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BRISTOL 450—FROM WIND TUNNEL TO STICKY-TAPE

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.

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Bristol 450. Illustration by Richard Corson.

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.

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Bristol 2.0-liter inline-6. Engine image from the Bristol Owners Club; valve gear image by Leo Bestgen.

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.

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The original Bristol 450, Le Mans 1953. Image from the Bristol Owners Club.

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.

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The Bristol 450, as it ran at Le Mans 1953. Image from the Kurt Wörner Collection/R&T.

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.

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The 450, revised for Le Mans 1954. Image from drawingdatabase.com.

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.

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The 450, as a trio of them ran successfully at Le Mans 1954. Image from the Corrado Millanta Collection/R&T.

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.

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Bristol 450, at Le Mans 1954. Note the gap at the top of the side window. Image from The Klemantaski Collection.

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.

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The Bristol 450 cars in open configuration finished in fine team form at Le Mans 1955, a race remembered for its horrific accident in which 84 perished.

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

One comment on “BRISTOL 450—FROM WIND TUNNEL TO STICKY-TAPE

  1. Gerrald Thoeming
    August 29, 2016

    Dennis, You were one guy whose work I always read every word of. Always worth it, and thank you for that. I just found your site because BAT has shown Two Bristols in the last few days. The 405, I honestly like, the 403, not so sure, but it prompted me to look up (What I later found out was) the 450 Coupe. Always felt there was something behind that “Look” and you knew what it was. They did very well in 1954 with 2.0 Liters. Myself, have a degree in Industrial Design, and I still harbor a huge desire to build Light Weight, Safe, Aero, Cars, that will not fly
    Glad I found your site.

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