The cog the chain is onWeight plates on a winch drum: the hillDial: push a foot needs at the pedalA motor turns a 34-tooth chainring in place of the rider; a torque sensor on the spindle drives the dial, which reads the push a foot would need on a 172.5 mm crank. The plates load the hub with 23.7 N·m, what an 85 kg rider and bike on an 8% grade put through a 700×25c wheel. A bigger cog turns the hub less for each pedal turn, so the push falls from 389 N on the 12 to 167 N on the 28, and the plates rise less per stroke: the same work, spread over more turns.