Myford ml8 motor cutting out

[Benquick80]

Hi everyone
I have a lovely cropton parkinson motor on my lathe. It was working ok but now it keeps cutting out when load is applied. I have tried rewiring the wires to the plug with thicker wire and have cleaned it out inside.
There looks like a cut off switch inside if i permanently attach it, will the motor work again with our cutting out?
Also if there's no hope for it how do I go about buying a new motor with variable speed that I can still fit on to my myford ml8?

Thanks

 

[Spectric]

Hi

Take it to a motor specialist who can give you a quote to rewind, that way you keep your original motor and it will last for many more years. I thought the speeds on a lathe are done using mechanical means so if you have to have a new motor it should not be a problem. I would suspect your biggest problem is finding a motor specialist in Cornwall.

 

[flh801978]

I don’t think anyone has ever regretted making their lathe variable speed.
So a new (or s/h) 3 phase motor £50-130
And a vfd @£50-100
And a few switches and potentiometer and you are good to go

 

[flh801978]

It’s a non starter having a motor that size rewound..its likely to be 3x the cost of a new one
Or even spending much having someone repair it
Get a new single phase or go 3 phase for variable speed

 

[Spectric]

VSD's stress the motor windings which can lead to insulation breakdown due to the fast switching waveforms and therefore avoid buying cheap motors, get a branded motor with reinforced windings. These issues are often worse with cheap VSD's.

I cannot see why you need a VSD on something with a mechanical gearbox and I have worked in many places with very large machine shops where the guys were producing components for a wide range of industries and none of the machines required VSD's.

 

[guineafowl21]

Before condemning the motor, it would be worth checking if the protection is at fault.

You would ideally measure the current drawn at the time it cuts out. If you can’t, bridging the switch temporarily might help to point to the culprit. If it is the cutout, it could be replaced directly or with a DOL starter with overload.

Before you do anything, show us some pics of the wiring and suspect cutout, and consider finding a decent electrician to check the motor out electrically.

 

[Benquick80]

I don’t think anyone has ever regretted making their lathe variable speed.
So a new (or s/h) 3 phase motor £50-130
And a vfd @£50-100
And a few switches and potentiometer and you are good to go

Thanks. What is a vfd though?

 

[Benquick80]

Before condemning the motor, it would be worth checking if the protection is at fault.

You would ideally measure the current drawn at the time it cuts out. If you can’t, bridging the switch temporarily might help to point to the culprit. If it is the cutout, it could be replaced directly or with a DOL starter with overload.

Before you do anything, show us some pics of the wiring and suspect cutout, and consider finding a decent electrician to check the motor out electrically.

Thanks when I get a chance I'll take some photos

 

[Roseland 2]

There used to be a motor rewind business near Stithians. I don’t remember the name but I’ll try and find it.
andrew

 

[Spectric]

Thanks. What is a vfd though?

It is a device that can run a three phase motor at a range of speeds by contolling the voltage and frequency. There are some specialist drives that can also provide variable speed on single phase motors but are not common. There are also versions that allow you to run a three phase motor with variable speed from a single phase supply, but only at 230Vac and limited to 3Kw due to some regulations.

 

[Benquick80]

Before condemning the motor, it would be worth checking if the protection is at fault.

You would ideally measure the current drawn at the time it cuts out. If you can’t, bridging the switch temporarily might help to point to the culprit. If it is the cutout, it could be replaced directly or with a DOL starter with overload.

Before you do anything, show us some pics of the wiring and suspect cutout, and consider finding a decent electrician to check the motor out electrically.

Before condemning the motor, it would be worth checking if the protection is at fault.

You would ideally measure the current drawn at the time it cuts out. If you can’t, bridging the switch temporarily might help to point to the culprit. If it is the cutout, it could be replaced directly or with a DOL starter with overload.

Before you do anything, show us some pics of the wiring and suspect cutout, and consider finding a decent electrician to check the motor out electrically.

This is the set up at the minute

 

[guineafowl21]

You have some problems there:

1. The earth does not appear to be connected. Running a faulty machine like this is asking for a fatal shock.
2. The incoming and outgoing wires are not glanded, and so crap has accumulated inside the starter.
3. Live wires are rubbing against the metal rims.

My guess is that the overload part has become faulty and over-sensitive, so you need a new DOL starter, set to about 6A. But we’re shooting in the dark here about the condition of the motor windings and capacitor.

If this is your work, and you’re happy to post a pic on an online forum, that shows a fundamental lack of knowledge. Please don’t plug in again till an electrician has looked at it. I mean no insult, merely concern.

 

[Benquick80]

You have some problems there:

1. The earth does not appear to be connected. Running a faulty machine like this is asking for a fatal shock.
2. The incoming and outgoing wires are not glanded, and so rubbish has accumulated inside the starter.
3. Live wires are rubbing against the metal rims.

My guess is that the overload part has become faulty and over-sensitive, so you need a new DOL starter, set to about 6A. But we’re shooting in the dark here about the condition of the motor windings and capacitor.

If this is your work, and you’re happy to post a pic on an online forum, that shows a fundamental lack of knowledge. Please don’t plug in again till an electrician has looked at it. I mean no insult, merely concern.
View attachment 106397View attachment 106397

Not my work. Inherited from friends dad.
What does glanded mean please?

Where Should the earth be connected to?
Would a DOL completely replace the switch compartment?

Thanks for your help and potentially saving a life!

 

[guineafowl21]

You said earlier that you’d replaced the flex to the plug, ie the orange bit.

For interest:

This is a gland:

The earth should be connected to the metalwork of the machine - there will usually be a bolted lug with a spiked shakeproof washer. Note this is chapter one, page one of electrical safety.

A DOL starter will replace the switch compartment, yes.

I’ll stop there before I arm you with any more of that little bit of knowledge that is dangerous. Electrician time, @Benquick80

 

[Benquick80]

You said earlier that you’d replaced the flex to the plug, ie the orange bit.

For interest:

This is a gland:
View attachment 106401

The earth should be connected to the metalwork of the machine - there will usually be a bolted lug with a spiked shakeproof washer. Note this is chapter one, page one of electrical safety.

A DOL starter will replace the switch compartment, yes.

I’ll stop there before I arm you with any more of that little bit of knowledge that is dangerous. Electrician time, @Benquick80

Yes I'll definitely get an electrician to sort out a new DOL.
( When I replaced the wires I just took a photo of what was there and replaced like for like)

 

[Benquick80]

Don't worry I won't do it. But just out of interest where would the earth attach to in the switch compartment on this old DOL or would it just by pass it and go straight to the lathe?
again I won't do it or even on anything else in the future just interested .

 

[guineafowl21]

Here’s a place on the motor box:

There might be a place on the switch box I can’t see. Main thing is to ensure that metalwork which might become live is securely earthed.

 

[Fergie 307]

I'm guessing your problems started shortly after replacing the cable, and may just be down to the poor wiring. The gland serves two purposes. Firstly in stops the cable chafing on the metal case, secondly it supports the cable so it doesn't get pulled out. If you measure the hole where the cable comes in you just need to get an appropriate sized gland. I would guess 20mm. You can get these from screwfix for a couple of quid. On the terminals you should have cup washers with a cut out on one side for the wire. The trick is to twist the strands of the cable together like a rope. Then form your loop by bending the twisted wire round an appropriate sized bar, the shaft of a screwdriver for example. When you put the loop over the terminal make sure it's going round clockwise, so when you tighten the screw it's not trying to push the wire out. The wire must sit within the cup washer, you don't want bits hanging out the sides like you have. And make sure there's a bit of slack in the wires, not pulled tight as you have. I would say it's never a bad idea to have an earth cable between the motor body and the main casing of the machine, as well as ensuring that the earth cable is properly connected to the motor. If I'm doubt get an electrician to do it for you, worth it for peace of mind and to avoid damaging the machine, or worse still yourself.

 

[Benquick80]

I'm guessing your problems started shortly after replacing the cable, and may just be down to the poor wiring. The gland serves two purposes. Firstly in stops the cable chafing on the metal case, secondly it supports the cable so it doesn't get pulled out. If you measure the hole where the cable comes in you just need to get an appropriate sized gland. I would guess 20mm. You can get these from screwfix for a couple of quid. On the terminals you should have cup washers with a cut out on one side for the wire. The trick is to twist the strands of the cable together like a rope. Then form your loop by bending the twisted wire round an appropriate sized bar, the shaft of a screwdriver for example. When you put the loop over the terminal make sure it's going round clockwise, so when you tighten the screw it's not trying to push the wire out. The wire must sit within the cup washer, you don't want bits hanging out the sides like you have. And make sure there's a bit of slack in the wires, not pulled tight as you have. I would say it's never a bad idea to have an earth cable between the motor body and the main casing of the machine, as well as ensuring that the earth cable is properly connected to the motor. If I'm doubt get an electrician to do it for you, worth it for peace of mind and to avoid damaging the machine, or worse still yourself.

Thanks very much. Very comprehensive. I'll get the bits you recommend and get a electrician to fit it all on for me.
Thanks

 

[Benquick80]

I'm guessing your problems started shortly after replacing the cable, and may just be down to the poor wiring. The gland serves two purposes. Firstly in stops the cable chafing on the metal case, secondly it supports the cable so it doesn't get pulled out. If you measure the hole where the cable comes in you just need to get an appropriate sized gland. I would guess 20mm. You can get these from screwfix for a couple of quid. On the terminals you should have cup washers with a cut out on one side for the wire. The trick is to twist the strands of the cable together like a rope. Then form your loop by bending the twisted wire round an appropriate sized bar, the shaft of a screwdriver for example. When you put the loop over the terminal make sure it's going round clockwise, so when you tighten the screw it's not trying to push the wire out. The wire must sit within the cup washer, you don't want bits hanging out the sides like you have. And make sure there's a bit of slack in the wires, not pulled tight as you have. I would say it's never a bad idea to have an earth cable between the motor body and the main casing of the machine, as well as ensuring that the earth cable is properly connected to the motor. If I'm doubt get an electrician to do it for you, worth it for peace of mind and to avoid damaging the machine, or worse still yourself.

Is this a suitable DOL?

https://www.screwfix.com/p/hylec-dms1-12d-s-automatic-dol-electric-motor-starter-7-5kw/6196g