What is Rollout?
Rollout is the total distance a vehicle travels per one revolution of the engine or motor. It is a key metric for tuning vehicle performance, particularly in RC cars and racing applications. By adjusting tire diameter, gear teeth, and drive ratios, you can optimize for either top speed or acceleration.
How to Calculate Rollout
Here is the formula:
[\text{Rollout} = \frac{D \times \pi \times P}{S \times \text{IDR}}]
Where:
- D is the tire diameter.
- P is the number of pinion gear teeth.
- S is the number of spur gear teeth.
- IDR is the internal drive ratio.
The result is in the same unit as the tire diameter, per revolution.
Calculation Example
A vehicle has a tire diameter of 15 inches, 20 pinion teeth, 80 spur teeth, and an internal drive ratio of 2.5.
Calculate the numerator:
[\text{Numerator} = 15 \times \pi \times 20 = 15 \times 3.14159 \times 20 = 942.48]
Calculate the denominator:
[\text{Denominator} = 80 \times 2.5 = 200]
Divide:
[\text{Rollout} = \frac{942.48}{200} = 4.71 \text{ in/rev}]
The rollout is 4.71 inches per revolution. Increasing the pinion teeth or tire diameter increases rollout for more top speed, while increasing spur teeth or drive ratio decreases it for better acceleration.