Slowing Down My Drill Press !!!

Hi. Did you do away with the large flywheel on the treadmill motor?
Thanks
 
Thanks for your replies and questions, all. Always interesting to see how other folks do it. For my part, here's what I've discovered, observed, and/or believe to be true:
  1. "Can you use the speed controller that comes with the treadmill?" Yes - but. In my experience, this can get a little complicated for a couple of reasons.
    1. In many cases, the controller requires feedback from a tachometer which is usually incorporated in the flywheel. Without it, the controller may think the motor is not turning when it should, conclude something is amiss, and shut down. There are three things I don't like about using the flywheel:
      1. it makes it hard to attach a pulley to that end of the shaft.
      2. it adds a lot of inertia to the system, making a more likely to snap a tap if it binds while threading.
      3. it's usually threaded onto the shaft, which is fine if you only run the motor and the direction that makes it tighter and never have and inertial load that wants to keep going and unscrew it. Of course, you could lock it to the shaft if you wanted to.
    2. the speed controller usually requires input from the treadmill control panel, which usually has speed up and speed down buttons integrated into a pretty complex circuit card. The whole panel is too large to use, but almost impossible to separate out the few components I need.
    3. having said that, it is possible to hack the speed controller, or to buy a general-purpose speed controller, or to create your own. I've done all three, as have others; these folks usually have some comfort and experience with electronics and safe power wiring.
      1. I mentioned the HF router speed control because I think it's by far the simplest way to get variable speed control. (You do need one additional component, the bridge rectifier, to convert AC to DC; in addition to the reversing switch which you need with the treadmill controllers as well).
  2. "Did you do away with the flywheel?" Yes. I tried leaving it on, but see point 1 above. Be aware that the cooling fan is usually part of the flywheel, so you may want to add a small fan to the back end of the motor. I have used computer fans, which are cheap. Having a separate fan is better anyway because it can run at full speed even when the motor is going slowly and even after it stops. It can get pretty hot when digging slowly through hard metal with a large bit.
  3. Unasked questions, just other thoughts or things I've run into:
    1. To set the speed, a tachometer is really handy, since you no longer know the rpm from the pulley diameters. Cheap handheld optical ones let you tape a piece of reflective tape on the chuck and read in two seconds.
    2. A motor is also a generator, so if you short its terminals (after opening the power switch, of course), it loads it down and stops it really quickly. The control system I'm developing has a deadman style foot switch - take your foot off stops my lathe with a 6" chuck in less than two seconds. It's a little more complicated than that in actuality because the current is huge at first and can fry most switches and relays.
    3. An ammeter is useful to tell the load on the motor and speed controller. If you put too much load on it, the motor will heat up and the speed controller fuse will blow (at least you hope that's what goes first!). I draw as much as 20 amps at times (at 120V)
    4. Many treadmill motors go as high as 3 HP.
    5. The router speed controls will make the motors hum; no harm, in fact you get an audible indicator of the loading. Treadmills often have smoothing components (huge inductor which looks like a transformer but only two leads, and/or a huge cylindrical capacitor).
    6. The way you get high torque even at low speeds is by pulsing a high voltage to the motor. The high voltage (actually, the high current resulting) gives you the torque, and pulsing gets a lower speed. The tech term is pulse width modulation, or PWM. If you're into DIY microprocessors, like Arduino or Raspberry Pi, you probably know something about this and may be able to apply it. Anyone on this thread exploring this?
    7. Treadmill motors were intended to run one direction, but will reverse if you reverse the current. It's best to install the motor so it's preferred direction equals the forward direction for your machine. The brushes will be happier. (If your motor has an internal fan or you left the flywheel on and it has fins you'll get better cooling as well. Even so, I think it's a good idea to provide independent fan as described above.)
 
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