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Thread: Welding Positioner help.

  1. #41
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    Quote Originally Posted by Willy View Post
    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.
    LMAO ...Way different! How do you suppose your house or shop lights work? Are you saying you can turn only one light on at a time?

  2. #42
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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.
    "Shortest" is a bit misleading. It really the ratio of resistance of the paths, and can be represented as resistor in parallel with the source with intermediate series resistors in the paths. The trick is simply to prove a very low impedance ("resistance") path before the path that will be damaged. The braid is typically several hundred times ( or more ) less then the bearing path.

    If it was for example 100X lower, at 100 amps roughly 1 amp would flow through bearings for every 100 amps though the braid.

  3. #43
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    Quote Originally Posted by CCWKen View Post
    LMAO ...Way different! How do you suppose your house or shop lights work? Are you saying you can turn only one light on at a time?
    Thru a completed circuit.

    Sending current thru a shaft held by bearings would in no way affect the bearing unless the path of the current flow had to traverse the those bearings. It does not have to as the electrical circuit consists only of the current passing from the grounding point on the shaft, then to the work piece, the arc from the welding power source, and finally back thru the welder and it's power source.
    There is no electrical potential between the bearings inner race and outer race. All of the commercial welding postioners that I've seen at least are designed to route current around bearings not thru them in order to prevent damage to those bearings. No need to do otherwise.

    Why would a bearing be damaged if no current passes thru it? Hey I'm open to learning something new if you can show me the error of my thinking.
    Home, down in the valley behind the Red Angus
    Bad Decisions Make Good Stories

  4. #44
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    Quote Originally Posted by Willy View Post
    That is one skookum little unit, looks more than ample for the task.
    Nice!

    Have to ask, why the duplex chain?
    The double chain is part of the "work with the junk I had" drive system.The double chain is looped together around two sprockets and allows the sprockets to act like "gears".The gear motor can be slid over to one gear or the other,or put in neutral by sliding it so neither sprocket catches.This gave me a final ratio of either 4:1 or 2:1.The gear motor has a jack shaft arrangement as well and can be changed from a 1:1 to a 1:2 or a 2:1 as need be,then the gear motor itself is a 60:1 90vdc with a VS/fwd/rev control. I did this because I needed a welding speed range of 0-12 rpm and a polishing/buffing speed range of 12-30 rpm.Some of the stuff I make on this "welding lathe" includes stainless steel augers that must have the welds buffed out and polished before I send them out for electro-polishing(food grade stuff).
    The sprocket at the end of the shaft,the one just below it and another to the right just out of view,are all the same tooth count so the lead screw( shaft below the spindle) and the PTO shaft (shaft out of view) are all driven 1:1 from the spindle.The lead screw is there for shaft build ups and weld overlays.It's a 1"-5 pitch acme thread that drives a carriage via a half nut and allows wrapping the item being built up with a near perfect overlapped weld bead,automatically.

    The PTO shaft is there for cutting pipe and tubing.Let's say I want to cut 90* saddles on 50 pieces of 2-1/2: sch 40 steel pipe.I take a 3" long piece of pipe,cut a saddle cope on it to make it into a cam,clean it up nice and smooth and chuck it in a small three jaw chuck that's mounted on the front end of the PTO shaft.The carriage has a spring loaded plunger that follows the cam and makes the carriage follow the motion of the cam.With a plasma cutter torch mounted on the carriage and the plasma trigger wired through the foot switch on the welding lathe.I can chuck a piece of pipe to a preset stop,step on the foot switch and automatically have it cut a perfect saddle cope in about as much time as it takes to chuck and un-chuck the pipe.Because I can adjust the speed and nozzle standoff the cuts finish up with little or no dross.

    This is the Mark IV version,I plan on doing a full write up on it and maybe a video or two when I get the Mark V version built.

    I just need one more tool,just one!

  5. #45
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    An easy solution to the bearing issue is to use ceramic balls, or if you really concerned, full ceramic bearings. Not even expensive.

  6. #46
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    Quote Originally Posted by wierdscience View Post
    The double chain is part of the "work with the junk I had" drive system.The double chain is looped together around two sprockets and allows the sprockets to act like "gears".The gear motor can be slid over to one gear or the other,or put in neutral by sliding it so neither sprocket catches.This gave me a final ratio of either 4:1 or 2:1.The gear motor has a jack shaft arrangement as well and can be changed from a 1:1 to a 1:2 or a 2:1 as need be,then the gear motor itself is a 60:1 90vdc with a VS/fwd/rev control. I did this because I needed a welding speed range of 0-12 rpm and a polishing/buffing speed range of 12-30 rpm.Some of the stuff I make on this "welding lathe" includes stainless steel augers that must have the welds buffed out and polished before I send them out for electro-polishing(food grade stuff).
    The sprocket at the end of the shaft,the one just below it and another to the right just out of view,are all the same tooth count so the lead screw( shaft below the spindle) and the PTO shaft (shaft out of view) are all driven 1:1 from the spindle.The lead screw is there for shaft build ups and weld overlays.It's a 1"-5 pitch acme thread that drives a carriage via a half nut and allows wrapping the item being built up with a near perfect overlapped weld bead,automatically.

    The PTO shaft is there for cutting pipe and tubing.Let's say I want to cut 90* saddles on 50 pieces of 2-1/2: sch 40 steel pipe.I take a 3" long piece of pipe,cut a saddle cope on it to make it into a cam,clean it up nice and smooth and chuck it in a small three jaw chuck that's mounted on the front end of the PTO shaft.The carriage has a spring loaded plunger that follows the cam and makes the carriage follow the motion of the cam.With a plasma cutter torch mounted on the carriage and the plasma trigger wired through the foot switch on the welding lathe.I can chuck a piece of pipe to a preset stop,step on the foot switch and automatically have it cut a perfect saddle cope in about as much time as it takes to chuck and un-chuck the pipe.Because I can adjust the speed and nozzle standoff the cuts finish up with little or no dross.

    This is the Mark IV version,I plan on doing a full write up on it and maybe a video or two when I get the Mark V version built.
    I'm impressed, very ingenious project. I see you've put a lot of thought into the layout and extra capability potential of this piece of equipment.
    I just knew there was more to this than just re-purposing what was at hand when I saw the lack of debris on the other side of the chain in your second photo showing the bronze brush.

    You crafty devil, good thinking!

    You'll have to tart it up and dust it off a bit for the video and write up.
    We'll be looking forward to it when you do the "feature".
    Home, down in the valley behind the Red Angus
    Bad Decisions Make Good Stories

  7. #47
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    Quote Originally Posted by lakeside53 View Post
    An easy solution to the bearing issue is to use ceramic balls, or if you really concerned, full ceramic bearings. Not even expensive.
    What am I missing here? Seriously.

    Where does the current flow to when traversing the bearing from the shaft thru the bearing balls and to the outer race in let's say a pillow block bearing for example.
    I can appreciate there being a voltage present but where is the current? What resistive element or load is present in order to draw amperage and current across the bearing in order to potentially damage it?
    Home, down in the valley behind the Red Angus
    Bad Decisions Make Good Stories

  8. #48
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    Quote Originally Posted by JRouche View Post
    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
    I think that possible galvanic corrosion of steel under the copper bushing may cause more problems than strap sliding on the shaft directly.

  9. #49
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    May 2011
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    N.E. Arizona
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    Hi Everyone,

    Well, I'm still above ground but way too busy to get back here...........until now!

    This was my solution to a 'brush' on the spindle to bypass the bearings:



    It has been working very well w/no arc pitting. I did isolate the brush using some flanged nylon bushings for the mounting screws.

    The entire build is here:

    http://bbs.homeshopmachinist.net/thr...ding-turntable
    Best wishes to ya’ll.

    Sincerely,

    Jim

    "To invent you need a good imagination and a pile of junk" - Thomas Edison

    "I've always wanted to get a job as a procrastinator but I keep putting off going out to find one so I guess I'll never realize my life's dream. Frustrating!" - Me

  10. #50
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    Aug 2004
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    Sunny So Cal
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    Quote Originally Posted by MichaelP View Post
    I think that possible galvanic corrosion of steel under the copper bushing may cause more problems than strap sliding on the shaft directly.
    Even with a strong tight fit? And what about the sliding resistance from copper on copper Joe talked about. Does seem like it might be a lil grabby? Thank. JR
    My old yahoo group. Bridgeport Mill Group

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

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