If the motor sheave diameter is increased from 2" to 2.5", what will be the fan RPM if the original RPM was 400?

When the diameter of the motor sheave is increased, it affects the speed ratio between the motor sheave and the fan sheave. The relationship between the sheave diameters and the RPM (revolutions per minute) of the fan can be understood through the concept of proportionality.

Initially, let's consider the original setup: the motor sheave has a diameter of 2 inches, and the fan is operating at 400 RPM. When the diameter of the motor sheave is increased to 2.5 inches, the larger sheave will turn slower to maintain the same belt speed, resulting in a change in the speed of the fan.

To calculate the new RPM of the fan after changing the sheave diameter, you can use the following formula:

[

\text{New RPM of Fan} = \text{Original RPM} \times \left(\frac{\text{Old Motor Sheave Diameter}}{\text{New Motor Sheave Diameter}}\right)

]

Substituting the values:

[

\text{New RPM of Fan} = 400 \times \left(\frac{2}{2.5}\right) = 400 \times 0.8 = 320 \text{ RPM}

]