Cut Motor repair

[badbert]

I installed the armature in the old housing, and mounted it to a board. I but a square bit in my trusty drill and mounted it to the board making a make-shift lathe. 57511
Starting with a flat file and ending with 1200 grit 57512and polished the armature up real nice.

One problem... the old housing was so melted i didn't pay attention to which wire went to which brush?!57513 Any one know?! Notice the shiny spot on the brush? I gave them some break-in time on the "lathe".

[TerryT]

Clever using the square drive bit, good job. Don't forget to clean out between the comutator segments so you don't have a short. I used to use a hacksaw blade but don't know if that will fit in this case.

[badbert]

Thanks Terry! Got any idea how to wire the brushes?

[Deolman]

Back in the days when I worked in the machine shop, we used a hacksaw blade that we sharpened a hook on the end. Then we stuck the sharp edge in between the armature cracks and pulled the blade along the armature removing the burrs. This usually worked quite well. 57521

[badbert]

I think it fixed it!! It is happily carving. It threw some sparks for a few minutes, but it is humming along now!

If you cross the wires the motor does in fact spin backwards!57526

[TerryT]

Good work Bert! This one needs to be kept around for referrence. I saw the same situation with another members cut motor a week or so ago. The same thing happened to his machine and the comutator was very rough. He is going to have to do the same thing probably.

[Digitalwoodshop]

Just sent pictures in a email but I see I am 4 hours late.... Good Job !!!!

AL

[badbert]

It turns out that even though I have done such repairs dozens of times (in the Automotive world) this could not fix the problem my motor was experiencing. There was a short to ground and four "soft" bars on the commutator. I found a local guy (1/2 mile from home!) http://allcityelectricmotorrepair.com/index.php?cID=1 who had much more experience, not to mention a fully stocked high tech machine shop, who properly diagnosed and was able to repair the armature. He pointed out that there were no 20,000rpm motors in the automotive field. He soaked it in mineral spirits then washed it and baked it. Somehow this brought the short to ground to 20 mega-ohms and also brought the four bars up to an acceptable level. When he chucked it up in the lathe he found another problem. The commutator was slightly out of roundness. He explained to me that a lower RPM motor, like a starter motor for example, would not have an issue with a small amount of run-out. But at 20,000 rpm the thing was like a cam lobe smacking the brushes away from the commutator. He trued it up and micro-balanced it. Then it went back in the bath and soaked overnight. This morning he baked it again and rechecked it. He said it wasn't perfect, but it should last for a while. The charge for all of this... 4 custom rod holders for his boat!!! :) I am so glad to have good Karma! It has been humming along for a couple hours now. No sparks and it sounds smoother than it ever has! There is no surge, it is so steady it sounds like a shop-vac!

[badbert]

He also is interested a sign for his shop. And maybe a custom wood insert for the dash of his boat. I am thinking some of that spalted hackberry with a marine epoxy finish! This guy is my new hero! http://allcityelectricmotorrepair.com/index.php?cID=1

[Digitalwoodshop]

He also might get some future business...... Good Job !!!!

AL

[henry1]

It turns out that even though I have done such repairs dozens of times (in the Automotive world) this could not fix the problem my motor was experiencing. There was a short to ground and four "soft" bars on the commutator. I found a local guy (1/2 mile from home!) http://allcityelectricmotorrepair.com/index.php?cID=1 who had much more experience, not to mention a fully stocked high tech machine shop, who properly diagnosed and was able to repair the armature. He pointed out that there were no 20,000rpm motors in the automotive field. He soaked it in mineral spirits then washed it and baked it. Somehow this brought the short to ground to 20 mega-ohms and also brought the four bars up to an acceptable level. When he chucked it up in the lathe he found another problem. The commutator was slightly out of roundness. He explained to me that a lower RPM motor, like a starter motor for example, would not have an issue with a small amount of run-out. But at 20,000 rpm the thing was like a cam lobe smacking the brushes away from the commutator. He trued it up and micro-balanced it. Then it went back in the bath and soaked overnight. This morning he baked it again and rechecked it. He said it wasn't perfect, but it should last for a while. The charge for all of this... 4 custom rod holders for his boat!!! :) I am so glad to have good Karma! It has been humming along for a couple hours now. No sparks and it sounds smoother than it ever has! There is no surge, it is so steady it sounds like a shop-vac!
Were those the brush you had Purchased from china that did this to the armature

[badbert]

Henry I would like to say yes. But I do not know for sure. Also the motor repair facility gets their brush stock from ebay. He filed down a set of brushes for this motor. Were his brushes any better than mine... who knows! The first set i installed did last. But when they failed, none of the sets would last longer than a few hours. So in the proverbial chicken and egg debate. Did the armature fail and destroy the brushes or did the brushes fail and destroy the armature? I know one thing it has been running for several hours (third project going now) and the motor sounds better than it ever has.

[Digitalwoodshop]

How many hours until you replaced the very first set of brushes? I got about 298 I think on a first set to STALL. Like to change them at 250 now.

Replaced my first brushes on 08/08/2007 :mrgreen: LHR saw this picture and another one I posted with my Hours METER and immediately put a entry in my file... OUT OF WARRANTY..... LOL...

05/17/2008 Hours Meter... :twisted:

AL

[badbert]

I changed out the first (factory) set about 300 hours (I think?). The first set of ebay brushes failed at ~100 hours. Again, I can not say for certain that the armature didn't fail destroying the brushes. Because after that fail, none of the brushes worked. It would eat them in a matter of hours. Also I say this because, there is a noticeable difference in how the motor performs. I got this machine with twenty minutes on the cut motor. It always surged. Now there is no surge. The motor is running steady and solid. It sounds like a shop-vac. The blower is a lot more powerful too.