[FTC]: FTC Mecanum Wheels

Is anyone interested in buying sets of mecanum wheels (4 per set)? They would be 3d printed and therefore allowed at competition. Also, they are not COTS and could be up to 6" while still attaching to a Tetrix mount.

As far as I understand rules, if 3D printed items are purchased, they must be on the list of items approved for purchase, and wheels over 4" would not be.

It is not clear that sufficiently rugged strength could be achieved by 3D printing mechanum wheels unless they were done using a newer, high end printer with a printhead capable of feeding the newest nylon 3D print materials. Most teams would be reluctant to commit to an unproven (in competition) 3D printed wheel design, and not would not want to be beta testers either.

I see no big advantages for going bigger than the current 4" diameter limit for a COT mecanum wheel size anyway, especially with the torque & RPM specs of the current FTC motors.

What do you feel are the shortcomings of the currently available off-the-shelf, 4" (or under) mecanum wheels (excluding the hub incompatibility with Tetrix H/W issue)? I can see where climbing over obstacles would be better accomplished with a larger mechanum wheel, but that is about the only obvious advantage I see for a 6" wheel. In the disadvantages category, the greater torque developed in order to adequately drive a larger than 4" wheel also demands a more robust drive train, an area where the Tetrix FTC components are notoriously weak (soft metal axles with flats & hubs with too weak set screws to engage them).

We no longer even attempt to drive any size wheels using Tetrix axle & hub H/W. Strictly direct drive, with the gears or preferably sprockets attached directly onto the wheels. We use free spinning, high strength 10-32 socket head cap screws for our wheel axles, and we have said goodbye to all our past bent axle issues.

Of the not so many mecanum drive train robots competing in Illinois this year, our team 3507’s design, pictured below, was the most robust and reliable. The VEX wheels we used performed extremely well, surpassing even our most optimistic expectations. They have an especially grippy soft urethane formula for their roller material. Highly recommended, but hub attachment is the challenge.

-Dick Ledford