The future is all about packaging and here’s the automotive take on it
In today’s world, the key to any successful design is packaging, be it our home, office or vehicle. Space is at a premium more than ever but amenities have increased tenfold. Imagine that in your car or motorcycle, if the engine or electric motor (EM) can be packed inside the wheel itself, the amount of space that will be liberated! Manufacturers are coming out with EMs installed inside the hub of the wheel to drive it directly i.e. direct drive in-wheel hub motor. With the gearbox, transmission shaft, differential, axle, universal joints out of the picture, the resultant weight and space savings are huge. Lesser frictional losses translate to better efficiency and range.
A wheel hub motor in a two-wheeler allows for better control and handling. It allows for a simple 2WD setup as well and should be quite capable off-road, since power and torque can be individually controlled on each wheel, as in 4WD, but without its complexity. It’s a win-win situation, but strangely enough, it hasn’t ticked with the masses yet!
That is because installing an EM inside the wheel hub upsets the physics of our vehicle. A wheel with a motor inside it is heavier, which means more inertia and difficulty in controlling it, especially while steering. An EM inside a wheel is an unsprung mass. Unlike an engine or EM conventionally installed inside an engine bay, a hub motor is not supported by the suspension. Thus the wheel along with EM experiences unwanted movements while going over a rough patch or off-road.
Michelin with its Active Wheel technology has a solution for this. Its motor controlled active wheel suspension provides variable damping as per changing road conditions. This electronically controlled arrangement is said to successfully contain any unwanted vibrations, roll and pitch and thus make handling characteristics more manageable and predictable. However, it is an expensive proposition for now owing to the hardware and computing involved.
Don’t be disheartened as hub motors are already popular among two-wheelers. Since the rear wheel is non-steerable, it can easily employ a hub motor inside it. It has made inroads as an electric propulsion system in India and has been adopted by mainstream two-wheeler giants. Some examples are the TVS iQube and Bajaj Chetak electric scooters.