Slickest drive transmission yet...

[dlavery]

For everyone that has attempted, or wants to attempt, to design their own gearbox/transmission design for the FIRST competitions, sit up and take notice - there is a new sheriff in town!

I had a chance to see the drive system designed and built by Team 33 this past weekend at the Richmond regional competition. It is, without a doubt, one of the most elegant designs I have seen in the nine years I have been working with the FIRST program. They have built a dual-motor, four-speed, shift-on-the-fly, AUTOMATIC transmission that is amazing.

It is the ultimate in simplicity - you can build it with a lathe and a drill press with an X-Y table. The gearbox itself is very small and compact - under two pounds. The gearbox and combination of the motors are separate subsystems, so the gearbox can be used with a single-motor (or triple-motor) design without any redesign. The shifting gears are all cut from 12, 14 and 20-tooth, 16-pitch pinion wire - the large tooth profile, small DP-to-diameter ratio, plus 15 mils of designed-in backlash makes on-the-fly shifting trivial.

But the best part is the automatic shifting function. The system detects wheel speed to determine the output of the gearbox. They have calculated the power curves for transmission in each of the four gears, and determined the optimal crossover points for the curves. The control system has been programmed to sense when the system reaches one of the crossover points, and automatically fires one or both of the shifting pistons to bump up or down one gear. All the robot driver has to do is push the throttle, and the system just goes. It auto-shifts all the way up to fourth gear for high-speed runs. Bump into something and need to start pushing harder? No problem - it just senses the drop in speed and auto-shifts back into first gear.

The Killer Bees have set up a great demo board with a prototype of the design all laid out, along with their design specs and performance analysis. They are very open with the design, and indicated that they will be writing up a white paper on it later in the year. If you are going to be at the Detroit or Canadian regionals, make sure you find a way to see this drive transmission in action (and if you end up against them in competition, you will definitely see how effective it is). My only regret is that I didn't get a chance to get any photos of their gearbox - if anyone has any, please post them!

-dave