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THE BRISTOL 450 legacy sends something of a mixed message of art versus science. Twice victorious in their class at Le Mans in the mid-1950s, the Bristol 450s evolved through engineering practices of this British aviation specialist, but there were elements of sticky-tape and cardboard as well.
Bristol was founded in 1910 as the British & Colonial Aeroplane Company. Its 1919 proposal for the Bristol Pullman aero-limousine showed advanced thinking. Years later, just after World War II, its Brabazon probed feasibility of a jumbo airliner.
Bristol got into car production as a byproduct of its World War II military connections. In postwar Munich, it was able to commandeer BMW automotive plans as well as key engineers. The Bristol 400 through 406, produced between 1947 and 1961, paid homage to prewar BMW design and engineering.
In 1953, Bristol combined its aero expertise with its engine prowess in the form of the 450 race car. This engine was the same 2.0-liter cross-head-pushrod inline-6 that powered prewar BMW 328 sports cars, not to say later Arnolt Bristols, Frazer Nashs and a variant of the AC sports car prior to Carroll Shelby creating V-8 Cobras.
The 450’s enclosed bodywork was developed in a wind tunnel, optimized for low coefficient of drag. Its dual rear fins provided stability in crosswinds. Its cabin had one significant problem: One of the team drivers was 6 feet 3 inches and simply couldn’t fit until modifications were made, both within and without.
Le Mans practice called for other changes. Passing lights had to be added. The oil cooler needed more airflow. Worryworts added leather bonnet straps.
The resulting pair of modified 450s ran Le Mans 1953 in rather less aerodynamic form than originally envisioned. What’s worse, both succumbed to engine failure before half-distance.
Repairing the mechanicals, relocating the oil cooler and trashing the bonnet straps, in October 1953 Bristol took one of the cars to the Montlhéry track near Paris. There it captured six world records for its 2-liter class. These ranged from 200 miles at an average 125.87 mph to five hours at 115.43 mph.
For Le Mans 1954, a trio of 450s had upgraded engines and less cobbled bodywork. In particular, headlights were deeply recessed and covered, other necessary lighting was faired in, cutout ducts were added aft of the front wheels to aid brake cooling, and overall width was reduced. This last diminished the car’s frontal area, advantageous because total drag, after all, is the product of frontal area multiplied by coefficient of drag.
Le Mans 1954 was a thrilling race, and particularly satisfying for the Bristol team. The three cars finished 1st, 2nd and 3rd in class, 7th, 8th and 9th overall, earning a rarely awarded Team Prize.
The aero enhancements for 1954 were successful indeed. Drivers noted exceptionally good stability at high speed, even in places where crosswinds were notoriously hazardous for other cars.
They also observed that side windows of the 450 were being sucked out into the air stream. One driver determined that if the windows were firmly closed, this deformation did not occur. However, if left open a tad, there was a gain of 150 rpm in top speed. A wag suggested this was what a driver did to alleviate boredom during a three-hour stint.
It rained heavily at Le Mans 1954, and Bristol drivers complained that windscreens and side windows were fogging up, made all the worse by oil mists from other cars. Engineers also recognized the coupe’s driving position being likened to a Tower of London torture cell.
The 1955 Bristol 450 Le Mans car did away with its roof (thus again reducing frontal area), had a small single windscreen and a massive tail fin that grew from the driver’s headrest.
Was the 450 roadster another example of Bristol’s aeronautical heritage? Not actually. Bristol development engineer Percy Kemish says it was “determined by eye. Ken Evans had the job of modeling the shape full scale, with cardboard, brown paper and sticky-tape.”
And it worked. Like the year before, the Bristols finished 1st, 2nd and 3rd in class, 7th, 8th and 9th overall, again honored with a Team Prize. Down the Mulsanne Straight, one of them posted a speed of 150.34 mph.
By the way, this item is gleaned from my SAE International Paper No. 2000.01.3556, “The Mulsanne Straight at Le Mans—the Early Years of a 5.6-km Open-Chamber Wind Tunnel,” 2000. ds
© Dennis Simanaitis, SimanaitisSays.com, 2015