Robotics Education & Competition Foundation
Online Challenges

One-Way Bearing with Conical Rollers


Entry ID #: 8784
Created: Mon, Dec 7, 2020 9:06 PM

This part was created to help solve the problem of ratcheting systems in Vex. Often vrc competitors are forced to use traditional hardware and rubber bands to create ratchets. While a large amount of these devices are effective, they take up a large amount of space and can cause significant frictional losses.      This part is a special type of one-way bearing that was specifically designed to be 3D printed in one part. Typical bearings use spherical rollers which are effective at reducing friction between the outer and inner race. However, spherical rollers are difficult to 3D print in one part due to layer adhesion. Our solution was to use cone-shaped rollers fitted on rails. This allowed us to print the whole bearing in one piece since the rails held the cone shaped rollers in place. This part would be used on a robot to restrict a shaft to only one direction of rotation. This would be useful in a robot where one motor is required to power two or more systems that function in one direction. The part works by using the frictional force between the rotor (which is directly connected to the shaft) and the rollers. When the rotor rotates in one direction, the rollers are pushed by the rotor and the device slips. When the rotor rotates in the opposite direction, the roller maintains its position initially until the frictional force of the rotor and of the outer ring lock the roller in place. This will cause the rotor and outer ring to rotate as a full system, therefore powering the robot’s gear or sprocket.      I used Fusion 360 version 2.0.9313 to design this part. In the past I used Autodesk Inventor but found the user interface for Fusion 360 more appealing. With this program I was able to adjust each of the components to the correct tolerances to allow for slippage or lack thereof. Fusion allowed me to quickly change a few dimensions and reprint the part constantly until my 3D printing tolerances were correct. Fusion 360 also has a team aspect that allows several people to contribute to a project at once. This makes collaboration far more efficient than through conventional messaging. Overall, CAD and specifically autodesk is the reason such problems are able to be solved.     We learned quite a lot about moving parts and how to design them properly so they perform the desired task. One of the most important tools for creating this part was the offset sketch tool. This function was required to create the proper sliding tolerances between the rotor, rollers, and outer ring. We also used the sweep tool a few times. The sweep tool allowed us to create the rails that support the rollers, as well as the outer ring. In the future I will hopefully use 3D design software to design my own RC aircraft since that has been a favorite hobby of mine. Additionally, I have been using such software to create parts for my computer or 3D printer that I don’t want to purchase, or that I want to customize. This software helps for competitive robotics because it allows us to plan our designs ahead of time so when it comes to building it’s a far simpler process. The software also allows us to quickly make changes virtually to see how it looks before possibly wasting valuable material and time trying to fit it to the robot. In the future I hope to be an engineer so 3D design software will likely be essential. Specifically it would assist me with designing mechanical parts that would otherwise be difficult to sketch and machine manually.


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