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#1 LilysDad ONLINE  

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Posted November 19, 2012 - 08:48 AM

The motor on my 6x48 stationary belt sander just died. It ran when I turned it off and wouldn't start again. It's a Chinese motor so no big deal but I would like to fix it, if possible. It a 3/4 hp and would cost if replaced with an American one.

I have replaced the starter and blown the whole thing out. I've disassembled and found nothing obviously wrong. No overheating, the points look good.(Say, how do I adjust the points when reassembling?)

#2 HowardsMF155 OFFLINE  

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Posted November 19, 2012 - 09:19 AM

You don't say why you are sure it is the motor that is at fault? An AC motor will usually show why it's not working, it smokes, it sparks, and just generally says "Hey, I'm not happy". Have you checked the switch and any safety interlocks? Power supply good?
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#3 ol' stonebreaker OFFLINE  

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Posted November 19, 2012 - 03:16 PM

If you're comfortable doing it start checking for voltage starting at the switch all the way to the motor connection points. One of the voltage sniffers are really safe to trace voltage.
Mike
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#4 chris m OFFLINE  

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Posted November 19, 2012 - 04:23 PM

The motor on my 6x48 stationary belt sander just died. It ran when I turned it off and wouldn't start again. It's a Chinese motor so no big deal but I would like to fix it, if possible. It a 3/4 hp and would cost if replaced with an American one.

I have replaced the starter and blown the whole thing out. I've disassembled and found nothing obviously wrong. No overheating, the points look good.(Say, how do I adjust the points when reassembling?)

could you snap a picture of the points?

#5 LilysDad ONLINE  

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Posted November 19, 2012 - 05:31 PM

I hot wired around the switch. I'll get a picture of the points later. If your not sure what the points are, there are a pair of flyweights that, when it reaches a certain rpm, it pushes a contact. The whole fly assembly slides on the shaft before the fan blade does. By positioning the assem. it sets the points. If you do know what they are, sorry!

Edited by LilysDad, November 19, 2012 - 05:32 PM.


#6 LilysDad ONLINE  

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Posted November 19, 2012 - 06:00 PM

First two pics are front and back of the points plate and the third photo is the fly weight assem.

Attached Thumbnails

  • 103_9782.JPG
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  • 103_9784.JPG

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#7 KC9KAS OFFLINE  

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Posted November 19, 2012 - 07:15 PM

I hot wired around the switch. I'll get a picture of the points later. If your not sure what the points are, there are a pair of flyweights that, when it reaches a certain rpm, it pushes a contact. The whole fly assembly slides on the shaft before the fan blade does. By positioning the assem. it sets the points. If you do know what they are, sorry!


I bought a used Craftsman radial arm saw, and had the same problem. The "points" as you call them actually work in conjunction with the "start" & "run" function of the motor. My weights were dirty and would not go to the "start" position after the motor was shut off. Once I cleaned the crud off of the weights and lubed them with a "dry" lube, it starts every time I hit the switch!
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#8 LilysDad ONLINE  

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Posted November 20, 2012 - 08:48 AM

When I put this back together do I set the governor to just touch the point spring or do I have to set a certain clearance for the points?

#9 ol' stonebreaker OFFLINE  

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Posted November 20, 2012 - 11:05 AM

IIRC the gov should be set so it closes the contact furthest from it while motor is at rest.It needs to close the contact closest to it when motor gets up to speed. Someone please correct me if I'm wrong. BTH, one of your wife's emery boards will work great to clean the points. The amount of subterfuge required to get it has to be determined by you,LOL!!!
Mike

#10 LilysDad ONLINE  

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Posted November 20, 2012 - 07:03 PM

There is only one contact point that closes when the engine speeds up.

#11 ol' stonebreaker OFFLINE  

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Posted November 20, 2012 - 11:23 PM

Sorry, my bad!! Guess I didn't RC.
Mike

Edited by ol' stonebreaker, November 20, 2012 - 11:24 PM.


#12 WNYTractorTinkerer OFFLINE  

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Posted November 21, 2012 - 05:24 AM

When I put this back together do I set the governor to just touch the point spring or do I have to set a certain clearance for the points?


The flyweights & points you are referring to are the starting mechanism. To start some electric motors, a special winding that gets things moving along with high power is used. When the motor is off it connects the switch points that enables that circuit If that stays connected all the time the motor is running, the motor would overheat and go kablooey . So as motor speed increases the inertia created by the spinning motor pulls the weights apart thus disconnecting the starting circuitpoints. The main (run) circuit takes over and powers the motor. Kinda sounds like what you are describing..

Edited by WNYTractorTinkerer, November 21, 2012 - 05:25 AM.





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