Bill Thomas Cheetah

Bill Thomas Cheetah

The Bill Thomas Cheetah was a sports car car built from 1963-1966 by Chevrolet performance tuner Bill Thomas as a competitor to Carroll Shelby's Cobra.^[1]

Design and development

In the late 50's, Thomas had notable success racing Corvettes and he gained the attention of leadership within GM. By 1960, Thomas had started his own company and he continued his chain of successes by making other GM products such as the Corvair and Chevy II perform beyond expectations, both on the street and the track. In 1963, Thomas gained covert support from GM (through the head of its Performance Product Group, Vince Piggins) to develop a concept vehicle. The prototype was designed jointly by Thomas and his lead fabricator at the time, Don Edmonds.^[2] Edmonds is also credited with the bulk of the construction of the car.^[3] Financing for the project came from private investors including Thomas himself and John Grow, a Rialto, California Chevrolet dealer. In fact, the first car belonged to John Grow. Using his racing connections, Thomas arranged for material assistance from Chevrolet for the major components - specifically, the Corvette 327 engine, Muncie transmission and independent rear-end assemblies. Other components were stocked from the larger GM parts bin, such as Chevrolet passenger car spindles, and NASCAR spec Chevrolet drum brakes.

Following delivery of the drive-train components, Edmonds laid them out on the shop floor and began taking measurements. Using chalk, Edmonds sketched the basic outline of the chassis.^[4] Per Edmonds, the original "blueprints" of the Cheetah consist of only a few simple drawings. This was Edmonds' trademark design methodology - sketch what he thought the car ought to look like, then build it. (The majority of the 600+ cars that Edmonds built in his career would be designed this way. Only his last few Indy cars would involve professional designers.)^[5] The bulk of the initial drawings show each major component drawn out in block form, with major dimensions marked. Given the basic chassis shape, Edmonds began sketching the body. Edmonds showed his drawings to Thomas and after a few minor changes, was given permission to begin construction of what was originally meant to be a "Malt Shopper" - a cruising machine or styling exercise. Thomas wanted a prototype vehicle to show GM what level of work his company could do with the intent to garner additional contract work.^[6] Sometime after construction began, Thomas decided the car would also compete on the racetrack to further promote the concept. This midstream change in purpose was partly responsible for the chassis flexibility problems that emerged once the car began to compete on the racetrack.^[7]

Once Edmonds had the lower half of a rolling chassis built, he constructed a plywood body form or "buck" on which fit on top of the chassis. The buck included removable metal frames which showed the outline of the windows. Once completed, the body buck and forms were sent off to California Metal Shapers and Aircraft Windshield Co. respectively. After the rough body arrived back at Thomas' shop, it was finished by Don Borth and Don Edmonds. A second car was also constructed with an aluminum body but the remainder of the cars were fiberglass. These fiberglass bodies were produced by two different companies - Contemporary Fiberglass and Fiberglass Trends.^[8] Ultimately, Contemporary Fiberglass was selected by Thomas to produce the bodies following some problems with the Fiberglass Trends molds; however, Fiberglass Trends continued to produce their own version of the Cheetah under the name "GTR" (and therefore are not considered to be Bill Thomas cars), but this car's chassis was suited only to drag racing. Note: It has been surmised by Thomas employees that the second aluminum car is the car that would eventually be sold to Chevrolet for evaluation purposes. It is also surmised that this is the same car that Thomas purchased back from Chevrolet to serve as a basis for the Super Cheetah, a project which was never finished by Thomas.

The chassis was constructed of Drawn Over Mandrel (DOM) cro-moly tubing that was heliarc welded (more commonly referred to as TIG or tungsten inert gas welding) using a P&H Mining DAR-200 welder.^[9] The design of the car was unusual in that it was front engined, but with the engine sitting so far back in the chassis that the output yoke of the transmission connected directly to the input yoke on the differential, basically making the driveshaft only a universal joint linking the transmission with the differential. With the engine positioned in this manner, the driver's legs were beside the engine. For this to work, the exhaust system headers passed over the top of the driver's and passenger's legs. The tops of the footboxes were curved to make room for Edmunds' handmade headers. This design takes the attributes of what is known as an FRM layout to an extreme. Consequently, this design gave a front/rear weight distribution roughly approximating a mid-engined vehicle without the cost of an expensive transaxle arrangement. This design style resulted in a hot driver's compartment - an issue that would impact the Cheetah's performance on the track.

Racing history

The racing history of the Cheetah is noteworthy in that despite the fact that the car suffered from the typical problems that plague any new project, the car won a number of races in 1964 in the hands of some experienced drivers. Originally, the car was designed with Dave MacDonald in mind as the driver; Thomas and MacDonald had established a long-standing racing relationship in Corvettes. This was not to be; Carroll Shelby offered MacDonald the opportunity to drive the Cobra, which MacDonald accepted and later, MacDonald died on 30 May 1964 driving at Indianapolis. Jerry Titus was a vocal advocate of the Cheetah as a contributing journalist for Sports Car Magazine; he would also drive the factory Cheetah race car in its early races. Another notable driver was Ralph Salyer who owned and drove the most successful racing Cheetah, in which he won 11 minor events between 1964 and 1965. His car was known as the Cro-Sal Cheetah, named both for its mechanic Gene Crowe and Salyer. It is also became the only Cheetah roadster after Crowe cut the roof off to keep Salyer from suffering heat exhaustion due to the aforementioned heat buildup in the driver's compartment. Note: many race cars of this era and even later suffered this same problem, as use of heat-insulating materials were not yet widespread in race cars, save for items such as exhaust wrap.

Besides heat impact on the driver, the engine was also prone to overheating, due in no small part to the failure to account for vents to draw hot air out of the engine compartment. Eventually, the overheating problems were solved by using a larger Pontiac NASCAR radiator, by cutting various configurations of holes in the hood and full-length belly pan and lastly by adding spoilers to draw the hot air out from underneath the hood (the first hood spoiler was actually a rope that ran across the hood from fender to fender.) Another major problem was due to the aforementioned mid-stream change in purpose for the vehicle; because the car was originally designed as a proof-of-concept, the chassis lacked the rigidity necessary for road racing (little triangulation was incorporated into the original design). Under changing loads such as those experienced on a twisting road course, the vehicle's suspension geometry continually changed and proved difficult to handle, even for experienced drivers such as Jerry Titus. Adding power only aggravated the problem; under hard acceleration, the trailing arms could bow outwards, allowing the rear wheels to toe in. Owners of the car were able to improve handling by adding gussets and triangulation to the chassis, modified (or completely re-engineered) trailing arms and disc brakes.

Despite some adverse handling tendencies on road courses, few cars could catch it in a straight line due to its Thomas-built 377 cu in (6.2 L) displacement, dual air-meter, fuel-injected Chevy small-block V8 based engine. At the dragstrip, the car reportedly posted faster numbers than the 427 Cobra.

Demise

Another major factor in the end of production was General Motors adhering to the automaker racing ban, and thus killing projects like the Cheetah which depended on a factory-backed parts supply. When the flow of parts dried up, there was no way for Thomas to achieve the homologation numbers needed for racing, which went from 100 to 1000 units. Lastly, race car design was evolving and the true mid-engined configuration represented the wave of the future. To illustrate this point, in approximately the same time frame, Shelby's Daytona coupes were rendered obsolete by the GT-40. Thomas, faced with the combined effect of negative factors, made the business decision to close the chapter on the Cheetah and move on to other projects, including collaboration on the Nickey Camaros.

Given their providence, high performance potential coupled with some race successes, popularity with slot car fans for their unique shape, the remaining original cars have appreciated in value and are largely considered collector items. No official records are known to exist documenting the exact number of cars produced, but best estimates indicate as many as 23 cars were built to varying degrees of completion and configuration. This estimate is based on the number of fiberglass bodies produced by the chosen manufacturer selected by Thomas and by the documented production number of the last known original Cheetah.

Bill Thomas died 10 October 2009.

Comparable vehicles

Shelby Daytona Ford V8-powered racing coupe of 1965, loosely based on the Cheetah's intended rival, the Shelby Cobra roadster.

References