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

Customizable Slip Gear Set


Entry ID #: 6156
Created: Mon, Jan 14, 2019 8:20 PM

Introduction and use: The slip gear, which only has some of its circumference filled with teeth, allows a mechanism to be driven for only part of its rotation. This could be useful in many scenarios. For our team, and many other teams across the globe, a slip gear is used within the gearing of our catapult. This means when the motor is activated, and the slip gear begins to rotate, the section with teeth will mesh with the driven gear, rotating the arm of our catapult backwards. Eventually, there will be no teeth left to mesh with the gear connected to the catapult, and so the system will “slip”. The catapult, which has rubber bands connecting it to the gearbox, will launch forward when the gearing is no longer holding it back from the force of the rubber bands. The issue with this useful gear, is that you can’t buy them, you must make them yourself. When creating a slip gear, we had to put the desired size gear into our gearbox, see how many teeth were required to crank the catapult back, mark that many teeth, and remove the rest. Besides the obvious time dedicated to removing the teeth and sanding what remains of the empty side of the gear, you would need to test it within your system. If you did not remove enough teeth, you’d have to take the gear out, cut, sand, repeat; if you removed too many, then you’d have to restart with a brand-new gear. Today we make the slip gear much more effective. By creating a customizable slip gear in both the 36 and 60 tooth sizes, you no longer have to go through that process. All you must do is put as many teeth as you need between the two connecter plates and screw them tight. If this doesn't work the first time, don’t worry about cutting more teeth off or restarting to remove less, just unscrew the connecters, place more teeth in or remove as many as you need, then screw the connecter plates back together, trapping the teeth in place. This allows VEX to provide the right slip gear for anyone without having to make each gear with its different amounts of teeth. Use of software and design: To reinvent the slip gear as its own product, I used Autodesk Inventor 2019. Since we needed this new part to be customizable, I went with a modular design where only 4 distinct parts could be sold to create many different slip gears. I started by manipulating the 36-tooth gear and 60-tooth gear, so that only 1 of its teeth where present. From this single tooth I added a “T” like extension that would allow it to fit within a grove of the connecter plates. Then, I had to create the plates for the two sizes. Throughout the plates I created holes that would allow the user to screw together the plates no matter how many teeth where used. Then I was able to assembly these pieces together with screws and lock nuts to show how the slip gear would be used in full. Conclusion: As an aspiring engineer, using the 3D CAD software has allowed not only me to visualize a design, but my team mates or stakeholders as well. Being able to see a full design helps for many reasons. First off, you can see how parts come together in a way you may not have been able to in your head, it gives you a glimpse at how they would work together in real life. This allows for you to realize mistakes before dedicating too much time or resources to making and testing that design. It also allows for quick modifications to a design, much quicker than modifying a physical one. Finally, it allows for an easy and quick way to create a simple prototype of that design in real life: just 3D print it. There are also a couple benefits to using CAD as part of robotics. Since we spend a lot of time putting together assorted designs, without knowing how they may work when you’re done, it is often helpful to first CAD the design to see how it may, or may not, come together. Prototyping with CAD also allows for you to create a bill of materials. This means you will know if you have everything you need to complete your build or not, and if you don’t, you know exactly what you need to purchase or ask a mentor for. If all else fails and you can’t get everything you need, you can always redesign in CAD, without having to scrap a build you just ran out of parts for. All in all, I learned that CAD may be frustrating or time consuming in the beginning, but it is sure worth it to use in the end.