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Adcock Shipley Bridgeport motor

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colin hamilton27/01/2022 15:36:23
137 forum posts
57 photos
Posted by Chris Evans 6 on 27/01/2022 11:26:16:

I would find working on that motor scary and take it to a rewind place. My 3HP lathe needs a similar procedure but I could not find anyone willing to do it. It runs OK on a Transwave static inverter whereas the 2HP Bridgeport would only run for a few minutes on the Transwave before tripping out. Bridgeport now happy on a VFD fitted by a friend.

Scary yep I would agree. But I'm also thinking it's still only wires. Worst comes to the worst I'm in for a new motor which is likely anyway if I can't sort it so what do I have to loose?

Chris Evans 627/01/2022 15:48:03
2050 forum posts
Posted by Emgee on 27/01/2022 12:01:43:
Posted by Chris Evans 6 on 27/01/2022 11:26:16:

I would find working on that motor scary and take it to a rewind place. My 3HP lathe needs a similar procedure but I could not find anyone willing to do it. It runs OK on a Transwave static inverter whereas the 2HP Bridgeport would only run for a few minutes on the Transwave before tripping out. Bridgeport now happy on a VFD fitted by a friend.

Hi Chris

Have you fitted a 400v 3 phase output VFD or are you running the motor at reduced voltage/power than the rating plate ?


As far as I am aware the Bridgeport now runs 240 volt three phase from the VFD. Not found any lack of torque or power. I am just not confidant to mess with electrical items.


Andrew Tinsley27/01/2022 17:10:41
1610 forum posts

A pity you don't feel confident to rewire in delta. That motor looks to be an easy conversion. However full marks for expressing your concerns about your ability.

Where are you located, someone may be near enough to do the job for you?


Clive Steer27/01/2022 22:20:06
91 forum posts
5 photos


Your list of steps to take is correct. Probably the most difficult task will be doing the retying to hold the wires in place as threading through a cord can be tricky. However if you just snip the original loops but initially leave them in place and you may be able to use them to pull new thread through. However you can use small thin cable ties instead.

From what I can see from your pictures you will probably find three wires, sleeved in yellow, emerging from the coils on the outer rim of the windings. Another three wires will emerge from their respective windings nearer the centre.

It doesn't really matter what are start and finishes of the windings provided you can identify each of the three individual windings so you can connect them in true delta configuration. The marking is only required to ensure the motor will rotate in the right direction when connected to a 3 phase supply but if it doesn't swapping any two phase wires will make it rotate in the opposite direction.

If you'd like to PM me I'll give you my phone number and I can talk you through the process as you do it. If you can make a FaceTime or Zoom call I can watch you do it and comment.

Clive S

colin hamilton28/01/2022 07:44:05
137 forum posts
57 photos

Clive thank you for the very kind offer I'll pm you now

Clive Foster28/01/2022 08:37:16
3103 forum posts
107 photos

On all the motors I've done shellac, varnish or similar protective coatings had been applied after tying. So things still stayed in place after snipping the string.

Adhesion wasn't high. More than post it note, less than sellotape. So some careful pulling and prising with non-metallic tools got the bits I needed to work on up and out into free space with minimal disturbance to the rest.

I left most of the old string behind as it clearly wasn't going to come out easily. Just snipped the trailing ends neatly close to the wiring. The coating soaked string was approaching MIG wire stiffness. Re-tied with some nice cotton string 'cos I had some.

Dunno what the modern advice is on re-coating. I "obtained" a small bottle of the then proper stuff about 40 years ago. Behaves like shellac in that it separates out of the carrier liaquid quite quickly and needs regular stirring up.


colin hamilton28/01/2022 09:10:23
137 forum posts
57 photos


What is the purpose of the shellac? Is it simply to stiffen up the ties to ensure they don't come undone? I was planning to replace with zip ties.

Mike Poole28/01/2022 09:32:13
3302 forum posts
73 photos

I think the purpose of the shellac was to stabilise the windings so that the wires could not fret and compromise the insulation, these days it seems to be a liquid epoxy. We used to use a flat cotton tape like the motor in the pictures and the shellac would be absorbed to deny any possibility of moisture being absorbed. We would use an off cut of the winding wire as a needle to thread the tape through the windings, bent to form a blunt end to avoid damaging the windings. The interconnections were made by twisting the ends and flashing them with an oxy-acetylene torch to fuse the connection into a neat ball. To solder the ends to the tails it is easy to burn the insulating varnish off the wire and scrape clean, just scraping is not so easy as the coating used Is extremely tough, if you use a flame use a small one and keep an eye on where you point it.


Clive Foster28/01/2022 09:35:21
3103 forum posts
107 photos


I don't know if the stuff I have or that on the motors I did actually is shellac but it clearly builds thin layer of insulation over everything.

I imagine the idea is to stop the string moving around due to vibration so it doesn't eventually work its way through the insulation coating on the wire causing turn to turn shorts. Clearly a bad thing. As I understand it the wire in the coils have vibrational forces on them when the motor is running, think transformer hum, so some sort of restraint is needed.


Edited By Clive Foster on 28/01/2022 09:43:38

colin hamilton28/01/2022 10:07:42
137 forum posts
57 photos

Mike and Clive thanks. Given the actual use mine will be getting I feel OK about securing with zip ties

KWIL28/01/2022 10:43:32
3549 forum posts
70 photos

What is the temperature rating of a zip tie? Methinks theyy will get very soft at normal motor operating temperatures.

colin hamilton28/01/2022 19:13:29
137 forum posts
57 photos

Check out what I found!!

Edited By colin hamilton on 28/01/2022 19:17:46

colin hamilton28/01/2022 19:18:54
137 forum posts
57 photos


Mike Poole28/01/2022 21:17:04
3302 forum posts
73 photos

The shellac we used sounds vey like the stuff you have Clive, we baked all our motors to harden the shellac and after baking it had set quite hard. I am not sure what the bake temperature was. I am not so sure as Clive that the connection of the coils doesn’t matter but if if doesn’t run sweetly then swap each winding in turn until it runs best. Motors can run at quite a high temperature without stress, in fact we have had to strip and bake motors that have been flooded to dry them out. Modern motors can run happily at temperatures that would be very uncomfortable to put your hand on for any time but to reach those temperatures they need to run at full load for extended periods. It looks like the star point extraction has gone well so good luck with the final assembly and testing.


AJAX29/01/2022 06:50:39
366 forum posts
42 photos

Standard cable ties (non heat resistant) made from 66 nylon are suitable for use up to 85 degrees C. I would remove those ties and use string sprayed with conformal coating, or use heat resistant ties instead. You won't know what is happening inside the motor until it fails.

John Haine29/01/2022 07:47:29
4622 forum posts
273 photos

It is important that the sense of each winding is correct, it doesn't just reverse the motor if you reverse one winding, the motor torque will suffer and it won't run so smoothly. This is because there is mutual coupling between the windings of a 3 phase motor and if the couplings are not all in the same sense the phase currents are unbalanced.

But it should be easy, if you connect the inner end of one winding to the outer of the next. Or putting it another way, the end that went to the star point of one goes to the not star point end of the next.

noel shelley29/01/2022 10:55:37
1278 forum posts
21 photos

As John has said, Now you have star point it SHOULD be easy ! If you take the 3 original wires as 3 starts, Test continuity, to the 3 tails at star point and take these as 3 finishes, then, start No1 to finish of No3 coil, finish of No 1 to start No2,finish of No2 to start of No3 ! You now have a 240v 3phase delta wired motor. IF it rotates in the wrong direction simply swap any 2 incoming phases. It is very important to re coat the work to prevent windings moving, breaking the insulation and causing shorted windings. Good luck, Noel.

Circlip29/01/2022 12:17:41
1499 forum posts

Years ago, rewound the stator coil on a Citroen alternator. This was vacuum impregnated with an epoxy resin after winding. This material was what was used to do transformers at the R&D labs for Decca R&T. not only to waterproof them but also to stop the windings 'Singing' in use.

When the first workshop machinery arrived from Taiwan many years ago, the first job after cleaning the sand from the castings (how times haven't changed since ROC took over) was to change the motors for Brit impregnated varieties. Insulation breakdown due to singing windings was a regular occurance.

Regards Ian.

Edited By Circlip on 29/01/2022 12:18:15

john fletcher 129/01/2022 12:52:46
783 forum posts

Colin, I've sent you a PM regarding getting the phasing sense correct and how to do it should you need to do. I have more details should you be in need of them. John

Clive Steer29/01/2022 13:05:10
91 forum posts
5 photos

I believe that a standard 3 phase motor is a symmetrical machine so winding "polarity" shouldn't be important but I stand to be corrected.

However for a 2 speed 3 phase motor, using a Dahlander winding configuration, winding "polarity" is important as the flux coupling from each winding interact to change the stator pole pattern from 2 pole (Hi Speed) to 4 pole (Lo speed). The special winding arrangement is also the reason why a Hi Volts 2 speed motor cannot be changed to a Lo Volt motor in the same way Star can change to Delta.

I will experiment with a 3 phase motor I have to check if my thinking is wrong.

Clive S

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