Lean Mobility

Article From: 7/1/2006 Automotive Design & Production, , Contributing Editor

The city car of the future may be a tandem seater that leans as it turns.

DaimlerChrysler may still be mulling what to do with SMART, but former Lotus and Prodrive executive Hugh Kemp is leaning toward production of a unique two-place city car that combines the maneuverability of a motorcycle and the cheekiness of DCX’s commuter-mobile. Plus, it will come in taxi and delivery versions for intra-city use. Indeed, the latter could be a very lucrative market. Recently, a Domino’s Pizza franchisee in the UK switched its delivery fleet to tiny Toyota Aygos to cut fuel consumption. Kemp’s car–estimated mileage is 100 mpg–conceivably could cut these costs even further.

“We are looking at this as a city car,” says Kemp. “There also would be a van that could carry a bulkier and heavier load than you’d give a [motorcycle] dispatch rider, but that would not be greater than 200 kg.” Then there’s the single-passenger taxi version. “According to the folks at London Taxi, 85% of their fares are hailed for a single passenger via mobile phone.” How they will respond to the appropriately named NARO Car (www.naro.co.uk) is anybody’s guess as most people think the current styling is a bit spidery. However, most seem comfortable with the tandem seating that places the passenger directly behind the driver. “The concept is based on studies of motorcycle riders and their ability to make it through traffic at twice the speed of cars and trucks,” says Kemp. Which means the NARO Car is designed to drive between lanes of gridlocked vehicles as they enter, navigate, and exit congested areas. “In London, you see motorcycles splitting lanes,” says Kemp, “but we also have the advantage of being able to park three of our cars in the space occupied by a conventional vehicle.”

At 2.5 meters, the NARO is the same length as a SMART, and has a sliding door that allows it to be parked close without impeding ingress or egress. That, however, is only half the fun. The NARO Car–wheels and cabin alike–also leans into turns like a motorcycle. Says Kemp, “You effectively steer the wheels out from under the vehicle to get it to lean into a turn. If you want to turn to the right, the wheels initially will steer slightly to the left to initiate the lean, and then follow to the right as you go around the corner.”

The suspension is by double wishbones in the front, and twin trailing links at the rear, with the spring loads taken from each wheel onto what Kemp describes as a “balance beam” that pivots in the middle of the car. “Basically, there is no roll stiffness. The loads between wheels are balanced by this beam.” Not surprisingly, the car also is capable of flopping side-to-side at rest, so a roll brake automatically clamps the beam relative to the structure at speeds below 7 mph. “There is no need for any action from the driver,” says Kemp.

The prototype–a steel structure with a Rotax engine mated to a CVT transmission, the unique suspension, its control system, and a single seat—is undergoing testing at Prodrive’s Warwick, UK, facility. Production vehicles will use different materials (“The basic concept is for carbon fiber and aluminum, but we are researching different materials to improve recyclability and keep costs down,” says Kemp), and weigh about 300 kg., though additional funding is necessary to reach production by 2010. The other problem facing Kemp is this: “Everyone who has driven it had so much fun, they ask for more power.” That, he says, will come with a more expensive version slated to sell for more than the $10,000 limit he has in mind.
The city car of the future may be a tandem seater that leans as it turns.