Team 2471 swerve drives

[Bryce2471]

http://youtu.be/dKpz8bJqr58

This off-season I have been investing quite a bit of my time into this project, along with several of my team mates, its finally begun to pay off. The link is to a video of the test bot on Monday, which was the first day we got to drive it for more than about 5 minutes. Keep in mind, this is not our hallway to bash, so we are driving a bit cautiously. This robot will compete in the Bunny Bot off-season event on 12/21/13 hosted by team 1540.
Most of the team that worked on the swerve project would agree that the initial programming was much easier than expected. we began integrating the code on Monday of last week, we had a vexing initial zeroing problem that took us until the end of Wednesday shop to solve. Then I went in on Saturday for a few hours and got the robot strafing. The next day I was in for literally less than 90 min and the first version of the code was done and working. The current code is a simple robot based drive that works well but would take a lot of driver practice to achieve what we want, so we will continue to add complexity from here.
I have posted about the mechanical design previously on CD but I assume that many people have not seen it. The upper gear box is constructed with a one piece frame because it has high strength, low weight, and provides a compact design. The CIM drive has a one to one belt ratio on top right now to save space, and in the castor it has a 3.5 to 1 chain ratio, geared for 17 ft/sec. In the future, we may use a 12 to 15 belt ratio on top for more torque. The steering is done by a 550 series motor through a 27 to 1 planetary gearbox out of a Black and Decker drill, and then a 15 to 48 belt drive. The BND gearbox was chosen because it is light weight, some-what compact, and cost $17. Each swerve ends up weighing ~7.5 lb, the hole frame (as shown in the picture, not in the video) weighs ~37 lb. The foot print of each swerve is 6" by 6", but at ground level, the castors are only 4" wide.
I also have a version designed for next year that would have a foot print of 3" by 9.375". I might post the designs here later if I get enough requests. I will also do my best to post another video of it driving once we get more intuitive code.
If you have any further questions or comments i'd be happy to here them. Also, I'm still undecided on the gearing change, so if you have an opinion, please post.