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  1. #1
    Join Date
    Jan 2008
    Location
    Metford
    Posts
    47

    Default tread mill motor

    I see another motor thread was moved but I dont know where to put this so I will put it here and see what happrns I have a Hare and Forbs Lathe with a 1.5 motor which only stopped once so far and was fixed under warenty. I also have a tread mill motor which some people seem to recomend as a good replacement because it has variable speed.
    The specs are
    HP 2.5
    RPM 4000
    Rotation CW
    duty treadmill
    field DM
    volts 180
    Could the motor be reversed to reverse the lathe?
    What is Field DM?
    Would this motor be suitable for this job?
    Would I have to use all the electronics to run it or would a pot do the speed controle?
    The treadmill has KPH, calory used , auto hills, and other features that are all electronic
    Kim

  2. #2
    Join Date
    Jun 2005
    Location
    sydney
    Posts
    8

    Default

    Hi

    Do you have any diagrams that go with this?

    may be able to work it out from them

    Doug

  3. #3
    Join Date
    Oct 2007
    Location
    Alexandra Vic
    Age
    69
    Posts
    654

    Default

    Kim, these are my thoughts on this concept. With the information supplied, it is all that I have come up with.

    In a treadmill application, most of the motor output is lost to friction in the transmission system and belt. The system does not/can not drive the user to higher speeds, at best it can only encourage them, and then trip them and grind them if they can't keep up. Therefore the motor does no useful work, and it is difficult to guess what it's particular torque output capability might be at any given speed.

    The motor will not operate without some form of drive electronics, similar to or the same as those used for the treadmill. A simple 'pot' would not cut it here, when it's trying to handle 2000Watts of electricity. It may be possible to discard the treadmill user interface and replace that with something simple like a pot to command the motor controller, but I suspect that the controller would expect a digital signal of some sort unless the current system uses a pot to vary speed.

    I am assuming that the original lathe motor is a 1440RPM one, as this gives the best torque for lathe applications.

    If the motor is rated at 4000RPM to run a treadmill, there would have to be significant reduction gearing attached somewhere.

    By my calculations, 4000RPM direct drive with a 100mm roller driving the belt would give a belt speed of about 75Kph. At that sort of speed, I would anticipate that slip between the belt and roller would be very considerable, in which case the normal solution would be to gear down drive to the roller and increase the roller diameter to increase contact area. I would anticipate a max belt speed of no more than 20Kph, so would suspect about 8:1 reduction and maybe a 150mm drive roller as typical.

    You are dealing with differing motor technologies here, and I am not sure why, but I am guessing that you want to dable with variable speed, since you mention a pot. The 2.5HP @4000 RPM motor would be producing significantly less torque than a 1.5HP @1440 RPM one would (for a constant torque, power is proportional to RPM). To produce the same torque at 4000RPM as the 1.5HP @1440, the motor would need to be rated at about 4.2 HP.

    There would be too many inponderables to guess what the performance of the motor would be like at reduced speeds, but I have a horrible notion that torque would be degraded further.

    With a lathe, the normal reason for operating at lower speeds is to control the cutting speed seen by the tool tip. As the speed is reduced, more torque is required and changing the drive reduction ratios with gears or belts accomplishes this well. If you were to opt for a VS motor system, I think you would have to limit the speed range to minimum 0.7/ max 1.4 x nominal speed for the original motor, or thereabouts.

    That suggests that you would need to incorperate a reduction drive of about 2:1 beyond the range built into the lathe for the original motor. My suggested variable speed range above would then provide drive speeds equivalent to the original motor operating in the range 1000 to 2000RPM, but with at best maybe 60% of the torque of the original motor.

    I suspect that DM indicates that the motor field is Directly Magnetised i.e uses Permanent Magnets and is like a giant slot car/HO train motor. If this were the case, the motor could concievably be reversed by stopping, reversing polarity and restarting.

  4. #4
    Join Date
    Jan 2004
    Location
    Mackay North Qld
    Posts
    6,446

    Default Convesrion to DC motor

    Hi Kim


    The following are Googled cut and pasted URL’s referring to installs of DC motors in lathes. Basically from what I glean is that the reductions are in the order of about 3 to 1 back to 4.5 to 1.Theres also a bit there on the reversal of polarity picked off the field windings.

    http://bbs.homeshopmachinist.net/arc...hp/t-4325.html

    http://www.bedair.org/Tmotor/Tmotor1.html

    http://tool20895.homestead.com/treadmill.html

    [ame="http://www.youtube.com/watch?v=lgAf0uIk7iw"]YouTube - Scratch built lathe test 2[/ame]

    http://www.cnczone.com/forums/archiv...p/t-11580.html

    http://www.stellar-international.com/lathe.html

    http://www.janellestudio.com/metal/a...d_switches.txt

    Its and interesting read. I am sure there are lots of us here who harbor thoughts of a conversion.It will be interesting to see if there are any existing here in Australia.
    If you succeed ,please post it here as at least I am interested in the details

    Cheers
    Grahame

  5. #5
    Join Date
    Jan 2008
    Location
    Metford
    Posts
    47

    Default

    Thanks for the replys guys
    Kim

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