T66
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| posted on 6/2/12 at 07:50 PM |
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Lathe - Power Supply
Had the lathe running on the bench today, it has a one of these on/off switches with the big red stop knerb....Sorry dont know its correct name.
It ran fine when I bought it, now the power to turn the chuck over is intermittent, motor gets warm/hot to the touch. IE it runs , glitches, slow
runs,glitches, hics , runs a bit etc. Sometimes doesnt fire up at all. When I whipped the switch cover off and worked the switch manually it generally
worked.
I ran the motor off the lathe with a plug on, and it threw my garage trip. However it ran smoothly and quietly prior to clicking the trip. So rather
than go for a dodgy on/off switch I have stripped and cleaned the motor. Brushless type, and all appeared well other than being grubby.
Ive just noticed the lathe headstock bearings were dry (now oiled) , could it be a "tight" lathe causing the hot motor and the trip
dropping out ? It was reasonably tight to turn over by hand...?
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mark chandler
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| posted on 6/2/12 at 09:23 PM |
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Has it got a capacitor strapped to the side of the induction motor, if this goes then it will struggle to start and if it eventually gets up to speed
will stall easily.
lathe should turn over easily by hand unless a high gear is selected.
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T66
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| posted on 6/2/12 at 09:40 PM |
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Thanks Mark - No capacitor on my motor, has a mount, case and the wiring into it from the big switch. Motor has no brushes to speak of , but a spring
load double contact on the spindle end.
Grubby inside, but not so bad it wouldnt work.
The headstock bearings were as dry as a dry thing, now cleaned and oiled.
Im rather hoping the motor was struggling to spin over the tight headstock, hence it getting hot and tripping out.
All going back on tommorrow for a test run.
[Edited on 6/2/12 by T66]
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motorcycle_mayhem
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| posted on 6/2/12 at 09:50 PM |
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From what you've described, sounds like the switch unit (I assume a double pole breaker type) isn't handling the current well.
Corroded/burnt/weak/chinese?
I'm only saying that because you imply that the motor isn't a delta starter equipped unit (large capacitor is normally the giveaway),
taking the big induction kick out of the start-up load (until the motor spins up to generate it's back emf).
If you can get/borrow a type D trip in your consumer box, it may not trip under test. You could then verify it's the
switch/delta(?)/lack_of_red_wine that's causing the problem.
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T66
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| posted on 6/2/12 at 09:56 PM |
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quote:
Originally posted by motorcycle_mayhem
From what you've described, sounds like the switch unit (I assume a double pole breaker type) isn't handling the current well.
Corroded/burnt/weak/chinese?
I'm only saying that because you imply that the motor isn't a delta starter equipped unit (large capacitor is normally the giveaway),
taking the big induction kick out of the start-up load (until the motor spins up to generate it's back emf).
If you can get/borrow a type D trip in your consumer box, it may not trip under test. You could then verify it's the
switch/delta(?)/lack_of_red_wine that's causing the problem.
With the motor off the lathe & plugged in , it ran spot on. It did seem a bit hot, but it doesnt have a fan, so Im really not sure how hot is not
good, if Im making sense.
Next step is to clean the switch, its all quite old so I doubt its Chinese.
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mark chandler
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| posted on 7/2/12 at 08:56 AM |
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I have a big motor like that, it came from a central heating water pump so I thought it would be good to power a compressor, it spins up quite happily
but under load dies really quickly and gets very hot 
If yours is the same the design is wrong in this application, it depends on how they wind them, constant run relatively low torque.
Nice solid looking lathe BTW
[Edited on 7/2/12 by mark chandler]
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T66
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| posted on 9/2/12 at 06:54 PM |
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Spent some time cleaning the motor up, its a Crampton 1/4 hp. The problem was with tight headstock bearings on the lathe.
I only noticed this with the motor off the lathe, when I spun the chuck over by hand it seemed far too tight. The headstock bearings are pinch type,
and have a small oil port. Loosened them off, oiled them and it spins over fine.
The lathes reluctance to spin up was the tight bearings, the cutting out was down to the hot motor pinging the switch off.
Thanks for the replies.
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Krismc
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| posted on 9/2/12 at 07:17 PM |
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Mate, i have a load of crampton 1/4 hp units, i use them as lift door motors and generally they are warm to hot, some can stall for hours and sit
cooking but still run fine once the blockage is clear. very strong units.
...so if it does get hot again dont worry.
[Edited on 9/2/12 by Krismc]
Built, Ivaed, Drove and now Sold - 2011 MNR VORTX RT+ 2000cc Zetec on R1 Throttle boddies.
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paulf
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| posted on 9/2/12 at 10:40 PM |
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If it is only 1/4 hp and reluctant to turn the spindle due to tight bearings then it will not be big enough to drive the lathe when doing other than
very light machining.I have a 5 inch lathe and have a 1/2 horse power motor which is barely powerful enough for heavy machining, 3/4 or 1 horse would
be more like it.
Paul
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T66
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| posted on 9/2/12 at 10:53 PM |
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cheers both replies
its a 3.75 x 14 lathe , but Ive not really had the chance to see what it can cut yet. The previous owners grandad used it for turning bullets for his
rifle, the only very light use tbh.
So heavier stuff may need a bigger motor.
Ive ran the motor tonight, for about 15 minutes without cutting and the case didnt even get warm. We shall see....
Still love it !
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