US F1: The Winning Formula

By Don Sherman

CHASSIS Designing and manufacturing any modern racing car is a computer exercise supported by powerful layout, analysis, and fabrication tools. After the design is optimized on-screen for aerodynamic performance, weight and balance, stiffness, strength, and other parameters, the resulting digital files guide computerized manufacturing machinery. Suspension control arms are milled from titanium and then clad with airfoil-shaped carbon-fiber reinforcements. The tub consists of carbon-fiber skins sandwiching honeycomb-aluminum core material. Hundreds of resin-impregnated carbon-fiber sheets are precisely cut according to specific patterns and positioned by hand inside a mold, which is itself made of carbon fiber. An autoclave - essentially a pressurized oven that uses vacuum to force the composite materials into conformity with the mold - cures each part at 225-300 degrees Fahrenheit in several hours. The finished tub has top and bottom sections nested together with four bulkheads; high-strength adhesives and fasteners hold that assembly together. Molded-in aluminum and titanium inserts provide attachment points for the engine, the suspension, and a titanium air-box gusset that protects the driver in the event of a rollover. Special Zylon-composite panels guard against side penetration. Collision forces are mitigated by energy-absorbing material built into the composite side pods and front and rear crush cones. The side pods house the radiators and guide air toward the compound rear-wing assembly. A fifty-five-gallon fuel cell (necessitated by the new ban on refueling) is loaded through a bottom aperture into the cavity between the driver and the engine. The front suspension has one coil-over damper per wheel operated via pull rods plus a third spring to manage brake dive. The rocker-arm rear suspension operates through push rods. Carbon/carbon brake rotors are gripped by AP calipers.

ENGINE The 2.4-liter V-8 supplied by Cosworth to US F1 (and four other teams) is the engine that the Williams team raced four years ago retuned for the current 18,000-rpm rev-limit era. Rules aimed at cost constraint define the bore, stroke, bore spacing, weight, and even the height of the engine's center of gravity. The number of valves, spark plugs, and fuel injectors is also specified. The block, heads, and pistons must be aluminum, and the crankshaft and camshafts must be iron or steel. Fuel injectors are positioned about three inches above very short intake trumpets. To allow the four valves in each cylinder to be canted toward the bore center for optimum breathing, there are finger followers between the cam lobes and the valve stems. Pistons are fitted with one compression and one oil-control ring. To trim both inertia and parasitic losses, the bare minimum amount of lubricating oil is used. In spite of the severe design restrictions, this engine generates nearly 4 hp for every pound of its weight. The fully fueled weight-to-power ratio of US F1's Type 1 is just over two pounds per horsepower.

GEARBOX The US F1 team's trump card is a clever gearbox that's light, compact, and aerodynamically efficient. A four-inch-diameter, six-plate clutch is supported by the aluminum gearbox housing to relieve the engine's crankshaft of thrust loads. A bevel-type input gearset doubles the torque and shifts the drive from a longitudinal to a transverse orientation. As torque passes to the four successive gear shafts, which provide seven forward ratios, it climbs about eight inches from crankshaft height (less than four inches above the pavement) to axle height. This narrow staircase arrangement affords an open path for air to flow over the rear diffuser, maximizing rear downforce. Gear changes and clutch movements are controlled by the driver's shift paddles.

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