A gearbox changes torque by altering the speed of rotation between its input and output shafts. Gearboxes allow you to increase torque while reducing the speed of your prime mover output shafts.
Understanding the Relationship
Gearboxes work based on the principle of mechanical advantage. When gears of different sizes mesh, they transfer rotational force.
- Input Shaft: Connected to the power source (like a motor or engine), this shaft has a certain speed and torque.
- Output Shaft: This shaft delivers the power from the gearbox. Its speed and torque will be different from the input shaft, depending on the gear ratio.
The core mechanism involves trading speed for torque (or vice versa) while preserving power (ideally, ignoring inefficiencies like friction). The fundamental relationship is:
Power ≈ Torque × Speed
If power remains relatively constant (which it does through a gearbox, aside from minor losses), then if speed decreases, torque must increase proportionally.
The Role of Speed Reduction
According to the reference, The output shaft of a gearbox rotates at a slower rate than the input shaft. This is typically achieved using gears where the output gear has more teeth (or is larger) than the input gear connected to the prime mover.
When the output shaft slows down compared to the input, This produces a mechanical advantage, which increases torque.
Think of it like using a lever: a longer lever arm allows you to exert more force with less effort over a shorter distance. In a gearbox, the larger output gear provides a mechanical advantage that multiplies the input torque while reducing the speed of rotation.
Practical Application
This torque multiplication is essential in many applications:
- Vehicles: Allows engines to provide high torque for acceleration and climbing hills despite having a limited speed range.
- Industrial Machinery: Enables motors to turn heavy loads slowly but powerfully.
- Robotics: Provides the necessary torque for moving arms or grippers with precision.
Speed vs. Torque Summary
| Characteristic | Input Shaft (typically) | Output Shaft (in a torque-increasing gearbox) |
|---|---|---|
| Speed | Higher | Lower |
| Torque | Lower | Higher |
By reducing rotational speed using gear ratios, a gearbox effectively increases the available torque on the output shaft, making it easier to move or rotate heavier loads.
