# Measuring brush timing



## major (Apr 4, 2008)

mechman600 said:


> Is brush timing measured on the centerline of the brush or the leading edge? I am reversing the rotation of a series wound forklift pump motor for the Electric Booger and I am eyeballing the timing in the reverse direction to match what it was in the original direction. On brush centerline, it is 11-1/2 degrees advanced, which seems about right to me.


Use the centerlines of the pole and the brush contact patch on the comm.


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## mechman600 (Oct 16, 2010)

Thanks again, major. Does 11-1/2 degrees sound about normal for advanced timing? It surprises me that a forklift hydraulic pump drive motor would have advanced timing in the first place.


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## major (Apr 4, 2008)

mechman600 said:


> Thanks again, major. Does 11-1/2 degrees sound about normal for advanced timing? It surprises me that a forklift hydraulic pump drive motor would have advanced timing in the first place.


11 degrees sounds a bit much for a 48 or even a 72V lift pump motor from the factory, but possible. And such pump motors are unidirectional and run at overload with slam dunk starting with just a contactor across a huge battery (meaning not a lot of sag), therefore a 4 to 5 degree advance was common when I was in the business. 

The pole bolts in line with the brush for neutral timing is a rule of thumb and applies to most every motor I know about but that alignment depends on a host of factors and a particular motor design or manufacturer may not adhere to it.


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## mechman600 (Oct 16, 2010)

I got the motor back together today and tested it out. Now it spins the right direction, so that's a good thing! It also seems to spin a bit faster than before (going by the pitch of the sound it makes), but I have been powering it up with a four battery cart that we jump start Peterbilts with, so it might have been low on charge during the before video.

This is what I went by for brush timing, the long line being the pole centre. Before:









After:

















Here is the before video, with the motor spinning in its normal direction:
http://www.youtube.com/watch?v=3Mo3fXn894o

Here is the after video, with the motor reversed and brush timing altered (and ridiculously nice Cat yellow paint job applied):
http://www.youtube.com/watch?v=u0aT2ZOhawM

I think the second one is much louder because the motor is running with the brush end up, as opposed to down in the first video.


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