Guru
Joined: 15/07/2006
Location: AustraliaPosts: 676
| Posted: 10:40pm 07 Jul 2010 |
Poling, don't know. Possibly was arching a bit. But I don't recall any burn marks on the armature when I changed the brushes. The motor still ran smooth after changing the brushes. A little clicking in the brush area. I just thought it was the new brushes.
There were some of the old brushes that had stuck in the brush holder. In the pic above you can see at the top left the longest one. It had stuck and not worn down as the others. There was a bit a variation between the brush lengths. But of course it was when the brush springs reached their limit when all stopped. I had not noticed any reduction in power the few Km's before it stopped. Only metres before, it missed a beat.
Whether it had been damaged before or not the damage was evident after I had made the advance. After the damage, I went been back to the reading and found that the ADC is already advance 10 degrees. I had added another 6. The Netgain WarP motors are advanced 12 degrees. So with new brushes, is why I assumed it to be the advance.
There is a copper spray on the field wire. This has come from in the armature winding just in from the commutator.
It is possible that carbon or copper from the old brushes were lodged in between the comm bars or somewhere in the motor. I did run a scraper through the gaps between the comm bars though and sanded the comm bars with wet and dry sandpaper before refitting the end plate with the new brushes. Hence the first picture of the comm bars being quite black and the second picture is much cleaner. Only a burn mark half the width of the brushes. The brush holders were a bit floppy and the brushes had not seated in properly. I have now fixed the brush holders.
Now saying that, it could also be that I expected too much from it with the brushes not seated properly. I did do high speed for at least 5 of the 9 Km.
No damage to the speed controller.
Trev @ drivebynature.com