[sanddrag]

Here's a quicktime movie of 980 shifting wheels. I think 258 did the same thing in 2002.

As for clutches, I don't think I've ever really seen one on a FIRST robot. It is really not necessary. For how relatively easy it is to slow down the motor(s) and for the wheels to slip on carpet, a robust shifting mechanism is all that is really needed to shift. No clutch required.

Here's one good use of clutches though. If the game requires you to get back to the endzone, but you are still out in midfield with 2 seconds left, you would want to race toward the home zone and then disengage the clutch right before the buzzer so you can coast the rest of the way.