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

Original Article ↗ Hacker News Discussion ↗

Mercedes‑Benz’s move to mass‑produce axial flux electric motors, based on technology from its UK subsidiary YASA, is seen as a notable step in EV drivetrain evolution, offering much higher power and torque density in a thinner, lighter “pancake” form factor. Commenters weigh the technical pros and cons—manufacturing complexity, cooling and high‑speed efficiency limits, potential for in‑wheel or multi‑motor layouts, and implications for regenerative braking and deleting friction brakes. The thread also surfaces broader themes about Europe’s and the UK’s ability to commercialize deep tech at scale, China’s rapid EV and battery progress, and how much better motors can really move the needle compared to advances in batteries.

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.