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Scooter motor to power wood lathe

Discussion in 'Sensors and Actuators' started by Deadhead4114, Jan 29, 2018.

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  1. Deadhead4114

    Deadhead4114

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    Jan 29, 2018
    Hi! I'm new here so if this topic has already been covered or if it's in the wrong category, be gentle.
    I know enough about electronics to make me dangerous. I have a wood lathe and want to power it with a DC motor to be able to get better speed control. I have seen people use treadmill motors. I happen to have a few old 24 volt electric scooters (the larger kind with seat not the smaller stand-up only kind). I'd like to use that motor. I want to use AC to supply power to it. I'd like a speed control that goes from 0% to 100% and be able to reverse rotation. What is the best way to go about this? Can I use the controller and speed control from the scooter and power it with a transformer or DC power supply? Do I need to buy a different controller?
    I don't have the specs for the scooters until I drag them out of storage (big job); I'm just looking for a general. You need to have a X big enough to supply Y with enough power kind of answer.

    Thanks!
     
  2. duke37

    duke37

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    753
    Jan 9, 2011
    The modern way of cotrolling lathe speed is by using a three phase motor and a variable frequency and voltage three phase supply, connected to the mains.

    Do you need an accurate speed conrtrol or would stepped pulleys do?

    You will need to get the motor specification to decide on the 24V power supply, maybe a poor battery on float charge would be adequate. Presumably you have a charger for the scooters. A 24V smoothed power supply will be a large and expensive lump.
    The wiring should be taken from the scooter and reproduced on the lathe with no modifications and it should do fine.
    Reversing would be achieved by altering the motor wiring, reversing the field or armature, but will the lathe fall apart in the reverse direction if the chuck is fitted with a screwed thread?

    Detailed specifications of the motor, battery and charger would help.
     
  3. Deadhead4114

    Deadhead4114

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    Jan 29, 2018
    Thanks for the reply. It is an old Delta lathe made when tools were made to last several hundred years. It has a speed control on it (mechanical changes the effective diameter of the pulleys). The motor is a 115/230 1/2 HP 3450RMP. The slowest speed is still faster than I'd like (1200 or so RPM). If you put a big block in the lathe it gets kinda spooky at that speed. I'd like to be able to go down to 200ish. The motor reversal Is so you can put a chuck on the outer side of the head stock and fashion a outrigger tool rest. Then you could turn platters or such up to 5 or 6 feet in diameter is so desired. I would probably just build an H bridge to reverse the polarity for such a case (it would be rare to do but desirable if not too much of a PITA. Worse comes to worse I could always just use a terminal block and reverse the wiring there. I'd prefer to dispense with the batteries entirely if possible.
    I'm open to other suggestions. But the scooters I already have.... I'll have to dig the scooters out and look at their motor specs. My other route is sourcing a treadmill for dissection. Again, I'm open to suggestions.
     
  4. duke37

    duke37

    5,343
    753
    Jan 9, 2011
    For 0.5HP at 24V you need 15A, quite feasible, you may be able to get away without smoothing so would not need a whacking great big electrolytic.
    To change direction, a H bridge would be nice but a relay would be adequate since it will not be changed often. The problem will be to get into the motor, find out its type and isolate the field winding.
     
  5. Deadhead4114

    Deadhead4114

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    Jan 29, 2018
    Without digging out the scooters, The attached is very similar to the motor I want to run (give or take 100 watts) and the controller. One plug on the controller to battery, one to charger, one to throttle, one to motor. The rest are for lights and key switch.
     

    Attached Files:

  6. kellys_eye

    kellys_eye

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    Jun 25, 2010
    I'd still go with the mechanical reduction - torque means a lot where lathes are concerned - but some variation of speed allows for 'trimming' between gear pitches.
    Reversal by a simple DPDT switch - nothing complicated.
     
  7. Deadhead4114

    Deadhead4114

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    Jan 29, 2018
    Thanks, I still cant get the lower speeds I need to turn larger pieces. I've seen a bunch of people doing these with treadmill motors. These motors do put out enough torque. I plan on keeping the mechanical system in place. Just driven by a motor that I can slow up a bit.
     
  8. Minder

    Minder

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    Apr 24, 2015
    As far as the T.M. motor, If possible I would go with one of the KB DC motor controllers available, these have the ability to reset the drive when you do a reversal by switching the motor leads, this means that regardless of the speed pot, the motor goes through acceleration.
    Also on a T.M. motor in this application you may want to remove the flywheel, some are threaded on, L.H. or R.H. thread used.
    M.
     
  9. Deadhead4114

    Deadhead4114

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    Jan 29, 2018
    And I have a very small pulley on the motor. No room to gear down there.
     
  10. Bluejets

    Bluejets

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    Oct 5, 2014
    Most lathes get low down speed by a simple back-gear arrangement. Just might be a lot less mucking about in the long run. Should be ample info about how to do it on Google.
     
  11. WHONOES

    WHONOES

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    May 20, 2017
    A little research shows that the motor you have presented. is a 500W O/P @ 2500 RPM brushed motor rated at 24Vdc and 26.7A at full load (from Motion Dynamics). A simple PWM circuit based on a large FET or two or three and the ubiquitous 555. It would be possible to incorporate load / speed compensation but, that is a different kettle of fish.
     
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