# Advance brushes on DC motor



## major (Apr 4, 2008)

tropes said:


> I would like to advance the brushes on my DC series wound motor. Am I correct in assuming that I must rotate the brushes in the opposite direction that the armature turns? NO GUESSES!!! I want to hear from those who have tried this.
> 
> Tropes


 
http://www.diyelectriccar.com/forum...irection-ccw-cw-70444p2.html?highlight=husted

http://www.diyelectriccar.com/forum...ng-forklift-motor-19433.html?highlight=husted

And more references if you search. Jim Husted used to have a nice clear diagram on his web site, but it is no longer available, unless somebody has a copy they can post.

I don't think you are running too high voltage or current, so don't advance too far. Advancing brushes effectively weakens the field so you reduce torque. That subject has also been discussed at length here.

After you make a brush position change, reseat them, or repeat the break-in. Examine the brush face before you do any adjustment. If it is not uniformly shiny, you're getting a false position to start with and need to properly seat those brushes.

The only way to tell if you are "spot on" with brush location is to observe arcing under load. So a camera during a pass would be required. Are you seeing streamers now? Why do you want to mess about with advance?

So, haven't seen you post lately. How's it running? Times? I forget what battery you ended with. ???

major


----------



## tropes (Jul 24, 2011)

major said:


> I don't think you are running too high voltage or current, so don't advance too far. Advancing brushes effectively weakens the field so you reduce torque. That subject has also been discussed at length here.
> 
> After you make a brush position change, reseat them, or repeat the break-in. Examine the brush face before you do any adjustment. If it is not uniformly shiny, you're getting a false position to start with and need to properly seat those brushes.
> 
> ...


Thanks. That answers my question.
This is the last thread I started: http://www.diyelectriccar.com/forums/showthread.php?t=74649&highlight=tropes
Why do I want to mess about with advance??? Well, as you can see I have plenty of torque but low top speed so I'm hoping to increase rpm at top end. If it wasn't for messing around I'd still be racing my 426 Hemi Dart.
Tropes


----------



## frodus (Apr 12, 2008)

In order to increase RPM, you need to increase voltage to the motor. Are you building a higher voltage pack?


----------



## major (Apr 4, 2008)

tropes said:


> Why do I want to mess about with advance??? Well, as you can see I have plenty of torque but low top speed so I'm hoping to increase rpm at top end.


That's not really a good reason to mess with brushes. You're better off adjusting the chain ratio.


----------



## tropes (Jul 24, 2011)

major said:


> That's not really a good reason to mess with brushes. You're better off adjusting the chain ratio.


I went with a larger sprocket on the drive end June 9th and ran about 1 mph slower. http://www.youtube.com/watch?v=2akGsAKoZ1E&feature=g-all-u


----------



## major (Apr 4, 2008)

tropes said:


> I went with a larger sprocket on the drive end June 9th and ran about 1 mph slower. http://www.youtube.com/watch?v=2akGsAKoZ1E&feature=g-all-u


If you can't get it with a ratio change, the brush advance won't do it. And you'll risk burning the comm. If it ain't arcing now, don't move the brushes. 

Time slips and videos don't give good solid data. You need to collect some real numbers...volts, amps, RPM, feet. A Cycle Analyst is a cheap way to do that.


----------



## tropes (Jul 24, 2011)

major said:


> If you can't get it with a ratio change, the brush advance won't do it. And you'll risk burning the comm. If it ain't arcing now, don't move the brushes.
> 
> Time slips and videos don't give good solid data. You need to collect some real numbers...volts, amps, RPM, feet. A Cycle Analyst is a cheap way to do that.


Sounds like good advice. I just downloaded the Cycle Analyst Manual.


----------



## tropes (Jul 24, 2011)

frodus said:


> In order to increase RPM, you need to increase voltage to the motor. Are you building a higher voltage pack?


My series wound dc motor seems to respond well to the advanced brushes. The rpm increased by about 400.


----------



## poprock (Apr 29, 2010)

Hi,"_*I went with a larger sprocket on the drive end June 9th and ran about 1 mph slower"*_
In ICE terms that would mean you need a bigger engine for that ratio.At current settings you have achieved the bestpossible.


----------



## tropes (Jul 24, 2011)

poprock1 said:


> Hi,"_*I went with a larger sprocket on the drive end June 9th and ran about 1 mph slower"*_
> In ICE terms that would mean you need a bigger engine for that ratio.At current settings you have achieved the bestpossible.


That was my opinion as well. I discussed this with the controller builder and he thinks the Raptor controller could deliver more current at full throttle when it acts as a switch between the battery and motor. i plan to install the taller gear after the next race and do some tests.
BTW, are there any electric junior dragsters in Austrailia?
Tropes


----------



## poprock (Apr 29, 2010)

The best Aussie to answer that would be our member "Ripperton"


----------

