my first motor failure and I haven't got enough knowledge in exact motor operation to make a precise conclusion, my gut feeling is something is not right with a brush contact.
I hope I am wright as I might be able to fix it without removing the motor otherwise I will have to remove everything to get it out and I feel sick just thinking of all the things I need to remove. Thanks for all your help


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## glaurung (Nov 11, 2009)

Hi, i used 5800 limit in my K10 when i had it in my Range Rover. It did fine but this of course is not a quarantee for others. It did eventually eat out brushes but 2500kg and four wheel drive might have something to do with that.
Regards, Harri


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