View Full Version : Rewinding Armature & Magnet Wire?

03-20-2007, 11:41 PM
Thanks to Darryl, I did some research on armature winding and mapped the coils on some automotive generator armatures. What I have is Simplex Wave Windings containing 21 coils of 9 1/2 turns in a 5 pitch and all CW wound. That was the easy part. When I looked around for magnet wire, I found there's a "Boat Load" of coatings. The coatings are what gives the temp ratings.

If the original was simply heavily enameled wire, do you see a problem using a modern double coat wire? Any suggestions for type of coating?

Here's one armature stripped to the skeleton.

A.K. Boomer
03-20-2007, 11:51 PM
as long as you can fit it all in, Double insulated may be more of a standard now but if something was built without it then the wire may be a little thinner, --- not a big deal but they all add up and it could make an already tight wind near imposible? just a guess on what i would worry about.

03-21-2007, 12:30 AM
Thanks AK but I don't think there will be a problem fitting it in. The original is c1919 enameled wire. It's like a heavy paint layer. (Think bell wire) :eek:

03-21-2007, 12:46 AM
Off hand, I don't know the difference between coatings, except as you say, temperature ratings. I would expect that any wire you could buy from a motor rewind shop would be entirely suitable.

At one time I ran across some wire which had a very low temperature rated insulation. I believe it was spec'd so that it could be soldered directly without having to strip the insulation. The heat from soldering did the job. http://img.photobucket.com/albums/v136/heinrich/magwirestripper1.jpg

This is a pic of an insulation stripper I made. Might be hard to tell from the pic, but the sharp edges that do the stripping (scraping, actually) are on the inside, towards the handle. This is just piano wire bent up and epoxied into an old plug case. I ground flats on the piano wire so there's a sharp, square edge where it needs to be. Just slip the end of the wire into the gap, press the wires together, and pull. Repeat as you go around the wire until bare copper shows all around.

You can cut the wires short and still use this tool, and it works on any gauge wire. I'm sure there's something niftier out there now, like maybe insert wire end, rotate tool, done- but I haven't seen one, nor looked for one. I've seen a pro motor rewinder using a jacknife to strip wires- whatever.

As far as the insulation increasing the size of the wire, I don't think that would be a problem. Choosing a gauge which allows the number of turns needed, and large enough to fill the slots- if you went one size larger or smaller, that's a much larger difference in wire diameter than the different thickness of insulation would account for. Sometimes you have to go smaller diameter just for the sake of being able to put the wire on. Good luck, Ken, getting that armature rewound.

03-21-2007, 09:16 AM

MW-16 magnet wire is polyimide coated and has the highest thermal stability. Next in line would be MW-35 which is an amide-imide coated wire. There are 2 other coatings with less thermal stability which I can't remember the numbers off the top of my head. If you need I can probably find those numbers.

For as much wire as you need the mw-35 would probably suffice, it seemed to be the workhorse for the industry. I would also use the heavy build wire.


03-21-2007, 10:22 AM
Back in the day I worked at a company that rebuilt, power distrubtion transformers. The guy was so cheap, he had firuged out that he could rewind any transformer with just six sizes of wire. And something similar for the rectangual wire we used. He had a thousand plus patents for that type product and test equipment.He would figure out the conversion factor for substition of the dia and turns ratio's ect. This was BC before computer adding machine and some kind of very large mechcanical calculating machine. The problem would be he wouldn't take in to account the differnce in the finished size of the windings when on the core. And that they wouldn't fit in the cans. I know there are a lot of them that went out with more fish paper and cardboard between the windings and can for the insulation factor.Then when they came in.The few motors we did always seemed to have the extra space from the windings and the top of the armature.
Good luck, and don't forget the cardstock in the grooves before you start winding the coils.:D

03-21-2007, 09:41 PM
Thanks guys. I've got some left over wire from a spool I got from a motor shop. It's the right gauge and triple coated but the rating is no longer visible. I was thinking it was double coated but located the spool today. The problem is that it's still much thinner than the original coating. I'll have to get on it tomorrow--Had to tractor all day today.

Good luck, and don't forget the cardstock in the grooves before you start winding the coils.:D

LOL... Yeah, it looks like that's what deteriorated and shorted a couple of coils. As I pulled the old wire out, I kept checking for the ground I had and found two coils that came clear after pulling them away from the slots. The paper in the slots just fell out in flaky pieces. I doubt it was fish paper. More like onion paper. :D

Again, thanks.