4" Wheel Mounting Attachment
Entry ID #: 8886
Created: Tue, Dec 8, 2020 12:48 AM
Team 8059X's "Make It Real" Online Challenge Submission: 4" Wheel Mounting Attachment Introduction The 4" Wheel Mounting Attachment is a compact, add-on part to the spokes of 4” wheels, which serves to provide mounting holes for a wider range of constructional versatility. These mounting holes were designed to line up with those on Vex gears and sprockets, but also can be used to connect wheels to one another or mount on any other Vex part easily. The 4" Wheel Mounting Attachment was conceived with the primary intent to solve many VRC teams’ desire to have mounting holes on 4” wheels similar to those on the 3.25” Omni-directional wheels; providing more mounting capabilities and design options. This was particularly sought after for teams that were considering sped-up drives be it geared or chained; where although 4” wheels were favored for higher efficiency in terms of work done and faster overall velocity, faced the drawback of having mechanical backlash due to wear and tear of the ¼” square holes where the Metal Shaft Inserts went. Indirect powering via gears or chain on the same axle in ratioed drives would further cause excessive backlash, and in turn, increased programming inaccuracy of the robot's autonomous motion. With this part, we were able to eliminate the backlash by easily screwing on Drive Shaft Bar Locks to increase the structural rigidity, reducing as much slop on 4” wheels ratioed drives to that of 3.25” ratioed drives. Plus, these holes also gave increased functionality in other practical building applications; such as easily screwing multiple 4” Traction wheels together as a flywheel, or easily mounting gears, sprockets, or other parts to the 4” wheels inside roller intakes. The design of the 4" Wheel Mounting Attachment also overcomes a prominent weakness of 3D printed parts, namely, that they are brittle and can easily snap, by sandwiching them between wheel spokes to prevent bending. The Process Since we could not ensure that our design would work on our first try, we made use of the Vex CAD files available from the Vex Robotics website. To work on this part, we made use of the Autodesk Fusion 360 software version 2.0.9313, Windows 64-bit. By importing the CAD file of the wheel, we ensured that our design would be precise and fit perfectly. In this way, we did not have to measure out the spokes and dimensions of the wheel’s axle but could make use of the CAD file to get accurate and precise dimensions. We also made use of Fusion 360’s Inspect function to get the dimensions of the wheel’s spokes and other parts. In order to create this shape, we sketched a cylinder then proceeded to overlay a CAD diagram of a 4” wheel. Then using the split body function in Fusion 360, we created the basic shape of the 4" Wheel Mounting Attachment. This shape is ideal as the 4" Wheel Mounting Attachment nestles itself in between the spokes of the 4” wheel, not only firmly wedging itself in place but also providing additional structural support to the wheel, which experiences high stress during use. We then sketched center diameter circles on the same 2D plane and extruded the shape in order to create holes on both sides of the 4" Wheel Mounting Attachment in order to mount the gear and the securing Metal Lockbars respectively.’’ However, even though our design at this stage may be precise and accurate in terms of its dimensions and fitting with the 4” wheel, we still had to ensure it would work and withstand the forces that it would experience when used on the robot. As such, we used Autodesk Inventor 2021 Professional 64 Bit edition, Build 183, Release 2021, to run stress simulations on our design to further refine it and test it, ensuring our final design would work in an actual match. We first defined our material as PLA plastic, then defined the constraints of our objects. Following this, we decided to define our stress as pressure acting on the sides of the wheel mounting. We estimated that a pressure of 3000 PSI would be acting on it when the Wheel Mounting Attachment was attached to the robot, but increased the simulated pressure to 5000 PSI to account for an in-game match where robots would be engaging in defensive strategy and our wheel mounting would be under more pressure. After defining our load, constraint, and material, we then proceeded to run the stress simulation. The stress simulation proved that our design was not only feasible but would also work in an actual match situation with high levels of defensive play. Additionally, this process of simulating our object under real-world conditions allowed us to refine our design to be more elegant, save more plastic used in printing, and still be functional. Conclusion Embarking on this online challenge, our team reaped many rewarding experiences. To be able to employ our engineering skills in solving this common issue has certainly inspired a greater passion and appreciation for STEAM and its nuances. The “Make It Real challenge” has opened our eyes to the endless engineering opportunities afforded by Autodesk CAD software; being invaluable when designing systems and components for competitive robotics. Ultimately, we are glad to be able to contribute back to the Vex community with the very skills this platform has helped nurture, and hope to continue doing so in the foreseeable future.
Links / Videos
This video depicts the use of the 4" Wheel Mounting Attachment in 2 primary applications - 1, its use in drive bases to reduce mechanical backlash, and 2, its functionality is being easily used to connect 2 wheels together as a flywheel.