What does the Stab Reactor do on a Miller Bobcat?
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  1. #1
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    Default What does the Stab Reactor do on a Miller Bobcat?

    My son recently purchased a Bobcat that appears to have spent its life on a service truck without actually being used very often. The welder seems to work well now that he has replaced the rheostat and a selector switch, but the stab reactor looks like it was sitting in water for a long time, has some rust on it and some of it's plates are disintegrating.

    What exactly does the stab reactor do and is there any way to pot it or strap it back together so that it doesn't shake itself apart any more while it is riding down the road or bouncing across a field on a farm truck?

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    The stabilizer is an inductor that is used to control how fast the welding current can change. The inductance value is selected to reduce splatter while welding. You have a combination constant current (stick) /constant voltage (mig) welder. The inductor may have multiple taps to provide the best welding characteristics for either mode of welding. A higher inductance is required to produce a longer duration arc during the short circuit process.

    The easiest way to pot the inductor is to place it in a very heavy plastic bag. The bagged inductor is then placed in a box of sand. The sand is used to push the plastic bag against the walls of the inductor. A very low viscosity epoxy is then poured into the bag. The trapped air is then removed with a vacuum pump and the top of the bag is tied off. After a initial set of the epoxy, the potted inductor is baked out at the recommended temperature. This can be done by running a low current through the coil.

    Another approach is to wrap the inductor in a number of layers of stretch wrap leaving the top open to form the outer mold The wrapped inductor is placed in a tank such as a old pressure cooker, the epoxy is poured into the improvised mold, and then,as the last step, the air in the tank is vacuumed out.

    A $15.00 hand operated brake line purge vacuum pump will do the job.

    The success of the potting process depends on a good cleaning and drying of the inductor before pouring the epoxy. Otherwise there may be hot spots in the coils during use.

    An alternative is to simply pour a more viscous epoxy onto the coils. It will not aid in heat transfer but it will keep the coils insulated and prevent vibration. There is a much older product called Gyptal that was used for the same purpose. If you would like to know more about the epoxys that are available, you will need to ask the question in the General forum with the title "Epoxy for potting coil windings".
    Last edited by Robert R; 10-26-2019 at 06:03 PM.

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    Quote Originally Posted by Robert R View Post
    The stabilizer is an inductor that is used to control how fast the welding current can change. The inductance value is selected to reduce splatter while welding. You have a combination constant current (stick) /constant voltage (mig) welder. The inductor may have multiple taps to provide the best welding characteristics for either mode of welding. A higher inductance is required to produce a longer duration arc during the short circuit process.

    The easiest way to pot the inductor is to place it in a very heavy plastic bag. The bagged inductor is then placed in a box of sand. The sand is used to push the plastic bag against the walls of the inductor. A very low viscosity epoxy is then poured into the bag. The trapped air is then removed with a vacuum pump and the top of the bag is tied off. After a initial set of the epoxy, the potted inductor is baked out at the recommended temperature. This can be done by running a low current through the coil.

    Another approach is to wrap the inductor in a number of layers of stretch wrap leaving the top open to form the outer mold The wrapped inductor is placed in a tank such as a old pressure cooker, the epoxy is poured into the improvised mold, and then,as the last step, the air in the tank is vacuumed out.

    A $15.00 hand operated brake line purge vacuum pump will do the job.

    The success of the potting process depends on a good cleaning and drying of the inductor before pouring the epoxy. Otherwise there may be hot spots in the coils during use.

    An alternative is to simply pour a more viscous epoxy onto the coils. It will not aid in heat transfer but it will keep the coils insulated and prevent vibration. There is a much older product called Gyptal that was used for the same purpose. If you would like to know more about the epoxys that are available, you will need to ask the question in the General forum with the title "Epoxy for potting coil windings".
    ...or you could just take it to a motor shop for a proper bake and VPI using the proper varnish (an epoxy version these days) and proper procedures.

    or play at home and maybe it will work...or maybe not....

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    Quote Originally Posted by digger doug View Post

    or play at home and maybe it will work...or maybe not....
    A challenge where visible rust is in evidence is whether, and how much more is out-of-sight between lamination layers.

    Red Glyptal works as well as ever. When there is no vacuum handy, it is meant to be diluted with Xylol, used in multiple thin applications so it "wicks" into voids. Last application can then go on undiluted.

    Not perfect, but proven "close enough" for one Helluva long span of years, GE lab invention of it to present-day independent company, it "JFW".

    If nothing else, it often takes higher heat and stays impervious to change longer than epoxies that are as affordable or well-proven.

    Which Glyptal ALSO make, BTW. Read the specs.

    Glyptal Inc.

    Lazy, Iyam, so I just keep a quart of 1201 Red handy:

    Glyptal 1201 Paint - The Eastwood Company

    Tough stuff. Very! Electrical uses aren't even barely the half of what it is good at. Think abuse-resistant inside coating of gearcases, crankcases, sumps, so it finds a use, not waste. And I can go worry about more interesting trivia.

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    Quote Originally Posted by thermite View Post
    A challenge where visible rust is in evidence is whether, and how much more is out-of-sight between lamination layers.

    Red Glyptal works as well as ever. When there is no vacuum handy, it is meant to be diluted with Xylol, used in multiple thin applications so it "wicks" into voids. Last application can then go on undiluted.

    Not perfect, but proven "close enough" for one Helluva long span of years, GE lab invention of it to present-day independent company, it "JFW".

    If nothing else, it often takes higher heat and stays impervious to change longer than epoxies that are as affordable or well-proven.

    Which Glyptal ALSO make, BTW. Read the specs.

    Glyptal Inc.

    Lazy, Iyam, so I just keep a quart of 1201 Red handy:

    Glyptal 1201 Paint - The Eastwood Company

    Tough stuff. Very! Electrical uses aren't even barely the half of what it is good at. Think abuse-resistant inside coating of gearcases, crankcases, sumps, so it finds a use, not waste. And I can go worry about more interesting trivia.
    1. it's a good deal of work to remove and re-install this piece.
    2. It's called upon to work, and needs to work always.
    3. It's got a rusting problem (as you described nicely above) and the OP is trying to
    "Save" it.
    3. "Glyptal" and most off the shelf epoxies are not thin enough to get into the laminations.
    Even in a VPI operation. If'n you thin glyptal, that thinner has to evaporate off, and the remaining material shrinks.

    Deffer to a professional if you want this to actually have a chance of succeeding.
    Any imperfection, anywhere, will result in a short to ground and immediate destruction of your reactor.

    I noted your location, and found a motor shop in weedsport that may be able to doo the work.

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    Quote Originally Posted by digger doug View Post
    3. "Glyptal" and most off the shelf epoxies are not thin enough to get into the laminations.
    Even in a VPI operation. If'n you thin glyptal, that thinner has to evaporate off, and the remaining material shrinks.

    Deffer to a professional if you want this to actually have a chance of succeeding.
    Glyptal is actually an Alkyd resin family critter. Sort of a specially "optimized" one, actually. Not an epoxy.

    So.. choices. Admit to being cornfused ever' since I put in that second toilet-paper roll holder...

    How about just do the best you can yerself with what works if you want to have a chance of sumthin' actually useful you can AFFORD to mess wit at all?

    Reckon if 1201 red Glyptal works as long as it has, as everywhere as it has, it might still work about as well as it always has?

    Kinda redneck'ish? So long as it is an improvement, what's not to like?

    Now.. perfection.. ever heard of "Ward-Leonard?"

    You happen to have the coin they charge for building motors for use in submarines and offshore oil rigs?

    You'd not be salvaging an old welder. Your BUTLER would be sending your private jet to fly in hired Angels to weld the crack of dawn. Just because you could!

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    Many thanks to everyone who replied to this thread.


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