Yes, the middle wheel was dropped on the 6 wheel. It was adjustable via placing different sized spacers between the thrust bearing on top of the module and the frame. I believe we ended up with somewhere around 1/8 of an inch drop.
I started designing the first mini-module probably a month or so after the end of the 2009 season (basically once the burnout had worn off). overall I believe I designed 4 mini modules, and at least 3 drivetrains (I made 4 and 6 wheeled versions). If you include the system we used during the 2010 season, I spent the majority of the summer, start of the school year, and 6 week build season working on this. As far as a hour count goes, I really don’t have a clue.
As you can tell by the way the mini-modules are constructed, we relied heavily on our sponsor’s waterjet in creating them. However, I believe it wouldn’t be terribly difficult to create a similar module using CNC, or even manual, tooling. Programming was a very difficult step for us, it took upwards of a week to finally get a glitch worked out that wouldn’t allow the modules to spin all of the way around, so I would recommend having a competent programming mentor.
The durability had a few flaws to begin with, but I believe we worked them all out by the end of the 2010 season. On the first mini-module we used banebots wheels, which did not stand up to the abuse when we placed a robots worth of weight on them and spun them on the carpet. The second module we tried using bushings in. This didn’t work, and created concentricity and drag issues. The module we used during the season ran into one major flaw. We tried running a needle bearing on the upper shaft, which was hard anodized aluminum. Right as the elimination matches of our second regional began, the wear on the aluminum became enough to throw the drive sprockets out of alignment, causing the chain to come off if we hit any large bump. The final thing that was a slight problem during 2010 was the bottom flanges of the module. I had to extend them out quite a ways to enable the robot to go over the bump, and because of this they could be bent. This was never a big issue.