In a belt drive system, as the pulley ratio increases, what happens to shaft speed on the driven pulley?

When considering a belt drive system, the relationship between the pulley ratio and the speeds of the pulleys is fundamental to understanding the mechanics at play. As the pulley ratio increases, that typically means there is a larger diameter difference between the driving pulley and the driven pulley.

In this setup, a larger driving pulley turning at a given speed will impart less rotational speed to a smaller driven pulley. This leads to a decrease in the shaft speed on the driven pulley as the pulley ratio increases. The fundamental principle here is that power is conserved in an ideal system; thus, if speed decreases, the torque must increase to compensate, assuming that the system's power transmission remains constant.

Therefore, the total power transmitted across the system (Power = Torque × Speed) remains constant, showing that as the driven pulley speed decreases due to the increased pulley ratio, the torque on the driven shaft increases. This relationship highlights the interplay between speed and torque in mechanical systems driven by belts.