Because some users turn the crank-handle faster and harder than others, a nifty three-stage gearbox and a dynamo based on powerful neodymium-iron-boron magnets is used to ensure that efficiency is largely independent of the torque applied.

ECONOMIST: MONITOR

When wheels are being driven directly by electric motors, different levels of torque can be applied to improve stability on corners.

ECONOMIST: Fast cars will go even faster with electric power