As you'd expect, the Tesla Roadster is essentially a Lotus Elise that has been adapted to electric power. Like the Elise, the Tesla is built around a chassis made from aluminum extrusions that have been bonded together. Compared with the Lotus, however, the Tesla's main chassis rails have been strengthened, which allows the doorsills to be lowered two inches to a height more compatible with a driver not as limber as a Romanian gymnast. Rearward of the B-pillar, these rails are carefully angled upward and attached to a rear subframe that holds the battery pack, a two-speed transmission, and a three-phase, four-pole AC induction electric motor that produces 185 kW (248 hp) of power.
It shouldn't add up, though, because the bundle of 6831 lithium-ion cells (a $20,000 item) weighs about 900 pounds, and the Tesla Roadster tips the scales at about 2500 pounds, a shocking 25 percent more than the Elise. And yet the Tesla shrugs off its weight penalty as soon as you lay into the accelerator. The brushless electric motor offers 260 Nm (192 lb-ft) of torque at 0 rpm, so there's a huge push in your back as the car instantly leaps forward, and it feels as if you have been strapped inside a great big radio-controlled scale-model racer. The electric motor spins in its twin ceramic bearings to 13,500 rpm with a pronounced turbine-like whine, and the power seems like it will go on forever.
Despite its weight, the Tesla changes direction as quickly as a water strider on a still pond. Compared with the Elise, its wheelbase has been stretched several inches (all of it behind the B-pillar) to accommodate the power pack, and the unintended consequences include weight distribution similar to the Elise (37.5 percent front/63.5 percent rear, a shift of only 1.5 percent to the rear despite the heavy battery pack) and a smoother-riding platform. First gear incorporates strong regenerative braking from the rear wheels, and the taller second gear can cope with driving from rest to the Tesla's top speed of 135 mph.
If you drive the Tesla slowly, you can expect 300 miles of cruising range; if you drive quickly, you might drain the batteries in 200 miles. Just about everyone should be able to get 250 miles of driving. The batteries recharge in about 3.5 hours with special equipment provided by Tesla, but you can simply plug the Roadster into a wall outlet if need be.
Of course, Tesla's agenda here is a demonstration of the cleanliness of electric power, the reduction of gasoline use, and an attendant reduction in global warming. The Roadster is meant to be a proof of concept, the first in a succession of more affordable, all-electric mainstream automobiles from Tesla. Eberhard argues very persuasively that the overall energy efficiency of electric power in an automobile is far superior to that of any other power source, including hydrogen fuel cells. Such efficiency clearly doesn't come cheaply, however.
We don't want to make too much of our brief experience with the Tesla Roadster. Some ten prototypes have been built, and we've ridden in numbers 001 and 002, while our actual driving time amounts to less than thirty minutes. The algorithms that enable the transmission to shift from one gear to another are still not quite ready for prime time, and the rock-hard, Elise-calibrated suspension will give way to a more driver-friendly setup once Becker completes his work. We hope to test a Roadster at length sometime next spring.
And yet the introduction of the Tesla Roadster is a remarkably significant event. There's an innovative spirit among the eighty people at Tesla Motors in the Silicon Valley that recalls similar enthusiasm in Detroit more than a hundred years ago, when Henry Ford literally crashed through the wall of the tiny workshop behind his home to show the world his own proof of concept, the Quadricycle. ...next page >>