Unlike in many industries, the companies that sell robotics parts tend to have pretty solid ties with their consumers. Many of them have close ties to teams, are small businesses, and/or tend to be active on Chief Delphi, the online forum many teams frequent. Most products these vendors develop are parts teams have been requesting for years, like the Kraken X60 motor, which has a Chief Delphi thread with over 1000 replies (and counting) over four months. Throughout my time on the team, our standard parts have shifted as these companies make new products. Recently, we’ve made some significant shifts towards REV robotics products. The two main ones are using MAXPlanetary gearboxes instead of VersaPlanetary or AndyMark Sport gearboxes and shifting to the REV ION tubes. Our Falcon 500s are also (likely) in the process of being replaced by the Kraken motors, but that may take a couple of years.

The most obvious design challenge that the MAXPlanetary fixes is the length of shafts attached to gearboxes. The MAXPlanetary gearbox is designed so that you can bolt any length of hex shaft while assembling the gearbox. If we were using the AndyMark Falcon Sport Gearbox, the only hex shaft length we could get was one inch. If we wanted it shorter, we could cut it down, but we would risk cutting it too short and ruining the gearbox. To lengthen the shaft, we would have to use shaft couplers or other methods to connect another hex shaft to the gearbox, which creates another potential point of failure and increases backlash.

Unlike gearboxes we used to use, this comes with each stage pre-assembled and all the tiny gears inside can’t fall out and get lost. Here you can see the 3:1 stage for both the VersaPlanetary and the MAXPlanetary gearboxes. The one on the left has five different gears which could easily fall apart and get mixed up or lost when not fully assembled into a gearbox. The MAXPlanetaries that we now use have cartridges instead, so not only are all the gears contained, but they’re also labeled on the side and we can bolt directly through two of the corners to put the gearbox together easily.

The MAXPlanetary gearboxes are also much stronger. As recently as my sophomore year, we had to check a chart to see if the gear ratio we wanted was acceptable or if there was a risk of it breaking the gearbox. While these two are comparing different sets of motors, you can see that the NEO and Falcon 500 have more red (bad) than green (good) on the VersaPlanetary load ratings chart, but for the MAXplanetary, any of the possible ratios are acceptable, even ones that weren’t with a VersaPlanetary gearbox.

We’ve also recently switched to MAXTube, which is REV Robotics’s line of structural tubing. Most robotics teams use 2” by 1” and 1” by 1” hollow aluminum tubing to create most of their robot structure. Our old tubes had .161” diameter holes, spaced an inch apart. This worked for 5/32” rivets but not very well for any bolt sizes. Theoretically, you could stick a #8 bolt in those holes, but a #8 clearance hole is supposed to be .177” so that seems like an odd claim, and #8 bolts are also too weak to trust with the integrity of our robot. The old tubes also only had holes on one side, so if we wanted to bolt through both sides, we had to machine that ourselves. MAXtubes have multiple options for hole patterns. We can buy tubes somewhat like our old ones (holes on one side), tubes with a “grid pattern” (holes going both ways), and tubes with the “MAX pattern” (a special shape that can fit either a bearing or their special tube. In addition to all these options for mounting, they also come with holes every half inch, so there are two times as many holes. Each of the holes is also .20”, which is large enough for #10 bolts (stronger than #8s) and can fit 3/16” rivets. This allows us to switch between rivets and bolts without drilling out any holes. Overall, these tubes provide significant benefits for strength, mounting, and ease of machining.

VersaFrame 2×1 (far left), no pattern MAXTube (middle left), grid pattern MAXTube (middle right), and MAX pattern MAXTube (far right).