How to find shaft torque for belt pulley arragement?

[sunil Gaikwad]

I am facing problem in calculating the shaft torque for my system.

Motor is driving pulley and that pulley is coupled with belt with another big pulley (please refer attached file image).
Motor power 19.4 kw, Torque- 71.8 Nm, Motor Rated speed- 2580 rpm, motor shaft dia=42mm
Pulley dia (refer attached fig):-
d1=124.78, d2=374.33, d3=124.78, d4=356.51, output shaft speed =291 rpm. (shaft dia is 80 mm)

How to find the torque of shaft? please tell me the methodology/procedure ...?

 

[insightful]

Torque simply multiplies by the ratio of the pulley diameters. The first pulley set diameter ratio is 3:1 so torque multiplies by 3. The second pulley set diameter ratio is 2.86:1 so torque multiplies by 2.86. Overall, torque multiplies by 3 X 2.86 = 8.6. (Note that this ratio is about 3% less than the ratio of overall speed reduction. This is because the effective diameter of a v-belt pulley is slightly less than the outside diameter; in your case, about 4 mm less.)