How to Calculate Stress for a Flywheel

Density of the Flywheel

• 1

  Find the density of the flywheel cylinder. If not readily available, this value can be calculated by dividing the volume of the cylinder by the mass of the cylinder. To find the volume, you must first measure the inner radius and outer radius of the cylinder using a ruler or other measuring device.

• 2

  Take the difference between the two values and square the resulting value; e.g., if the two radii are 5 cm and 3 cm, then 5 cm - 3 cm gives 2 cm. Multiplying this value by itself gives 4 cm^2. Multiply the resulting value by pi--3.14159...--and the height of the cylinder. This is the volume.

• 3

  Find the mass of the cylinder using the scale.

• 4

  Divide the volume of the cylinder by the mass of the cylinder. The resulting value is the density of the cylinder.

Angular Velocity of the Flywheel

• 5

  If a value of the angular velocity is not available, it can be found using the flywheel. Make a point on the outer radius of the flywheel using a pencil.

• 6

  Start rotating the flywheel, and begin timing when the point you have marked passes a predetermined position. Once the point you have marked on the flywheel reaches the predetermined position again, stop timing.

• 7

  To find the angular velocity, multiply 2 by pi, then divide this result by the time you measured in the step above. This is the angular velocity, measured in radians per second.

Stress on the Flywheel

• 8

  Square the value of the outer radius of the flywheel.

• 9

  Square the value of the angular velocity of the flywheel.

• 10

  Multiply the two values from the steps above--the square of the angular velocity and the square of the radius--together, and multiply the result by the density of the flywheel. The result is the stress on the flywheel.