DC gearmotor sounds unhappy

Zachary Hoyt

Well-known Member
I haven't used my 18" Woodmaster planer in over a year but today I had 100+ 1x6 boards to plane. The feed is run off a DC gearmotor and a variable speed controller, not sure of the proper terms. The feed system seemed okay at first, then it blew the fuse on the control box partway into the first board. I took the board out, changed the fuse and ran the feed motor again on no load. It turned about 1/2 turn while sounding unhappy and blew the fuse again. I took the belt off the rollers and found that they were a little stiff, so I oiled up the bushings where the shafts run. I unbolted the gearmotor and took the cover off the reduction, I found that there did not seem to be as much grease in there as there might have been. There is a black ring all around the electric motor where the brushes run, I am not sure if this is the armature or if I am mixed up. I put it back together and put in a new fuse and it runs but still sounds unhappy. The half round magnets inside the case seem to be loose, all that keeps them from spinning in the case is the two screws that hold the motor together. I also got a mild electric shock from the case when I touched it. I don't know if the problem is in the motor or the gears but I am inclined to try adding more grease to the gearbox and see if that helps. I would appreciate any advice about how to proceed, and if the grease seems like a good idea I would like to know what type to put in there. Thank you very much, I am sorry this is so long.
Zach
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If those magnets are indeed loose, you have a problem. They might be able to be glued back in place with a silicone based glue. This may be a difficult task. I have had small success with this. Be extremely careful not to break the magnets and get them back in in the proper orientation. Perhaps repairs best be done in professional shop.
 
Hello Zachary Hoyt,

Old brushes will draw a lot of current when worn.
You need to take them out. They are on the opposite end of the gear box, where the red and black wires are. Each side should have a slot you can get access to the brushes that way. If the look burned or short, you'll have to replace them. They may just need a clean up. You should also clean the commutator, you may have to take the cover off where the brusher are, to get to it. That's my guess...........

Guido.
 
That's known as a "permanent magnet" motor. The magnets are epoxied to the inside of the case. Once the epoxy lets go, the magnets drag on the armature (the spinning part) and cause massive over amperage on the motor and controller. That's why it blew the fuse.

Best solution is to replace the motor.

If you're a diehard fixeruper, you can try to epoxy them back in, if they're not broken, and if you can get them and the inside of the case completely clean. Keep them in the same position they come out.
 
Thank you all, I am glad to learn all of these things about how these
motors work. I will probably replace the motor as I am not at all
confident in my ability to glue the magnets back in successfully. I
have been looking on eBay for what might be suitable, and
tomorrow I will call the company and see what they can offer and at
what price. The one I have is a 90VDC 1/6 HP 40 RPM output, and I
am assuming I will need to stick with 90 VDC in order for the
control box to work with it.
Zach
 
We had a motor home that the 12 volt DC water pump started sounding strange. I took it apart and found that one of the two magnets had come loose. I glued it back in place with construction adhesive. That fixed it and it never came loose again.

Dusty
 
If you're thinking of just replacing it anyway, it wouldn't hurt to try fixing it.

I bought an electric hose reel for a couple bucks at an auction years ago. The dc motor was froze up. It had rusted under the magnets and pushed them out enough to lock the motor.

If I recall correctly, it had roll pins or some sort of clip that wedged in between the magnets to hold them in. I just drove them out, cleaned the rust out and put it back together.

I doubt rust is your issue on a planer, but my point is that maybe a 1/4" roll pin or something similar might work to hold them in instead of glue.
 
glue your magnets back in . I have done them years ago I think I used fiberglass resin no fiber just the resin as glue. get them right the first time cause there not coming back out in one piece.
 

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