Nidec announces in-wheel motor prototype

Motor manufacturer Nidec has announced a prototype for an in-wheel EV traction motor. The company aims to begin mass production of the motor around 2023.

The prototype motor fits within the wheel hubs of an EV, a design which Nidec claims allows for higher efficiency and lighter, more compact designs than motors occupying the engine compartment. The prototype consists of a motor with integrated reduction gears and an oil cooling system. The motor weighs 32 kg and can achieve a power output over 100 kW. It fits inside a 20-inch wheel and is compatible with rear-wheel, front-wheel and four-wheel drive systems.


Source: Nidec

  • Luke William

    When did we stop caring about unsprung mass?

    • Neale Upstone

      My thoughts exactly. It’ll have applications though. Could work fine on trucks, tractors and various specialist vehicles

    • Sai

      Me and a coworker were just talking about this today: Koenigsegg makes hollow carbon wheels with hollow spokes. What if you could mass-produce carbon wheels in a configuration that allows the stator or the rotor of the motor to be inside the hollow portion of the wheel? Not only do you have natural pathways for cooling, but it also partially solves the unsprung mass problem. In addition, considering the fact that battery packs naturally reduce the CG over any ICE-powered automobile, tuning a car with independent in-wheel motors to have the right suspension dynamics is not as much of a challenge as one might think.

      • Luke William

        CF wheels shed like a couple kg. These motors weight like 30kg… 😐

        • Sai

          A couple kg? LOL. A forged 20×12 track wheel weighs about 12kg. Koenigsegg’s 21×13 wheels weigh 6.5kg. Truck wheels can weigh 15-20 kg. But consider the fact that the motor would take the place of the spokes and, like I said, be integrated into the design of the wheel itself. You could have a 20kg motor and a 5kg wheel barrel instead, which is not unreasonable considering this is just a prototype. 25kg is four times as much as a hyper-lightweight hollow carbon wheel, but we’re not talking about something that is outside the confines of physics.

          • Luke William

            Well there perhaps there is an application for trucks and heavy vehicles. But surely not for sports car where the drive would be towards reduction of unsprung mass, not trying to keep it the same.

  • Phil Schaad

    Immediately, I see two major challenges with this, and any, in-wheel motor system when applied to automobiles or motorcycles:

    1 Significant unsprung mass.

    2 incorporating a friction brake.

    I do believe that improved in-wheel motors may be successfully applied to small low speed vehicles and possibly, a wide variety of off-road machines where unsprung mass and physical dimensions are less significant. Use of in-wheel motors in bicycles and scooters is already proven.

  • Steve

    What’s 32kg of unsprung mass when you reduce the weight of the vehicle by several times that? Don’t whine about unsprung mass until you drive a vehicle optimized for this configuration.

    • Colin Frank

      With 32kg of unsprung mass, reducing the (sprung) mass of the vehicle actually makes problem of unsprung mass worse. You want a high ratio of sprung : unsprung mass. That said, EVs have the advantage of a massive battery that’s sprung, fixed, and vary low.

      • Steve

        The other thing to remember is that this is not intended for race cars. Many think that every car must be pushed to its limit, but many commutes fail to get much beyond 40mph. Smooth city roads at low speeds is a valid use for a vehicle.