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[4]

Alternative motor?

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Dave Paine

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#2
That is a standard NEMA Frame 56 1/2HP 1725 rpm. You should be able to find replacements on EBay, internet sites, a local Tractor Supply or Harbor Freight.

One example internet site

DealersElectric 1/2HP motors
 

Eddyde

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#4
I agree with Dave, that is a very common motor and readily available. However, it might not be totally fried, it could be that the capacitor is bad. What are the symptoms?
 

wa5cab

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#5
It will be more expensive as at least the last two that I bought there still claimed to be US made, unlike anything that you would get from HF. But WW Grainger will also have several choices. If you do buy a new or good used one, make very sure that if it has a thermal overload breaker, it is manual and not automatic reset. The automatic reset type is dangerous and can kill or maim you if you don't take the proper precautions (basically unplugging the machine before you touch anything if it ever trips.

But as Eddy said, there are several things that can go wrong with a capacitor start motor that are relatively easy to fix and not as expensive as buying a new or used replacement motor.
 

Olddaddy

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#6
Symptoms are that is doesn't start turning as it normally did, sits there and hums. I checked the wires and the black one looks like it might be burnt a little at the connection point. If it is a capacitor, what's the fix?
 

wa5cab

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#7
Take the belt off, turn it on, and give the pulley a spin in either direction. If it starts and runs quietly, and when you unplug it and it coasts to a stop you don't hear a Click, the centrifugal switch is probably stuck open. If you do hear a click, then probably either the starting capacitor is bad or the centrifugal switch contacts are burned or otherwise not making a connection.

So the fix is to lubricate and exercise the switch, replace the starting capacitor or burnish the switch contacts. Or maybe all three.
 

Olddaddy

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#8
I will give it a try in the morning. I don't believe spinning the pulley got it to start though. I was in a hurry when I posted this morning, had to get to work, but will have more time tomorrow. Appreciate the replies. I'd love it to be a simple fix and not a motor replacement.
 

markba633csi

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#10
Robert's advice above is correct. Either your starting capacitor is bad or you are having centrifugal start switch troubles; fixing either or both of those
is sure a lot cheaper than buying another motor.
A very few motors have an odd flat capacitor mounted in the base- if yours is like that, you'll have to substitute a cylindrical type and mount it outside the
motor somewhere and run wires in. They don't make 'em like that anymore :)
Mark
 

whitmore

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#11
..., the centrifugal switch is probably stuck open.
Yes, that's the likely case. I've pushed a chopstick between the slots to reseat such a switch, but usually
it's better to pull the bell housing off (after dismounting the motor...), and burnish the contacts.

If there were a capacitor, it would have been noted on the dataplate; no mention of uF, so the start
mechanism has a centrifugal switch and the 'hum but no spin' symptom usually means
dirty contacts (sawdust?).
 

Olddaddy

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#12
Well, I am befuddled....As suggested I turned on the motor and spun the pulley by hand. Sure enough, it starts to spin up, but very quickly the switch clicked and it coasted to a lower rpm then clicked again spins up, switch clicks, coast down and so on, but never reaches full speed. I pulled the bell end off and inspected everything. It's very clean inside, no signs of arcing anywhere. The centrifugal switch moved freely. Points were ok, but I cleaned them up a bit. I put some lube on the centrifigal switch. Put it together and symptoms remain the same.
 

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Downunder Bob

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#13
Is there one or two caps, sometimes the start and run caps are in one case sometimes they are separate, does the cap have 4 leads or only two. The runswitch could also be changing to a different set of windings, as well as cap.
You say it runs up, then click and slows down , then click, and speeds up again, then click and slows down. Sound like the start windings and cap are ok but the run windings/cap are not. the switch appears to be switching.
 

David S

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#14
Yes it sounds like an open run winding or connection to it. It starts with help on the start winding, switches off the start > slows down until the switch closes again and repeat.

David
 

Olddaddy

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#15
Yes it sounds like an open run winding or connection to it. It starts with help on the start winding, switches off the start > slows down until the switch closes again and repeat.

David
And you are the winner! I decided to give it up and take it to the motor shop tomorrow for a fix or replace decision. As I pulled the wiring apart to remove the cord I saw it- a yellow wire was laying loose, not attached to anything. Further inspection revealed it have arced or burnt or something to cause it to come loose from the post it was originally attached to. The post was toast as well. So, I installed a new screw/post and refastened the yellow wire and all is well again in my shop! Many thanks to you all. Your advice and input caused me to think it through and with some dumb luck, solve the riddle. All is well!!
 

Olddaddy

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#16
David, you are the winner! I looked closely at each wire and discovered this yellow one loose and not attached to anything. The post it had been attached to was burnt and the wire had broken off from the ring attaching it to the post. A new screw/post and wire end and all is well. The advice here made it possible to save the motor and continue the use of the lathe, at no expense! Many thanks Gentlemen!!
 

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David S

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#17
Glad that it all worked out. Others were homing in on the same conclusion.

David
 

wa5cab

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#18
OK. Glad that you found the problem. New motors aren't cheap.
 
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