FLL City Shaper Single Motor Challenge Part 5: The Bridge!
Simple in concept. The first incarnation of this device drifted right and spun one wheel rather than climbing the grade. This model has a limited-slip axle running in parallel with the differential axle, so when the bot is going forward the LS axle keeps both wheels in synch, but when in reverse and the right wheel is prevented from turning due to the ratchet, the LS axle is overcome and the left wheel rotates backwards.