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direct drive VFD conversion

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  • direct drive VFD conversion

    this is promising!

    the variable speed sheave on my Yamazen Lancer project is shot- I had a Baldor 1HP 1140 rpm motor and Teco EV collecting dust so I thought I`d give it a shot.

    scrounged a serp belt from the local garage and gutted the variable speed set-up.

    not much to it- super easy install.

    the 1140 rpm motor gives me about 250rpm @ 30hz, 500 rpm @ 60 hz, and 1000rpm @ 120 HZ - toss in the backgears and it seems just about perfect for my screwing around.

    not done any cutting under load yet, but it seems to have plenty of torque on tap.

    it will be interesting to see how it works once everything is done - even now with the motor mount still unsecured it`s very smooth.

    crappy video, but it gets the point across- I`d do better but am limited to about 45 seconds with my ipod-

  • #2
    Coolness. You're going to like the VFD.


    • #3
      1 HP meas 1 HP at the motor's name plate of 60 HZ. You'll get roughly full HP up to about 75 Hz but the motor power drops off thereafter. My WAG is your 1 HP motor will develop about 1/2 HP at 120 Hz, maybe a bit more.

      Goint the other way, the motor's developed HP drops in proportion to frequency: 1/2 at 30 Hz, 1/4 at 15 Hz etc.

      You may have hated the mechanical varispeed drive but it insured you had roughly foull motor GHP over the lathes operating range.

      All this is set-up for the following. If you work larger diameters at max stock removals your HP limtations at the low and high speed ends of the VFD range will posed real limitations. If you seldom take a heavy cut you will have no problem.

      If you wish for original performance stock removal, I propose three options.

      1: refurb/restore the varispeed drive

      2: add a 2 step jack shaft pulley whose common ratio is the square root of the back gear ratio. This will give you 4 effective mechanical reductions couting steps and back gear. You run with it in high rannge most of the time but if you wish to max stock removal in a certain range of speeds you can shift the belt and get more like full available HP.

      3: change out the existing 1 HP motor for a 3 HP with suitable VFD. This motor will give you 1 HP down at 20 Hz thus the stock removal performace of your lathe will not suffer.

      - that is if you desire stock removal over the full spindle speed range. If your cuts are light, treat the above as commentary not a suggestion.
      Last edited by Forrest Addy; 05-27-2013, 05:59 PM.


      • #4
        agree about the HP limitations and will likely go to a 3HP motor in the near future.

        with an 1140 rpm motor @ 3HP it seems like it would be ideal.

        especially the 200 buck price of admission!