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kumar narendra

How to calculate torque?


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Dear Kumar Narendra, 

In order to calculate the Torque required to make any rigid body move in the desired direction we must have clear cut idea of the motion. Here, you need to provide us the diameter of the screw shaft that will make the saddle do the motion. This screw shaft actually transfers the powers output from the motor (in the form of Torque) to the power for Saddle for translation in the particular direction ( in the form of force). 


Thus, once we know the diameter of the screw shaft and load acting on the screw threads due to the weight of the saddle, we can find the torque using " d/2 * force equivalent".

This is the minimum torque that a motor should be able to produce.


Once you know this Torque, you can easily find the RPM of the screw from the Translatory speed of the saddle. This will help you find the Power Required.


I can solve all the things mathematically ( in the form of expressions) if required.


For more details and easy to make designing and calculation visually enhancing, you may start using CAD tools. You may visit some of these websites for more details:





I can send you the details of some websites as well that provide you the details how to make use of CAD models to make such calculations easy to understand.

Thanks and Regards.


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You should provide more detail.   But if we assume some data i.e the diameter of the screw shaft to be used to move the saddle is 0.3 m, then one rotation will move the saddle by 2*3.1415*.15=0.94 m. 

For 2m/60sec it will require more than 2 rotation/min.

Let the rpm 2.5, diameter 0.3m, mass of saddle 3500kg= 34335N force

Torque= 34335*0.3=10300.5N-m

Neglecting other factors like friction, mechanical loss etc. 

Power required=(2*3.1416*2.5*10300.5)/60=2697 watt=2.7kW.

Hope it will be helpful.


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Who said there was a screw? Did I miss something?


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Torque (also called moment — mostly by engineers) is calculated by multiplying force and distance. The SI units of torque are newton-meters, or N*m (even though these units are the same as Joules, torque isn't work or energy, so should just be newton-meters).

In calculations, torque is represented by the Greek letter tau: τ.

Torque is a vector quantity, meaning it has both a direction and a magnitude. This is honestly one of the trickiest parts of working with torque because it is calculated using a vector product, which means you have to apply the right-hand rule. In this case, take your right hand and curl the fingers of your hand in the direction of rotation caused by the force. The thumb of your right hand now points in the direction of the torque vector. (This can occasionally feel slightly silly, as you're holding your hand up and pantomiming in order to figure out the result of a mathematical equation, but it's the best way to visualize the direction of the vector.)

The vector formula that yields the torque vector τ is:

τ = r × F.

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