If a contractor wants to increase the car speed from 100 FPM to 125 FPM, what size sheave is required if it currently has a 12" sheave?

To determine the size of the sheave required to increase the car speed from 100 Feet Per Minute (FPM) to 125 FPM while maintaining a consistent drive ratio, it is important to understand the relationship between sheave size and speed. The speed of a car in a hoisting application is directly proportional to the diameter of the drive sheave.

Using the formulas that relate speed and sheave diameter, we know that if the diameter of the sheave increases, the speed will also increase, given the speed is directly related to the circumference of the sheave. The initial speed of 100 FPM corresponds to a 12-inch sheave size.

To find the new sheave diameter that would provide the increased speed of 125 FPM, you can set up the following proportional relationship, using the current speed and sheave size versus the desired speed and unknown sheave size:

[

\frac{Speed_1}{Diameter_1} = \frac{Speed_2}{Diameter_2}

]

Where:

• Speed_1 is 100 FPM,

• Diameter_1 is 12 inches,

• Speed_2 is 125 FPM,

• Diameter_2 is the unknown size we need to