Gearbox for mechanism or appendage

[Andrew Duerner]

Let me start with a little background. I'm a professional mechanical engineer and I love robotics! I mentored for a team two years and went to several regionals and two championships. I also love solving problems and inventing. About seven years ago I came up with a new eccentric gearbox, it worked pretty well but it was too costly to produce. After being involved with FRC I started adapting the design to fit the competition requirements, low cost, available motors, ease of use, etc. After many iterations, kudos to the inventor of the 3D printer, I believe I have a design that can help a lot of teams improve their performance of the competition challenges.

Here are a few details on the gearbox. Its’ approximate size is 5”x5”x2” and weighs around 2lbs. It directly mounts a 2.5” diameter motor with a keyed 8mm shaft (CIM family). The base mounts to 1” 80/20 extrusion on four sides. The output has the same mounting provisions to make multi degree of freedom arms and gimbals easier. Right now there are three ratio options, 552:1, 264:1, and 168:1. There is an integrated bearing track approximately 4” in diameter to support the output load. Right now gearbox is made of ABS plastic fabricated on an FMD 3D printer. I believe this will be plenty strong for competition if it is installed correctly and used to manipulate game pieces, not for taking the load of an opposing robot crashing into you (which is true for many mechanisms in FRC). If the demand is warranted I could see transitioning to injection molded parts with better plastic to be stronger and cheaper. As for cost for the current design, I’m trying to keep it under $100.

This effort was directed at the general FRC community. I know that some “elite” teams fabricate all of their own gears and can machine anything they want ending up with something better suited for the competition, but there are many teams that I saw coming to the competition with a drive base and limited game functionality. I really want to help elevate teams to have success with their available resources.

Special thanks to Chase (also an FRC mentor) for help with cost cutting ideas and general improvements along the way.

I attached a picture of one mounted with some 80/20. If anyone has feedback or is interested in more information please post below or send me a PM.

Thank you,
Andrew