Motor problem

[oldjim]

I am in the middle of making some parts for a project and the motor on my lathe just died, (sort of).
It had been running perfectly. Tried to turn it on after running back after a cut. Got a loud howl. Thats all. Lifted the drive belt and the spindle is free.
Took the motor drive belt off and tried it. Same howl! Tried giving the motor pulley a good spin then hit the power and motor starts and runs perfectly.
I remember replacing the starting capacitor maybe 25 or so years ago but can't remember what the symtoms of the problem were then. (Lucky I can still remember where the lathe is!)
Motor is a simple 3/4 horse 1750rpm frame G56 motor. Furnas reversing switch.
The capacator is a Hi Torque 460/552 mfd.
I went thru my junk motors looking for a similar capacitor to try but find nothing really close.

My question is: Is it likly that the capacitor is shot? Or is the motor itself the problem? When I hand start the motor and then shut it down I can hear something giving a big "click" after it slows down. (Centrfugal switch dropping out,maybe?) Can anyone tell from the above info what the problem is?
Be nice if I only have to change the capacitor as the motor is a pain to get at.

[SGW]

No - on second thought, I don't like that guess.....



[This message has been edited by SGW (edited 02-02-2006).]

[Evan]

What the heck. I'm going to second guess your guess and raise you five. Motor bearings?

[Yankee1]

Hello Jim,
I would check the contacts in the centrifugal switch. They provide current to the starter windings. If they are not making contact then you don't have the starter winding assistance required for start up. After startup the centifugal switch drops out and is no longer needed until another startup is required.
Chuck

[Dawai]

I'm guessin capacitor.

It'd be worth a try.

To test a capacitor, put a ohm meter on it. It should swing, then come back. Reverse the leads, same thing.

I have seen them test okay, and still be bad. No clue? Partial short? they are a roll of paper and foil inside with a sticky PCB cancer causing oil in them. Don't eat the oily paper.

(Catfish, a electrician-character) , a engineer was on a job and all worried about getting the PCB oil on him. Catfish looked at him in the eye, told him that stuff was great to deep fry catfish in. I used to wipe my sidecutters down in it to keep them from rusting. Stick them in my back pocket. WOnder I don't have cancer of the ass.

On a Nickajack job, we removed some sixties-installed neutral bus capacitors I had to barricade off the area, put them into a leak proof enclosure, my men had to wear gas masks and tyvek suits, rubber gloves. Once inside the barricade tape, everything was Kosher. You could undress out of saftey clothes. Two feet and magic barricade tape.

[Evan]

What about the howl?

[Dawai]

www.grainger.com can have you a capacitor next day. If they don't have one in stock. Drop it right on your doorstep.

[Dawai]

More like a growl Evan? Like a stepper overstepping. The rotating magnetic fields around a stopped armature.

Long distance troubleshooting sucks.

[Evan]

Loud howl sounds like loose bearings, where the shaft does the chicken dance around the inside of the bearing. Spin by hand might avoid that enough for it to take off. The heater in my Rover does that until it warms up. Someday I'll fix it. Been doing it for about 30 years but still works.

Try some heavy oil in the motor bearings.

[Fasttrack]

If i had to take a guess, i'd say the contacts in the centrifugal switch. Something to consider anyway. I had a 1.5 hp westinghouse froms eons ago and it started making a funny squeal and i had to start it by wrappinga rope around the pulley a coulple of times and giving it a yank, then switching it on once it was spinning and i made sure the rope was free. After a few times of this, i figured it most be in the switch, took it apart and found the carbon contacts screwed up.