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# How can we calculate the required torque to move a big object by means of gear assembly?

Question asked by Vinay Mishra in #Mechanical #Automobiles on Feb 2, 2020
Vinay Mishra · Feb 2, 2020

I need to know the required torque of a motor to move a vehicle of about 100-150 Kg. The vehicle is equipped with gear assembly and required to run at 20 to 25 Km/h.

One of my friends suggested me to read about tractive torque. But it was little confusing.Only one thing that I understood is the formula-

Tractive Torque =  Tractive Force x mean wheel radius

Can anyone help me out of this?

Posted in: #Mechanical #Automobiles
Noothan Kumar · Feb 22, 2020
Rank C1 - EXPERT

Hi,

Rolling Friction

The torque required [Nm] at the wheels is Maximum force[N] x radius of the wheel{m]

T(wheel) = F x r

This has to be converted to the torque required at the machine side, which is a ratio. Ignoring all losses, power in = power out, but one can generally allow for a loss of about 2% therefore,

T(motor) x w(motor) = T(wheel) x w(wheel) where T is in Nm and w (angular velocity) is measured in radians per second.

To include gearbox efficiency of 98% this becomes

0.98 T(motor) x w(motor) = T(wheel) x w(wheel) (you will need more torque at the motor side to overcome the inefficiencies)

To convert rpm to radians per second: w = rpm x 2Pi / 60.

Thank You. Happy Concepting.

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