How to Produce Higher RPMs With Pulleys

Pulleys are devices consisting of a wheel and axle with a grooved notch. Within the notch either a belt, rope, chain or cable rests which transmits the applied force from one pulley to another. Pulleys are considered a simple machine because they produce work by multiplying the input force through a mechanical advantage. Pulleys are used in many applications, including hoisting and drive trains. Pulleys work similarly to differently sized gears. Reducing the size of the secondary pulley in relation to the primary pulley increases the rotational velocity of the secondary pulley. A simple ratio between the pulley diameters and rotational velocities can be used to design the pulley system that meets the design requirements.

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Reducing the diameter of the secondary pulley increases the RPM of the system.

Increasing the RPM of the secondary pulley

Step 1

Measure the diameter, D1, of the drive (primary) pulley.

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A tachometer measures the rpm of the rotating pulley.

Step 2

Determine the rotations per minute, rpm1, of the drive pulley, using a laser tachometer.

Step 3

Plug in the desired rpm, rpm2, into the equation D1/D2=rpm2/rpm1 to determine the size of the secondary pulley that will give the desired rotational speed.

Step 4

Use a laser tachometer to verify that the rotational speed of the secondary pulley meets the design specifications.