After having gone through 2 regionals, here's an update on what we learned with this drivetrain.
First thing to mention, I never showed our method of locking the drivetrain into 6wd mode. This was done by using a 4" stroke, 1.063" diameter cylinder that pulled a line connected to the front of the rocking mechanism. When activated, this forced the middle wheel down into the carpet with just enough force to allow it to lift the front/back wheels into the air, effectively putting all of the weight of the robot onto the center wheel. We used a Spectra line with an adjustable eye-splice on one end so that we could vary the length of the line, effectively making our "center drop" adjustable. You can see the cylinder and line in the picture below (click for large). Rubber bands are used to keep light tension in the line.
I think it's important to note that
our drivetrain would have been a disaster without this feature! The suspension evenly distributes weight among all of the wheels, which is good for crossing uneven terrain, but makes it nearly impossible to turn on carpet. Toggling to a 6wd mode lets us drive like normal on flat ground.
During our first regional, we ran into some issues with the belt tension and wheel alignment when we went into the elimination matches. We hadn't been maintaining the drivetrain during qualifications, and it caught up to us. Each wheel is held on with a Versablock assembly, and by the time we got to eliminations many of the Versablocks had worked themselves loose. (by "loose" I mean "why is there only one bolt holding this on???")
A fun result of loose bearing blocks is misaligned shafts, which lets the belts put some side load on the pulleys, which pops the flanges off. I recommend avoiding that.
At our second regional (Vegas) we corrected the alignment and tension in all of the belts and kept a close eye on them, and never had any issues. I was actually surprised at the beating the drivetrain was able to withstand, as nothing worked loose or bent after our driver repeatedly rammed the robot over defenses at full speed. It can take much more abuse than I expected!
We do hear occasional belt skipping when the drivetrain is under heavy load (full reverse when going full speed forward, for example). I believe that the serpentine belt on the rocker mechanism is able to deflect the shafts enough to skip over the idler pulley. It runs over 5 shafts in total, and each is cantilevered, so there is quite a bit of deflection under high load. This is the portion that I think would need the most improvement in the next iteration.
Overall, I'd rate it 10/10 based on entertainment value, but 5/10 on effectiveness. Probably wouldn't do it again, but it's nice to have around.