Hello Mark, As I said before, the rear brushes are shunting the front brushes. The rear brushes are closer to the armature circuit connections to the communtator bars, thus a more resistance path to the front brushes.
This is normal in the three motors that I am using in my EV. I run three types of motors in my EV. One is a WarP-9, a WarP-11 and a GE-11 which the WarP-11 motor frame is the same frame as a GE-11. I have run the GE motor for 10 years where the rear brushes worn down 1/4 of the original length of 2 inches. The front brushes only worn down about 1/8 inch. Every 10 years as per GE maintenance, pull the motor, check spring tension, resistance tests and check the communtator surface. I had my motor shop verify if the communtator needed any work. They said, do not touch it. It still had a very smooth surface. It is noted that there were twice as many of communtator bars segments than the WarP-11 motor. The brush angle is set very steep to where the brush face contacts five communtator bars where the it makes with the next bar, while the last bar is still in contact. This results in no arcing. Also note the motor is design only for clock wise rotation looking at the pilot shaft of the motor. If you run this type of motor in the reverse direction, you will chip the sharp edges of the brushes. The communtator bars are very hard and the brushes hardness are set one point lower in hardness than the bar hardness. The brushes are very smooth looking like tool steel. They are a silver-graphite compound. The WarP-9 and WarP-11 motor brushes are much softer and will wear faster. You can get a option silver-graphite in the correct hardness for these motors. Every 10 years, I switch the rear brushes with the front brushes. I am still running the brushes in the GE-11 for 24 years where both are now at the same length. Roland ----- Original Message ----- From: "Mark Hanson" <[email protected]> To: <[email protected]> Sent: Wednesday, May 15, 2013 5:25 AM Subject: [EVDL] Dissimilar brush wear - data point > Hi Folk's, > > > > Since swapping the brush locations (front rear), the rear brushes that > were shorter are still wearing faster than the other 4 just now in the > front location so it appears that the first one's to seat, suck most of > the current (on the 9" "Impulse"). I ordered a milli-ohm meter (to > compare to the one I borrowed) to verify the .2 milli-ohm between the bar > that feeds the front brushes. George at Netgain has been very nice > sending 3 sets of brushes over the last 10k miles since the motor is over > a year old and I'm sure out of warranty. I'm just curious to what is > causing the disimilar brush wear and the pattern seams consistent. It's > always the rear brushes that seat and then wear first shunting the current > away from the front. But when I swap the positions the shorter brushes - > now on the front continue wearing fast (wear down in 3K miles). I'm > treating the others like a spare tire, giving another 3k miles for 6k > total but most of the current is really gooing through a sing > le brush instead of two, thus overcurrenting it and resulting in faster > wear. > > > > Best Regards, > > Mark > > www.REEVA.info community service RE & EV's > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20130515/d6c258b2/attachment.htm> > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > For EV drag racing discussion, please use NEDRA > (http://groups.yahoo.com/group/NEDRA) > > _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
