Weird and wonderful Indy cars: Bettenhausen’s smooth Thermo King Special

Published On November 17, 2016 » 10460 Views» By Marshall Pruett » Blogs, IMS History, Indy 500

Regular #SpeedRead readers will recall Marshall Pruett’s eight-part series on “Weird and Wonderful Cars of the ‘500’” that appeared in the weeks leading up to the 100th Running of the Indy 500 presented by PennGrade Motor Oil. Now, the feature continues with one car featured biweekly.

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Wedges were all the rage at Indianapolis in the late 1960s. Almost every chassis conformed to the concept: low, wide noses, hiked hindquarters, and narrow, tapered flanks became the de facto formula until the pursuit of downforce took control of designs in the 1970s.

It makes 1969’s Indy 500 and the first allowance for winged protrusions a wonderful bridge between the great race’s past and future. Of all the cars that straddled the shifting technology, Gary Bettenhausen’s Thermo King Special and its smooth, subtle aerodynamics, speak to the newfound possibilities in chassis development.

The Gerhardt chassis piloted by the Indy 500 legend was powered by another bridge technology—the renowned Offenhauser four-cylinder engine adorned with a newfangled turbocharger—that put enormous power to the ground. With the door opened to the use of small wings, applying downforce to deal with increased cornering speeds would become a necessity.

And that’s where Gary B’s Thermo King Special nestles into an interesting space at Indy. Compared to the car Lotus brought to Indy (above) with front and rear wings that exploited the full nine-inch maximum width allowed outside the body, and Mario Andretti’s multi-winged Hawk that won the 1969 race (below), the Thermo King Gerhardt took a conservative approach to the 500’s new aero freedoms.

Where the Hawk and Lotus squeezed as many wings past Indy’s technical inspectors as possible, Gary B’s Gerhardt took baby steps. Some wedges ignored the idea altogether, waiting for 1970 to get in on the downforce game.

Even though it failed to maximize the outright performance advantages the nine-inch wings could provide, there’s something uniquely elegant about the choices made with Gary B’s 1969 car.

If wings can be considered cute, the little fella positioned atop the radiator between the front wheels was a wonderful attempt to apply downforce directly across the front axle. And just behind the wing, starting at the base of the windscreen, two small air diverters—items referred to today as flow conditioners—sit in front of four more that were used to wrap the wake coming off the wing around the cockpit.

The back of the Gerhardt also received a thoughtful approach to housing and shrouding the Offy’s turbo.

Starting ninth, Gary B had the No. 8 Thermo King Special flying early in the 1969 race, but a broken piston halted his charge on Lap 35. Finishing 26th seems unfair for the tidy Gerhardt; it returned in 1970 with Gary B behind the wheel (but without the little wing) and wasn’t particularly competitive.

Starting 20th and finishing 16th in ’70, the car underwent one final redesign for its return in 1971 (above) with its tall rear replaced by wing-like ramps that helped its beloved driver to qualify 10th and place 13th before he moved onto extreme power and downforce with a McLaren-Offy in 1972.


About The Author

Marshall Pruett

Marshall Pruett transitioned from more than 20 years as an open-wheel and sports car mechanic, engineer and team manager into his current role as a writer and reporter in 2006. Follow him @MarshallPruett []