3 Studs Wide Differential Lock
An idea on how to lock the new, 3 studs wide differential in a compact, reliable way.
The 8297 set came with a new, 3 studs wide differential, which is already a third generation of Lego differentials. It’s narrower than the previous ones, and much easier to transfer the drive to, but lacks any specific means to lock it (at least at the time of the 8297 set’s release). The solution shown here is the most compact locking mechanism I was able to develop so far. It relies on the transmission driving ring, which is a rare part but very easy to engage/disengage. It’s so compact that the driving ring actually touches the differential case, but the resulting friction is minimal thanks to its smooth surface. The 16-teeth and 20-teeth gears are well meshed and capable of handling a considerable torque, while their ratio reduces the torque transferred to the transmission driving ring by 20%. I suppose the driving ring and the differential have similar torque resistance, but the driving ring is a much more expensive loss