A gear ratio trades speed for torque at a fixed power. Getting this arithmetic right before the build is the difference between a robot that climbs and a robot that stalls.
The formulasLink to this section
- Ratio = driven teeth ÷ driving teeth.
- Output speed = motor RPM ÷ ratio.
- Output torque = motor torque × ratio × efficiency.
- Wheel speed (in/s) = RPM ÷ 60 × π × wheel diameter.
Worked exampleLink to this section
A 6000 RPM bare motor with a 19.2:1 gearbox gives 312 RPM. Through a 2:1 chain reduction that is 156 RPM. With 96 mm wheels: 156 ÷ 60 × π × 3.78 in ≈ 30.9 in/s free speed.
| Mechanism | Typical target | Reason |
|---|---|---|
| Drivetrain | 50–65 in/s free speed | Fast but controllable |
| Linear lift | 2–4 s full travel | Cycle time vs. tipping |
| Arm | 0.5–1.5 s sweep | Torque for the payload |
| Intake | Surface speed > game element | Reliable acquisition |