Could be an easy welding turntable?

  1. Ped

    Ped Member

    Messages:
    192
    Stamford, uk
    Hi all,
    I've had this electric motor and gearbox for years. I bought it with a load of other stuff and it's just been sat at the bottom of a cupboard. It's was originally intended for reaming head tubes and seat tubes on bicycles after brazing. You put a reamer in the socket, slide the frame onto the reamer and hold the frame as tight and as square as you can. Pretty primitive stuff but it kinda worked.

    I've just had a brainwave that I might be able to easily convert it into a rotary welding table. The output shaft turns at 25rpm, obviously too fast for Tig welding so I need to slow it down. It it just a case of fitting a VFD? And is it risky to just get a cheapo unit direct from China? I've seen them for around £50.


    IMG_1563.JPG IMG_1564.JPG IMG_1565.JPG

    Will something like this do it?

    https://www.ebay.co.uk/itm/5A-Singl...m=142652537607&_trksid=p2047675.c100005.m1851
     
    • IMG_1567.JPG
  2. Dcal

    Dcal Forum Supporter

    Messages:
    2,001
    Location:
    Antrim Northern Ireland
    Nice looking bit of kit

    I've no experience of the Chinese inverts, I have always managed to get them second hand but should work OK.
    Another option would be to gear it down again with gears or pulleys, to give more torque and less speed. (still need the inverter for speed and direction control.)
    I've done something similar with a bead roller and am thinking of using the drive for a welding rotator.

    Electric motors like to work closer to the design speed and are not happy running at very low (or high) speed. You will need to watch the motor cooling, if you are going to use it for welding you will need to reduce the speed by 10 or 20 times so the motor will be running really slow and the fan won't pull the same air for cooling. Might not be a problem for low duty cycle but something to watch.
    Also not sure if a inverter will like stray welding currents and spikes. You need to be sure the work piece is well earthed and the inverter insulated from the welding circuit.
    I was thinking of using rubber belts or pulleys for the final drive to the rotator and maybe big carbon or copper armature brushes.
     
    Ped likes this.
  3. rtbcomp

    rtbcomp Moderator Staff Member

    Messages:
    18,615
    Location:
    Sheffield UK
    Looks like a single phase motor, so make sure you get a single phase VFD.

    If you use rubber a belt (^^ Good Idea) then you'd be better off using pulleys to reduce the speed.
     
    Ped and slim_boy_fat like this.
  4. 500e

    500e Always buy fire insurance a flood is hard to start

    Messages:
    4,576
    Location:
    SWest UK
    A heavy braided strap wrapped round the table drive shaft is also a way, spring loaded to keep tight
     
    ronan and Ped like this.
  5. Jim Davey

    Jim Davey R H Davey Welding Supplies Ltd

    Messages:
    5,429
    Location:
    Southampton
    Ideally you'd have a reduction gearbox between that output spindle and the table itself. Positioner/turntables that don't turn slowly enough yet still maintain torque for smooth running, are a massive pain in the bum.
     
    Ped likes this.
  6. RedOrZed Member

    Messages:
    313
    Milton Keyneses
    Might it be possible to re-gear the gearbox to slow it down?
     
  7. Jim Davey

    Jim Davey R H Davey Welding Supplies Ltd

    Messages:
    5,429
    Location:
    Southampton
    Anything is possible, you’d need a reduction gearbox between the output of your current gearbox and suitable mountings/couplers.
     
  8. fizzy Forum Supporter

    Messages:
    6,242
    uk
  9. Shox Dr

    Shox Dr Chief Engineer to Carlos Fandango

    Messages:
    15,264
    Location:
    East Yorkshire
  10. fizzy Forum Supporter

    Messages:
    6,242
    uk
    How do drill controllers work? Down to almost stationary? I suppose they use fancy electronics?
    I would have thought there was almost no force needed for a welding turntable - then again the drag from the gearbox would need some force to turn it.
     
  11. Pete.

    Pete. Member

    Messages:
    9,337
    Location:
    Kent, UK
    That's a single phase induction motor, you cannot speed-regulate it either with a VFD or that speed controller box. Even with a VFD you'd struggle to get it slow enough without one more step-down in gearing because if it was doing 50rpm at 50hz you'd need to be down around 5hz for welding speed.

    Brushed motors that you get in drills etc can be speed regulated (most of them anyway).
     
    fizzy likes this.
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