Following is a step-by-step procedure which details how one selects a precision gearhead. The procedure includes the calculations necessary to determine the appropriate speeds, torques and ratios.
Minimum Data Necessary to Specify a Gearhead
- Required Output Torque [Mo]: oz-in.
- Radial Shaft Load : oz.
- Axial Shaft Load: oz.
- Required Output Speed [n]: rpm.
- Maximum Available Space [diameter, length]: mm.
- Required Output Torque = 17oz-in.
- Radial Shaft Load = 72 oz.
- Axial Shaft Load = 14.4 oz
- Required Output Speed = 30 rpm
- Maximum Available Space = 18 mm diameter, 60 mm length.
Step #1: Pre-Selection:
Choose a MICROMO gearhead that has a continuous output torque greater than the one required for the application. If the required torque load calls for intermittent use, selection is based on the output torque for intermittent operation. In this example, we must select a gearhead for continuous operation. Searching for a unit with desired diameter, length, and shaft loading characterisics, we find that gearhead 16/7 meets the specified parameters:
- Continuous Ouput Torque = 42.5 oz-in.
- Radial Shaft Load = 108 oz
- Axial Shaft Load = 18 oz
To calculate the theoretical reduction ration, the maximum available motor input speed for this gearhead is assumed to be 5,000 RPM. Dividing the available input speed by the required output speed will give you the reduction ratio required:
Step #2: Confirming the Calculations
The input speed to the gearhead is the product of the output speed and the actual gearhead ratio,
30x159 = 4770 rpm
This is the new required input speed.
Calculating the input torque requirement
Mi= (Mo) / (i x n)
n= efficiency of the gearhead expressed as a decimal between 0 and 1
i= the reduction ratio
Mi= the input torque needed
Mo= the requested output torque specified
Mi= (17) / (159 x 0.60) = 0.178 oz-in
For continuous operation the motor suitable for the gearhead must be capable of producing twice the required output torque. For this example, MICROMO DC motor type 1624E024S supplied with a 14 VDC motor input voltage will produce the required speed and torque. We recommend that when you specify, you select a "ball park" component, then verify its performance in your actual application. Recording the applied voltage and the observed current values at the unit's operating point will help you select the appropriate motor + gearhead. In the practical world, the application of an "ideal" motor + gearhead drive is not always possible. This is especially true if you would like to specify with off-the-shelf components. As no other micromotor company offers a wider range of motors with matching gearheads, we encourage you to consult our Applications Engineering Department if you would like a no-cost, no-obligation review of your application requirements.
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