AERODYNAMICS VITAL

Press, Volume CXIV, Issue 33435, 17 January 1974, Page 12

AERODYNAMICS VITAL

For years the design of . racing car bodywork has been something of a rule-of-thumb operation. The regulations require exposed wheels, and more recently maximum body width and maximum wing dimensions. These factors apart, designers are free to adopt whatever shape they choose. From time to time new shapes emerge—the most obvious in recent years being the wedge—and if : they work other people ■ tend to copy them. Some of these shapes are said to be “wind tunnel tested.” though it is doubtful whether anyone has yet reached anv irrefutable con-

clusions about open-wheel bodywork in this way; in fact in many cases there has been considerable disparity between the findings of the wind tunnel and the evidence of the race track. Because of this, some designers use the race track as a wind tunnel. To this end a test car is fitted with a multi-point manometer, connected to a series of pitot tubes located wherever readings are required. All the driver has to do is maintain a predetermined speed long enough for the levels to stabilise—and then pull a lever which closes valves and maintains them at

these levels, so they can be read in the pits when the car is stationary. The pitots can be used to measure air pressure at almost any point on or near the body and they are also extremely useful for checking air pressure at various points on water radiators, for measuring the pressure drop through the radiators, or for establishing ideal locations for things like oil coolers or brake cooling ducts. If the oil cooler is doing an adequate job even though it is in an area of low pressure, then it is presumably bigger and heavier than it needs to be. Information of this

sort can often be of more practical value than basic aerodynamic data. In recent years the chief developments in body design have been made in the area of wings. The main problem with wings is to get sufficient downthrust at the rear without excessive drag. It is very easy to get adequate downthrust at the front, but the effectiveness of most rear wings —and especially the central part of them—is im-i paired by the proximity ofi the engine. From an aerodynamic point of view the worst: things on a racing car are the tyres.