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Skateboard Bearing Tester
This Project was submitted to Parallax by David Wayne.
The following is a skateboard-bearing tester. It comparatively tests the rolling resistance of skateboard bearings while inserted in a polyurethane skateboard wheel.
To run a test the user switches to a "setup mode" where a Parallax serial LCD prompts you to enter a desired target “set point” RPM. After the desired RPM is selected the user can then switch to “test mode”. Selecting “test mode” informs the BASIC Stamp 2 microcontroller to turn on a solenoid that pneumatically lifts and engages a DC motor drive assembly into contact with a flywheel. Activation of a second solenoid follows that pneumatically lowers onto the flywheel a weighted top assembly consisting of the skateboard wheel and the bearings under test. The display then prompts the user to hit the “start” button.
 Once the “start” button has been actuated the BASIC Stamp 2 microcontroller begins ramping up the speed of a DC motor driving the main flywheel. A twelve pulse per revolution optical reflective sensor/encoder on the flywheel provides the feedback required by the BASIC Stamp 2 module to drive a DC speed control. The LCD displays the RPM target set point and the actual RPMs being clocked by the BASIC Stamp 2 module. After the actual RPM target set point is accomplished and locked in, the BASIC Stamp 2 microcontroller then pneumatically drops out the DC drive motor assembly in contact with the flywheel. At that moment the BASIC Stamp 2 microcontroller begins counting the encoder pulses from the now coasting flywheel on which the weighted skateboard wheel assembly is still resting.
 As soon as all coasting wheels have come to a complete stop the LCD will display a count value: typical readings are in the range of 180 to 340 counts for the bearings under test (count/12 = flywheel revolutions). This device has proven to be a powerful tool to better understand and quantify differences in bearing quality, materials, lubricants, seals design, cage design, and of course marketing claims made by competitor’s bearings. The global skateboard industry supports sales of more than 30 million bearings a year!
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