This custom-designed plastic wheel has a rubber tire measuring 1.65" (42 mm) in diameter and is designed to fit the output shafts on our micro and mini metal gearmotors as well as the Solarbotics metal gear motors. Teeth on the hub optionally allow a reflectance sensor to be used for encoder feedback.
Motor Connections
This rugged wheel is designed to fit securely on the output shafts of our micro and mini metal gearmotors. These gearmotors should be mounted onto the side of the hub with the protruding teeth, as shown on the right. The output shaft will slide into the socket easily at first but will achieve a snug fit when pressed through to the other edge of the hub.
The output shafts on the Solarbotics metal gear motors will also fit these wheels, but because they are shorter they will have to be mounted onto the other side of the wheel where the fit is tighter.
Our extended micro metal gearmotor bracket is specifically designed to work with this wheel.
Specifications
- Diameter: 1.65" (42 mm)
- Width of tire: 0.75" (19 mm)
- Weight: 0.55 oz (16 g)
Encoder Feedback
The hub has twelve teeth, each 3 mm wide and separated from its neighbors by 3 mm gaps. Because the teeth are white and the tire is black, a compact reflectance sensor such as our QTR-1A can be used as an encoder. Note that in order to get the QTR to fit within the hub, you will need to cut or file off the mounting hole portion of the QTR’s PCB. You can then mount the QTR on the motor or motor bracket so that it is inside the hub looking outwards at the teeth that protrude from the rim.
The following oscilloscope capture shows the results of a test we conducted using a QTR-1A sensor to look at the teeth as the wheel rotated at around 380 RPM. Mounting two such sensors 90° out of phase would allow for quadrature encoder feedback.
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| QTR-1A output signal when looking out at the interior rim of the Pololu wheel 42×19 mm. |
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