【正文】 oublewishbone design uses two wishboneshaped control arms to guide each wheel39。s upanddown motion. Each arm has three mounting positions two at the frame and one at the wheel hub and each joint is hinged to guide the wheel39。s motion. In all cars, the primary benefit of a doublewishbone suspension is control. The geometry of the arms and the elasticity of the joints give engineers ultimate control over the angle of the wheel and other vehicle dynamics, such as lift, squat and dive. Unlike road cars, however, the shock absorbers and coil springs of a Formula One racecar don39。t mount directly to the control arms. Instead, they are oriented along the length of the car and are controlled remotely through a series of pushrods and bell cranks. In such an arrangement, the pushrods and bell cranks translate the upanddown motions of the wheel to the backandforth movement of the springanddamper apparatus. Specialized Suspensions: Hot RodsThe classic American hot rod era lasted from 1945 to about 1965. Like Baja Bugs, classic hot rods required significant modification by their owners. Unlike Bugs, however, which are built on Volkswagen chassis, hot rods were built on a variety of old, often historical, car models: Cars manufactured before 1945 were considered ideal fodder for hot rod transformations because their bodies and frames were often in good shape, while their engines and transmissions needed to be replaced pletely. For hot rod enthusiasts, this was exactly what they wanted, for it allowed them to install more reliable and powerful engines, such as the flathead Ford V8 or the Chevrolet V8. Photo courtesy Street Rod Central1923 TbucketOne popular hot rod was known as the Tbucket because it was based on the Ford Model T. The stock Ford suspension on the front of the Model T consisted of a solid Ibeam front axle (a dependent suspension), a Ushaped buggy spring (leaf spring) and a wishboneshaped radius rod with a ball at the rear end that pivoted in a cup attached to the transmission. Ford39。s engineers built the Model T to ride high with a large amount of suspension movement, an ideal design for the rough, primitive roads of the 1930s. But after World War II, hot rodders began experimenting with larger Cadillac or Lincoln engines, which meant that the wishboneshaped radius rod was no longer applicable. Instead, they removed the center ball and bolted the ends of the wishbone to the framerails. This split wishbone design lowered the front axle about 1 inch ( cm) and improved vehicle handling. Lowering the axle more than an inch required a brandnew design, which was supplied by a pany known as Bell Auto. Throughout the 1940s and 1950s, Bell Auto offered dropped tube axles that lowered the car a full 5 inches (13 cm). Tube axles were built from smooth, steel tubing and balanced strength with superb aerodynamics. The steel surface also accepted chrome plating better than the forged Ibeam axles, so hot rodders often preferred them for their aesthetic qualities, as well. Some hot rod enthusiasts, however, argued that the tube axle39。s rigidity and inability to flex promised how it handled the stresses of driving. To acmodate this, hot rodders introduced the fourbar suspension, using two mounting points on the axle and two on the frame. At each mounting point, aircraftstyle rod ends provided plenty of movement at all angles. The result? The fourbar system improved how the suspension worked in all sorts of driving conditions. The Future of Car SuspensionsWhile there have been enhancements and improvements to both springs and shock absorbers, the basic design of car suspensions has not undergone a significant evolution over the years. But all of that39。s about to change with the introduction of a brandnew suspension design conceived by Bose the same Bose known for its innovations in acoustic technologies. Some experts are going so far as to say that the Bose suspension is the biggest advance in automobile suspensions since the introduction of an allindependent design. Photo courtesy BOSEBose?Suspension Front ModuleHow does it work? The Bose system uses a linear electromagnetic motor (LEM) at each wheel in lieu of a conventional shockandspring setup. Amplifiers provide electricity to the motors in such a way that their power is regenerated with each pression of the system. The main benefit of the motors is that they are not limited by the inertia inherent in conventional fluidbased dampers. As a result, an LEM can extend and press at a much greater speed, virtually eliminating all vibrations in the passenger cabin. The wheel39。s motion can be so finely controlled that the body of the car remains level regardless of what39。s happening at the wheel. The LEM can also counteract the body motion of the car while accelerating, braking and cornering, giving the driver a greater sense of control. Unfortunately, this paradigm（范例）shifting suspension won39。t be available until 2009, when it will be offered on one or more highend luxury cars. Until then, drivers will have to rely on the triedandtrue suspension methods that have smoothed out bumpy rides for centuries. For more information on car suspensions and related topics, check out the links on the next page. 16 / 16