Made for students, by students Motor Selection Guide
Figure 15: Location of torque and speed measurements 13
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- Figure 16: Required Motor Torque vs. Gear System Efficiency
| Figure 15: Location of torque and speed measurements 13
In this example, the gear system would require a gear reduction in the range of 31.6 to 63.2. Physically, this means the gear system output shaft would turn once for every 31.6 to 63.2 turns of the motor. On the gear system data sheet, the reduction or gear ratio is typically listed as a ratio, such as 31.6:1. Rarely is the exact gear ratio you want actually available, but a great rule of thumb is the lower the ratio required, the better the efficiency. It’s best to aim for a gearing system that is just above your minimum gear ratio. If a gearbox is selected with a 35:1 ratio, the motor speed (nmot) is calculated with the equation below. It is important to double check that the calculated motor’s speed is still safely within the motor’s continuous operation range (of less than 8000 RPM in this example), as this may not always be the case even if that gear box is made by the motor’s manufacturer.
The next item to review is the torque multiplication. As the speed is reduced, the torque is increased by a similar, but not necessarily the same, ratio. If the gearbox ratio selected is 35:1, the output speed will theoretically be exactly 1/35 of the input speed. However, the output torque (ML) will actually be slightly less than 35 times the input torque (Mmot) due to inefficiency and friction in the gear system. The equation to calculate the motor torque required is shown below for a gear system with 35:1 ratio and 80% efficiency.
Depending on the efficiency of the gearbox, the torque required from the motor can vary by a significant amount. In Figure 16 below, motor torque is compared to the gear system efficiency. The efficiency of the gear system clearly has a large role in determining what torque the motor must produce. 
Figure 16: Required Motor Torque vs. Gear System Efficiency The calculated motor torque and motor speed can then be used to calculate the motor power required to input to the gearbox. 
To summarize, with an 80% efficient gear system and a 35:1 ratio: Directory: intel intel -> Using Abstract Language Signals Power intel -> Intel Corporation intel -> Intel Corporation intel -> Intel® WiDi 38. 0 1 Production Version ReadMe File intel -> The Intel Celeron Processor intel -> The Sensational State Quarters Unit Plan intel -> Profitability & Effectiveness (ttm) intel -> Q: How much of the world’s computation is in high-performance computing clusters vs normal clusters vs desktop computers vs other sources? A Download 9.04 Mb. Share with your friends:
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