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Thread: Weld rotator

  1. #1
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    Default Weld rotator

    The other day I was watching a 'This Old Tony' video and discovered that he made a small welding turntable (https://www.youtube.com/watch?v=ny5Xxwwpkxs). Looks like one of those occasional use but very useful when needed items. He made his with a worm drive gear box and a 24V DC motor. His design is simple and seems to work (at least as far as the viewer can see) but raises some questions about how he has done things as well as whether there are other ways to do this. I'd be interested in other's thoughts -


    • For starters, he runs his platten axis straight through the worm drive gear box. I always thought that stray welding current was disastrous for rolling element bearings - so should some insulating sleeves be between the metal shaft and the bearings? Given the low speeds involved, would plain plastic bushes work just as well (mount the plattern shaft in bushes and drive the shaft with a chain from the gearbox/ motor). On the other hand, what about stray heat?



    • Similarly, his earth clamping method is the earth clamp on the other end of that shaft and as the plattern rotates, the (spring) clamp slips on the shaft. Other weld turntables I've seen locally use a bit of welding cable, stripped of insulation and then wrapped around the shaft (with a little bit of tension) to get the contact. The clamp is cheap and I guess does the job, but not sure it's all that good for the shaft or the clamp.



    • He has used a 24V DC motor with a speed control board to drive his rotator. Nothing wrong with that, but looking around there do not seem to be many of them out there. As alternatives, perhaps a 1/4 or 1/2 Hp motor with VFD (and speed reduction gearboxes too - his rotator speed seems to be 0 to around 20rpm, so something is needed). The other option was a beater of a battery drill - 12 or 18 volts. The advantage of the drill is that there is already a speed control mechanism in there. Would a drill run as 0 to 600rpm and then through a 20:1 gear box (I just happen to have collected one in Tas while there) have enough torque? If I had one of these, it would be used for small parts with the plattern being say 6 to 8" diameter. The other alternative for motion would be a treadmill motor but I would have to find one of them as well. Are any of these options better than any other given the strong electric fields that welding currents would generate?



    • Lastly (for the moment), his rotator can drive both ways. Is that a feature worth chasing if it is not already in the control circuit? I've been trying to think why rotating both ways would be necessary and as it is used for circular welds, can't see why there would be a need to change hands.


    Anyway, my questions/ thoughts for the moment.
    Michael

  2. #2
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    Hi Michael,

    If the welding current does not pass through the bearings then you are right ! The shaft is directly connected to the table and the earth is strapped to the shaft, which means that you need to be able to reverse the rotation to unwind the earth strap.

    A local guy has a welding turn table and he just grabs the steel table with the earth clamp. Though I've seen him put the clamp directly on the work piece as well.
    Best Regards:
    Baron J.

  3. #3
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    For starters, he runs his platten axis straight through the worm drive gear box. I always thought that stray welding current was disastrous for rolling element bearings - so should some insulating sleeves be between the metal shaft and the bearings? Given the low speeds involved, would plain plastic bushes work just as well (mount the plattern shaft in bushes and drive the shaft with a chain from the gearbox/ motor). On the other hand, what about stray heat?
    As John has mentioned, as long as the current doesn't go through the bearings, it should be fine.
    Provided that it wasn't used in a professional manner, stray heat shouldn't be a problem.

    • Similarly, his earth clamping method is the earth clamp on the other end of that shaft and as the plattern rotates, the (spring) clamp slips on the shaft. Other weld turntables I've seen locally use a bit of welding cable, stripped of insulation and then wrapped around the shaft (with a little bit of tension) to get the contact. The clamp is cheap and I guess does the job, but not sure it's all that good for the shaft or the clamp.
    I've seen used where a decent size spring with a brass button was under tension rubbing on the shaft, to create the return lead.
    • He has used a 24V DC motor with a speed control board to drive his rotator. Nothing wrong with that, but looking around there do not seem to be many of them out there. As alternatives, perhaps a 1/4 or 1/2 Hp motor with VFD (and speed reduction gearboxes too - his rotator speed seems to be 0 to around 20rpm, so something is needed). The other option was a beater of a battery drill - 12 or 18 volts. The advantage of the drill is that there is already a speed control mechanism in there. Would a drill run as 0 to 600rpm and then through a 20:1 gear box (I just happen to have collected one in Tas while there) have enough torque? If I had one of these, it would be used for small parts with the plattern being say 6 to 8" diameter. The other alternative for motion would be a treadmill motor but I would have to find one of them as well. Are any of these options better than any other given the strong electric fields that welding currents would generate?
    You could use a 12V motor, like a wiper motor with something like this used. https://www.ebay.com.au/itm/1500W-DC...vIUT:rk:3:pf:0
    When I had my business in Adelaide, a bloke next door had a contract for welding a piece of bright pipe onto a ratchet handle, which was for a ratcheting system for moving a caravan or similar. He had a 240V electric motor drive through a gearbox of unknow origin, with a speed controller on it. What motor he used, I can't remember and have lost contact with him.
    Found this one utilising a variable speed drill, remote speed controller, foot pedal, and a rotary table.
    https://www.youtube.com/watch?v=o1G1Pb0arQ4
    https://www.ebay.com.au/itm/Rotary-T...0Gu-:rk:7:pf:0
    • Lastly (for the moment), his rotator can drive both ways. Is that a feature worth chasing if it is not already in the control circuit? I've been trying to think why rotating both ways would be necessary and as it is used for circular welds, can't see why there would be a need to change hands.
    I can't think of any real reason to reverse the rotator, apart from requiring to weld back hand or fore hand?

    Kryn



    To grow old is mandatory, growing up is optional.

  4. #4
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    I think it would be worth making it rotate both ways. Sometimes you might want to weld into a corner, or maybe out, depending on circumstance. Not every circular weld is going to be a full 360 degrees round the outside of a pipe.

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    Quote Originally Posted by KBs PensNmore View Post
    I've seen used where a decent size spring with a brass button was under tension rubbing on the shaft, to create the return lead.
    Hadn't thought of that one but that would be another way and potentially less sparky than wrapping a cable around the shaft

    Quote Originally Posted by sossity View Post
    Not every circular weld is going to be a full 360 degrees round the outside of a pipe.
    Good point

    Michael

  6. #6
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    Quote Originally Posted by KBs PensNmore View Post
    ...Found this one utilising a variable speed drill, remote speed controller, foot pedal, and a rotary table.
    It's an interesting set up but seems overkill & expensive in terms of achieving a rotary drive for a welding turntable. I lean more towards a fabricated turntable on some simple/ cheap bearings. While perhaps not as smooth as a proper wormgear, a helical gear can be driven with a worm and for the application is probably quite smooth enough.

    In the final iteration he seems to have dropped the idea of using a coolant tube as a flexible drive (with wear it would slip) and is using a battery drill directly driving the RT. On low gear the drill would likely have a maximum speed of 500 to 600 rpm, so through a 40:1 box , a top speed of 12 to 15rpm?

    Michael

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    - The bearing issue is not a big deal, reduction boxes are used in welding fixtures all the time without any known issue relating to bearing failure.

    - Most of the ones I have seen have used a flat piece of earth strap against the shaft and spring to tension it, some a brush holder type setup. You could have a replaceable collar on the shaft perhaps made from brass if you are that concerned about wear.

    - I too think make it rotate both ways as sometimes when you go to start the weld you may have issues and it would be a lot quicker to go back to the start rather than having to do another 360 degrees rotation to get back there.

  8. #8
    BobL is offline Member: Blue and white apron brigade
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    I've thought about making a rotator a few times especially as I already have a bunch of 24V motors in my stash, even some with built in reduction gear boxes.
    However, instead of using a gear box my plan was to drive the turntable from under and close to the outside of the rim so what I have been chasing is some flexible toothed track that I could form into a circle and attached to the turntable. I have also thought about using bike chain but finding a small enough drive gear to get the required reduction becomes a problem. I have an exercise bike that uses a much finer chain and a suitable small drive gear than is used by regular bikes that would work but i need the bike for my bung knee exercises. A few years ago I found a fine chain that would work but have no gear for it although I suppose it would not be that hard to make one.

  9. #9
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    We have 2 rotators we built at work. neither have insulation between the table and the gearbox, never had a problem. The big rotator has a heap of spring loaded carbon bushes that run on the underside of the table for the earth. The small rotator has a bit of copper flat bar sandwiched between the end of the shaft and a spring loaded washer. I would make the rotator run both ways, and make it so it can be mounted horizontally or vertically.

  10. #10
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    Thanks for the thoughts so far. Another one that I've been mulling over is the need for a central hole in the table. I ask because I have a raft of 80mm bore ball bearings, so could have a through hole easily (the drive may then need to be via chain, but that is no big deal). Again, it's not something that I can see an immediate need for, but easier to do during initial construction rather than regret later.

    Michael

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    Yeah I would go for a hole in the centre as well, may as well.

  12. #12
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    Quote Originally Posted by Michael G View Post
    Thanks for the thoughts so far. Another one that I've been mulling over is the need for a central hole in the table. I ask because I have a raft of 80mm bore ball bearings, so could have a through hole easily (the drive may then need to be via chain, but that is no big deal). Again, it's not something that I can see an immediate need for, but easier to do during initial construction rather than regret later. Michael
    I'd definitely go with the hollow centre, you never know when you need to weld a collar onto a shaft.
    There's no need for the chain drive, as you could use gears like this, DSCF0644.jpg
    These are what Ralph cut for me for a Miniature Christmas Float.
    Very easy for someone with the correct cutters.
    Kryn
    To grow old is mandatory, growing up is optional.

  13. #13
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by KBs PensNmore View Post
    I'd definitely go with the hollow centre, you never know when you need to weld a collar onto a shaft.
    There's no need for the chain drive, as you could use gears like this, DSCF0644.jpg
    That'll work for me

    I checked out my 24V motor stash and found a couple of motors with gear box outputs of 24 and 30 rpm.
    One problem is these are synchronous motors so will need frequency control to get speed control.

  14. #14
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    I have a non finished weld rotator that I might get back to finishing one day.

    Michael the other thing that may be of use that I was contemplating also was to make the gun holding bracket with a small adjustable stroke crank and motor to weave the weld, just a straight line weld out of the gun is not always adequate.

    cheers, shed

  15. #15
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    Forgot to mention that on the unit the bloke next door made, he had a mount on it to hold a MIG torch with a timer. The size didn't require a weave, but certainly a good idea if it could be set up to oscilate with the rotation of the top.
    Mind you, some of us have a natural weave, as we get older.
    Kryn
    To grow old is mandatory, growing up is optional.

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