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• # Linear Force from 3HP motor

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

1. ### JoeSNew Member

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Nov 2014
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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 EngineerActive Member

Joined:
May 2012
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What happened ?

Which came first the chicken or the egg?

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

4. ### bdeuellMember

Joined:
Mar 2014
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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. ### PierArgWell-Known Member

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Mar 2013
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Hello JoeS and welcome to the forum!

The problem is rather simple: if you know the mechanism geometry it is simple to transform the motor torque in linear force.

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Sep 2010
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