This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
I have a biking nemesis: During my regular rides around the six-mile outer loop of New York’s Central Park, the big hill at the north (uptown) end of the park invariably sucks the very life out of my aging legs. Yesterday, however, pedaling up the big incline was another story altogether. It was as easy as climbing a small rise. My new-found prowess had nothing to do with any improved fitness, of course; it was the bike I was riding, the Twist Freedom DX from Taiwan’s Giant Bicycle, Inc., which augments every pedal stroke with a finely timed electric boost.
The Twist Freedom DX incorporates a battery-powered electric motor in the front wheel that relatively seamlessly supplements your leg muscles to “smooth out” your ride. This means you can maintain a nearly steady pace no matter what road you take. The overall effect is to give you “light feet,” as if you set a stationary gym bike to a low resistance level--one that enables you to just pedal away with abandon. The power boost is especially noticeable when you start out; the electric-assist makes it effortless.
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Giant’s Hybrid Cycling Technology is based on a torque sensor in the pedal crank that measures how much pressure the rider exerts with each stroke. Some rather sophisticated software algorithms in the I² Driver Unit’s computer located just aft of the seat tube takes this force data and converts it on the fly into “smoothed” power-transmission commands for the electric motor. The motor is a Sanyo DC brushless unit that can produce from 150 to 350 watts of synchronized power as needed. As a result, the rider can take on hills or long stretches of road without breaking a sweat, should he or she so decide.
A ride controller on the handlebar lets you choose among three operating modes: Economy (minimum power output), Normal, and Sport (extra boost). Setting the bike’s seven-speed Shimano Nexus transmission system to just the right gear to accommodate the terrain, the power mode and your pedaling effort fine-tunes the Twist Freedom DX’s ride to a very pleasant “T.” As a result the set-up mostly avoids the timing lag riders have often experienced when pedaling previous electric auxiliary-power bicycles. That annoying phenomenon occurs when the stroke is not fully synched with the power-boost.
Electric power in the DX is supplied by a pair of four-pound (2 kilogram) lithium-ion battery packs that fit over the rear wheel. These lockable modules sit snugly under fabric pannier bags. The batteries, which are engaged in sequence via a handlebar control, together supply juice for about 70 miles (113 kilometers) in Economy mode. The user can rather easily extract them for recharging via a home wall-plug, which takes a maximum of six hours. The bicycle works just like a regular bike when the power is disengaged.
Note that the DX’s power-assist system responds only to pedaling and has no stand-alone throttle capability, so it’s no electric bicycle or scooter. It’s really a different breed. Some purists might debate whether one would define it as a true “hybrid” as it does not incorporate a muscle-driven electric generator, or downgrade or braking energy-recovery system to recharge the batteries, but such technology may have just ended up adding weight, complexity and cost with no certain payoff. The DX does, however, combine electric and muscle power so that makes it a hybrid to most of us.
Last year in China, dealers sold almost 20 million bicycles with auxiliary propulsion systems. And this technology is big in Europe, where it is seen as a low-cost and green alternative to cars. In Germany, for example, where they’re called “pedelecs,” several companies besides Giant offer electric-powered models. They include the Gazelle Orange Innergy, the Hercules EMove sport sl, the Matra I-Step Cross and the Riese & Mueller Delite Hybrid. I look forward to seeing these products hit our shores one day (if they haven’t already).
Giant’s DX hybrid bike has been commercially available for two years in Europe, where it has received extensive customer use, so potential buyers in the U.S. shouldn’t worry about potential operating problems, such as biking in the rain and so forth. The thing felt pretty bulletproof during my short test-drive. Weighing in at around 50 pounds (23 kilograms), it’s certainly no lightweight, but the power-boost mostly offsets that potential problem. Otherwise, the DX seems a solidly built and rather slick package, one that looks like a regular bicycle.
Although most people would probably describe the DX as a commuter or urban cruiser, the bike’s clean and straightforwardly utilitarian design should attract buyers interested in a little help with their daily work run or rides around congested cities, spread-out ‘burbs or longer trips to and from the country. And it’s quiet enough that fellow bikers may not even notice that you’re getting a performance-assist as you pedal up hills...
The Twist Freedom DX is priced at about $2,000 (MSRP) and goes on sale this week at 20 of Giant's top retailers around the U.S. For more information, go to the Giant Web site.
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