3400 Generator Brushes

KV Bruce · Oct 13, 2021

Working on my 1970 3400 with the Lucas generator. After troubleshooting, I found one of the commutator brushes not touching the commutator. (pivot point dirty and not moving freely) The wire was also pinched under the cover and it broke when I removed the cover. I found new brushes on EBay and they should be here next Monday. So my question is, should I just install the new brushes and let them wear into the commutator or grind them closer to the correct angle??

Notice in photo one brush is shorter than the other.

shaun wallace · Oct 13, 2021

Theyll wear in in short order. The short one is the hot brush other is ground.

Fritz Maurer · Oct 14, 2021

You dont have to grind them close... you can get them exact. Set the armature in the end cover and put a strip of 180 grit sandpaper between the brush and the commutator. Rotate the armature back and forth a few times and the brush will mate the commutator perfectly. Really ought to find someone with a lathe and true it up beforehand, though. If you had one stuck brush there is bound to be arc pits in the copper.

KV Bruce · Oct 15, 2021

Update: The brushes arrived earlier than expected. The old brushes were not significantly shorter than the new and there was an angle on the new ones. Installed new brushes with the pivot points clean and moving freely. (I believe this was my real problem) Installed generator, ops checked good. During my troubleshooting I can across this youtube video and thought I'd share. I enjoy reading this forum and learning something new. Thanks to all.
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3400 Generator Brushes

KV Bruce

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shaun wallace

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Fritz Maurer

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KV Bruce

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