Arcing Brushes??

Vladymere said:
As people have said, armature. Armatures wear down, diminish in diameter, the mica between poles is now equal to the diameter of the copper. The copper is burned. Armatures can be turned down to provide a clean even surface and then the mica cut to below the level of the copper.

This is a common problem with DC motors but most motors are scrapped instead of repaired.

Vlad
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thanks, Vlad for that thought ... it seems like, given that this may be a common problem, the use of a treadmill motor on, say, a wind generator, is not really such a good idea after all ... I would think a wind generator would quickly rack up a bunch more "miles" than a treadmill with an unenthusiastic owner. However, even a high mileage treadmill motor would probably have plenty of life to live as a drill press or mill.

Yesterday I put a VOM on the commutator segments [a rather poor excuse for a VOM] and, while none seem to be shorted to the armature or the shaft, some pairs do seem to be open ... I guess that's my problem. So, I will have to tell my wife that it's not fixable as a treadmill [that part's good], but, unfortunately, it's also not useable as a DP ... bummer. I suppose a new motor would only be $75 or so on eBay or whatever [or a different treadmill off Craig's List for a bunch less] but, oh, I do love "free" stuff.

So ... I'm not ready to throw in the towel on the DP project just yet ... we'll see ... Has anybody tried a treadmill motor conversion to a tablesaw?? The variable speed thing seems like it would solve the biggest problem with table saws: bogging down under load ...
 
deandad said:
Has anybody tried a treadmill motor conversion to a tablesaw?? The variable speed thing seems like it would solve the biggest problem with table saws: bogging down under load ...
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I'm not sure how a variable speed motor would solve the bogging down problem. The problem is not enough torque to handle the load.
 
RJSakowski said:
I'm not sure how a variable speed motor would solve the bogging down problem. The problem is not enough torque to handle the load.
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yeah ... I guess you're right ... if you had the torque capacity, why wouldn't you be using it all the time, rather than ripping slowly??
 
Open windings will definitely cause sparking . A dead sure test is to rotate the armature to different positions. The motor will not start if on open winding.

Regarding fixing breaks at the commutator, I have successfully repaired open windings on drills and on a Dremel. What I did was to first find the break, usually with a magnifier. Then I teased the broken wire out of the varnish or epoxy it was usually embedded in. Next, I scraped some of the insulation off so I could solder a short stub on. Then, the commutator copper had to be cleaned to allow soldering the stub to the commutator. Finally, I checked the winding for continuity and rebedded the repair with epoxy.

Bob
 
RJSakowski said:
Open windings will definitely cause sparking . A dead sure test is to rotate the armature to different positions. The motor will not start if on open winding.

Regarding fixing breaks at the commutator, I have successfully repaired open windings on drills and on a Dremel. What I did was to first find the break, usually with a magnifier. Then I teased the broken wire out of the varnish or epoxy it was usually embedded in. Next, I scraped some of the insulation off so I could solder a short stub on. Then, the commutator copper had to be cleaned to allow soldering the stub to the commutator. Finally, I checked the winding for continuity and rebedded the repair with epoxy.

Bob
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sounds tedious ... but it's FREE!!! ... sort of. Definitely something to think about [and certainly take another look at ... with that magnifier] ... if it were to end up being something I could see, I might just be inspired to try a fix ... it will either work or it won't: either way I'm learning something and gaining some skills ...

the motor does seem to be reluctant to start at times [maybe because it's on an open winding??] ... when that happens, i can usually make it start by raising the speed on the console ... I guess that could be burning the surface of the commutator somewhat ... maybe I should just try rotating the armature a little bit rather than raising the speed ...

thanks for all the input, guys
 
In the good old days, armature coil wires were soldered to the commutator bars but I expect now they're all swaged by machine and probably not visually inspected. If you see some that don't appear to be connected, they could be your problem. However they did it, the connections should all look alike, and the resistances between any two adjacent bars should be the same.
 
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