MadModder
Gallery, Projects and General => How do I?? => Topic started by: John Rudd on October 29, 2019, 09:07:46 AM
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Is there anyone here versed in the art of rewinding universal motor armatures?
I have an armature that I would like to rewind, but my experience is virtually non-existant...,
That said, I rewound the field coils for the drill that matches the armature....
I fear it has shorted turns, there is excessive sparking at the comm, the field coils are warming up too as a result I suspect due to excessive current...
Please help... :zap:
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I know it might be a daft question but you can't find a suitable donor machine to rob the armature from?
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Pete,
No chance at all, its a vintage Stanley Bridges Wasp from my collection...made around the early 60's I think.
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there are a few of the old "Newness" published electrical series that cover armature winding, if you can get your hands on them, I will check out mine tomorrow at the wshop and see if I can find any details, You need the armarture in a jig where it can be rotated or fixed, and several coils of enamelled copper wire of the correct size, fiddly but doable! My grandfather was a coil winder who specialised in armatures, but that is no help now!
Phil
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This £20 one on ebay no good for a donor?
https://www.ebay.co.uk/itm/VINTAGE-STANLEY-ELECTRIC-DRILL-5-16-WASP-BRIDGES-DR2T-FULLY-WORKING/401933097873
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I already saw that one, its not a Wasp....that particular drill shares the same cartridge motor as the DR5S, the DRCD and the Hornet...The differences are in chuck size and whether they have a thermal cutout fitted.. The armatures are a different size too, the Wasp is slightly smaller in diameter, the field coils are smaller too.
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The motor on my Boxford Little Giant grinder started getting hot. The armature looked OK so I rewound the field coils. It still got hot. At that stage I gave up and bought another one.
If you should happen to find someone who can do a reasonably cheap job, then please share the info. The firm in Croydon I approached wanted £150 :bang:
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I used to have loads of motors rewound by a place in south London when I had the Launderettes as they seemed to have an over abundance of ones with specially long shafts, or double ended shafts. In later years it became more and more difficult to find people who could, and more to the point would, do the rewinds - a dying art sadly.
The theory is pretty simple but my fear was always loosing track of the plotting out of windings as I unwound them and not knowing what had to go back in which slot :bugeye:
I suppose iPhone cameras nowadays reduces that risk.
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Try this one, there several others advertising in "Automobile" magazine.
http://www.vehicle-electrical-rewinds.co.uk/
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Thanks for that link. They look like a possibility.
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Also worth a try, AES Rewinds in Ash Vale, Surrey (aesrewinds.co.uk), have been helpful to me in the past.
Dave H. (the other one)
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Thank HD, although whether or not they'd be interested in a tiny fractional-horsepower universal motor remains to be seen.
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I've looked closer at another armature I have from a Stanley Fatmax drill that has lost a comm segment...it appears that this armature is wired in the classic 12 pole winding arrangement....
I'm tempted to have a go, got a new commutator on order from ebay, just need some copper wire n stuff...
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sorry John, my search came up blank, I was sure one of my dads books covered armatures, but if it did I can't find it!
Phil
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Phil,
Thanks for looking... :beer: but dont waste too much sleep over it....
I have other ideas.... :scratch:
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I can report after much knowledge searching and copper wire.....
I have succeeded in rewinding my armature...
I wound the coils with some 28SWG en copper wire that I had just to prove the practicalities...
Suffice to say when tested on my bench power supply it ran the wrong way!
Armed with the knowledge, I can now proceed to rewind it with the correct gauge of wire and terminate the connections at the comm the right way round...
In true madmodder style, some workshop equipment was pressed into service to aid rewinding...
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Nice one John! Looking forward to the video, demonstrating how you do it.
Pete
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Thanks Pete, :D
If anyone wants to know info on armature winding and contruction, just ask.....I'm no expert but I'll try and answer..... :zap:
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:thumbup: Looks excellent, and very neat - be hard pushed to differentiate it from the original factory product.
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:thumbup: Looks excellent, and very neat - be hard pushed to differentiate it from the original factory product.
Thanks for the compliment... :thumbup:
Suffice to say, its far from factory std.....its a quick lah up to prove that it can be done and to determine rotation direction....
When I 'do it for real' it will be a lot neater...( well thats the plan.... :scratch: )
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That looks really nice.
How did you reverse engineer it?
Did you found instruction book in PDF or something to help?
Good work!
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PekkaNF,
Reverse engineering was difficult but not insurmountable....
First, determine number of slots in armature, count number of segments in commutator....
Then cut off the rounded ends of the windings...punch out the wire in between the slots, put to one side at least 3 sets.....
Clean everything up.
To the wires, count the number of wires in the 'clump'.... Then take an individual wire and carefully measure its diameter....
Now we know how many turns per 'coil' and wire gauge....
If the commutator is removed, ensure its position is noted relative to rhe comm stack....look at the slot and the segment relationship.....
To be honest, I watched various Youtube videos and trawled the internet for bits of information before embarking on the winding..,,,
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Well done that man!! if you need to reverse this type of universal motor, you can do it by swapping the brush connections around. not easy because they are usually just the right length to reach the brush holders. Best of luck with the final rewind!
Phil
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Phil,
You are correct, swapping the brush wires over does the trick.....
But, yes they are a fixed length lead.....
I'd rather not do this as it then means that things are not 'original'... The armature is from a vintage Stanley Bridges drill I'm restoring..
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Nicely done John. I'll send you mine when you have time :D (Just kidding :thumbup:)
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Well done John!
In my youth I had an apprentice job building those stacks of laminations and winding small motors but I never had to do a rotor because they were special (at the time) brushless dc motors. Winding them is just a matter of patience and being methodical, as you have found. Encapsulating the windings is also important so they don't rub together in use, and hang them vertical afterwards whilst the varnish dries so you don't upset the balance too much.
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Pete,
Thanks for the tip on varnishing the turns and rubbing.... I intend to get some 'electrical laqcuer' for completion...But didnt realise it had a primary function of retaining...
Does your expertise stretch to 'terminating the coils to the comm segments' ?
Reason I ask is, if the coils are terminated round the comm, does the direction matter? Mine runs the wrong way, so I guess I should have connected up the opposite way?
I have another armature to rewind for a Stanley Fatmax hammer drill,( the field coils are burnt out too..) but a job for another day...
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The direction of winding is the critical part. You could, at a push, reverse the tails of every winding, but that's very much a bodge, crossing wires everywhere. Easier to swap the brush leads in my opinion.
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The direction of winding is the critical part. You could, at a push, reverse the tails of every winding,
I think thats how it was wound originally, but as the coil tails were buried in epoxy, it was difficult to tell....
The field coils remain as they were originally......
I think more research required before proceeding with another rewind..... :scratch:
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Yes the turns direction is crucial as said. I can't help with questions about commutators because of course those brushless motors didn't have them. One thing I did learn from reading is that brown coloured commutators is normal and you shouldn't clean them up shiny just because they look brown.
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So to update this, after several ( maybe should read many,many) rewinds I got it down but its not a complete success!
Turns out ( no pun intended...) that the shaft is bent...
I have learnt that there are different ways of terminating the coil ends...This is called Retrogressive or Progressive winding...
Then there is lead throw and coil throw...
Lead throw is how the coils are terminated, relative to the comm segments.
The coil throw is dependant on the number of armature coil slots and the number if brush pairs....
It is 'normal' practice to nite all this info prior to embarking on a rewind!
Fortunately I was lucky to find a mentor who was willing to tutor me.
So for now, the armature is sitting in the workshop awaiting further attention....( a get round to it job..)