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AlanT

Restoring wiper motor armatures

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Since I wrote about wiper-motors in TR-Action it's probably no secret that I rebuild the early Lucas wiper-motors.

 

About 10% of those that come my way have a problem with the armature. This is not a problem with the DR2 type, because I have a good stock of new armatures for these, left over from other activity. Ask if you need one.

 

But the more common DR3A type armatures are a problem to get. Now and again I get lucky and find one for £20. Sometimes I get forced to pay £40-50. This really makes a motor rebuild uneconomic.

 

Even if I find an NOS one there is no guarantee it will be in good shape. Often they have rusty shafts and other corrosion, having sat too long in damp packaging.

 

Anybody on here who finds he has a commutator ploughed up by the brush arms, will be in the same position as me. Except I'll be on eBay bidding too.

 

Apart from damage from being run with worn brushes, there is the dreaded "black-wire" problem.

 

Here is one I fixed recently for a Register member:

 

32144827136_74490673a1_b.jpg

 

This happens if they are powered up, but stalled or jammed for any reason. At least 10A will flow and the temperature gets high enough to melt the solder joints. You can see this on one of the tags.

 

This is the inside of the motor. You can see the witness left by evaporated varnish:

 

31372572493_00543c014e_b.jpg

 

Armatures like this continue to run. May do so so for quite a while. Annual MOT and running about to summer shows and you'd be OK, most likely. But one dark wet night on the motorway and after running hot for a few hours, don't bet on it.

 

I DON'T SELL THESE. No doubt many others on eBay would. Be careful !

 

So I have a dozen laying about and a worsening supply problem. I asked every motor rewinding-shop I could find, to quote for rewinding them. NOT ONE REPLIED. I am rather glad they didn't bother.

 

The reason is that they know what I now know. It's not just the wire. The copper commutator-segments are moulded into the phenolic bush. This is probably the hottest spot.

 

When you strip one down this happens:

 

33147643114_53544e5923_b.jpg

 

This is probably a more likely cause of terminal failure than the wire. A segment gets loose, catches the brush and game over.

 

Rewinds are POINTLESS on these, unless you fit a new commutator. Nobody has these, which is why nobody would quote me. To be fair I asked in the RFQ for new commutators, just to shut out the rogues.

 

I thought about making new commutators. I'd do this if I just wanted one, maybe!

 

I considered other things like nicking them from DR2's. These are not exactly the same but close.

I could get them off but I'd scrap the shaft. It would mean lathe-work and this would be slow.

 

Then I found these:

 

33991333255_f5c6acb0b9_b.jpg

 

New, not identical, but very close. They would be cheap too, were it not for shipping, VAT, customs-handling etc. i took a £100 punt and got ten.

 

All the ploughed up commutators got fixed in an afternoon. Four perfectly serviceable armatures from the scrap heap, economic even if I count labour at a commercial rate. Brilliant!

 

Now then, what to with the black-wire ones? You can all guess what comes next I expect.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Excellent work Alan, there's not much left on a TR that you won't tackle and exposing the dreaded "death by black wire" failures may save a few on here buying them.

 

Mick Richards

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Hi Mickey, lots of stuff I did before digital photography made this kind of thing possible.

Gearbox stuff, OD stuff, all just has a few quick old fashioned "snaps".

 

These days I can try to amuse and educate a bit.

 

I was just musing to myself that I rewound the motor from a toy car I had. I didn't go of course but I was only 8 at the time. However I can remember doing it and I'm pretty sure I know how I went wrong.

 

Two repairs jobs I did in the London area stick in my mind too. They were of a rather urgent and delicate nature. In both cases I was escorted to and worked on the job under armed-guard. One in transport, the other in telecomms. Failure was not an option.

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Alan,

Now we're all interested......go on :ph34r:

 

Jerry, once upon a time electronic repair engineer ;)

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Thanks Jerry. I planned this as a bit of Bank-Holiday entertainment.

 

But I stop posting until someone else comments, otherwise it's just me banging on.

 

Now my work-life experiences are off-topic really. So more stuff shortly, on ARMATURES! Sorry.

Edited by AlanT

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The simple trick of smelling a wiper motor, or any other motor you are thinking of buying at auto jumbles, may well find out if an item has the dreaded 'black wire problem' due to electrical overheat.

Unless the seller will let you take the end cover off...

 

Peter W

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Like most specialised industrial processes, armature winding needs it's own bag of special tools, jig and fixtures and other equipment.

 

Here are the special tools I collected up while rewinding the my first armature:

 

https://flic.kr/p/TMGu2P

 

I also found it nice to make use of an "armature-winders bench". Armatures like to roll off a normal bench and the shafts get bent when they hit the floor. The proper bench prevents this.

 

Mine also has storage for copper to be recycled.

 

https://flic.kr/p/Sv9mdj

 

You'll need a fixture to hold the spindle vertical when doing the lacquer impregnation. Fortunately my two-level phosphate/caustic cleaning facility offers something suitable:

 

https://flic.kr/p/TMGtxT

 

Seriously the most important thing is a secure way to hold the armature in a comfortable manner. This needs to allow easy rotation when required but otherwise be rock-stable.

 

I have a Rolls-Royce solution here, ER25 collet in a collet-block. I did the first one just in the vice. Was OK but frustratingly wobbly at times.

 

33689680040_593982b23f_b.jpg

 

I saw a bloke on Youtube do this with a reel of wire in one hand and the armature in the other. He did a mains-motor with thousands of turns. Some people have a higher pain threshold than me!

 

All up these armatures have just 260 turns, spread over ten coils. These go on as pairs on opposite sides of the shaft. A simple pattern which you discover when you unwind the old wire.

 

Copper wire is springy stuff with a mind of it's own. You need two free hands.

My Dad got the vice FREE, by smoking a lot, in 1971. It's not bad actually.

 

Oh and keeping track of the turns, even though there are only 26-turns in each coil, is quite taxing on the brain when you are concentrating on routing the wire and controlling tension.

 

So you'll need a "turns-counter". Here is mine. Point at it with the wire-cutters and when they get to 26, cut the wire with them. If you get confused, a turn or so either way won't be a show-stopper.

 

33262550553_50beef5196_b.jpg

 

Hope you are getting the message that this is really rather simple.

Edited by AlanT

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I used to rewind my own motors for Scalextric cars back in the 60`s to make them go faster, Also had to rewind the hand controllers too as the resultant heat used to fry them!

I agree once you know the way the windings go then its relatively easy to redo them.

Stuart.

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The next thing is materials. All the materials are available, but the problem is quantities and minimum orders.

However this rather useful company trades in small quantities and is good to deal with.

 

http://www.brocott.co.uk/

 

The wire stripped from an armature weighed 87 grams. So a 500g real will do five or so.

 

The Nomex / Polyester Laminate (NPN2102), is just the right stuff for lining the slots and a 900 x 200 mm sheet will do dozens of armatures. You can probably cadge a bit from me. This is actually made by DuPont and is vastly superior to the original paper-based stuff.

 

And the clear varnish is brilliant stuff that runs in well, but sets quickly. It's a high-tech, high-voltage, potting compound from AEV. Aerospace material. Probably has quite a lot of uses on other electrical parts.

 

The cost per armature of wire, insulation and varnish is more or less insignificant if you do half a dozen or so.

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I just bought this for doing the field-coils. These have 700 turns and are often ropey. This is far too many to mess about with.

 

http://www.ebay.co.uk/itm/282054552715?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

 

And yes, this does look too good to be true! But then I just bought a fancy video camera for £50.

 

On the armatures every turn must be precision guided down the slot and the automatic machines have a lot of "bits" to do this. They must have needed quite a bit of set-up. Remember the slots are not in line with the shaft and the gap is only 1.5mm wide.

 

It takes about 15-20 minutes to do each armature coil. And there are TEN. It's pretty grueling work to do all ten in an afternoon because of the concentration required. An hour session or so and spread the job over a few days is a much better plan.

 

I use "winding-cheeks". These speed the job up, but create a risk that the wire gets in between the metal laminations and the slot insulator.

 

This demands constant vigilance. If you don't notice and carry on you'll need to unwind everything to get at the problem.

Edited by AlanT

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This will give you some idea of the machine process:

 

 

BUT

 

This is a big slot of constant width. The slots line with the shaft. A whole lot easier I would think.

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So how well can you do this by hand. Well the photos below show the second one I've done. The first one came out OK and ran properly. Indistinguishable from an original in fact.

 

I ran it for 8-hours at 16V. About half way through the motor stopped. I soon found that the original field-coil had developed a short-circuit. The factory crossed over the wires just below the brush-arms. One wire is bare and the other sleeved with old-fashioned woven tube. It was this old insulation that failed.

 

Here I have completed the first pair of coils:

 

34164476725_cfeb2e2a67_b.jpg

 

 

This shows the job with two-pairs of coils on and about to start the third pair. You can see the winding-cheeks. This are just cut from the same material as the slot insulation. They guide the wire into the very narrow slot. But because they are held by the slot-insulation there is a chance the wire will slip behind the insulation. You just have to be very vigilant about this.

 

34033733151_610d8275df_b.jpg

 

This is the completed job:

 

34164474625_6c92182d0c_b.jpg

 

The "finish" end on one coil must join the the "start" end on the next coil round. This is done by taking a loop around the end of the laminations so that the wire moves on to the next slot. You can just about see these end-loops.

 

33353290523_971f45f297_b.jpg

 

From the commutator end, if you compared this to a factory unit, you would notice that I have arranged the wire ends so that both "start" and "finish" lay on the outside of the coil. On a factory unit they burrow into the depths of the windings.

 

There is a bit of extra manipulation of the wire ends to make it like this. But the big advantage is that a wire break at the commutator can be easily repaired. If you try this on an original you will only have a few mm of wire to get hold of. This is the "traditional" way of finishing and makes no difference to the performance.

 

You can see that this one has had a short test-run from the carbon tracks on the commutator.

 

At present it's Ultimeg impregnation is drying out, before this one also gets its 16V torture.

Edited by AlanT

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Very nice work Al. Couldn't you leave the slot insulation proud, thus having integral winding cheeks, and trim them after finishing the winding?

 

Pete

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So how well can you do this by hand. Well the photos below show the second one I've done. The first one came out OK and ran properly. Indistinguishable from an original in fact.

 

I ran it for 8-hours at 16V. About half way through the motor stopped. I soon found that the original field-coil had developed a short-circuit. The factory crossed over the wires just below the brush-arms. One wire is bare and the other sleeved with old-fashioned woven tube. It was this old insulation that failed.

 

Here I have completed the first pair of coils:

 

34164476725_cfeb2e2a67_b.jpg

 

 

This shows the job with two-pairs of coils on and about to start the third pair. You can see the winding-cheeks. This are just cut from the same material as the slot insulation. They guide the wire into the very narrow slot. But because they are held by the slot-insulation there is a chance the wire will slip behind the insulation. You just have to be very vigilant about this.

 

34033733151_610d8275df_b.jpg

 

This is the completed job:

 

34164474625_6c92182d0c_b.jpg

 

The "finish" end on one coil must join the the "start" end on the next coil round. This is done by taking a loop around the end of the laminations so that the wire moves on to the next slot. You can just about see these end-loops.

 

33353290523_971f45f297_b.jpg

 

From the commutator end, if you compared this to a factory unit, you would notice that I have arranged the wire ends so that both "start" and "finish" lay on the outside of the coil. On a factory unit they burrow into the depths of the windings.

 

There is a bit of extra manipulation of the wire ends to make it like this. But the big advantage is that a wire break at the commutator can be easily repaired. If you try this on an original you will only have a few mm of wire to get hold of. This is the "traditional" way of finishing and makes no difference to the performance.

 

You can see that this one has had a short test-run from the carbon tracks on the commutator.

 

At present it's Ultimeg impregnation is drying out, before this one also gets its 16V torture.\

 

 

That is a site that takes me back to my youth.

I was told 500v megger is needed not 1000v to check insulation on low voltage stuff . - I have one on the shelf but never used it.

Do you bake the armature laquer? - That is a smell I recall.

Do you use one of these to arrange the windings in the slots?

 

 

 

 

Cheers

Peter W

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Your have more patience than I !

 

Just bought one of the coil winding machines above, I do occasionally wind coils, & this must be better than using a hand drill, & loosing count half way through !.

 

Ridiculous price.

 

Bob.

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I use wooden tools for moving the wires about. There is a photo of them early on, both associated with takeaway food!

 

The lacquer is Ultimeg 2000/372. This is air-drying, but it does take a few days. The motor will bake it out on the 16V torture run. But DO NOT do this until the lacquer really has set. I had a "near miss" by not doing this.

 

If I left the slot-insulation long and it's common to do this, it would be really hard to trim it back. Its a very tough polymer and whilst cutting from a sheet with scissors is easy, cutting flush with the top of the laminations wouldn't be.

 

It also might expand or move out a bit. There is almost no air-gap in these motors and armatures are always hitting the poles.

 

The cheeks also stop you get confused and dropping a wire in the wrong slot.

 

Doing work like this is probably not for a person with a full-time job. But I can easily find an hour or so a day, to do a bit. It's of no consequence if I finish this tomorrow or next week.

 

Doing my third this afternoon. Your fingers learn subtle little tricks and I've speeded up a bit.

 

For a while I worked on a factory production line. Electronic assembly. Almost everybody else was female and Indian. They were quick, having done it for years some of them. I used to race them. Sometimes I'd win. I look back on doing this as quite a pleasant experience. Stress free and fun.

 

Not long after I got a real job, at five times times the hourly rate. Not stress free and not really fun. Kind of DEADLY serious.

 

I ran a costing on those winding machines. I seems that in China you can make a 40-tooth straight cut cast-iron gear for 10p. In Europe a cast-iron blank for this would cost several pounds. Gear cutting is one of the slower machine operations, basically you go one tooth at a time.

 

Maybe some foolish Chinese estimated the world demand for such machines as many millions, which it isn't and now has to find homes for them.

Edited by AlanT

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Fancy re-winding this one then ?

 

post-12009-0-33780000-1492858397_thumb.jpg

 

Bob.

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Ha ha I`ve got one like that!

Stuart.

 

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Well at least there won't be many turns.

 

There would be the same problem I had with the wiper motor. How to get a commutator.

 

This is where I got mine. I think they do ship one off.

http://eurtonelectric.com/

 

Getting the copper might be a problem too.

 

I'd guess this is one where you make a wooden former and use it to knock the turn into shape.

Edited by AlanT

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No, this is one where you throw it in the bin, & buy a new one :D:D :D

Mine was off a ride on mower using a Honda V twin motor, I can only assume the key got stuck in crank mode after engine started.

 

Bob.

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Mine was from a cheapo so called Hi Torque starter, again in the bin and buy a proper one!

Stuart.

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Alan: Excellent exposition of the problems, pitfalls and solutions.

 

In the late '50s/early '60s, I owned an Austin 7 Special which had 6 volt electrics. The dynamo had a moveable 3rd brush which permitted the current output to be adjusted. If one were too greedy, the solder on the armature would melt and one had to dismantle and re-solder, which I did more than once!

 

At the time, I was an apprentice at Evershed & Vignoles in Acton Lane Chiswick, the manufacturers (amongst many other things) of the 500V and 1000V Meggers. Eversheds was not a large company (about 500 employees), but a world leader in electrical instrumentation and control systems, and it made almost everything in-house, recruited a large number of apprentices every year from the Chiswick/Acton area, and ensured that they were trained properly, obtained ONC and HNC qualifications, and even sponsored a small number of us to attend Brunel College, which at the time was located behind the Fire Station at the top end of Acton High Street. I feel very grateful for the opportunities which Eversheds gave me at the start of my career in engineering.

 

Ian Cornish

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Alan just bench tested my 2 speed motor and it's getting hot ,I've opened it up and can't see any black wire but the brushes look low but not sure if this can cause the problem,any ideas .

Regards

Nick

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I run them at 14V for four hours. They get too hot to pick up. Even at 12V they get pretty hot.

 

The fact is the wire gauge is about half what the book says for an industrial machine, continuous running without fan cooling. In other words Lucas pushed their luck a bit.

 

Measure the supply current in the 12V lead. On the bench this should be about 3A. Less on fast speed. If it is then you are OK at least for a while.

 

If its 4A or more then the bearings are tight, out of line or the armature is rubbing on the pole-piece or something.

 

The grease if original, will be pretty hard and not helping much. Strip, wash in Turps, relube refit. Often saves about 1A.

 

When you put it back it takes awhile for the self-aligning bearings to well self-align. Leave the end-cap a bit loose and get running. Gradually torque them up as the bearings settle. This can be a nuisance.

 

Check for about 10 thou end float on the armature.

Edited by AlanT

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