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Re: [taigtools] Success!

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  • Ken Cline
    Heat dissipation is a big issue for a motor this small. During bench testing with a frictional load on the shaft, I have run the motor at 180 watts (1/4 HP)
    Message 1 of 10 , Feb 4, 2008
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      Heat dissipation is a big issue for a motor this small. During bench
      testing with a frictional load on the shaft, I have run the motor at
      180 watts (1/4 HP) input for a short time without overheating, but I
      didn't want to hold on to the shaft for a while afterwards! I'm
      confident I will be able to use it for the sort of jobs I have in
      mind, but I'll be mindful of the load. The lathe is not ready yet so
      I can't report about its actual use.

      The motor is designed for 10-15 minutes of hard use with a stream of
      air flowing over it for cooling. Compounding the problem is
      frictional heat generated by the worm gear. The one thing that gives
      me hope is that I don't need 1/2 HP - one quarter of that should
      generally suffice. The new heat sink will help (did *you* hide my
      heat sink compound???) and I can connect a fan if it turns out to be
      necessary. Also, the controller will cut out if the speed drops
      below 5000 RPM (500 RPM at the pulley) or so. This setup won't burn
      up if it stalls.

      Brushless model motors are optimized for efficiency, weight and size;
      they spin fast; and they are expensive. None of these factors are
      needed to drive a lathe. I would not recommend my approach unless
      you are as stubbornly determined to go that route as I am.

      Tony - yes, I'm using a 12 volt sealed leas acid battery rated at 35
      amp hours, and trickle charger. The manufacturer gives data for
      running it between 8 and 12 cells (about 10-16V).

      Mark - I'll report back after I get the lathe running. I have yet to
      lap the ways and assemble everything, plus I need to shield the gears
      and electronics from flying chips. The motor is a Jeti Phasor 30-3.
      "Direct drive only".

      Ken

      On 4 Feb 2008, at 2:37 AM, Bertho Boman wrote:

      > Nice job Ken! I have also been thinking about using one of those fancy
      > motors but I have been worrying about heat dissipation. On an
      > airplane the
      > prop dumps a lot of air into it for cooling but not for stationary
      > use.
      > High peak power is great but what is the steady state rating. I
      > have had a
      > hard time finding any specs on that.
      >
      > 12V * 35A at 83% efficiency means that there is over 70 Watts that
      > got to be
      > dissipated in that little motor.
      >
      > Bertho



      [Non-text portions of this message have been removed]
    • Don Rogers
      Ken, I’m sure you have considered this, but I’ll point it out anyway. Airflow. It is critical to those motors and to their controllers. LOTS of air.
      Message 2 of 10 , Feb 4, 2008
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        Ken, I’m sure you have considered this, but I’ll point it out anyway.
        Airflow. It is critical to those motors and to their controllers. LOTS of
        air. They were designed for a steady 20 to 30 MPH flow of air into them and
        without a semi steady flow at that speed, they overheat and in the case of
        the controller, shut down. The ESC’s are designed to shut down on over temp
        and over current, as well as under voltage. Also, they want a pure DC
        source. One concern I’ve had is the duty cycle for them. In a model
        airplane environment, a 10 minute flight followed by 20 to 30 minutes down
        time is normal. In a lathe, I can see some long run times, and if you are
        doing CNC Mill work several hours between shutdown should be expected. I’m
        not sure they are up to that environment, yet.

        They are incredible little motors though. I’ve seen setups with four of
        them in a planetary arrangement that were pulling close to 5KW, while
        turning a 24” prop. There is even a full sized plane now flying on that
        type of motor and Lipo batteries. I think it has a 30 minute range though,
        so it is not practical yet. The way battery technology is going though it
        shouldn’t be long.

        Don


        [Non-text portions of this message have been removed]
      • Ken Cline
        Thanks, Don. I completely agree. This motor would likely overheat doing production work. I don t expect to push it very hard. If it gets hot, I ll point a
        Message 3 of 10 , Feb 4, 2008
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          Thanks, Don.

          I completely agree. This motor would likely overheat doing
          production work. I don't expect to push it very hard. If it gets
          hot, I'll point a fan at it. If that's not enough, I could make a
          liquid cooled heat sink. Honestly, though, I don't expect to use it
          hard enough for that to matter.

          As for power, I'm using a hefty lead acid battery with only 0.03V
          noise (peak to peak) when charging. No worries there. A power
          supply scavenged from an old computer could also be an inexpensive
          option, though I don't how those supplies behave under the extremely
          low load condition when the ESC is drawing standby power.

          I'm not sure why you said they are not up to this environment yet.
          Industrial brushless motors are avalable to at least 10 HP. They are
          beautiful, but expensive and not actually that much more efficient
          than DC motors at high power.

          Ken

          P.S. I think I described this as a 3-phase AC motor. I used the
          wrong terminology. AC motors are driven by sinusoidal signals and
          have sinusoidal back EMF. Brushless DC motors operate on square or
          trapezoidal waves.

          On 4 Feb 2008, at 11:52 AM, Don Rogers wrote:

          > In a model
          > airplane environment, a 10 minute flight followed by 20 to 30
          > minutes down
          > time is normal. In a lathe, I can see some long run times, and if
          > you are
          > doing CNC Mill work several hours between shutdown should be
          > expected. I�m
          > not sure they are up to that environment, yet.



          [Non-text portions of this message have been removed]
        • mike maxim
          I use a yogurt container and mounted a fan at the bottom and put it over my dc motor so the bottom is now the top. I turn it on when I start the machine and
          Message 4 of 10 , Feb 4, 2008
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            I use a yogurt container and mounted a fan at the
            bottom and put it over my dc motor so the bottom is
            now the top. I turn it on when I start the machine
            and it keepes the motor cool.
            mike
            --- Don Rogers <Don@...> wrote:

            > Ken, I’m sure you have considered this, but I’ll
            > point it out anyway.
            > Airflow. It is critical to those motors and to
            > their controllers. LOTS of
            > air. They were designed for a steady 20 to 30 MPH
            > flow of air into them and
            > without a semi steady flow at that speed, they
            > overheat and in the case of
            > the controller, shut down. The ESC’s are designed
            > to shut down on over temp
            > and over current, as well as under voltage. Also,
            > they want a pure DC
            > source. One concern I’ve had is the duty cycle for
            > them. In a model
            > airplane environment, a 10 minute flight followed by
            > 20 to 30 minutes down
            > time is normal. In a lathe, I can see some long run
            > times, and if you are
            > doing CNC Mill work several hours between shutdown
            > should be expected. I’m
            > not sure they are up to that environment, yet.
            >
            > They are incredible little motors though. I’ve seen
            > setups with four of
            > them in a planetary arrangement that were pulling
            > close to 5KW, while
            > turning a 24” prop. There is even a full sized
            > plane now flying on that
            > type of motor and Lipo batteries. I think it has a
            > 30 minute range though,
            > so it is not practical yet. The way battery
            > technology is going though it
            > shouldn’t be long.
            >
            > Don
            >
            >
            > [Non-text portions of this message have been
            > removed]
            >
            >



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