Incomplete section. You can help by adding missing info.
They are large grey gears, with eight big blunt teeth.
Cogs spin counter-clockwise, and some clockwise. Their purpose is to obstruct the racer. If a regularly moving cog manages to trap a racer, the cog will continue to move normally for a few seconds then suddenly jerk in the opposite direction in order to free the racer.
↑Game Developer's Blog - Nitrome:
Flipside, 14 Nov 8, retrieved 16 Aug 17.