Getting an ML7

Thanks.

No offence taken. I'm Ok on sorting dodgy electrics on old bikes, but 240 volts mains supply is deffinitely not something I'm comfortable with. I don't have much spare cash, and so I'm anxious not to spend too much on what may not be the best solution. Quite handy for me is "The Electric Motor Man" at Ilminster. I visited him yesterday and he was helpful, doing his best , to explain how I should check which wire does what. Fortunately he is very familiar with Myfords.

I think I can check out the wires coming from the switch as he suggested, but as the terminals on the motor are not marked, I cannot see how I can determine which terminals serve which set of windings. The Motor man did point out that even if the Dewhurst switch worked, it may not do so for much longer and explained he can supply a new switch, and a new 3/4hp motor if need be. He also suggested getting an electrician to sort out the wiring, but of course there is cost involed there and so I wonder whether the smart move would be to go for a modern swith and motor, preferably with wiring instructions which I could follow.

Peter,
I cannot read the rating plate on your motor. Does it definitely say it is single phase? Just 3 terminals suggest 3 phase. is there a 4th hole just visible behind that bit of masking tape?
You now say there are no terminal markings. That is unusual. Is it possible to view the underside of the terminal block for any markings? It just may have been put back the wrong way up and rigged for some other purpose - non Myford. The screw on the frame at bottom right of your picture is the earth connection. Do you have a meter to measure resistance (ohms)?
Can you take the cover off the capacitor and take pictures of its connections and any evidence you can see of internal connections. Two reds, 2 Blacks and a green (for earth) are fairly common from the Dewhurst switch but do those connections come directly from the switch or is there an 8 way terminal block somewhere that your motor cable comes from?
Someone from Ilminster area may come in here and help you out directly. Whatever you do, do not apply power until someone has made sense of it for you. You have not loaded any pictures of the rest of the machine but evidence of rust on the motor pulley suggest it has not been run for a long time and may not be part of your machine.

Tread carefully for now. Dennis

Peter that is an old motor, it immediately requires an Insulation test using a 500 volt Insulation tester often a Megger. your mate the MOTOR man should have one, or see your friendly electrician, he'll have one. Once you have proved that the insulation is good on all four wires to earth then you can sort out which wire is which. Have you got access to a multimeter of any kind ? If so, set the meter to low Ohms range and with one lead connected to any wire poke around with the second lead until you find a complete circuit and its record its resistance. Mark the pair some way. Do the same with the other pair, you have four wires showing.. The pair with the highest resistance value will be the START pair Z! & Z2 connect them to 6 & 2 on the Dewhurst switch. The other pair which is the lowest resistance connect to 5 & 7.Supply to 3 & 1. i notice you didn't mention a capacitor attached to the motor. I hope that will be of assistance. John

Thanks guys. Sorry that was not the clearest photo. The plate has "1" stamped in the box maked "PH" so I assemd that would be "single phase"

The history is as follows. The lathes serial number dates it as 1974. I bought it from a guy I know and it had been his Dad's. Dad now past away Richard wanted to sell it on (he runs a Boxford) He said as far as he could remember, his dad had it for about 40 years which would make it not an old lathe when he first had it. I don't know when it was last run, but I can ask. Rust on the motor pulley I do not think is significant. The lathe was stored in a lock up. Not a wet one, but not as dry as your average workshop and when placed there no particular precautions seem to have been taken in that respect. The lathe in general has not suffered.

I realise that the motor could be older than the lathe. I haven't taken the board out of the connection box yet. But also not visible in the photo, under the red lead with clth tag marked "Z" there is a vacant hole which would have had a 4th terminal in it. Perversly, this has the only marking on the visible side of the board, with a rather feeble torch, I think its marked "A".

The Motor man's view was that this once had the black wire from the motor that is currently not connected and he thought it Ok th use a "chocolate block" scew connector to make the 4th connection. Unfortunately he's away at the moment so I'll have to wait to pick his brains on it. So I tend to agee that there may well be something odd in its history as a motor.

The unconnected black lead visible in the photo can be seen to have pale discoloured area towards its end. I suspect that this is the trace of a similar adhesive tag, like the one marked " Z" on the red wire. So when I have a go at identifying wires, hopefully tomorrow it will be interesting to find out what might have been on the missing tag!

Friendly electrician? Is there such a thing ? Moved here 3 years ago and haven't met one yet. Not at their prices anyway. But I admit, if I'm going to use this elderly set up, It'll make sense to get it checked.

I'm actually near Langport, but anybody who'd like to call in and offer encouragement will be very welcome and refreshment will be available.

Note to JF1, Peters other photos in his album show a capacitor box.
OK Peter, definitely single phase so has 4 connections and that vacant hole is where your 4th wire should be but……….The other 3 wires may have moved from their correct spot and even deeper into it the capacitor may have been messed about with. Determining what those feint marking by the terminals are (and they obviously exist) does not help much as different manufacturers used their own combinations and even changed them after a company take-over. From studying form on the internet they are most likely A’s with or without a following number and Z’s with or without a following number if that helps you pick them out. Also from the web, the blacks are start winding and the red are the run winding but you really do need an electrician or someone with a meter and basic knowledge to prove the windings continuity and for short circuits to earth as JF1 says. Take the motor into that Ilminster shop (just the motor) and slip him a few quid. It will take him 5 minutes tops to instantly tell you if it is any good or not and what the winding connections are and take it from there.
You need a brass screw and nuts, M6, 0BA or similar in that vacant hole. Do not use a steel one.

One reference I have come across for Gryphon says the starter winding and running winding have there original labels of A1, A2 and Z2, Z3. I hope that helps further. I used to live in Bridgwater but am in Chester now. Otherwise I might have come for that refreshment.
Dennis

Edited By DMR on 28/08/2020 22:22:53

I really do appreciate all the recent advice, especially the patient encouragement to have a go at fettling the current motor. But this morning, the caution about playing with mains power and what can be expected from old equipment is winning.

I can't afford it on this months buget, but wait 3 weeks and I'll get a new motor and switch. Meanwhile I'll get everything else cleaned & sorted so its really ready to roll when up to date power is installed.