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Stator fried, what to use for insulation?

  1. Mar 25, 2012 #1
    Ok guys I have a stator/alternator on one of my motors, and the thing finally gave out on me. You can tell where the wire got hot and burnt through the insulation. I have heard that you can use thinned down JB weld as a good insulator. How important is it that the insulation be the same resistance value as it is factory? Would a variance change the amperage sent back from the charging system? Thanks guys!
    With wire
    Fried insulation
  2. jcsd
  3. Mar 25, 2012 #2

    jim hardy

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    What's important is to get the shorted wires separated if only by a thousandth or two.
    If they didnt spot weld together you can probably fix it. If you can pry apart any spotwelds you can fix it. What's deadly is one you can't reach.

    My dishasher motor did same thing last summer. The entire start winding turned black.
    The fault where the wires had spot-welded was visible, thank goodness for it's a $220 motor !

    I poked the wires apart with an orange-stick from wife's manicure kit then soldered one back together where it had burnt in two.
    Next I saturatated the windings with polyurethane varnish because it's nice and thin and will run down into the crevices between conductors. I massaged the windings to encourage wires to separate. After varnish dried i re-laced the winding with nylon twine..
    Still running quiet and smooth , no more burnt motor smell. (knock wood)

    I've never thinned JB weld. For your application it sounds like overkill .
    I'd say use plenty of paint or varnish..
    The electromagnetic forces act on the conductors themselves so you want both mechanical support against faint vibrations and electrical insulation.

    Not very. Dont worry about resistance of varnish at this low voltage.
    To put it in practical terms, all you need is 'quite a bit'...
    Last edited: Mar 25, 2012
  4. Mar 25, 2012 #3
    Thanks for the reply Jim. The wire has already been removed, and now I have a fresh roll of laminated magnet wire. The plastic that kept the wire apart from the armature is what I want to replace. Are you thinking a layer of high temp metal paint or varnish around the armature? I have had some suggest, that since I have high temp insulated magnet wire, to simply wrap the armature with the fresh wire and call it a day. What would you do??
  5. Mar 25, 2012 #4

    jim hardy

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    I've had trouble with the sharp corners of an armature getting through the varnish and shorting a brand new winding.

    I'd cover the armature with something to make a softer bed for your new windings.. Scotch 27 is a stout fiberglass electrical tape that'd be good.

    Alternative is wind each coil on a wood form just slightly bigger than armature, then slip it over the armature and bed it in your JB weld.

    I didnt realize yu were going to re-wind. But that's good - keep us posted !
  6. Mar 25, 2012 #5

    jim hardy

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    Photo looks like they wound their coils on nylon forms. Can you salvage those?
  7. Mar 25, 2012 #6
    They sure did Jim. Some of the nylon forms are burnt all the way through. That is why I was thinking of just wrapping some insulating tape around them and then the wire. I just dont want to alter the properties of the stator.
  8. Mar 25, 2012 #7
  9. Mar 25, 2012 #8

    jim hardy

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    I've never use Kapton but specs look good.

    Grainger carries both
    http://www.grainger.com/Grainger/SCOTCH-White-Electric-Tape-2A457 [Broken]

    and they've got a closeout on 1 mil Kapton, ~2/3 off makes it comparable to the 27.
    But it's not self-stick . The others are

    http://www.grainger.com/Grainger/wwg/search.shtml?searchQuery=kapton+tape&op=search&Ntt=kapton+tape&N=0&sst=subset [Broken]
    Last edited by a moderator: May 5, 2017
  10. Mar 26, 2012 #9
    Gotcha but should I just stick it to the old nylon caps or straight to the metal?
    Last edited by a moderator: May 5, 2017
  11. Mar 26, 2012 #10

    jim hardy

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    I'd wind the wire right over whatever nylon bobbins are still in good shape.

    Where they're destroyed try to make something from your tape that serves the same function, protecting your wire from the iron corners.

    After it's wound check with ohmmeter to verify it's not shorted to metal armature, then soak all the windings good with varnish so the wires dont vibrate against one another.. (that'd abrade the factory varnish which is probably Formvar, a tough varnish for magnet wire insulation )

    It's more of a mechanical matter than electrical.
    Objective is to get the wire in place treating its thin insulation as gently as possible, then secure it.

    old jim
  12. Mar 26, 2012 #11
    Cool great info! So the plastic/nylon is more of a mechanical protection, that makes sense. Now what type of varnish do you recommend? Could it be something that I could buy from Lowe's?
  13. Mar 26, 2012 #12

    jim hardy

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    On my dishwasher motor i used some polyurethane furnitiure varnish i had laying around. I think it was Minwax brand.

    The best stuff i know of is "Glyptal" but it's industrial priced.

    Grainger sells an insulating varnish. I've never used it but saw it mentioned on a car forum someplace. They liked it.

    http://www.grainger.com/Grainger/SPRAYON-Insulating-Varnish-1D276?Pid=search [Broken]

    Where does this thing go? You might consider getting a can of hot-rod high temperature engine enamel.
    Last edited by a moderator: May 5, 2017
  14. Mar 26, 2012 #13
    It goes on my 1967 65hp Mercury Outboard.:cool:
  15. Mar 27, 2012 #14

    jim hardy

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    Ahh i love vintage outboards. But i'm an Evinrude guy. Have a 56 Fleetwin 7.5 and a coiuple old 10hp projects.. am getting good at adapting modern fuel pumps to those old dual-hose pressurized tank style motors so you can use new tanks.

    Under flywheel where your stator lives shouldn't be terribly hot. I was worried it was in motorcycle primary chaincase or something.
    Was that motor ever overheated ?

    Are a couple of the coils made from much smaller wire, for the ignition ?

    Lastly, you know to pay great attention to direction coils are wound.
  16. Mar 27, 2012 #15
    I am an OMC guy as well. This is the only Merc that I own, and the motor with the most issues. :) Motor never overheated as far as I can tell. Not sure about ignition coil, cause the insulation is in tact. I will be very careful as I have taken many pictures and counted the windings. Here are some of my babies...... P2090927.jpg P2090929.jpg P2090931.jpg P2090932.jpg
  17. Mar 27, 2012 #16


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    I should send you my 6hp Evinrude to upgrade. :biggrin:
  18. Mar 27, 2012 #17

    jim hardy

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    Clearly off topic
    but you run across bargains in fifties-vintage motors because of the pressure tank issue.

    Make a mountng bracket for modern pump. Drill it and partway through and install a tube to connect to actuating pressure port, the hole in center.
    Underneath reed valve cover remove ONE of the poppets that feeds the old pressure port and block the other. I use a piece of gasket paper.
    Old pressure port is now the pulsating pressure you need to operate modern fuel pump.

    I mount the bracket to rear housing support where it's out of the way. Most recent conversion was a friend's '55 Johnson 5. Used 3/8 aluminum plate for bracket.

    Those old 'rudes have the intake silencer and are quietest smoothest longest-lasting outboards ever built. Sailboat guys crave them for auxilliaries. I see your 6 is longshaft...

    One of my 15's has alternator and electric start.

    Thanks for sharing your 'family photos' .
    I hope this digression isn't too off-topic.
    To waste human effort is a sin IMHO and i hate to see these wonderful joy-giving machines sent to the scrap heap.
    Maybe this will help somebody get one running again. Great learning project for a teenager.
  19. Mar 28, 2012 #18
    All topics are on topic as far as I'm concerned. That little 4hp longshaft is running like a sewing machine!! I cleaned all the water passages, new gaskets, ignition system, carb, fuel pump, and water pump. Sooooooooo reliable!!!
  20. Apr 2, 2012 #19
    Okay Jim, I finally got my scotch 27 in, and re-wired the stator. Now keep a few things in mind. What I did was keep the nylon because I felt like it held the wires on tight, and I just wrapped them with scotch 27. See photos. Also, when I rewound the coils, I got them as tight as I could, but the wires didnt wrap as neat tight as they did from the factory. How important is this? I have plenty more wire if I need to just bite the bullet and rewind it. I made sure to count the wraps, and follow the wrap pattern. Thanks for your input and support!!
  21. Apr 3, 2012 #20

    jim hardy

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    That looks to me like an excellent job.

    Tightness of wraps will not make much electrical difference at all.
    Biggest reason for tight wrap is to keep wires from vibrating against each other and wearing through their varnish insulation. This is what - a ten amp alternator? Not very much force on them. I believe you'll be fine.

    Check it with ohm-meter to make sure nothing's shorted to metal
    then try it out .

    Nice looking work !
    Perhaps apply a little 5 minute epoxy or even spray varnish over ends of tape so they dont fray or separate?

    old jim
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