Elevator Mechanic Practice Exam 2025 - Free Elevator Mechanic Practice Questions and Study Guide

To determine the required sheave size when increasing the speed of an elevator car from 100 feet per minute (fpm) to 125 fpm, it's essential to understand the relationship between the sheave diameter and the elevator car speed.

The elevator car speed is directly proportional to the sheave diameter; as the sheave diameter increases, the speed of the elevator car also increases. Conversely, to achieve a higher speed, a larger sheave is required, given that all other factors, such as the motor power and gearing, remain constant.

When calculating the new sheave size, we can use the ratio of the speeds to determine the necessary diameter to achieve the desired speed increase. Since the current setup uses a 12-inch sheave for a speed of 100 fpm, raising the speed to 125 fpm requires a proportional increase in the diameter of the sheave.

By calculating the ratio of the desired speed to the current speed (125/100 = 1.25), it suggests that the sheave diameter needs to increase to maintain the higher speed. To obtain this new diameter, we multiply the current sheave size (12 inches) by this ratio:

12 inches * 1.25 = 15 inches.

Thus,