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Thread: Welding Positioner help.

  1. #31
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    I've seen lots of them using a commercially available roto-ground, Tweco among others make them.

    Have also seen some with the spring loaded copper ground strap and a section of copper tubing soldered to the shaft.



    One has to remember that the actual run time is not going to be hundreds of hours per month, probably closer to minutes per month of actual arc on time.
    Electrical current should not have to go through the bearings if the path is well laid out, only though the shaft and the chuck. If the chuck is tight when welding no arcing should occur there.

    This spring loaded copper grounding lug looks easy enough to fabricate.


    Home, down in the valley behind the Red Angus
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  2. #32
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    Here's a picture of the brush block I built for my positioner at work.Just a Micarta block drilled for some 1/2 holes and a few attachment plates screwed on.


    The brushes are just 1/2" 932 Bronze with the ends turned down and threaded for 5/16-18 nuts.


    I think I have more in the copper cable lugs than I do the rest of it.This will handle 250 amps continuously and has been in service for about 8 or 10 years running 100 or so hours a year.So far no wear on the brushes.
    I just need one more tool,just one!

  3. #33
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    Quote Originally Posted by nickel-city-fab View Post
    Most shops I've ever used a positioner in, either bolt the ground directly onto the work (preferred) or use a strap against the shaft. Some guys have rotary ground clamps, they even have magnetic ones. Remember the juice will always take the easier path, so its not necessary to *completely* isolate the bearings, all you have to do is give the electricity a more attractive alternative. Quick dirty and cheap but effective: flatten out some copper pipe and bend it into a hook. bolt your ground onto the straight end, and just hook it over the work and let it hang there. Its not going to move fast enough to tangle.
    What? Electricity will take all paths available! That's why parallel resistance works.

    The braided strap should last a long time. While the strands are zinc plated, there are many and zinc is a natural lube.

  4. #34
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    Quote Originally Posted by CCWKen View Post
    What? Electricity will take all paths available! That's why parallel resistance works.

    The braided strap should last a long time. While the strands are zinc plated, there are many and zinc is a natural lube.
    OK, the *bulk* of the current will go thru the path of least resistance, all other paths in proportion. Happy now? And usually this is the shortest physical path to the ground cable. If your ground is on the shaft, I see no reason why any of it should be going thru any bearings.

  5. #35
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    Quote Originally Posted by nickel-city-fab View Post
    OK, the *bulk* of the current will go thru the path of least resistance, all other paths in proportion. Happy now? And usually this is the shortest physical path to the ground cable. If your ground is on the shaft, I see no reason why any of it should be going thru any bearings.
    Exactly.
    No different than a bird sitting on a high voltage wire. He may be "energized" but until he is part of a completed circuit no harm will come to him.
    Home, down in the valley behind the Red Angus
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  6. #36
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    Quote Originally Posted by wierdscience View Post
    Here's a picture of the brush block I built for my positioner at work.Just a Micarta block drilled for some 1/2 holes and a few attachment plates screwed on.


    The brushes are just 1/2" 932 Bronze with the ends turned down and threaded for 5/16-18 nuts.


    I think I have more in the copper cable lugs than I do the rest of it.This will handle 250 amps continuously and has been in service for about 8 or 10 years running 100 or so hours a year.So far no wear on the brushes.
    That is one skookum little unit, looks more than ample for the task.
    Nice!

    Have to ask, why the duplex chain?
    Home, down in the valley behind the Red Angus
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  7. #37
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    Quote Originally Posted by darryl View Post
    contacts can run on that. Of course the piece of copper pipe would be bonded to the shaft in several places, or maybe just compressed into place using hose clamps. And the more contact points you have the better.
    Kinda what I am leaning towards. Copper pipe press fit to steel then copper fine strand cable running on it. Copper on copper. Thanks. JR
    My old yahoo group. Bridgeport Mill Group

    https://groups.yahoo.com/neo/groups/...port_mill/info

  8. #38
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    The only thing I'm wondering about the copper on copper rubbing like that is the friction between the two pieces both being the same material, also sticking and wear.

    Maybe copper braid to steel shaft is the better bet.

    JL................

  9. #39
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    Quote Originally Posted by Willy View Post

    Have to ask, why the duplex chain?
    Since there is only a single sprocket driving the duplex chain I'd guess it's a matter of using what is on hand.

    Mike

  10. #40
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    Quote Originally Posted by MikeL46 View Post
    Since there is only a single sprocket driving the duplex chain I'd guess it's a matter of using what is on hand.

    Mike
    That's what I was thinking as well.
    Just didn't look like the second set of rollers had very much for debris on them. Perhaps the drive sprocket is is duplex as well.
    Not important as long as it does the job and you're utilizing what's on hand.
    Home, down in the valley behind the Red Angus
    Bad Decisions Make Good Stories

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