We run a weekend event in the fall intended to give potential new members some hands-on experience with tools, the FRC control system and so on by building a very simple robot. It carries the bare minimum of control system parts, drives around and that’s it.
We’ve always done a 4-wheel design, with two driven traction wheels each driven by one drive motor – this year, the other two will be omni wheels (the sole purpose of which is to keep the robot off the ground).
In previous years, we had used the VEX single-reduction clamping gearbox. This year, I’m considering using the REV MaxPlanetary (1:15 ratio) driving a HTD belt to the shaft with the drive wheel, but I’m concerned with using a planetary gearbox on the drivetrain.
Here are my thoughts:
(1) Never would have done this with a Versaplanetary – just too small – but the REV gearbox is a lot beefier.
(2) The robot itself is going to be very lightweight
(3) The robot itself will see very light use (Once the season starts, we’ll repurpose the gearboxes and their associated motors/motor controllers to mechanisms on our competition robot.)
(4) Low-risk: If it breaks, then it’s a great teaching experience.
You’ll be fine. The only thing I’ve experienced with MPs is a loose output shaft, so give the retention screw some special attention during assembly. Otherwise, it’s well within load ratings.
The Giftybot ran two maxplanetaries with 5" wheels and a 9:1 ratio. I used these plates to pickup 4 bolts on the bottom of the planetary and also bolted into the 2 face mounted holes -
The biggest thing I’d recommend is using some very strong loctite on the hex output shaft or constrain it elsewhere too to ensure it doesn’t slip out. If that slips out of the planetary you’re dead in the water. We ended up using red loctite on it and it never came out again.
We have ran planetaries on drivetrains for years doing mecanum drives (at least 5 robots that I can think of). Never had any major issues using the banebots p80 gearboxes.
They’re probably plenty durable for drivetrain use. Teams have used andymark planetary gearboxes on drivetrains for a long time without any issues, which seem to be comparable.
Definitely not very weight efficient, but it doesn’t sound like you care about that in this case.
Never tried this with MaxPlanetaries, but we’ve run drivetrains with Andymark Sport planetary gearboxes before. Our 2019 robot had a mecanum drive that had the wheels mounted directly on the output shafts of the gearboxes. We yeeted that thing off the second HAB level every match, during both the season and off-season, with no problems whatsoever. I’m sure that the setup you’re proposing will survive just fine.
