VEX Spur Gears

  The Vex Robotic Design System offers 4 different spur gears that can be utilized in a multitude of configurations. In some design, they can be used to convert the output of the motor for speed or force. Others can be configured to provide the power further down from the motor. With the use of derlin bearing, shafts, and collars, the gears fit within the patterns of the metal components. So no major alterations are needed to get the gears to fit together.

The four spur gears that are available are:

Teeth	Diameter
12	15mm
36	40mm
60	65mm
84	90mm

  In the VEX RPM Dynamometer project, the gearbox is designed to slow the rotation of the output of a motor down to a speed for which the optical encoder can handle.

  In this design, the motor is attached to a 12 tooth gear. The 12 tooth is then mated to a 36 tooth which will give a reduction in RPMs to 12/36 or 1/3. So if the Motor is running at 3000RPMs the shaft on the 36 tooth will only be moving at 1000RPMs (3000*1/3).

  The 36 tooth is tied to another 12 tooth gear to produce another reduction in speed. Since both are tied together there is no conversion.

  This 12 tooth gear is then mated to the 60 tooth attached to the optical encoder. This will further reduce the RPMs down 12/60 or 1/5. Using the output of the prior conversion 1000RPM (not the 3000RPM of the motor), the Optical Encoder will rotate at 200RPMs (1000*1/5).

  This gearbox gives a speed reduction of 1/15th (1/3 * 1/5). The VEX controller will need to multiply any results by 15 to get the output of the motor.