Stepper motor torque help

Discussion in 'General Electronics Chat' started by GarrettVD, Apr 13, 2013.

  1. GarrettVD

    Thread Starter New Member

    Apr 13, 2013
    10
    0
    Hi all,
    I am building an automated homebrew system, and I am looking for a proper stepper motor that fits the bill. I've done the force calculations myself, but I am no expert when it comes to physics and motors. Am I correct in believe that, if I have a 40lb mass that I need to raise and lower, using a 4" diameter pulley, that I will require a stepper motor with 80lbf/in torque? Also, if anyone can PM me some websites to find a motor that would fit the bill, that would be great as well.

    Cheers,
     
  2. MrChips

    Moderator

    Oct 2, 2009
    12,437
    3,360
    With such a heavy load any direct drive motor would have to be very large.
    You need a reduction gear in order to lift 40lb.
     
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  3. GarrettVD

    Thread Starter New Member

    Apr 13, 2013
    10
    0
    Thanks, Mr. Chips. So, after a bit of research on gear ration, am I correct in thinking that if I have a 2" radius driving cog, and a 4" radius follower cog, the amount of force exerted by the follower cog is double; while the rpm would be 1/2 of the original rpm?
     
  4. vortmax

    Member

    Oct 10, 2012
    103
    18
    yes.. The output torque is doubled while the RPM is halved.
     
  5. MrChips

    Moderator

    Oct 2, 2009
    12,437
    3,360
    Look into a worm gear if you want it to be self locking, i.e. the load cannot fall back down when the motor stops.
     
  6. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    Maybe you could use a threaded rod and a nut? A threaded rod with pitch less than 2mm is common, and with a typical size-23 stepper motor should easily produce linear force of 150-200 kg (300-400 lb).
     
  7. Rbeckett

    Member

    Sep 3, 2010
    205
    32
    Motiontek.ca has steppers and drive components. I am using quite a bit of their stuff on my three tier tower and control system. I am using pneumatics to dump the HLT and DS18B20's as temp sennsors for my PID's. I am driving all of the electronics from a 12VDC, 5A PS and several AC/DC SSR's. Eventually I will automate the valves to better manage my fluid circuit as well as the over all brew cycle. Good luck, an how about some pics of you tower too.

    Bob
     
  8. tubeguy

    Well-Known Member

    Nov 3, 2012
    1,157
    197
    How fast and what distance do you need to move the mass ?
    And how accurately do you need to position the mass ?
     
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