A Train With No Wheels

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A Train With No Wheels

BY AWAKE! WRITER IN HONG KONG

EVEN before boarding the gleaming new streamlined train in Shanghai, China, passengers sense that they are traveling on a railway with a difference. That feeling is heightened as the train whispers away from its ultramodern station and accelerates rapidly and smoothly to more than 265 miles [430 km] an hour, making it the fastest commercial railway on earth. It completes the 19-mile [30 km] journey to Pudong International Airport in just eight minutes. But there is something particularly special about this train—it has no wheels!

The Shanghai-Pudong line boasts the world’s only commercial magnetic levitation, or maglev, railway. Rather than riding on metal wheels, the train is supported entirely by a magnetic field. And instead of having a human driver, it is fitted with technology that constantly monitors its exact position and radios the data to a central control station. There, human operators, aided by computers, precisely control the train’s movements.

Maglev Versus Conventional Railways

The construction of this special train and its guideway posed a number of challenges. For instance, only a narrow air space separates the moving train from its guideway. Hence, because of Shanghai’s soft soil, engineers had to include special joints in the guideway that can be adjusted to compensate for natural settling. They also had to keep in mind the slight deformation that concrete beams experience, including temperature-related expansion and contraction.

Still, maglev technology offers a number of advantages. For instance, it produces no motor or wheel noise and no harmful exhaust emissions from the vehicle itself. Track and equipment need less maintenance. And as a mode of passenger transport, the energy efficiency of the train is about three times that of an auto and five times that of an airplane. In fact, the energy the train uses to hover is less than that consumed by its air-conditioning system! Additionally, the train can climb steeper slopes and handle tighter curves than its wheeled counterpart, thus reducing the need to alter the landscape.

With all these advantages, it might seem surprising that more maglev railways have not been built. One factor is the greater initial cost. Indeed, Chinese officials have put on hold a proposal to build a maglev line between Shanghai and Beijing because construction would cost twice that of a normal high-speed line. Also, a maglev line would not be integrated with China’s existing rail network.

The Shanghai maglev railway uses German technology, and maglev research continues in Germany, Japan, and elsewhere. In December 2003, Japan’s developmental maglev train set a world rail speed record of 361 miles [581 km] an hour. For now, the train in Shanghai remains unique as a commercial enterprise.

As the maglev leaves Pudong on its return trip to Shanghai, the eyes of the passengers are glued to the digital speedometers located in each car, keen to see when they indicate top speed. Indeed, on their first ride, many passengers miss much of the scenery, so they make a second trip. Watching the terrain flash by, they fully understand why the maglev has been called a “plane without wings.”

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HOW DOES MAGNETIC LEVITATION WORK?

Electronically regulated electromagnets (1) attached to the skirts of each car, together with magnets on the underside of the train’s guideway (2), elevate the train until the two sets of magnets are separated by nearly half an inch. Other magnets (3) keep the train aligned laterally. Coils (4) in the guideway produce a magnetic field that propels the train along.

To conserve electricity, the central control station applies power to a section of the guideway (5) only when the train is passing over that section. Greater power is applied in areas where the train must accelerate or climb a grade. When the train has to slow down or go in the opposite direction, the magnetic field of the coils in the guideway is reversed.

IS IT SAFE?

Although the maglev train travels at very high speeds, its wraparound skirts (6) hug the guideway, making derailment highly unlikely. Safety belts are not required, and passengers are free to move about, even when the train is at cruising speed. In case of a loss of power, special brakes, powered by onboard batteries, produce an opposing magnetic field that slows the train to six miles [10 km] an hour. The train then gently sets down on skids and glides to a stop.

Do the train’s powerful magnets pose a health risk—for instance, to passengers with pacemakers? Test results show no cause for concern. In fact, the external magnetic field is weaker than that surrounding some conventional trains.

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More than 265 miles an hour!

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AWAKE!