Comment by dllu

The externally spinning Waymo Laser Bear Honeycombs do indeed cause whacking and pinching and occasionally get gunked up with wet leaves and debris. One reason why they are like that is because these have very large fields of view. A cylindrical plastic cover seriously degrades optical quality especially when the beam is hitting it at a steep angle. Another reason is that it has a heatsink on the back of the spinny part. Earlier Waymos like the Firefly in fact cover up this lidar, e.g. on the "nose" and the side mirrors [1]. But they went back to leaving it exposed for better performance.

Likewise with the big spinning lidar on top, which was covered in the older Chrysler Pacificas but externally spinning in the newer Jaguar I-Paces.

[1] https://commons.wikimedia.org/wiki/File:Waymo_self-driving_c...