Mid-drive motor

A mid-drive (or mid-mounted) motor sits on the frame near the swingarm pivot, or on the swingarm itself, and drives the rear wheel through a belt or chain reduction, much as an engine drives a motorcycle's rear wheel. The Ather 450 series uses this layout with a belt; most electric motorcycles use a chain.

• Battery DC goes to the controller, which converts it into three-phase AC for a permanent-magnet synchronous motor.
• The motor spins fast, far faster than a wheel ever turns, and its shaft carries a small pulley or sprocket.
• A belt or chain runs to a large pulley or sprocket on the rear wheel. The size difference, often combined with a small internal gear stage, multiplies torque by several times and lets the motor stay compact.
• The rear wheel is a plain wheel: light, cheap and easy to remove.

Keeping the motor on the frame instead of inside the wheel keeps unsprung weight low, so the suspension works better over broken roads, and it lets the motor be cooled by air flowing over fins or, on bigger machines, by liquid. Because it runs through a reduction, a mid-drive motor can be smaller and lighter than a hub motor of the same output.

What you notice: strong, consistent acceleration that holds up on long climbs, a faint belt or chain whine, and the same light-wheel feel as a petrol bike. The price is a final drive to look after: a belt needs only inspection, a chain needs lubing and adjustment, and the motor and controller take up space that a hub-motor scooter can use for storage.