Robotics Education & Competition Foundation
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Custom Flex Wheel Inserts


Entry ID #: 8999
Created: Tue, Dec 8, 2020 9:46 AM

After hearing that Flex Wheels would be legal in VRC this year, we were excited to test them on our Change Up intakes. However, after receiving the wheels, we noticed a lot of setbacks, especially with the Versa Hub, which serves as an insert for axles. The main problem is that the large size of the Versa Hub restricts the areas of the wheel that compress, thus massively reducing the wheel’s flexibility. Additionally, the hub has a hexagonal hole, requiring another insert to have an axle-shaped hole, and if a team is using a low-strength axle, which is usually the case, the wheel needs yet another insert to have the right shaped hole. Having three stacked inserts on each side of the wheel adds a lot of unnecessary weight and width. 

We created this custom insert for Flex Wheels that solves all of the problems with the Versa Hubs. This insert gets pressed into each side of the compliance wheel and can hold either a high strength axle or you can place the VEX low-strength axle insert in the square hole in the center and place a low strength axle inside it. This insert requires minimal assembly, is very lightweight, is thin, and it allows the user to maximize the flex in the compliance wheel. This part can be used whenever a team is using the flex wheels and wants a custom insert that allows for more flex. For instance, this year it could be used on intakes of a Change Up robot to compress the ball more. Change Up intakes also need to be as thin as possible to fit inside of a goal, which these inserts would help with. The inserts could also be used on a flywheel, which requires a lot of compression to shoot a ball and accelerates faster when it's lighter.

We used version 2.0.9313 of Fusion 360 to create this part. The Flex Wheel and axle insert CAD designs from the VEX Robotics website served as templates to size the inserts around. We started with a 0.3” tall hollow cylinder to fit inside of the central hole of the wheel. We then added another thin cylinder to the outside of the wheel that was slightly larger than the diameter of the central hole. This created a lip for the insert to be pushed in the right amount. An extruded sketch that extends from the circle to one of the large pockets in the flex wheel serves as a latch. There are three of these latches on the insert, which keep the insert from slipping within the wheel when under a lot of torque. We made this latch as thin as possible in order to maximize the wheel’s compression, while remaining thick enough to maintain the durability of the wheel. We added the axle hole in the center, using the VEX axle insert as a size reference. Lastly, we used fillets to make the design cleaner and smoother.

This was a good project to improve our CAD skills, and to practice creating custom parts. We all compete on a VEX AI team as well as VRC, so we plan on printing these inserts to use for that competition, which allows custom parts. Learning new features of Fusion 360 will help us create custom parts for VEX AI and VEXU in the future. In VRC, even though we are not allowed custom parts, we use CAD to design our robots before building them, making the building process much quicker and more efficient, and allowing our robot to work better as everything fits together perfectly. CAD is also useful outside of robotics - 3D printed parts can be used in countless real life situations. Learning 3D design software can help in many career paths, such as engineering, architecture, and graphic design, all of which use software such as CAD to create 3D designs and simulations.

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