Electric motor problem

I have a small drilling machine driven by a 1/4 HP induction moto
(British) sometimes it fails to start and just hums, if I switch of
and try again normally it runs. This happens not on a regular basis sometimes it goes for days OK then plays up. Is there some sort o maintenance needed? Davi
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On Wed, 25 Jul 2007 14:47:15 -0500, stereotype

What tune does it hum ?
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uk.rec.models.engineering wrote:

Anything, it doesn't know the words, so it has to hum.
Regards,
David P.
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sounds like the start /run cap is on its way out. when its not working if you spin it up by hand does it run? new caps are quite cheap.
of course I could be wrong, no doubt someone more knowledgeable will be along shortly.
Dave
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stereotype wrote:

Check all the wiring for continuity and tight connections first, especially the leads that go into the motor terminals. They can sometimes work loose on older motors. As someone else said, after that, it's most likely the start capacitor, or it's wiring...
Chris
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If it has a centrifugal starting switch (you can hear a click when it starts and again when it is nearly stopped) the switch contacts and the mechanism to operate it can be in need of cleaning. This usually requires disassembly of the motor. No lubrication is normally used.
Don Young, USA
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Don Young Wrote:

Thanks for all your input, yes Don it is a cetrifugal start motor, i'l take it apart and check the contacts. Davi
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I have this problem on two bits of kit I have just bought second hand. I can clearly hear that the centrifugal switch does not always 'click' back in when the motor stops so I assume that some lubrication is required. I'm planning on investigating further when I get some enthusiasm...
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I think cleaning is called for but I do not think that these mechanisms are generally lubricated. It might be ok in an enclosed motor where the dirt is kept out if no lubricant gets on the switch contacts.
Don Young, USA
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Lubrication is normally the enemy of these switches as it harbours dirt. Complete cleanliness is normally the the best way IMHO
Bob
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Pretty sure it the cap that's getting old & 'leaky'. Hasn't failed altogether as it would never start or possibly blow mains fuse. They just get a bit worn out sometimes. Your cheapest and quickest option is to replace the cap, they don't cost much and are (normally) external so dead easy to get access to & replace. Tip - just be careful fiddling with any connections if you have recently attempted to start it, as the cap may hold a nasty residual charge which might make your hair stand on end, eyes light up and teeth rattle a bit!
Mike
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