Rewinding a motor stator

it

running

was

ammeter

former

cord

the

found a useful table in a 70 year old book. Wire qauges one way and columns of wires per sq in packing, weight per 100 yards and ohms per 1000 yds. So the former dimensions are determined

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

That's pretty cool, I've toyed with the idea of rewinding a motor like that just for fun but never actually done it.

give

that

the

voltage

100

that

Making up a former was easier than I thought. The first thing to lay down is some loose loops of lacing cord, about 8 loops diametrically , 45 apart, around the former before winding the turns, then cutting the cord into indivuidual loops and tying off after wire winding and before removing. So the exact shape of the bulking of the wires into a hank does not matter that much as the tying-off of the lacing cords while still on the mandrel would form the cross-secion of the hank into a circle. I will do the winding today. If it should be wrong in demensions , then I've a large drum of 29 SWG wire to have plenty of other attempts. As always the winding on a coil winder takes no time at all, its the preparation thats time consuming

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

(via email response) For anyone else too embarrassed to ask on-thread why I use left hand drill bits. This week an amp, as received from a well respected UK maker, had a knob effectively seized on. The owner had never touched them. The grub-screws were brass and overtightened so one nib of the

2 nibs, making a screwdriver blade slot, had broken off at assembly.

Tip To free seized equipment knobs For the situation where the knobs are seized onto the shaft by rusted grub screws,especially where the screw penetrates the shaft; after you have butchered the grub screw slot try this. Make up some guide tubes,small enough to just slide into the hole in the knob containing the grub screw,these tubes drilled on a lathe with a clearance bore to take a drill bit. This drill bit usually needs to be extended by brazing onto a longish rod (so the chuck of the drill misses the face of the equipment). Use some cutting oil and drill into the grub screw. Ideally use left hand drill bits and left-handed power drill rotation, such drill bits are available from specialist suppliers , other suppliers may kook at you as though you're trying to wind them up (anti-clockwise). To convert a right hand drill bit well enough for this use grind the cutting face back on the opposite rake angle, swarf clearance is not relevant here. Often the bite into the drill bit into the screw or the localised vibration or heating is enough to shift the screw. Now use a small "easi out"(maybe this is a UK trade name),but consist of a coarse left-handed cutting thread on a coarse taper. Wind into the hole in the grub screw and hopefully extract. If this fails repeat the first procedure with larger diameter drill bits until nothing remains of the grub screw,retap a larger hole and use a larger grub screw for knob reuse.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

I thought that ovalling the axial parts to squash in the slots in the motor core would be a problem but all went fine, though 7mm diameter when squashed to a circle, rather than original about 6mm. The hank resistance of 7.1 ohm compared to 7 ohm was good. I could not decide if the original was 29 or 30 swg but looks as though it was nearer 30 swg. A rifenement is to lay a dowel or rod axial and outside the core to tie the hank back to while pushing the axial sections into the core slots. The overall circumference was too long so the ends of the hank overhanged at the open ends too much. I will recalculate for 30 swg and have another go. There was space in the housing to try out my effort so did have a go assembling and running without lacquering in, and it worked fine.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Out of curiosity, how much time have you spent reviving your $10US drill? :)

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Snipped account of rewinding stator.

Ohhh - that`s not the point.. We Bwitish will spend forever trying to keep our old tat working. It`s a national pastime :)

Ron(UK)

motor

squashed

ohm

30

the

the

There

assembling

:)

is

in the

A change is as good as a rest. I wouldn't take on someone elses motor of any sort to repair. I like to have an excuse to dig out my old coil winding machine that I brought back to working order from a seized rusted mess combined with mice nest that was in a leaky shed for decades. I originally thought the hank lay up would have to be over a 2 part former like a pulley split in two, the awkward way, but with a semicircular laying up section. Then having to manually lay-up (as the auto traverse flip is only per item , not per layer) something like 3 turns,6,9,12,14,16,17,18 and down again to 3 for 190 turns. But I know now that a complicated former and intricate lay-up is totally unnecessary.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

That explains a great deal right there. Otherwise, motor rewinding is a difficult and obscure art, at least for most of us. I've been building electromagnets for demonstrations at the science museum, and it doesn't take long for even the simplest coil to turn into a mighty mess if you're not careful.

I have a vacuum pump that's essentially integral with its squirrel- cage induction motor, and the stator overheats. The fellow at the motor shop gave me some insane estimate of several hundred bucks to rewind the thing; I'm ready to try it myself.

M Kinsler

That will likely not be fun, winding machine or not!

How badly/quickly does it overheat?

I assume you're sure it's set for the correct line voltage, if that's changeable.

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mice

If you can run it on reduced voltage with monitor lines added or probes to the stators then the bad one will be substantially lower volts than the other one. The hot coil may well be the ok one, being forced to take more current along with the armature, i didn't think to check that and too late now.

My second hank was too small and the third attempt was Goldilocks. Waiting for the lacquer to harden and will reassemble tomorrow. I will write it up with data , dimensions, handy hints discovered along the way and a few pics and add it to

probably tomorrow. It should give some idea of the dimensions for a similar sized motor.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

It's not just you guys, I've done the same sort of thing on occasion. It's not so much because it makes practical or economic sense as it is just because it can be done.

You know, I borrowed a vacuum pump the first time I did some A/C work but I later found I could buy new surplus rotary compressors designed for window AC units for $5-$8 and they pull a stronger vacuum than the real vacuum pump I had! Pegs the mechanical guage all the way down to 30 in/hg which is plenty lots of things and the price is hard to beat.

About 3/4 down this file

title Stanley Bridges ? drill repair

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on