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Thread: Motor for a home made welding positioner

  1. #1
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    Question Motor for a home made welding positioner

    Leeson Gear Motor, 90VDC, 30:1 ratio, runs @ 60rpm, 56 lb-in torque.

    I think the above has home made welding positioner written on it.

    From what I gather, it is not the highest amount of torque (there seem to be lots with about double that) but there is at least one commercial model available that has exactly that.
    From reading the rpm needs to be dropped quite a bit further, I was thinking of a belt drive (chain?) with a very large pulley having a large center hole so as to allow for tubing to be dropped through enabling flanges to be welded to pipe.

    Knowing next to nothing about electrics, the first questions would be is the above motor appropriate? How complicated is it so as to eventually run off 115v and have control over varying the speed?
    Aiming to have about 3rpm and lower final drive. Have to do a bit more reading but that 3rpm may end up being a bit high [bookmarked a lot of builds yesterday, have not had time to read fully and recall there was one with a speed chart on it (diameter v. rpm needed)]

    Thoughts? Suggestions?

  2. #2
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    Quote Originally Posted by RussZHC View Post
    Leeson Gear Motor, 90VDC, 30:1 ratio, runs @ 60rpm, 56 lb-in torque.

    I think the above has home made welding positioner written on it.

    From what I gather, it is not the highest amount of torque (there seem to be lots with about double that) but there is at least one commercial model available that has exactly that.
    From reading the rpm needs to be dropped quite a bit further, I was thinking of a belt drive (chain?) with a very large pulley having a large center hole so as to allow for tubing to be dropped through enabling flanges to be welded to pipe.

    Knowing next to nothing about electrics, the first questions would be is the above motor appropriate? How complicated is it so as to eventually run off 115v and have control over varying the speed?
    Aiming to have about 3rpm and lower final drive. Have to do a bit more reading but that 3rpm may end up being a bit high [bookmarked a lot of builds yesterday, have not had time to read fully and recall there was one with a speed chart on it (diameter v. rpm needed)]

    Thoughts? Suggestions?
    If you are going to buy new, I would think you could find one with the RPM you want, or closer. You don't give any site references. Where are you buying it from? As for the DC aspect, you will need to come up with a power supply that can handle the current. Not a big deal, but one more thing you need to do. Then a motor controller if you want to vary speed. Don't use a rheostat, it should be what is called "Pulse Width Modulation" which essentially turns the power to the motor on and off rapidly, "pulses" The more frequently the pulses, the quicker the motor spins. If you visit a CNC site, there should be discussions on motor speed control. Getting the motor speed control in place, then you are just left with youe mechanics but you could burn up your nice new motor by not getting the right power supply/controller in place. I am not a motor control expert, just have a general electronics background. Perhaps someone with some CNC experience could chime in here. Having said that, I think my lathe has a DC motor on it, iirc.

    Good luck
    Last edited by ShawnR; 02-12-2013 at 08:07 AM.

  3. #3
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    Look on ebay for the KB or Baldor SCR 90VDC drives, You can even apply a foot pedal type that has a pot in it to vary the rpm on the pedal if you wish.
    These connect directly to 120vac.
    Max.

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    Your best option would be an old or cheap pipe threader. You get massive torque and low rpm. Add a router speed controller and you are set. I'm sure you can find a suitalbe way to drive with it.
    Who do I think you are...?

  5. #5
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  6. #6
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    Quote Originally Posted by RussZHC View Post
    Leeson Gear Motor, 90VDC, 30:1 ratio, runs @ 60rpm, 56 lb-in torque.

    I think the above has home made welding positioner written on it.

    From what I gather, it is not the highest amount of torque (there seem to be lots with about double that) but there is at least one commercial model available that has exactly that Thoughts? Suggestions?
    You don't need all that much to drive a welding table, you need to couple the G.B. output to the table somehow so just incorporate some reduction there and you should be OK.
    Max.

  7. #7
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    Russ,

    I made a welding turn table 35 years ago to buildup cross fire tubes for GE gas turbines. I used a small (1/10 HP) 120VAC right angle worm drive motor with a speed controller and a tig foot control for on/off. It had friction drive to turn a steel wheel 3/8"" thick and 12" in diameter. The 8" 3 jaw chuck that held the work piece was fixed to the 12" wheel and the motor and drive shaft were insulated from the wheel. Carbon brushes and holders from an exciter rode on the back side of the 12" wheel to allow current to flow through a rotating piece. The welder used the foot control to start and stop the rotation and the speed control to control rotational speed. The turn table is still in use.

    Also, some windshield wiper motors and their controls make excellent fixture motors.

    Ron

  8. #8
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    60 rpm is far too fast.
    Read this thread.

    http://bbs.homeshopmachinist.net/threads/33496
    .

    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.




  9. #9
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    Shawn: "scrounging" local Kijiji (think Canadian version of Craigs but with, IMO, usually a lot better photos), that particular Leeson has been languishing there for a few months now...the more direct route would be to find something on EBay, and I have, but the shipping for that sort of weight kills any sort of "deal" on the original cost. Said motor seems to be the most likely candidate so far. The hope would be to locate the heavy stuff locally and then get controllers and other small bits on EBay or elsewhere online.

    HAP: had not thought of that...hmmm, reasonable shot too locally, perhaps better than finding a really low speed gear motor...am also considering nearly every other gear motor from wheelchair, to tread mill lifting motors (adjustable incline type tread mill), to garage door openers, to power seat motors, to slide out (trailers) motors, and on and on...one of the issues, and I could be very wrong here, that I see is some of those types of motors are not meant for "continuous" duty...just saying all but the wheelchair have relatively short working periods.

    John: that happens to be one of the threads I did read...previous thought had been to "gear" down the 60rpm through a couple of pulleys, reducing as I go but I can see that getting complicated quickly (I do have some other gears that could make up some sort of more proper gear train though...) BUT there is also, locally, what I think could be an appropriate right angle gear box that has a 30:1 ratio, this would get it down to 2 rpm but from some of the numbers I recall, that is still not quite slow enough.

    More reading and re-reading ahead.

    Max: found several of the two makers you mention. Sort of assume the Baldor BC 138, BC 140 and BC 154 are not hugely different but sort of updated versions (higher numbers)? Found a couple of candidates from KB, their Camco "Vari-pak" and "Penta Drive". Those are/were complete boxes so to speak. There were a few that were more "just the boards" but there does not appear to be much gained once you start adding in given resistors, speed pots etc. Or that is the way I am viewing the offerings. Be gentle, I am definitely one of those plug it in and use it guys...I can do the work but definitely need help with understanding the dos and don'ts.

    Thanks, all, Russ

  10. #10
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    nc5a: not that the positioner you mention was but it amazes me sometimes of the longevity of a build that is "only temporary". Sort of also confirms what some reading has hinted at, that being which does what in terms of speed and on/off (which is foot and which is hand so to speak). The TIG foot control was something I knew about but had not thought of it in this context...another route to go.
    Maybe I am not going at this quite right, perhaps I should just be looking at off the shelf parts for the guts and just build the box/frame...

    Edit: any recall/thought as to how much the wheel plus 3 jaw weighed? Do you think there is any concern regarding weight or for that matter balance? From what I can recall there were some pretty amazing photos, guys "testing" by sitting on one and spinning around but also some quite long and heavy "arms" attached and then lifted (I mean to lift the end of maybe a 10 foot bar off the ground when the other end is bolted to the faceplate/wheel takes some "guts")
    Last edited by RussZHC; 02-12-2013 at 04:22 PM.

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