Looking for small high torque motor

Discussion in 'General Electronics Chat' started by james211, May 7, 2016.

  1. james211

    Thread Starter Member

    May 29, 2012
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    I'm looking for a small high torque motor, preferably AC, somewhere between 40 & 60 RPM's, direction doesn't matter. I realized after researching these that there are a lot of terms I'm not familiar with so I'm looking for some help. The motor is for stirring coffee beans over an 8in fan, so it needs to be small. I purchased one that I thought would be fine, but once it reached any resistance it would flip between CW & CCW.

    Let me know if there is any more info I can provide.

    Thanks!
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If you want small AND high torque for that rpm, gearing may be the solution, also DC brushed may also be the best option.
    Max.
     
  3. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    3,853
    How many pounds of beans are you stirring? What is the geometry of your stirred "tank"? Height x width? How full is it (inches).

    Here is a start but you may need a bigger motor (more power). This is geared down 66:1 but it really depends on your load (how many beans you need to stir.

    Also, how wet/sticky are the beans through the process - I assume you are drying/roasting green coffee beans. Any physical resistance (viscosity or inability to "fluidize" the pot full of dry beans) will add to the load.
     
  4. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    @GopherT The beans will have been roasted already. I use a small home roaster, so at most the cooler will have 250grams of beans at a time. The beans are not sticky or wet....in fact, it will be closer to 200grams, as they lose about 15% of their weight after roasting.

    I think you forgot to attach a link by the way.

    @MaxHeadRoom The only reason I was trying to stay away from DC was because right now I'm able to tap into the power supply of the fan, which is AC, so I can avoid having two plugs, or misc bulk to the unit. If DC will be the most cost effective option I'll work it out. What is the smallest AC/DC converter you know of that I could use?

    Heres a little video of what I currently have.

     
    Last edited: May 8, 2016
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
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    That appears to be a small synchronous motor with gearing.
    The reason it reverses is it stalls momentarily and cannot handle the full load.
    You need a similar set up, either a higher gearing ratio or a slightly larger motor/gear combo.
    Something along these lines may provide more power ebay 222106365225, just needs a 12vdc supply or a simple 120v/12v bell transformer and a bridge rectifier.
    Max.
     
  6. Tonyr1084

    Active Member

    Sep 24, 2015
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    If stir rate is not critical and you have access to an old microwave oven with a turn table, those AC motors (some rated at 120 volts, others rated at odd voltages - but still AC) can stir at 1 revolution per 10 seconds. In other words, 6 RPM. True, if overloaded, they will reverse direction, but they may be geared low enough to stir the pot (so-to-say).

    I've scrapped out a few microwave ovens for parts. Some ovens have faster motors that rotate a microwave deflector plate (to enhance even heating), but they are closer to the range of RPM you're asking for but they will certainly not be able to handle the torque.

    I've seen rotisserie motors for grills that aren't "Slow" but they aren't the speed you're asking for. Here's one on Amazon for $25.00 and can handle an 18 pound bird. Nothing on the specs for torque so I don't know if it will handle your load. It's 6 RPM.

    Here's the link: http://www.amazon.com/Rotisserie-Mo...=1462723847&sr=8-12&keywords=Rotisserie+Motor
     
  7. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    I'm going to give one of these a try.
    image.png
     
  8. ronv

    AAC Fanatic!

    Nov 12, 2008
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    We don't know where you live, so 50 or 60 Hz? 120 or 220 volts?
    Is there a plate on your motor that tells the voltage, current, and/or watts?
     
  9. james211

    Thread Starter Member

    May 29, 2012
    210
    2
    120v 60Hz. The DC motor I mentioned above arrived (thanks Amazon same day) and I do believe it will have enough torque. The downfall is now I have to run two power cords, which less face it, we all want less cords. If there's a small enough power converter that I could strap to the side and tap into the mains for the fan that would be ideal, but I'm not sure what that would be.

    So I guess if there isn't a small, inexpensive AC motor that will work for me, then I could build a small power supply box that would have both 120v and 12v outputs. I have a couple of these meanwell switching supplies laying around.

    Any other suggestions?
     
  10. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
    1,150
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    Synchronous motors will do that especially if there is no capacitor. They tend not to know what direction to turn and have very little torque.

    Measuring the torque required would actually be a big help. A spring scale and a distance. e.g. 1 lb and 1 ft is 1 ft-lb. Weights work if you can utilize gravity.

    40 oz-inches is pretty strong.

    Torque changes with speed. Speed is dependent on frequency for a synchronous motor. See: http://www.hurst-motors.com/lyg55geared.html

    The website has other choices. You just won't like the price.
     
  11. ronv

    AAC Fanatic!

    Nov 12, 2008
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    There are a few on ebay:
    http://www.ebay.com/sch/i.html?_fro...ear motor&rt=nc&_mPrRngCbx=1&_udlo=1&_udhi=30
    The trouble you may have with the little DC motors will be brush life.
    But since you have it just splice a wall wort power supply into the fan wires.
     
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