• Welcome to engineeringclicks.com
  • Linear Force from 3HP motor

    Discussion in 'Calculations' started by JoeS, Nov 18, 2014.

    1. JoeS

      JoeS New Member

      Joined:
      Nov 2014
      Posts:
      2
      Likes Received:
      0
      Hello All,

      I just found this website and thank goodness it exists.

      So I have a motor turning an eccentric arm that drives a rod pushing a plate back and forth (imagine an old locomotive).

      The motor is running at 3 HP at 1725 RPM. The stoke is 1.75" (so the radius of the eccentric arm assuming it is a disk is .875"). It moves a plate that weighs 75 lbm.

      I need to find the tonnage force the plate pushes.

      I'm thinking I need to get torque and translate that to the linear motion in one direction (the push stroke vs the pull stroke), but it seems like I keep getting too low of a force....thoughts?
       
    2.  
    3. Auto Engineer

      Auto Engineer Active Member

      Joined:
      May 2012
      Posts:
      29
      Likes Received:
      0
      What happened ?

      Which came first the chicken or the egg?

      A bit more detail given in this thread to work with?
       
    4. bdeuell

      bdeuell Member

      Joined:
      Mar 2014
      Posts:
      21
      Likes Received:
      0
      torque output will vary with the speed of the motor, the actual speed under load not the rated speed.

      there is a good image of the torque speed curve for induction motors here (if thats what you have):
      http://www.engineeringtoolbox.com/electrical-motors-torques-d_651.html

      Im sure you have done the same calculation already but i calculated your motors torque output at rated speed and power. I got 9 ft-lb which would yield a minimum linear force of 125 lb assuming no loss in your mechanism.

      hope this helps.
       
    5. PierArg

      PierArg Well-Known Member

      Joined:
      Mar 2013
      Posts:
      100
      Likes Received:
      0
      Hello JoeS and welcome to the forum!

      I quote bdeuell answer.
      The problem is rather simple: if you know the mechanism geometry it is simple to transform the motor torque in linear force.
       
    6. Dana

      Dana Well-Known Member

      Joined:
      Sep 2010
      Posts:
      341
      Likes Received:
      3
      HP = torque * rpm / 5252, so your 3HP at 1725 rpm gives 9.13 lb-ft or 110 lb-in torque. At mid stroke (when it's moving fastest) with a 0.875" lever arm, that's 125lb force. At the ends of the stroke when it's stopping and reversing, the theoretical force is infinite.

      Whether that force is sufficient to accelerate and decelerate your 75lb plate at 1725 cycles/sec is left as an exercise for the student...
       

    Share This Page