[Jeff Waegelin]

One of the things with a three-speed transmission is that it's almost better to build a four-speed transmission after a certain point. If you're using pneumatics, you have to have two shifters to get three speeds, and at that point, you might as well throw on a fourth speed. You'd need 4 sets of gears anyways, why not use that to your advantage. URL=http://www.howstuffworks.com/transmission.htm]HowStuffWorks[/url] has a good explanation of four-speed manual transmissions work.

Keith is right, however. If you don't already have a gearbox designed, a one-speed drive, wheel shifter, or maybe a drill shifter (see the white papers) might be a better solution. Multiple speeds are nice, but don't spend too much time on it. We did that last year, and ended up assembling our robot in the last 3 days because we spent too much time on our transmission. Don't let your desire for a three-speed bot hinder your performance in other areas.