The sixties was a time when there were many fewer restrictions placed on race car designers than today, and innovative engineers were looking for alternative power sources for racing cars. In this period various gas turbine powered cars appeared, such as Andy Granatelli's STP-Paxton, Colin Chapman's Lotus 56 and the American Howmet Corporation's TX sports-racing machine of 1968.
The Howmet project was conceived early in 1967 by the enthusiastic Ray Heppenstall, a sports car racer from Philadelphia. Heppenstall reckoned that a suitable lightweight turbine mounted in the back of a conventional sports-racing chassis would be a competitive proposition. He also convinced one of his racing friends, Tom Fleming, then sales vice-president of Howmet, one of the United States leading metal companies and a major supplier of precision castings to the aircraft gas-turbine industry. Fleming and Heppenstall convinced the Howmet board that running a race-car program would be an ideal promotional tool for the company.
A suitable power unit was found at Continental Aviation & Engineering, who had recently lost out in a bid for a US government contract for a light observation helicopter engine and had ten TS325-1 turboshaft engines left on the shelf from its development work. This unit developed 325 bhp at the output shaft and applying the current FIA's engine equivalency formula it was rated at 2,960 cc, slotting it neatly into the Group 6 sports-prototype three litre class. Continental contributed two of these engines for installation in a relatively conventional tubular space-frame chassis built by Bob McKee.
The turbine was mounted at the rear, above a single speed transmission driving the rear wheels through a specially designed quick-change differential which allowed ratio changes. Suspension was by conventional wishbone and coil springs and shock absorber units, with outboard disc brakes.
The TS325 engine comprised a two-stage gas generating turbine driving the two-stage compressor while also providing gas to the power turbine whose output shaft, via reduction gearing, drove the rear wheels. Heppenstall's solution to the turbine lag was to insert a wastegate between the gas-generating and the power turbines. The first third of throttle pedal movement controlled fuel supply to the combustion chambers, and thus the speed of the engine. But once spinning at its maximum 57,500 rpm and delivering full power, the final two-thirds throttle movement activated the wastegate, thus controlling the amount of gas directed to the power turbine, and hence the rear wheels.
The TX's first race was the Daytona 24 hours in February 1968 and two cars were brought, the car offered here with a modified 2.25 inch longer chassis and chassis number 1 as a spare; drivers were Dick Thompson, Ed Lowther, and Heppenstall. After 34 laps, and running as high as third, the wastegate valve stayed shut as Lowther arrived at a tight corner leading from the infield to the banking, the resultant contact with the wall putting the car out. At the Sebring 12 hours the car qualified third, just 1.2 seconds adrift of the pole. In the race, the TX was running seventh when one of the engine mountings broke, and retired just before the seventh hour.
At the BOAC 500 at Brands Hatch in April, British driver Hugh Dibley joined Thompson and the TX qualified seventh. In the race the wastegate problems struck again, sending Thompson into the bank at Druids after seven laps. Dibley then drove in the Guards Spring Cup at Oulton Park the following weekend. Here he qualified second, and was running in fourth place until he pitted for fuel, but the starter failed and there was no way he could rejoin.
We believe that Heppenstall then campaigned the cars in a number of SCCA regional events. The first race finish came in May in the Cumberland 200. The following race at Marlboro, Dick Thompson joined him for the 4.5 hour 300 mile race. Thompson won the qualifier, then the following day with Heppenstall the feature race also, leading from start to finish.
The Watkins Glen 6 hours in July was the next FIA Championship outing, and for the first time both TX's were raced, with Thompson/Heppenstall being joined by Hugh Dibley/Bob Tullius in the older car. The cars qualified 8th and 9th, and were running well in third and fourth places, until the final hour. Heppenstall and Thompson maintained third place until the end, but the transmission of the Dibley/Tullius car broke, although they managed to cross the finish line and be classified 12th.
At the 24 Hours of Le Mans on 28/29th September the team again had bad luck. After only three laps Thompson came back in to hand over to Heppenstall, feeling that his car wasn't quite right. A fuel system problem limited the engine to 70 power and strangled the speed on the straight. They kept going however, and had worked up to 29th place when, at 9.45pm, Thompson crashed at Indianapolis corner and rolled, damaging the car although unhurt himself. Le Mans marked the final race appearance of the amazing TX's, Howmet choosing not continue with a race program in 1969.
The following year Howmet sold the two cars, a coupe and the now converted Mk II Spyder, to Heppenstall for the symbolic sum of one US dollar, although the engines had to be returned to Continental. The Mk.II Spyder, less engine and transaxle, eventually found its way into the hands of enthusiast and collector Chuck Haines who entrusted the restoration to Bob McKee in Lake Zurich, Illinois. With the original turbines no longer available, secondhand Allison 250C18 turboshaft helicopter units were obtained, providing a similar power output and weighing around 20 lbs. less.
This car, chassis no. 2 has been recently restored by Bob McKee to earlier Coupe specification and is now presented in as new and 'ready to go' condition. The original spyder bodywork converted from the coupe in period is offered with the car as well as an extensive history file including invoices original documents and photos. It was shown in public for the first time again at the Elkhart Lake meeting in July 1996, and has also appeared on three occasions at the Goodwood Festival of Speed and was shown in 2006 as a race eligible car for the event on the 'Le Mans Classic' stand at the Rčtromobile show in Paris.
Text thanks to Wouter, borrowed (with no intention of returning) from this article.
1968 Howmet TX #1
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