Sparking Motor Brushes

[jbrunot01]

I just replaced the cut motor brushes...

Started a new carve project and smelled something burning...

Looked thru the small vent slots on the cut motor housing and found that there were sparks shooting off the newly replaced carbon brushes.

I hit the stop button...

Is this normal until the brushes take on the cylindrical shape of the motor armature?

Any input would be helpful.

Thanks,

Jeff Brunot

[bergerud]

Did you inspect the commutator when you replaced the brushes? If it is scored up and worn, it may take awhile for the brushes to, as you say, wear in. It could also be that the armature has a short and is drawing too much current.

I would run the cut motor test for awhile and see if things improve. I would also try and get a good look at the commutator. If some parts of it are black and burnt, the armature may be bad.

[Digitalwoodshop]

This is the main reason that I suggest opening the cut motor covers and inspect and blow the dust out. Since 1/2 of the fan sucks air in through the brush air vents and THROUGH the motor.. Having a sparking as it is seating brushes feeding sparks into dry sawdust inside the motor and being blown on by the fan.... I hope you have a smoke detector above your machine... Hours later the motor could catch on fire.... smoldering for hours.....

This is the WORST possible case... But we need to think about it....

Yes, opening the case can lead to a broken wire... even I have had it happen.... and a pinched wire putting it back together....

You can see by the dates this is a normal thing for dust to build up in the motor....

Something to think about...

AL

[Mugsowner]

I have not taken any of mine apart yet, but seeing that themotor can be torn down nicely, Shows me that the brushes may be seated. Seating the brushes will ncrease the life of both brushes and commutator. To seat the brushes, you will need to tape a piece of narrow sandpaper, long enough for a wrap on the commutator, just tape one end. Put motor together, install new brushes. Rotate motorin a direction to keep the sandpaper winding tight. Rotate 20 - 30 times. Remove brushes and disassemble motor, remove sandpaper and tape, put it all back together. Brushes now will be much closer to commutator shape. This will cause less arcing and chance of arc damage to commutator and brushes. Oh and while to have it apart be a very good time to clean up the dust in it.

[bergerud]

The brushes from LHR are already arced to fit the commutator. A few minutes of running and I would think they would be run in pretty well. My worry would be that the commutator was either damaged by the last set of brushes or the armature has a short. If it was my motor, I would take it apart for a close inspection. (What did the old brushes look like? How many hours were on them?)