Myford Hoover Motor

[Alan CulpittParticipant @alanculpitt14314]

Hello, I'm new to the forum. thanks for taking the time to read my question.

I want to try my hand at model engineering. In order to do that I need a lathe, I bought a Myford ML7 on eBay that used to belong to a bagpipe maker in Edinburgh. It's a bit tired and painted a nasty blue colour

It has a 13 amp plug on the wire to the hoover motor, nothing else. I read somewhere that it needs a proper switch in order not to damage the motor. I tried a while ago to run it and it seemed to work ok but I'm concerned that I'll damage the motor. Also I want something a bit more refined than thumping a 13amp plug into a socket to start the lathe I tried it again recently and it blew the circuit breaker for the garage, I think because I hadn't run the lathe for a while and the motor was a bit sticky.

It's a Hoover Motor type 2130 HAE, 1 phase 50 cycles, WDG (winding?) SP PH 3.6 Amps 1/2 HP 1425 RPM.

**LINK**

I know very little about electrics but I'm a reasonably competent mechanic.

If I can get it to start then I'll start worrying about levelling the lathe etc,

[Alan CulpittParticipant @alanculpitt14314]

Do I need a switch

[Howard LewisParticipant @howardlewis46836]

Ideally, you need a No Volt Release switch, for a start. This will prevent an unexpected restart after mains power being restored after an outage. Otherwise, you might have you hands amongst the "works", when power is restored and the machine restarts.

Most people also like to have a switch which will cause the motor to run in either forward or reverse.

BUT be careful, chucks are screwed on to Myford (and lots of other lathes as well ) so running in reverse, certainly cutting, can cause hte chuck to unscrew. Having a chuck weighing some 10Kg spinning on the loose, around the workshop, can be dangerous for you, the machine, and your environment.

Most of us have run a lalthe in reverse, at some time and been lucky not to have the chuck come loose or come off. So you need to be extremely careful, if you do run in reverse at all.

As a newvbie, I would suggest buying some books to prepare your self for machining, if you are unfamiliar. A lot of questions will be answered by such books as:

The Amateurs lathe – L H Sparey,

The Amateurs Workshop – Ian Bradley

The Myford Series 7 Manual – Ian Bradley

or books by Harold Hall on Lathework.

Neil Wyatt and Dave Fenner have written books on the mini lathe, although not about the Myford, the basic principles remain the same; just the detail of the machines.

If you can get hold of back numbers of Model Engineers Workshop, Neil Wyatt did a series of articles on basic lathework, admittedly not on a Myford, but setting out the basic principles.

They will be time and money well spent, that answer questions, and prevent you making mistakes, as well improving the quality of what you produce.

These books will guide you through such things as tool sharpening, so that you learn what extra accessories and tools are needed. Once you have a lathe, you need to know how to sharpen tools, how to set them, and what measuring equipment is need for various tasks.. Also you will learn the abilities, and the limitations, of your machine. (Not to mention, your own! )

As you become more experienced and proficient, your horizons will expand and the need for more accessories become apparent, so that they can be acquired and used.

We all had to start somewhere. Once it surprised me to find that a given reduced the diameter by twice as much!

I am not a lifelong machinist, the basics were taught and then I did not touch a machine tool for another 25 years, although in industry I saw a lot.

Find a local Model Engineering Club and join. You will meet fellow enthusiasts, who will advise, help and demonstrate face to face. You can learn a lot just by watching!

HTH

Howard

[Frances IoMParticipant @francesiom58905]

presumably the garage supply is undamaged but merely switched off the current – ? did it trip on overcurrent (eg if your garage fed only with 5A) or did it trip on earth leakage – old motors tend to have tired insulation that breaks down with increased leakage or was there some mechanical impediment such that the motor current ran above a 13A limit?

It may be better to find a friend better qualified + with the necessary measurement gear to look at the motor before spending more money on the necessary switchgear

Edited By Frances IoM on 01/12/2020 17:39:20

[not done it yetParticipant @notdoneityet]

A 1/2Hp is about 375Watts. 13Amps at 230V is about 3kW. A 13 amp fuse will run for some time at overload (depending on the current, of course). Your motor would start smoking very quickly if overloaded by a factor of two – let alone a factor of ten!

Your motor is likely to draw as much as 5 times its normal running current at initial switch-on (power on at zero rpm), so it does require a fuse large enough to withstand the starting current (think here a resistive load at zero rpm and two windings to be energised until one is disconnected when the motor is running a) in the correct direction and b) at a suitable speed for the run winding to continue to accelerate the load to full speed.

The plug fuse is simply to protect the supply lead to the motor, nothing else.

[Alan CulpittParticipant @alanculpitt14314]

Wow! Thank you all for the generous response,

Howard – I've ordered a drum switch from China (an original Dewhurst switch was a bit beyond the budget), how I wire it up I'll figure out when it comes. I don't quite understand why I'd want a machine running in reverse so not too worried about getting that bit to work. I'll definitely be adding the books to my Christmas List as finances allow. I haven't got much of a plan at the moment short of getting the lathe set up correctly. I'm into classic cars and plan to machine various drifts for putting them together and taking apart. I'll see where that leads

FrancesIOM & Not done it yet – It did trip on overcurrent rather than the RCD. I'm thinking that's a good thing right? I think the motor was slightly sticky ive turned it over by hand and it's running smoothly. Will a new switch help prevent the initial starting current problem or do I just a bigger circuit breaker?

Thanks again

Alan

[not done it yetParticipant @notdoneityet]

I’m not an electrician but I understand there are different grades of the same ‘size’ of circuit breaker, depending on the response time required for the installation. Domestic ones trip more easily (less time lag) than industrial equivalents.

[SteviegtrParticipant @steviegtr]

Posted by not done it yet on 01/12/2020 22:47:48:

I’m not an electrician but I understand there are different grades of the same ‘size’ of circuit breaker, depending on the response time required for the installation. Domestic ones trip more easily (less time lag) than industrial equivalents.

Yes you are correct. A type A would be used on a standard lighting circuit incandescent. Or a type B if there was a lot of capacitive load like fluorescent fittings. A type C would be used for most ring mains. In the worst circumstances a type D could be used . This is where there are high inductive loads. A bit like an electric welder etc. We always had to fit type D to the battery chargers on the fork trucks.

Steve.

[Dwayne ClarkParticipant @dwayneclark63130]

Just curious, was the bagpipe maker Hugh MacPherson? Hugh made my first set of pipes.

Cheers

Dwayne

[David George 1Participant @davidgeorge1]

Hi Alan the Dewhurst switch was to enable you to run a machine in reverse when needed ie screw cutting. I have wired my lathe with a no volt push button switch as well as the rotary switch to change direction. Don't try to change direction whilst the lathe us still in motion as it may not change direction as you may think it should. When I change direction my no volt switch disconnects as it is wired through a spare contact on the rotary switch and needs pressing to restart motor in selected direction.

David

[Howard LewisParticipant @howardlewis46836]

You really should have a No Volt Relase switch between the plug and the drum switch.

Nowadays, Drummond type drum switches are none too popular, because of the lack of the NVR feature.

If you search back through previous threads, you will find wiring diagrams for the Drummond switch.

(Somewhere I have probably got one! )

To safeguard the contacts in the drum switch, it is worth stopping the motor with the NVR switch before stopping or reversing the motor with the Drum switch. This procedure will prevent the contacts being burned by arcing.

You may not need to reverse the motor often, be careful if you do – only at minimum speed, possibly after using a Tap or Die, but the need may arise.

If, rightly, you are wary, make and use, a Mandrel Handle with with to rotate the chuck. It will be a useful learning exercise to help you become familiar with the machine, and leave you with a useful tool for use in the future.

If you cannot find details of such a gadget, (There are several different designs ) PM me with an E mail address, and I can send you pictures of one that i made for a mini lathe, both of the kit of parts and the completed device.

The dimensions you will need to decide to suit your particular machine.

Howard

[john fletcher 1Participant @johnfletcher1]

Hello Alan, first of all get your friendly electrician with his Insulation tester (Megger)to carry out an insulation test on the motor. That will prove the motor is safe to run being an elderly one, and you did say the lathe was in your garage and hadn't run for some time, is the garage damp as elderly insulation is prone to absorbing moisture. Old insulation wasn't as good as the latest modern type is. A motor starter won't reduce starting current, its a push button switch, it will automatically switch off / disconnect the electric supply to your motor when there is a mains failure, BUT won't switch the power back on again until you the operator, presses the Green button. If the insulation test was OK slip off the belt and run the motor on No load and see if it then trips the breaker. I suggest you follow David George 1 route, buy a proper motor starter which will have No-Volt release and over loads as well. Reversing isn't used very often, ( don't bother follow Howard's suggestion and reverse by hand) in fact the only time I have used mine is when screw cutting metric threads, so not often at all. John

[Alan CulpittParticipant @alanculpitt14314]

I'm really obliged to everyone for the advice, I'm going to go for an NVR switch and a new MCB type C which will hopefully help, The insulation on the wiring looks to be modern plastic and its been in a dry garage so I'm not too worried there. All I have to do now is level the lathe, buy some new tooling and then perhaps I can start learning how to machine

[SillyOldDufferModerator @sillyoldduffer]

Posted by Alan Culpitt on 01/12/2020 16:28:44:

…

It has a 13 amp plug on the wire to the hoover motor, nothing else. I read somewhere that it needs a proper switch in order not to damage the motor. I tried a while ago to run it and it seemed to work ok but I'm concerned that I'll damage the motor. Also I want something a bit more refined than thumping a 13amp plug into a socket to start the lathe I tried it again recently and it blew the circuit breaker for the garage, I think because I hadn't run the lathe for a while and the motor was a bit sticky.

It's a Hoover Motor type 2130 HAE, 1 phase 50 cycles, WDG (winding?) SP PH 3.6 Amps 1/2 HP 1425 RPM.

**LINK**

I know very little about electrics but I'm a reasonably competent mechanic….

First the good news – small single phase motors don't need a special starter. Although not best practice from a safety point of view, plugging straight in won't harm the motor. BUT machines are easier to control with a conveniently placed switch and not having an NVR/Emergency stop was a common cause of blood spilling accidents.

Bad news next. The motor blew the circuit breaker. Something is wrong and it's unlikely fitting an NVR and changing the circuit breaker will fix it. The motor plate isn't encouraging:

I think it's a Shaded Pole motor and Andrew Johnston explained why they're warty beasts in a parallel thread. Worse, it's an old motor, which means the insulation is likely compromised inside. The windings can be damaged by heat or damp, resulting in shorted turns and earth leaks. And the motor plate suggests a criminal past. The serial number has been carefully beaten out carefully! In the past, a motor fitted for cheapness, not necessarily ideal for the lathe, and maybe abused in a a previous life.

I'd start with some basic checks with the power off:

1. With belts fitted and gears engaged, can the chuck be turned by hand, such that the motor spindle turns. If the lathe is jambed solid for a mechanical reason, the motor might pop the breaker. Motor innocent, lathe guilty.
2. With the belts off, how easily does the motor turn at its pulley? If the motor is very stiff, something mechanical nasty inside – seized bearings, dirt, corrosion, loose winding, or laminations etc. Open it up – might be an easy fix.
3. If the motor can be turned freely by hand, try plugging in it. It might run unloaded and watching it carefully as it warms up over a few hours might free up neglected bearings, gunge and dry out damp and restore normality. I'm nervous of this kind of 'fix' because leaky insulation is a shock hazard if the earth connection fails for any reason. I would replace the motor unless a Megger proves it's OK.

Technology limitations meant new Myford lathes were almost always fitted with single-phase motors. Not ideal, even in perfect working order, and fitted with a Centrifugal Switch rather than a yuk shaded pole. Today, many Myford owners faced with a dud motor replace it with a 3-phase motor and VFD, a better combination providing smooth speed control and more torque.

Well-maintained old machines can be mechanically as good as the day they were made. Not so the electrics. If that motor trips the breaker again, I'd replace it.

Dave

[larry phelan 1Participant @larryphelan1]

My pennyworth, for what it,s worth !

Motors are cheap enough replace it and get moving.

Also get a proper switch and be finished with it.

Only need reverse for left hand threads, not often.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi, if you have dampness in the motor windings, it can be dried out by stripping it down and then placing the housing with the coils, in a stream of warm air from a fan heater for about 6 hours or so. Don't place it up close to the heater, but say 300-500mm in front so the air stream travels through the inside and around the outside. If you can megger it, it needs to be above 1 megger ohm at least, but higher is better. In the absents of a megger ohm meter a good multi meter with a 10 megger range or above, will give you some guidance as to the state it is in and of course any multi meter will detect a dead short in the windings.

Regards Nick.

[Grindstone CowboyParticipant @grindstonecowboy]

Only need reverse for left hand threads, not often.

And not even then – just arrange your gear train to move the carriage away from the headstock.

Rob

[Clive FosterParticipant @clivefoster55965]

Unlikely to be a shaded pole motor.

Those fully enclosed "square" Hoover motors were among the best quality mass production single phase devices. You won't find anything approaching that quality at home shop guy affordable prices today.

Odds are that any problems are due to the centrifugal start winding switch inside.

Best thing about those motors is that they were primarily designed for domestic and low end industrial appliance duties. Washing machines and the like. So not only are they well sealed but they also have a lower start current surge than most motors.

Well worth an investigation to see if any problems are simply resolvable. I'd not greatly worry about winding insulation. Voltages between adjacent coils in the windings are small. Flexible flying leads to the tag board are the main offenders as aged rubber insulation tends to flake off. Especially when disturbed.

Clive

[Alan CulpittParticipant @alanculpitt14314]

Everyone I'm really grateful (and a bit overwhelmed) by the number and length of responses. I'm going to try a test run unloaded on the motor and see what happens

[Howard LewisParticipant @howardlewis46836]

Hopefully, when you switch off, and the motor runs down, you will hear a click as the centrifugal switch makes contact again, ready for the next start up.

The switch takes the start windings out of circuit as the motor runs up to speed.

Howard

[not done it yetParticipant @notdoneityet]

SillyOldDuffer,

Read the thread again? Poster is clearly limited for expenditure. Motor turns and runs smoothly.

Yes, likely misappropriated at some time – but that would not necessarily mean abused.

I ‘m surprised it is 1/2HP for a washing machine, but good that it is. Motors rarely fail completely and some cheap maintenance is often all they need – new bearings, lubrication, or overhauling the centripetal switch.

It most certainly needs an earth resistance test for safety – but it tripped the overload breaker, not the RCD, so likely it’s good. A winding short is still a possibility – which would write off the motor. Replacement, if it fails, by a three phase motor and VFD is a good idea – but likely not this side of Christmas?

My main machines are all running with VFDs – lots of advantages – but I have only personally changed two of the five drives to VFD operation – and the latest was already three phase but the wrong voltage.

[SillyOldDufferModerator @sillyoldduffer]

Posted by not done it yet on 03/12/2020 20:04:35:

SillyOldDuffer,

Read the thread again? Poster is clearly limited for expenditure. Motor turns and runs smoothly.

…

Two things in Alan's post jumped out at me:

• 'I tried a while ago to run it and it seemed to work ok', and,
• 'I tried it again recently and it blew the circuit breaker for the garage, I think because I hadn't run the lathe for a while and the motor was a bit sticky.'

Not quite an assurance the 'Motor turns and runs smoothly'.

But quite right, I didn't mean Alan should dump the motor without trying a few things first. Worst comes to worst though, and the motor is a dud, then I think going 3-phase is the besr solution, money permitting.

I do suggest a half horse motor shouldn't ever trip a circuit breaker. Something ain't right. Earth leak would be my bet.

Dave

[Maurice TaylorParticipant @mauricetaylor82093]

Posted by SillyOldDuffer on 03/12/2020 22:36:35:

I do suggest a half horse motor shouldn't ever trip a circuit breaker. Something ain't right. Earth leak would be my bet.

Dave

 

 

Hi,A 1/2 hp Brook motor on an ML7 takes nearly 50A for 100mS on start ,this will sometimes trip a domestic mcb but probably wouldn’t trip an inductive load mcb ,as previously mentioned .An earth leakage fault would trip the elcb not the mcb.

Maurice

PS   If I’m writing rubbish , electrical experts please correct me.

Edited By Maurice Taylor on 03/12/2020 23:54:08

[AJAXParticipant @ajax]

Posted by Maurice Taylor on 03/12/2020 23:39:52:

Posted by SillyOldDuffer on 03/12/2020 22:36:35:

I do suggest a half horse motor shouldn't ever trip a circuit breaker. Something ain't right. Earth leak would be my bet.

Dave

Hi,A 1/2 hp Brook motor on an ML7 takes nearly 50A for 100mS on start ,this will sometimes trip a domestic mcb but probably wouldn’t trip an inductive load mcb ,as previously mentioned .An earth leakage fault would trip the elcb not the mcb.

Maurice

Maurice, I'm interested in your scope setup. I'm familiar with the picoscope as I have one myself but never seen or used the automotive one. Are you using it with a clamp meter probe? I have a clamp meter but not for the scope. If I needed current logging I might use a current sense resistor and do it that way.

[not done it yetParticipant @notdoneityet]

Maurice,

Thanks for the ‘scope print-out. You seem in much agreement with me – where I also clearly pointed out that it was an overload trip and not the RCD. An RCD trip would have sounded alarm bells for me as any imbalance would likely indicate a leakage to earth.

All the evidence ( ‘I think because’ was a very speculative suggestion with no actual evidence supplied – I took that to likely mean it could have been the whole lathe that was stiff, not necessarily just the motor) indicates the motor is likely in fair fettle, but possibly needing maintenance.

A good earth connection (readily checked with a normal DMM) should protect the user in the event of leakage, but a resistance test for the motor is, of course, the far better option – as long as the motor windings are completely dry, of course.

[Author]

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