Mercedes‑Benz starts large‑scale production of electric axial flux motor

Original Article ↗ Hacker News Discussion ↗

What an axial flux motor is

  • Motor where magnetic flux runs parallel to the shaft in a thin, “pancake” disc; typically two rotors sandwich a stator.
  • Contrasted with conventional radial flux motors where flux is radial and rotor sits inside the stator.
  • YASA’s design uses yokeless, segmented stators to reduce iron and weight.

Perceived advantages

  • Much higher power and torque density for a given volume and diameter; examples cited of >40 kW/kg.
  • Very compact (on the order of 8–9 cm thick in the AMG application), enabling new drivetrain packaging.
  • Potential to place motors close to or in wheels, enabling per‑wheel torque vectoring and removing differentials.
  • Less material (especially iron) can lower cost and simplify supply chains at scale.

Limitations and technical concerns

  • More poles and switching events can reduce efficiency at high speed; not ideal for very high‑speed generators.
  • Cooling and stator overheating are harder due to low mass and geometry.
  • In‑wheel placement raises unsprung-mass and durability concerns.
  • For most EVs, batteries and aerodynamics, not motors, remain the main constraints.

Mercedes/YASA and industrial context

  • YASA is a UK company acquired by Mercedes; some see this as another case of UK-origin deep tech being scaled abroad due to capital, industrial base, or policy issues.
  • Debate over whether this is driven by Germany’s auto scale and industrial policy vs UK financialization and early exits.
  • Some praise Germany’s mechanical/electrical engineering strength; others note past weaknesses in software and batteries.

Regenerative braking and “no-friction-brakes” idea

  • Enthusiasm about regen potentially matching carbon-ceramic brake power density and even enabling deletion of friction brakes.
  • Counterpoints:
    • Regen is limited by battery charge rate and state of charge (cannot absorb energy when full).
    • Brakes are still needed for low-speed stopping, parking, system failure, and extreme/emergency braking.
    • Ideas like supercapacitor buffers or resistive dumps are discussed but seen as bulky or niche.

EV industry and competitiveness

  • Some see this as incremental versus transformative: current motors are already highly efficient; battery improvements matter more.
  • Others argue that lighter, cheaper motors still bring meaningful gains and will trickle down from premium sports cars to mass market.
  • Comparisons made to Tesla (still on radial motors) and to rapid Chinese EV progress; disagreement over how far “ahead” or “behind” different regions are.