# Brush wear pattern - Please help me diagnose



## GizmoEV (Nov 28, 2009)

I'm by no means an expert on this but when I started reading your post I immediately thought of low spring tension. I remember the guy from Helwig who presented at the EVCCON 2011 saying that it was very common for the spring tension to be too low in the standard EV motor and also that the brush holders were not always stiff enough. The talk is at the end of http://media3.ev-tv.me/news102111-1280.mov.


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## major (Apr 4, 2008)

b2600ev said:


> Setup: ADC FB1-4001A, Curtis 1231C-8601, 44 TS-160 cells (141V nominal), 1993 mazda b2600 pickup.
> 
> I have a little over 1000 electric miles now. Everything is working great except that sometimes under heavy load (going up a hill) and high RPM (~3500) I will start to hear a buzzing sound. ............. except that I have one bad hill that I have to climb when I leave my office, while accelerating to highway speed. So for this hill I have to apply continuous full throttle for ~30-45 seconds.
> 
> ...


Hi b26,

I look at the brush face and see about 50% seat. My suggestion is to get a dressing stone, use it on the comm and brushes and then go through a break-in. Dressing stones are sometimes called seating stones, but they shape the brushes, not seat them. Seating requires time and current and RPM. While such dressing stones may be available on-line, I suggest you find one locally where you can get advice on use.

Using the dressing stone will shape the brush faces to the comm diameter (almost). After that it needs a good break-in. Jack up the drive wheels. Leave it in gear. Disconnect controller from motor. Use a 12V battery with a high amp charger to power the motor. Run it for 20, 30 or more hours. Get a fan blowing air over the motor. That should get you a good start on proper brush seating.

That hill sounds like a bitch. How many motor amps do you pull going up? Anyway to avoid the hill for the first 1000 miles after the break in? Can you use a lower gear and run the motor higher RPM and less current? Slow down on the hill?

Maybe stronger springs would help, but I don't know if they are available. And you cannot adjust the present springs.

Regards,

major


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## DIYguy (Sep 18, 2008)

b2600ev said:


> Setup: ADC FB1-4001A, Curtis 1231C-8601, 44 TS-160 cells (141V nominal), 1993 mazda b2600 pickup.
> 
> I have a little over 1000 electric miles now. Everything is working great except that sometimes under heavy load (going up a hill) and high RPM (~3500) I will start to hear a buzzing sound. This is RPM dependent (vary RPM and the buzz freq changes). If I ease back on the throttle it stops. I have been wondering if this is some kind of arcing of brushes.
> 
> ...


If you are considering new brushes. . . 
You may want to contact Helwig carbon. The brush guru there is Nitin Kulkarni. He helped me a lot. You can send him pictures at [email protected]. 
For trailing edge discontinuities it indicates electrical stress. Split brush design will help this. You should consider a different material grade like their H49 compound and the red top. You should pull back the brush lead cover and see if there is any discolouration, if so, you may need larger diameter leads also. The spring force should be even on all brushes and Nitin may suggest something closer to 5 psi (brush area must be calculated). You may notice one of two brushes in each pair shorter, this is a polarity effect and normal, if you have advanced brush timing, this may be exaggerated.
If you get new brushes, do like Major suggests and run them in . . . even for several days . . it's better.
Do you know the advancement of your brush timing if any?
Another good resource is here;http://www.nonstopsystems.com/radio/article-PANTRAC-carbon-brushes.pdf


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