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Thread: Need a very slow motor (like 1 RPM).

  1. #11

    Join Date
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    Re: Need a very slow motor (like 1 RPM).

    Quote Originally Posted by Struan Gray View Post
    Butcher a clock. Use the second hand drive for 1 RPM. Change the photo-taking rate for other speeds.
    That was my first thought, but:
    a. most second hands move jerkily - how could smooth motion be achieved?
    b. would a clock motor support a load of say a kilogram?

    Kumar

  2. #12

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    Re: Need a very slow motor (like 1 RPM).

    Kumar, I don't think there are general answers to that. A lazy Susan usually has a bearing, so they spin quite freely. You would have to find a clock that can generate enough torque, but the torque involved won't be that high. Ditto on the jumping second hand: you just need to find a sweep hand clock.

    FWIW, *I* would do this by raiding my children's LEGO box. LEGO make nice compact low-speed high-torque motors, and they're designed to be used robustly. They can be controlled by everything from an on-off switch and a battery box to full-on microprocessor control. Gear trains and pulley systems are easy to rig up too. New equipment may break the budget here, but second hand is available.


    PS: the OP might want to Google for astronomer's homebrew solutions to a motorised azimuthal mount. The rotational speed is even lower, but many of the rigs solve the same problems.

  3. #13

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    Re: Need a very slow motor (like 1 RPM).

    Thanks, Struan, the LEGO sounds promising. It might be better than using a clock.

    Kumar

  4. #14

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    Re: Need a very slow motor (like 1 RPM).

    The Mindstorms motors are the most flexible in terms of connections and programming. But they are also the most expensive.

    Easy to rig up a motor and a wheel with a tyre driving the lazy Susan by friction.

  5. #15

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    Re: Need a very slow motor (like 1 RPM).

    This place is totally unpredictable, since they have whatever they have, but a good look around their website is never wasted time: https://www.sciplus.com/ I see there's a little geared 3/5 RPM motor on their front page today, in fact, for $3.95!

    My wife is always wary when I want to go there because I inevitably come out with a bunch of questionable junk that might someday be useful, maybe.
    Thanks, but I'd rather just watch:
    Large format: http://flickr.com/michaeldarnton
    Mostly 35mm: http://flickr.com/mdarnton
    You want digital, color, etc?: http://www.flickr.com/photos/stradofear

  6. #16

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    Jul 2010
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    Re: Need a very slow motor (like 1 RPM).

    Surplus shed have geared motor with an output of 2/3 RPM. Their Ref M2106P price $8.50

  7. #17
    Tracy Storer's Avatar
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    Re: Need a very slow motor (like 1 RPM).

    Quote Originally Posted by AtlantaTerry View Post
    Also, how do I calculate something like gear reduction? I know if I have a motor with a small spindle that I can put something like a pulley on it then run a belt around the surface. Can't I by changing pulley sizes make the surface rotate faster or slower?
    For gear and belt drive pulleys, looks at circumferences. (diameter x pi) A pulley with circumference "2x" will spin at half the rate of the drive pulley of circumference "x" (the drive pulley goes around two turns to turn the driven pulley one turn.)
    With gears, its the same, but go by tooth counts.
    This is a big part of what you need to know to set up gear trains for thread cutting on a lathe, by the way.
    Tracy Storer
    Mammoth Camera Company tm
    www.mammothcamera.com

  8. #18
    Tin Can's Avatar
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    Re: Need a very slow motor (like 1 RPM).

    Quote Originally Posted by mdarnton View Post
    This place is totally unpredictable, since they have whatever they have, but a good look around their website is never wasted time: https://www.sciplus.com/ I see there's a little geared 3/5 RPM motor on their front page today, in fact, for $3.95!

    My wife is always wary when I want to go there because I inevitably come out with a bunch of questionable junk that might someday be useful, maybe.
    That place was more fun 30 years ago...
    Tin Can

  9. #19

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    Re: Need a very slow motor (like 1 RPM).

    Tracy - forget PI - it cancels out! Just compare the diameters.

    Neil

  10. #20
    Tracy Storer's Avatar
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    Re: Need a very slow motor (like 1 RPM).

    Absolutely true, pi becomes a common denominator.

    Quote Originally Posted by barnacle View Post
    Tracy - forget PI - it cancels out! Just compare the diameters.

    Neil
    Tracy Storer
    Mammoth Camera Company tm
    www.mammothcamera.com

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