Robotics Education & Competition Foundation
Inspiring students, one robot at a time.

Ratchet Gear for Flywheel


Entry ID #: 2109
Created: Sun, Jan 10, 2016 9:30 PM

        This part is a ratchet gear for a flywheel, similar to a bike hub. For this year's VRC game, flywheels are a popular design to launch balls into the net. However, this design comes with an inherent flaw. When the flywheel is stopped, the enormous kinetic energy and momentum of the flywheel remain. This can damage the gearing, as flywheels are geared for speed, so the energy in the flywheel is geared for torque from the output axle to the input. There are a few ways around this. The flywheel could be run continuously, or could be slowed down gradually, but running the flywheel continuoulsy risks tripping the motor internal PTCs, and neither of these strategies allow for the flywheel to be suddenly shut off at the end of each match. Another method is to use a ratchet gear. While VEX sells a ratchet gear, it is neither simple nor easy to implement on a flywheel. My part uses the VEX ratchet gear to conserve the momentum of a flywheel. The driven axle goes through the VEX ratchet and into a round hole in the new gear. The driven axle drives the VEX ratchet, which drives the new gear. The gear can then drive the flywheel through its axle hole, or further gear down the input. This new part has other uses, as well, such as creating a drive train or other mechanism that cannot be backdriven, or creating a mechanism that has one effect when driven forward, but triggers another effect when driven backward (e.g. it turns the flywheel when driven forward, but triggers a lift when driven backward). See the attached images at the bottom for setup.          I used Autodesk Inventor Professional 2016 to create this part. To make this part, I first used the design accelerator to create a gear face for a 84 tooth gear with the same diametrical pitch as the VEX gears. I then extruded that gear face, cut a spot for the VEX ratchet gear, added the space for the axle, and added holes. I then used the mirror function to create an identical, but reversed gear, to allow for a ratchet for both directions.         From this project, I learned that the designing that happens in my mind doesn't always translate smoothly to aluminum. What works in my head should written down, checked, and adjusted. I will certainly use Inventor in the future as a powerful designing tool for the rest of my VRC career, and after that, as well, in engineering. Being able to not only design accurately and easily, but also to show other what I envision is a very powerful tool in any engineering career.