The 20D mm line of brushed DC gearmotors are available in three different gear ratios: 29:1 (440 RPM free-run speed and 25 oz-in stall torque at 6 V), 73:1 (180 RPM free-run speed and 60 oz-in stall torque at 6 V), and 154:1 (90 RPM free-run speed and 120 oz-in stall torque at 6 V). All three versions have the same dimensions except for the length of the gearbox, and they are intended for use at 6 V. In general, these kinds of motors can run at voltages above and below this nominal voltage, so they should comfortably operate in the 3 – 9 V range. Higher voltages could start negatively affecting the life of the motor, and lower voltages might not be practical.
The gearmotor face plate has two mounting holes threaded for M2.5 screws, and you can use our custom-designed 20D mm metal gearmotor bracket (shown in the left picture below) to mount the gearmotor to your project via these mounting holes and the screws that come with the bracket.
|Pololu 20D mm gearmotor with bracket and hub.||
|White Pololu 60×8mm wheel on a Pololu 20D mm metal gearmotor.|
This gearmotor has an output shaft with a diameter of 4 mm; the Pololu universal aluminum mounting hub for 4mm shafts can be used to mount our larger Pololu wheels (60mm-, 70mm-, 80mm-, and 90mm-diameter) or custom wheels and mechanisms to the gearmotor’s output shaft (see the right picture above). Alternatively, you could use our 4mm scooter wheel adapter to mount many common scooter, skateboard, and inline skate wheels to the gearmotor’s output shaft. The gearbox’s output shaft also works directly with the 120mm-diameter Wild Thumper wheels, as shown below.
|Dagu Wild Thumper wheel 120×60mm (metallic red) with Pololu 20D mm metal gearmotor.|
The picture below shows the dimensions (in mm) of the 20D mm line of gearmotors. The value of
L depends on the gear ratio of the gearbox: 29:1 is 15.7 mm, 73:1 is 17.2 mm, and 154:1 is 18.6 mm.
|20D mm metal gearmotor dimensions (units in mm; L depends on gear ratio).|
Note: These motors are intended for use at 6 V. In general, these kinds of motors can run at voltages above and below this nominal voltage, so they should comfortably operate in the 3 – 9 V range. Lower voltages might not be practical, and higher voltages could start negatively affecting the life of the motor.
Note: The older, discontinued 25:1 and 67:1 versions of this gearmotor now had a different mounting hole spacing and work with a slightly different bracket. This bracket is with the 29:1, 73:1, and 154:1 20D mm gearmotors we currently offer.
Selecting the Right Gearmotor
We offer a wide selection of metal gearmotors that offer different combinations of speed and torque. Our metal gearmotor comparison table can help you find the motor that best meets your project’s requirements.
|Some of the Pololu metal gearmotors.|
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