Truing an out of round commutator
Truing an out of round commutator
(OP)
Hello all,
I work for a ski resort and we are having trouble with one particular motor. We have discovered that the commutator is out of round and we believe that is giving us trouble. The first thought is to remove the LARGE motor with a crane from a remote location and deliver the motor to a rebuilding shop.
My idea is to turn the motor via a backup diesel and attach some type of cutting tool that is similar to a lathe. Anybody have any experience and/or ideas with this?
Thanks,
Mike
I work for a ski resort and we are having trouble with one particular motor. We have discovered that the commutator is out of round and we believe that is giving us trouble. The first thought is to remove the LARGE motor with a crane from a remote location and deliver the motor to a rebuilding shop.
My idea is to turn the motor via a backup diesel and attach some type of cutting tool that is similar to a lathe. Anybody have any experience and/or ideas with this?
Thanks,
Mike





RE: Truing an out of round commutator
We adapt a small portable turret to the frame or end brackets and displace the cutting tool by handwheel operation. That should be a similar situation with your motor driven by an engine. You need to undercut the mica insulation between commutator bars too.
RE: Truing an out of round commutator
I would imagine that they take the brushes out and keep a vacuum cleaner on to keep fine swarf out of the motor.
RE: Truing an out of round commutator
Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA
RE: Truing an out of round commutator
RE: Truing an out of round commutator
a problem will exists on undercutting and chaffing of commutator bar segments which will require a good working access to the unit. where on chaffing works, you will maintain the 90 degrees segment edge separation. an experienced technician is required on this matter. whilst, a poor quality chaffing will decrease the length of the carbon brushes faster as expected.
RE: Truing an out of round commutator
From aolalde
<< We have turned the commutator outside diameter of the generators on site.>>
Do you have any pictures of the setup? And do you have any information how one builds the cutting tool/portable turret?
Mike
RE: Truing an out of round commutator
Carefull evalutation will be required as you will likely be 'reaching' with the tool which subjects it to chatter or worse.
RE: Truing an out of round commutator
I have completed this type of job many times on draglines, lift motors, winder motors and electric trucks (Komatsu).
1. How far out of round is the commutator...have u checked with a dial gauge to confirm your theory? If it is out of round you will notice excessive bruch wear also
2. Initial thought should be given to the length of the cutting tip to the tool post mount, if the distance is more than 6-8inches you could be playing with fire. There is nothing worse than a commutator that has been machined on-site.....and is worse when finished. Excessive vibration caused by a cutting tool can be a killer!!!
IDEA - You can run the DC motor via 2 welders....one will be connected to the "armature circut" and the other to the "field circut"...the field circut will be your speed control.
Ideal cutting speed will be between 100-400 rpm.
3. If it is successful you will then need to undercut and chamfer the commutator bars. This is not a job for an inexperienced person, it is critical that the angles of the chamfer are correct. If all has been successful make sure u check again with a dial gauge....for furture reference. *** Make sure u do not have any high MICA***
4. Don't be afraid to stone the commutator after all has been done.
Note: If the commutator has bands, give them a tap test and make sure thay are all solid. Sometimes loose bands can cause comms to lose shape!
Good Luck...hope some of this has been a help, if you want any other details or pics......show your email address and i will send some pics. Cheers, Chris (Australia)
RE: Truing an out of round commutator
RE: Truing an out of round commutator
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Depending on the damage/severity you have on-site, this may get you out of trouble. This should only be seen as a short term solution, the machine may have to be removed to fix this problem...once again...good luck...chris
RE: Truing an out of round commutator
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A comment about hooking up to a welder. Yes, it works but watch out for dangerous, blinding, flash over. Many years ago I watched a service engineer do this in a ship. Told myself at the time that I would never be that hungry for a job!
RE: Truing an out of round commutator
J.