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  1. #1
    Join Date
    Dec 2014
    Location
    Tasmania
    Posts
    102

    Default Electric drive motor issue

    Hi All,

    So I made a bit of a mistake yesterday, I engaged the back gears so that I could remove the headstock chuck and insert a milling cutter, and when I was ready to go I hit the power but forgot to disengage the back gears. The motor made a very decent pop sound and a flash of blue light, but did infact start spinning and just slipping the belt.
    The problem is now that when it runs its making a good racket, kind of like if you stuck a business card in a desk fan.. It does still run just as fast and strong but now with this awful noise. It's been a while since I looked at it but as I recall its a Crompton Parkinson 240v motor. If I had to guess, perhaps the brushes in the motor shorted and now are scraping instead of contacting smoothly?

  2. #2
    Join Date
    Aug 2008
    Location
    near Rockhampton
    Posts
    6,216

    Default

    It will not have any brushes.

    I would guess you have blown the capacitor as it is a 240V motor.
    Gold, the colour of choice for the discerning person.

  3. #3
    BobL is offline Member: Blue and white apron brigade
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    7,182

    Default

    I've opened up a motor like that and found a couple of the plastic insulator/spacers rubbing on the rotor. What had happened was the motor had over heated and expanded the plastic spacer. If it is that A short term solution would be to cut away the bits of plastic BUT BEFORE DOING ANYTHING an insulation test would be in order.

  4. #4
    Join Date
    Dec 2014
    Location
    Tasmania
    Posts
    102

    Default

    I used the lathe for about 40 minutes last night and after that session the noise was considerably less than before. It's still there but I would say perhaps whatever was catching and making the noise is sort of wearing down. I guess I will just see how it goes.. I probably wouldn't be that put out if the motor gave up the ghost because then I would have a decent excuse to look for a more powerful one. Sometimes I wish it had a bit more grunt, it doesn't take much to slow it down if you make heavy cuts on steel.

  5. #5
    Join Date
    Dec 2014
    Location
    Tasmania
    Posts
    102

    Default

    Update on this -
    So the motor continued making popping sounds accompanied by blue spark flashes until it did a big one, which tripped the circuit breaker for the garage. I decided that was enough and called a motor repair place who basically said the cost of them having a look was approaching a new cheap motor. So I went and bought a new 4 pole Crompton Greaves 1400rpm motor, was a direct fit replacement, same 5/8 shaft and the mounting holes also matched so it bolted right in. Wired up the reversing switch after a bit of head scratching and plotting and shes all good.
    It has thrown up a couple of issues though. Firstly its dimensions are somewhat different to the old motor in that I now cannot put the belt guard cover back on, the pulley fouls on it and I cant get enough adjustment to resolve it. I can live with that for now I guess but it could be solved with another pulley, mine is the 2 size kind and it fouls on the large side.
    The other and more serious issue though, even though the new motor runs smooth and sounds nice and quiet its actually vibrating a bit, and it is especially evident when operating the cross slide, it feels like its 'buzzing' as you turn it. The old motor did not vibrate in the slightest, so I noticed it immediately. And while making a part yesterday and advancing the cross slide I noticed this buzzing now actually sort of 'helps' it turn as you operate it.

    I'm a bit disappointed that a brand new Crompton motor does this, even if it is made in India, I expected better because I decided against getting a cheaper chinese motor and opted for a more pricey Crompton.

    Is there anything I can do about it? I thought maybe I could remove the motor and put some rubber between it and the mounting plate and see if that helps, but it does earth through the motor so I would have to wire an actual earth wire if I did that.

  6. #6
    Join Date
    Jun 2007
    Location
    sydney ( st marys )
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    64
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    4,887

    Default

    Does it vibrate without the belts?

  7. #7
    Join Date
    Dec 2014
    Location
    Tasmania
    Posts
    102

    Default

    I don't know actually I haven't tried disengaging the belts, will do tonight and see what happens. Are you suggesting that maybe a belt misalignment could produce the vibration? I would be chuffed if that's all it was, because I'm already thinking about looking for a good 'old' motor to replace it with.

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