Lathe motor popping

[Philip PowellParticipant @philippowell34749]

[Philip PowellParticipant @philippowell34749]

I have a Smart and Brown Sabel lathe with a motor that keeps making popping noises. The motor is a 1/2HP Crompton and Parkinson 240V single phase. The “pop” normaly happens on startup and is acompanied by a blue flash from the motor and and it makes me jump every time!

 

The previous owner had the lathe in a wood workshop and the first thing I did when I got the lathe home was to clean out all the oily sawdust sludge out of everywhere. There was sludge in the motor grills and I put the pops down to sawdust in the motor, but I’ve had the lathe a few weeks now and it still pops. Also the motor bearing are bit noisey and sound quite loud when spun over by hand. Another thing I’ve noticed is the lathe shakes when on 1200rpm the highest speed. Could this be motor related?

 

I’m thinking of replacing the motor with a 3PH motor and an invererter drive, would this be a worthwhile option? I hear good thing about 3PH motors and I thought the variable speed would be handy.

 

Any thoughts?

 

Thanks

 

Phil.

[Sam StonesParticipant @samstones42903]

Hi Phil,

The Crompton & Parkinson 1/4 hp single phase motor fitted to my Myford ML7 used to do the same.

In my case, (and because the motor was uncovered), metal swarf was finding its way into the electrics via the motor’s ventilation holes. The shorting was not sufficient to blow fuses or trip the leaky earth switch, but it certainly made a loud popping noise when it happened. There was also a sizzling noise (mechanical not electrical), which once again was swarf. This time the swarf was rubbing against the rotor. I would guess that steel swarf was being attracted to various parts as a result of the magnetic field(s).

I cured this problem by applying metal fly wire (readily available in Australia), over the vents.

The original lathe owner had a `wonderful’ way of starting the lathe. When I bought it from his widow, the centrifugal switch inside the motor was stuck in the `open’ position. It was clear that the owner (who had removed the belt guard), was using the large pulley to spin-start the lathe motor.

Once the motor was stripped down, it took very little to free the switch.

Both problems were duly fixed and never returned.

I no longer have my workshop, but fitting a 3PH motor seems to be a very common improvement. See other postings.

Best regards to all,

Sam

Edited By Sam Stones on 01/03/2011 21:26:52

[Philip PowellParticipant @philippowell34749]

Hi Sam

 

Ah, I’m not the only one who’s had a popping motor then! It’s ineteresting that yours was caused by swarf as I suspect mine is has some oiley woody swarf inside that I disturbed when moving the lathe to it’s new home and then given a good clean.

 

I like your story about your Myfords previous owner spin-starting the motor sounds a bit hairy to say the least!

 

Thanks

 

Phil.

[Sam StonesParticipant @samstones42903]

Thanks Phil.

 

Good luck with your 3PH conversion.

Curiously, over a period of several years (before I bought the lathe), I had on occasion to walk past the previous owner’s house.

Over that time, I had actually seen the belt guard of the ML7 hanging from the picture rail of his upstairs box-room workshop. However, I had no idea what piece of machinery could be operating without a belt guard. Furthermore, I could never have realised that one day I would become the proud owner of his Myford.

Besides the issue of seeing the belt guard hanging from the picture rail, the centrifugal switch may have been stuck open for a considerable time, because the previous owner had worn off a substantial amount of paint from the rim of the large pulley, and introduced a sort of polished patina to its edges.

Sam

Edited By Sam Stones on 02/03/2011 05:38:22

[Roger HartParticipant @rogerhart88496]

Sounds like you have this sorted. I had this problem and found it was caused by an arc tracking across the mica insulation of the centrifugal starting switch to earth. Probably due to muck/dust having accumulated. Once this problem is established it is hard to fix because it is not easy to replace the insulation. Eventually the problem gets bad enough to pop the earth leakage trip an annoying number of times…..

 

I fixed mine by running the motor through a BIG isolation transformer.

 

Roger H

 

[KWILParticipant @kwil]

I am sorry gentlemen to say, that you are “playing with fire” ( I hope this does not come true). With electrical problems you really must cure the problem, not just produce a workaround.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, I have to agree with Kwill. Isolation transformers are very usefull for isolating equipment from the mains for a number of reasons, but the output still has the potential to cause fires, electric shocks ect., and damage to equipment, so the same safegaurds that you would expect to use on the mains should also be used on the output of your isolation transformer.

 

If your have electrical problems with a motor it should be fixed by a compotent person, or replaced.

 

Fualty motors can become very hot and cause a fire when you least expect it, and may even smoulder inside and start to burn when you have shut your workshop up for the evening.

 

Don’t ignore electrical problems and hope they go away, they won’t. Get them fixed.

 

Regards Nick.

[Jeff DaymanParticipant @jeffdayman43397]

Also agree with KWIL and Nicholas. Fix the problems before they kill you or set fire to your shop.

 

The ultimate way to do this is to get a modern TEFC (totally enclosed fan cooled) motor. These are bulletproof and there is no opening for anything to enter the motor space. Waterproof too. In North America these cost about $180-$250 for a 1/2 HP one, not sure about cost ROW. Replace your cables with rubber jacketed industrial cable while you are at it. No more electrical issues and safety is assured.

 

JD

 

 

 

[Philip PowellParticipant @philippowell34749]

Kwil, Nicholas and Jeff

 

Thank you for your input, I do intend to replace the motor but my question was is it worth paying a bit more for a 3ph motor and inverter rather than repairing/replacing the existing 1ph motor. I have heard that 3ph can be much smoother and quiter, is this true? How much difference will it make?

 

Thanks

 

Phil.

[KWILParticipant @kwil]

The answer is YES, quieter and smoother. I run 4 machines all on Inverters.

 

Three phase motors are not that expensive cf single phase. You also have complete control of speed and also soft start (slower ramp up to speed) as well as ramp down. Jogging, (very slow) for clocking under power and also useful for thread cutting. Full motor protection. Anything more? See previous Inverter threads.

[Jeff DaymanParticipant @jeffdayman43397]

I’ve used many 3ph (industry) and 1 ph (home shop) motors on tools of all descriptions and practically I would say there is no difference in quietness and smoothness of good name brand motors in 3ph vs 1 ph. There is a big power vs size difference though, but a 1/2 hp rated motor is a 1/2 hp motor so it makes no difference to usability, if it fits physically.

 

There is of course BIG difference in money required for all the expensive electrical inverter/switchgear kit you need to buy and maintain for 3 ph if you don’t have 3 ph supply to your shop.

 

Good brand names here in NA are Leeson, Baldor, Marathon, Reliance. Stay away from the Chinese import motors, they are where you find buzzy rough running motors.

 

My advice is to save a pile of money and use good brand name TEFC motors for 1 ph mains current. You will get many years good quiet smooth service from them and there is no additional inverter/switchgear componentry to go wrong.

 

JD

 

 

[Bryan RozierParticipant @bryanrozier80712]

Hi Phil,

 

I’m considering this upgrade to my Myford.

 

Everyone I have spoken to about it suggests it’s the best thing since sliced Bread!

 

Three phase motors run with “perfect” balance so you get less vibration and this equates to less noise and a better surface finish.

 

Unless you are doing very heavy work you can also avoid a lot of belt changing.

 

Best regards

Bryan

 

 

 

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