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How In-wheel Motors Work


In-wheel Motor Power
The Mitsubishi CT concept uses the Mitsubishi In-wheel Electric Vehicle (MIEV) hybrid powertrain, which employs an electric motor in each of the vehicles four wheels.
The Mitsubishi CT concept uses the Mitsubishi In-wheel Electric Vehicle (MIEV) hybrid powertrain, which employs an electric motor in each of the vehicles four wheels.
AP Photo/Paul Sancya

So far, we've learned that the combination of several in-wheel motors can put out more than 600 horsepower and that they can receive their own energy while braking, but what about the instantaneous power that's sometimes required at the wheels? In other words, do these in-wheel electric motors provide enough torque for every application? After all, torque plays an important role in any automobile's response time and performance, doesn't it?

In a vehicle equipped with in-wheel electric motors, there's plenty of torque available -- almost instantly, as a matter of fact. Electric motors produce a high amount of torque, and since that force is transmitted directly to the wheel, very little is lost in the transfer. Each wheel can be equipped with sensors to determine how much torque is required at any given time. Similar systems exist in cars on the road now, but the response times are slightly slower due to the number of components involved and the more complex electrical communication pathways.

On a vehicle equipped with in-wheel electric motors, several major systems are housed within the wheel itself. So, it only stands to reason that many of the core components of a traditional automobile can be removed. We mentioned at the beginning of this article that the engine, transmission, clutch, suspension and other related parts can be eliminated on vehicles equipped with in-wheel electric motors because the in-wheel components handle all of these functions. This replacement of mechanical functions with electrical functions is often referred to as by-wire technology -- such as drive-by-wire, or brake-by-wire, for example.

Eliminating the engine makes it possible to add design and structural enhancements to a vehicle. To date, testing of the in-wheel electric motor system has been conducted by many automakers and technology companies, including the Venturi Corporation of Monaco for use in its Volage concept vehicle, but questions of reliability, durability and safety are difficult to report without widespread usage of the system.

For more information about in-wheel electric motors and the companies developing and testing the technology, follow the links on the next page.


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