[sanelss]

Originally Posted by GeeTwo

A differential gear system is standard equipment on automobiles, easiest to understand on old rear-wheel drives. A drum is turned in the direction that the wheels should turn as an average (using bevel and crown gears in most cases), and another bevel gear is mounted to the inside of the drum to turn the wheel axles. If the wheels both move at the same speed as the drum, this later bevel gear does not rotate about its axis. If one of the wheels has to move a bit faster (e.g. in a turn), the bevel gear will rotate to let one move a bit faster than the other. The extreme case is when you're stuck in the mud and one wheel spins freely while the other does not turn at all. The net result is that average speed of the wheels must equal the speed of the drum. Inverse differential is if you run the differential backwards - put motors where the wheels normally are and use the common shaft as an output.

I'm not sure what flying means in this context.

flying in the sense that at top speed they are moving REALLY fast... it's rather scary especially when we had it mounted to a bench spinning at top speed unloaded....