Electrifying design

Saving Space: "To make room for the battery pack, we had to moe all the action to the rear wheel," says Vectrix VP of Technology Peter Hughes, posing here with a prototype of the company's new electric scooter.

Newport, RI— If engineers at Vectrix Corp. had any doubts about the industry's reaction to its new electric scooter technology slated to debut in early 2004, those doubts were dispelled recently when they took their vehicle to a Peugeot test track in France. There, they laid their scooter's reputation on the line in a drag race of sorts against a top-of-the-line gas-powered competitor.

"In a one-kilometer race, they couldn't catch our scooter," recalls Peter Hughes, vice president of technology for Vectrix Corp. (www.vetrixusa.com). "They ran the race repeatedly and our scooter kept winning. They were stunned." If that weren't enough, Vectrix then took its product to Germany and demonstrated it for a major motorcycle manufacturer.

"The chief engineer there took off on our scooter and we didn't see him for 45 minutes," Hughes notes. "When he came back, he stuck his finger in my chest and said, 'You have designed a weapon.'" Weapon, indeed. If observers are correct, the battery-powered Vectrix scooter could turn out to be a weapon in the battle for the hearts, minds, and pocketbooks of European consumers looking for a better way to commute to work. If the scooter is successful, however, its success will be attributable to more than just being in the right place at the right time. Vectrix's effort to breathe life into the scooter involves a determined seven-year engineering effort.

Two-Wheel 'Challenge'

Although scooters comprise a small market and are not well understood in the U.S., their popularity in Europe is growing rapidly.

Still, Vectrix's up-and-coming status in the scooter arena carries a distinctive irony. Coming from the U.S., where most consumers don't know what a scooter is, and where electric vehicles failed miserably in the 1990s, the identification of a major opportunity in the scooter market had to be considered unlikely at best.

Vectrix's founders did see the light, however, during a meeting at Lockheed Martin Corp.'s Marietta, GA-facility during 1997. There, Vectrix's founder Andrew MacGowan struck up a deal with Lockheed: He would provide business assistance to Lockheed if the aerospace company would lend technical and engineering expertise to MacGowan's as-yet-undefined entrepreneurial effort.

Parts Count: Engineers eliminated the traditional belt drive by employing a single-stage planetary gear that rotates with the rear wheel.

During a two-day brainstorming meeting in Marietta that followed, two dozen Lockheed engineers helped nail down a technical concept in the relatively untapped area of two-wheel electric vehicles.

Once the decision was made, the three-man engineering team from Vectrix faced the complex task of designing a vehicle that could compete with its gas-powered cousins.

Most important was the issue of range. "The challenge was to come up with a two-wheeled vehicle that performs the same as 250-cc gas-powered vehicles in speed and acceleration," Hughes says. "We also wanted it to weigh the same and not cost any more than the competitors in that class."

Hughes and his team knew that others had tried to do the same, but had failed. The failures, however, had generally been at the very low end of the market (50-cc scooters) that started out as gasoline-powered products, and were subsequently reengineered as EVs. Most of the resulting scooters lacked the power to compete with gas-powered competitors.

Vectrix decided to deal with that issue by immediately opting for higher voltage and higher power. Instead of operating in the 36 to 48V range, as previous electric scooters had, Vectrix engineers employed a 125V-dc battery bus. As a result, their peak power number jumped from about 2 kW to around 20 kW. The company's engineers also opted for about 180 lbs of on-board 30 Amp-hour nickel-metal hydride batteries from Gold Peak Batteries (Hong Kong) to give them the power they needed. The downside of that decision, however, was that the vehicle, targeted between 360-420 lbs, now had a serious weight problem.

Stop-And-Go: To determine a scooter performance requirements, Vectrix engineers studied typical patterns associated with urban commuting. What they discovered -- not surpisingly -- is that city drivers spend a lot of their time starting and stoping and drive relatively short distances at a constant speed. Thorugh DSP-based motor control, engineers were able to tminimize energy consumption (right), thereby increasing the travel range of the scooter on a single battery charge.

To deal with that, engineers went to work on reducing the weight of the scooter's frame. By teaming with engineers at the Alcoa Aluminum Technical Center in Pittsburgh, Vectrix engineers designed a patented aluminum frame, the bottom half of which carries the battery pack. The aluminum frame's castings attach to the bike's suspension and to extruded aluminum swing arms that connect a rear-mounted drive to the rest of the frame. "To make space for the batteries within the frame, we had to move all the 'action' into the rear wheel," says Hughes.

Indeed, by designing the frame and drive system in that way, Vectrix engineers say that they made the scooter lighter and more energy efficient. The reason: The scooter employs a direct drive that eliminates the need for a drive belt, which would ordinarily run between an engine sprocket and the rear wheel.

Vectrix engineers say they eliminated the traditional belt drive by employing a single-stage planetary gear box from Getrag Corp. (Newton, NC) that actually rotates with the rear wheel. Instead of transferring power through mechanical linkages, the motor resides on the aluminum swing arm and is splined to the planetary gear box. To make the pieces work in unison, Mechanical Engineer Dan Baldwin performed extensive finite element analysis on the frame and worked closely with the Alcoa Technical Center.

High Energy: Engineers investigated a variety of battery technologies, selecting NiMH for its high energy density and proven reliability.

The resulting frame achieves its weight reductions by employing variable thicknesses that dip down to as low as just 1.5 mm at the belly pan, which carries the batteries. Baldwin says that by going to aluminum, the engineering team reduced the frame's weight to 25 lbs, compared to 85 lbs for a typical tubular steel frame used on similarly-sized gas-powered scooters.

Digital Soul

Achieving the high accelerations and speeds needed to compete with conventional scooters, however, was another matter. The use of a lightweight frame helped, engineers say, but by itself wasn't enough to provide the performance they wanted.

To meet the performance goals, the scooter's powertrain employs brushless dc motors that peak at 27 hp. Engineers say that the dc motors, supplied by Parker Hannifin's SBC Division (Milan, Italy) and by Kollmorgen (Radford, VA), inherently provide instant torque. In addition, the direct rear-wheel drive configuration also gives an acceleration boost, because there's no torque wind-up or backlash, nor a need to wait for fuel to pass through a carburetor.

Engineers also boosted the scooter's range by employing an intelligent drive system that "looks" at the surrounding conditions and optimizes the phase angle advance of the motor to get the most efficient operation out of it. To accomplish that, the drive system employs a digital signal processor (DSP) from Texas Instruments (Dallas, TX) that looks at the command signal from the scooter's throttle and compares it to the position of an encoder on the motor's shaft. From that input, the DSP "decides" (via a look-up table) how to control the system's insulated gate bipolar transistors (IGBTs). By doing so, it generates a pulsewidth-modulated signal that makes the dc motor operate as if it is running off a three-phase ac electrical supply.

"With this design, we can control the voltage and the current, and get the motor to do exactly what we want," Hughes explains. "That's why we say the DSP is the heart and soul of this system."

Cultural change

Vectrix engineers claim that the resulting scooter offers a 0-50 km/hour acceleration of time of just 3.6 seconds, compared to 5.0 seconds for a typical four-stroke, 250-cc gas scooter. It also offers a 110-km range, which is ten more kilometers than the company's original goal. Its weight is about 200 kg, compared to approximately 170 kg for a typical gas scooter.

What's more, the scooter is considered to be a zero-emissions vehicle, which is inducing some countries, such as England, to consider offering financial stipends to consumers who buy the product.

Despite the relatively high cost of a 180-lb nickel-metal hydride battery pack, Vectrix engineers also say they managed to minimize their product's cost through the use of the integrated aluminum castings, which enabled a dramatic reduction in the overall parts count. Their scooter, they say, consists of about 250 parts, whereas a typical gasoline-powered scooter has about ten times that many. The result, the company says, is that its assembly is far less labor intensive than that of a gasoline-powered competitor. The reduction in labor will yield a scooter that costs the same as a gas-powered 250-cc equivalent, the company says.

Late this year, Vectrix plans to roll out eight pre-production vehicles that will incorporate fully-functioning lights, seats, and body panels – elements that have been left to the very last stages of design. By next spring, Vectrix engineers plan to move to full production. Their goal is to target the 125-cc-and-over European scooter market, which exceeds annual sales of more than a million units per year. Ultimately, they hope to look to the enormous potential market in Asia.

Observers believe that the technology's only possible Achilles heel might be its reliance on a cultural change. "Instead of pulling into the petrol station to put a carcinogen in the tank, users will have to adapt to a regime of charging the bike for a couple of hours every few days," notes one observer. "That's really its only disadvantage."

Vectrix executives say that their scooter shows that electric vehicles have a place in the market, as long as they stay within their sweet spot. "The auto industry has proven that even if you invest a billion dollars, it doesn't ensure success," MacGowan says. "We invested a fraction of that, and look what we've done in the two-wheel world."