Team 7461 is proud to release what we hope will be a valuable resource to teams through the entire FIRST Community - a collective set of modifications to the AM14UX series of chassis, that we hope will iron out many issues teams have had with it to date.
Sample Chassis using an 8WD configuration, with 4" SDS Treaded Wheels
The modifications detailed here were made with adaptability, serviceability, and robustness in mind, and most can be made with hand tools, though nicer versions can be made with access to a Lathe and 3D Printer.
The defining trait of this chassis, in my opinion, is the use of a piece of 1/2" ThunderHex stock bored out to 3/8 of an inch as a spacer between the bolt and the wheel, which allows for easy wheel swaps without having to fiddle with bolt spacers and simultaneously trying to align the bolt, as well as the use of self-aligning weld nuts riveted to the inner plate to retain the axle, which eliminates the need to reach into the robot with a wrench to remove a wheel.
The ThunderHex axle can utilize snap rings, spacers, or shaft collars to axially retain the wheel, depending on teams’ manufacturing capabilities.
Another neat addition is the use of 1/4-20 aligning weld nuts riveted to the outer plate for bumper mounting, which is an easy yet robust way to quickly attach and remove bumpers.
A few other minor modifications were added, including putting both pulleys on the inside, to maximize the wheelbase, 3D printed nut holders for the outer plate, for quick and painless removal if you need to replace a center wheel, and NEOs on the drivetrain rather than CIMs.
This set of modifications should be adaptable to any configuration of the KOP Drivetrain, and can be used with any wheels with a 1.875" bolt pattern and 1.125" bearing bore.
Wheel configuration using 4" SDS Treaded Wheels, and snap rings for axial retention
Wheel configuration using a 6" HiGrip, and spacers for axial retention
OnShape CAD can be found at: https://cad.onshape.com/documents/e387957b63ee0962199a29d0/w/fc6095508e8127e3bf2c20ac/e/ae3ff4ebfc9109c79dbab270
Next steps on this project include creating a series of documents and/or videos detailing how to fabricate it, and creating more example configurations for teams.
Special thanks to @nuclearnerd from Team 5406 for providing suggestions and inspiration through the course of this project, as well as everyone who posted in the Interesting AM14U2 and AM14U3 upgrades thread, and the folks at AndyMark for putting together such an adaptable and robust system for teams to use.
If you have any questions, thoughts, comments, or concerns, please feel free to post them here, and we’ll try to respond. Good luck in Infinite Recharge!