Figure 13: Maxon DC motor and planetary gear system 11

Gearing systems, which are often referred to simply as gearboxes, are an attachment added to the end of the of the motor’s output shaft, kind of like a plug adapter, as shown in Figure 13. Similar to the adapter, a gearing system can be thought of as an energy conversion mechanism. In theory, a gearing system changes the input torque and speed of the motor to a different torque and speed of equivalent power at the gearing system’s output shaft. In practice, the converted output power is always somewhat lower than the input due to gear efficiency losses (η_G).

This conversion effect can be seen graphically as well. Adding a gearing system to a motor effectively changes the motor’s torque curve slope, shown in Figure 14 below. Although the motor may be spinning at the same speed and torque output, the output shaft of the gearing system is spinning at another speed and torque, and that transformation is indicated by the adjusted torque curve for the combined system. As a result, this also changes the effective operation range of the motor/gearing system combination. The goal will be to pick a gearing system that will adjust the torque curve so the desired operating point of your system will be within the adjusted torque curve’s continuous operating range.