Re: Drop-center drivetrains: Why?
 

If what I've suggested is "new for the sake of new" implementation of 6WD/WCD is "a solution searching for more problems". I made the benefit pretty clear, but perhaps a more in-depth explanation is required. In short, the benefit to raising the middle wheel on the fly is to maintain a level of functionality while removing the derived assumptions realized by a more advanced/coupled design. Indeed, I did not even imply those assumptions, but then again no one ever really talks about them.

Reduce the team in question to an average team who seeks to maintain most of the same capabilities as the 'best' 6WD while also maintaining other requirements they've set forth for their robot. Perhaps 4-6 motors and a COTS shifting transmission on the drive train is deemed a lower priority than having extra power/weight for other robot subsystems for a team. To be honest, this is a very reasonable assumption for any team.

If the extra power/weight in the team's manipulators were to pay off in on-field success, many other teams would come to defend them.

Thus the team would be subject to defense via turning due to its gearing choices and wheel base when it competes against another robot with more power/capability in the drive train. Adding a potential design to raise the middle wheel using simple pneumatics in order to remove the disadvantage may prove to be a superior design for that team's overall robot depending on their time, available resources and funding.

Re: Drop-center drivetrains: Why?
 

We had a variable drop center chassis this year. In simplest terms, it allowed our middle wheel to raise up while going over the bump (4-5"). This allowed us to have smoother and faster transitions with less impact on the robot/chassis. This was a key component of our strategy as we knew that for many matches we would start in the back and work our way forward and did not want to be limited by the potential tunnel pinch point. Our analysis (check white papers) showed a flat or rock 6x6 would have a considerable amount of problems going over the bump (not impossible, just not pretty).

The variable drop middle wheel also allowed us to flatten the chassis to "hold" directional heading (very important in 2005, 2006 and 2007). As it turns out, this year holding a particular heading was not as essential as those other years. You were either pointed at the goal to take a shot, or you were not. If we had been allowed to store multiple balls, this would ahve been a different story, but it also would have been a very different game.

This variable ride height middle wheel did cause issues with our collector.

Re: Drop-center drivetrains: Why?
 

We did something similar in our non-dropped 6wd (wide) for Lunacy. It was actually a pneumatically actuated wheel that lifted up the back four, which was great for both turning on a dime acting as a break on the regolith. We could even strafe on occasion, though certainly not as well as nonadrive.

Lesson being there are a lot of novel "dropping" options to achieve your desired results--it need not be just the center. (photo)