Electricians

[Roger Hulett]

An “indirect link to a Scott ” problem. I have purchased a small lathe to use during my bike renovation. It is powered by a Hoover A/C single phase 3/4hp electric motor. There is one cable coming out of the motor containing three wires, Red, White, and Blue. Can anyone advise me what these wires are for ?
Thankyou Roger Hulett

[Roger Hulett]

Hoover say they are unable to help as the motor was made in Cambuslang factory which has now closed down.

[efr215]

Is there not a legend plate somewhere on the motor? If so can you post the details, it’ll help running down the right information.

If no details are forthcoming and it is a “small” lathe, say 3.5″ or 4.5″ centre height, (Myford/Boxford size), then you could change the motor for a 1/3 or 1/2 HP one which will be ample for this type of machine.

While these machines in good condition are capable of accurate work the limit of their cutting ability is their overall stiffness not the power of the motor. You are after all not looking for production rates of metal removal! My 4.5″ Southbend can do a 1/4″ cuts on mild steel with its 1/2 HP motor wiithout strain, surely enough for any “man-in-a-shed”!

[James]

@Roger Hulett wrote:

An “indirect link to a Scott ” problem. I have purchased a small lathe to use during my bike renovation. It is powered by a Hoover A/C single phase 3/4hp electric motor. There is one cable coming out of the motor containing three wires, Red, White, and Blue. Can anyone advise me what these wires are for ?
Thankyou Roger Hulett

shouldn’t it just be
hot

neutral

ground?

[efr215]

“shouldn’t it just be
hot

neutral

ground?”

Life ‘aint never that easy!

Most motors of this size require a “kick” to get them going, mostly either a set of start windings or a big capacitor and some form of automatic switch to get the motor up to speed.

[BRIAN MARSHALL]

Do NOT under any circumstances try and connect the cable to a domestic 13 amp plug and socket. A 3/4 hp motor draws a lot of current on start-up, and will burn the contacts in the switch. It must be wired to a combined starter/emergency cutout device. My old Myford lathe has this positioned at thigh height on the cabinet. It has a green start button and a red kill button on the front. If I were to get my sleeve caught up with the chuck, even both arms or the front of my overalls, I can just lean against the red button or bring my knee up to it in order to stop the lathe. I even keep a Stanley knife in the drip tray, to use in an emergency to cut through entangled clothing. My compressor also has a starter/cutout device on the top, and I never use the switch on the wall socket to turn it on or off. SAFETY FIRST !!
Brian

[efr215]

“A 3/4 hp motor draws a lot of current on start-up,”

Quite true, it can be as much or more than 300% of the running current draw.

Which is why we need Roger to come up with the full S.P. on this motor if we are ever to come up with the right answer.

Failing the correct information being forthcoming for this motor then it’d be better to swop the motor for one of a known specification.

As I said earlier a 1/3 or 1/2 HP is quite big enough, even a 1/4 HP would do the job, after all it ‘aint that long ago that the darned things were treddle driven!

[Roger Hulett]

Thankyou for your replies. The plate on the motor reads :-
Hoover a/c motor Type 2310HAF1240M Ser No 45542 TO Rating 1/2 HR WDG CAP ST Volts 230/250 Amps 5.0
Phase 1 HP 3/4 Cycles 50 RPM 1425
The problem with replacing the motor is that the bolt holes in the cabinet,the bracket for the intermediate pulleys and the motor pulleys are all in place and aligned with the belt. My thoughts would be that if it worked satisfactorily for the previous owner (unfortunately deceased) then it should work for me. I think one of the most interesting comments (Brian Marshall)concerned the safety switch. This lathe does not have one at the present time. I need to get one.

[James]

maybe email this guy to see how he did the wiring test?

https://www.ebay.co.uk/itm/Single-Phase-Electric-Motor-/181322673011?nma=true&si=GZnL%252BlFsEDvITplUKYqSwzX8zKU%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

[efr215]

@James wrote:

maybe email this guy to see how he did the wiring test?

https://www.ebay.co.uk/itm/Single-Phase-Electric-Motor-/181322673011?nma=true&si=GZnL%252BlFsEDvITplUKYqSwzX8zKU%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

The problem there is that he says that he has tested the motor not that he repaired it and anyway that motor looks to be pretty well unmolested.

On the other hand Rogers motor has at the very least three unconnected wires . . .

One other thiing that might help work out what we are dealing with is does this motor look anything like a standard industrial type, is it for example anything like the motor in the ebay advert? Or is its construction more open as if was at one time incorperated inside a machine that itself provided the protection?

If the latter then that might offer an explanation of the three wires, two for the supply and the third for the start windings via an external cut-out switch and capacitor to the supply .

On the subject of switching, a “Dewhurst” type would be very suitable, you may not have twigged it yet, but trust me, sooner or later you are going to want reverse!

[Roger Hulett]

Thanks everyone. I phoned Ray (advertising the Hoover motor) he was unable to help. His motor had (he thinks) 2reds,black,green & blue. His motor looked similar except his has a box on the side as well as the capacitor,mine only has the capacitor. He suggested that the 3 wires were Red-live Blue-neutral and white-earth. He suggested wiring up to a 3amp fused plug so that if it was wrong it would quickly blow the fuse.

[gammakeith]

If your motor has a capacitor then the following should help;

https://bchpe.com/blog/2013/3/19/how-to-wire-an-ac-induction-motor

I sorted my own motor out that was “bare” like yours but it was many years ago and I forgot the details of how they work. I have a 2 hp motor driving my lathe and I had to run a separate fused feed from the fuse box to run it. As Brian says please use a no-volt release cutout….

Keith

[BRIAN MARSHALL]

I suspect that if Roger just puts the wires into a 13amp plug he will prove nothing, because even if he gets the polarity and earthing the right way round, the starting current would instantly blow the fuse anyway, to say nothing of burning the contacts in the plug and socket, or even welding them together ! NOT a good idea…..
Brian

[gammakeith]

+1 on that. If (like mine) you have no reverse gear on the lathe then using a suitable contactor you can get reverse by switching the polarity to the capacitor.

Keith

[efr215]

So the motor has a capacitor. Would have been nice to know that! At least seems to rule out it being a “Split Phase” motor. If so that is good news as they are not designed for start / stop operation, the start windings draw a very high current albeit for a split second and need time to cool down or they will die.

Is the capacitor wired up to the motor? It will have two terminals and/or wires if connected which may well dissapear inside the motor.

Would it be possible to put a meter across the red, white and blue wires to get some resistance measurements?

The run windings will have the higher resistance. ‘Tis my guess that one end of the start winding will be connected somewhere inside the motor, the other end being one of the three. Somewhere in between should be the capacitor and centrifugal switch.

If it were mine I’d want to dismantle the motor, they are not exactly complicated, mainly to be sure I knew exactly where each wires went and also to re-grease the bearings.

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