Calculating Torque

[JohnDoe]

Hi!

I'm having some trouble choosing the appropriate engine to run a mechanism. So maybe someone here could help me with the problem.

Simplified, the engine is rotating a cylindrical shape body of over a worm drive.

Since torque is M = F x v, i'm not sure what force i should use there to see what the momentum should be to make it possible for it to run.

 

Hope it's understandable what's bugging me since English is not my mother tongue.

 

Thx for any help you give me.

[baxtrom]

JohnDoe,

the torque required to drive the mechamism depends on what you attach to the other end of the worm gear. If, lets say, your mechanism is a wheelbarrow, where the wheel is driven by a motor through a worm gear. Say your worm gear has a gear ratio of 100:1, the wheel diameter is 0.5 m, and you want your wheelbarrow to be able to pull a load of 100 kg up a 10 degree slope. That means, friction losses aside, that the force required to push the wheelbarrow up the slope is 100 kg x 9.81 N/kg x sin(10 deg) ~ 171 N. In order to produce that force, the torque driving the wheel needs to be (force times radius) 171 N x 0.25 m ~ 43 Nm. Since the worm gear has a gear ratio of 100:1, the motor will need to produce just 0.43 Nm.

 

Further, if you want to drive your wheelbarrow up the slope at say 5 km/h = 1.4 m/s, the wheel needs to rotate with a speed of 0.9 revolutions per second or 5.6 radians per second. This means your motor will need to produce 43 Nm x 5.6 rad/s ~ 240 Watts of power, or about 1/3 hp, at 90 revolutions per second or 5400 rpm..

 

(Edit²: corrected error, again..)

Edited May 4, 2011 by baxtrom

[JohnDoe]

Thx. Your info was very helpful