What information is needed to calculate the gear ratio in a gear drive system?

To calculate the gear ratio in a gear drive system, the pitch diameters of the gears involved are essential. The gear ratio is defined as the ratio of the rotational speeds of the two gears, which is directly related to their diameters. Specifically, the formula for gear ratio is often expressed as the ratio of the pitch diameters of the driven gear to the pitch diameter of the driving gear.

The pitch diameter is crucial because it represents the effective diameter at which the gears mesh, ensuring that the calculations reflect how the gears will actually interact in practice. This dimension is fundamental for understanding how the input speed relates to the output speed and the torque transferred through the system.

Other factors like the number of teeth can provide insight into the gearing system but aren't directly used in calculating the gear ratio when pitch diameters are available. Thickness and material of the gears are also not relevant to the gear ratio calculation, as they do not impact the speed or torque relations between the gears, but rather influence the durability and strength of the gears themselves.