Gas turbine cars have been attracting considerable attention over here this winter, and 1968 may well be the year that these engines come into their own in racing—both for Indianapolis cars and for road racing machinery. The most recently announced Indianapolis project is a team of two cars to be built by Ken Wallis, the man who was largely responsible for the design and construction of Granatelli's STP Turbocar with which Parnelli Jones so nearly won last year's Indianapolis 500. The project is being sponsored by Goodyear and Shelby Racing Co. Inc., who will actually enter and manage the cars at the Speedway. (Shelby is Goodyear's Western U.S. racing tyre distributor.) The new cars, which will be known as "Shelbys," will be driven by McLaren and Hulme.
The engines for the new cars will be General Electric T-58 gas turbines that are now being modified by the manufacturers to Wallis' specifications. The modifications include reducing the inlet area from 41 to 15.92 sq. in. This will bring the engines within the limit of 15.999 sq. in. imposed by U.S.A.C. after last year's race. The Pratt and Whitney engine used in the STP Turbocar had an inlet area of 21 sq. in., 2 sq. in. less than the limit then in force.
Like most designers, Wallis is reticent when it comes to power output, but Larry Truesdale, Goodyear's racing manager, says the equivalent of 640 b.h.p. is already being produced by the G.E. turbine in its modified form. This contrasts with the 550 h.p. listed by Pratt and Witney for their engine and the 500 h.p. given by Ford as the output of their 4-overhead camshaft Indianapolis engine in 1967 when running on straight methanol.
Outwardly at least the new Shelby bears some resemblance to the Turbocar but since the G.E. turbine is only 12 in. in diameter (compared with 19 in. for the Pratt and Whitney engine), Wallis has had an easier time arranging the side-by-side configuration of driver and engine.
Perhaps the most interesting feature of the new car (and for that reason the feature about which the least information is forthcoming) is a new concept in four-wheel drive. Wallis describes this as a "hybrid mechanical system which achieves many of its functions hydraulically and the basic ones mechanically." The system allocates the torque to each wheel on an individual basis, giving "more versatility and more performance potential on the track." Just how this is done Wallis will not reveal at the moment but he indicated the system differs significantly from most other four-wheel drive transmissions—including the modified Ferguson system used on the Turbocar—which allocate the torque almost equally to all four wheels.
In all the furor about the STP Turbocar last May most of the criticism was directed at the turbine itself. The four-wheel-drive transmission was virtually ignored but a number of astute observers pointed out that it was the transmission, not the engine, which enabled Parnelli Jones to use far more of the track than other competitors and to pass virtually where and when he wanted to, whether in line or out of it. If Wallis' new concept works in practice it may well provide McLaren and Hulme with an advantage over their competitors, quite apart from the turbine power.
Wallis, incidentally, brings a lot of British experience to bear on this Indianapolis project. Although he has now lived in California for several years, he is a former R.A.F. officer and at one time worked as a design engineer and test pilot for Vickers Armstrong. He worked on nuclear power projects for English General Electric for 3 while and later was employed by the Associated Engineering Group at Rugby. After moving to the United States he became director of experimental systems in the aircraft division of Douglas Aircraft. He spent the better part of three years on the STP Turbocar, first as a design consultant and for the final 18 months as chief engineer.
While the various turbine projects have been attracting the limelight, Ford has not been resting on the laurels gained by its ubiquitous Indianapolis engine. Their answer for 1968 is the Turbo-Ford—not a turbine, but a turbocharged version of their 4-overhead camshaft V8. The bore of the new engine remains the same but the stroke has been reduced to bring the capacity down from 4.2-litres to the 2.8-litres permitted for supercharged and turbocharged engines. A new camshaft is also used, since the turbocharger requires much less valve overlap, and extensive modifications have been made to the exhaust system. With the exhaust-driven turbocharger providing a boost of 20 lb. per. sq. in., Ford engineer Danny Jones is looking for a reliable power output of well over 600 b.h.p. Ford will supply the regular 4.2-litre engine to its customers for this year's Indianapolis 500 but conversions kits will be readily available for those who want to try the turbocharged version.
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Indianapolis doesn't have a monopoly on gas turbine powerplants. The North American season begins this month with the Daytona 24-hours, the first race in the 1968 Manufacturers' Championship, and one of the most interesting cars entered is the Howmet TX (for Turbine Experimental). The Howmet Corp. of New York is a supplier of industrial metals such as aluminium, magnesium and titanium, super alloys and prosthesis (surgical implants) and its object in building the car was to demonstrate the firm's technological capabilities in the world of metallurgy. The car is powered by a Continental Red Seal turbine and meets all the regulations imposed by the F.I.A. Group 6 category.
The Continental turbine was originally designed to U.S. Government specifications for use in military helicopters but it never went into production. Using the F.I.A.'s equivalency formula for turbines, the engine has a capacity of 2,960 c.c.—which brings it conveniently under this year's 3-litre prototype limit. The inlet area is slightly less than 12 sq. in. and the power output is 325 b.h.p. on an average day at sea level. The engine, which is mounted above the single-speed transmission, is 39 in. long and 22 in. high, including the transmission. The engine/transmission combined weigh less than 250 lb. and an electric motor is used for reverse.
Two of the major problems in the automotive applications of gas turbines has been the lag in both acceleration and deceleration. These problems are tackled in the Howmet car by installing a waste-gate system between the gas generating turbine and the power turbine. The system consists of a series of holes in the "block" which can be opened or closed by the driver. With the waste-gate open, part of the gasses is diverted to the atmosphere before reaching the power turbine. Under this no-load condition the gas generating turbine continues to spin at maximum r.p.m.—so that when the driver closes the wastegate, full power is delivered almost immediately to the power turbine. Similarly, when the driver wants to decelerate he opens the wastegate and this immediately reduces the gas flow to the power turbine. (The waste-gate never diverts all the gas from the power turbine because it is this turbine that drives the gas generating turbine.)
The car itself is a relatively conventional space frame that was designed by Ray Heppenstall, a Howmet engineer and former S.C.C.A. class champion who was the project manager on the Essex Wire team of Ford GT40s that won the Sports Car Manufacturers' Championship in 1966. The car was built by Bob McKee, who has designed and built a successful line of Group 7 sports cars for several years. It employs conventional coil-shock absorber units all round, with unequal length A-brackets at the front and reversed lower A-bracket and a single upper link at the rear. Outboard disc brakes are fitted all round and the rack-and-pinion steering provides two turns lock to lock. The body is made from Howmet aluminium. The special alloy turbine blades were also made by Howmet.
The engine is mounted in the rear, above the transmission, and drives only the rear wheels. It draws its air from a periscope on the roof. A 32-gall. fuel tank (JP-4) is mounted between the cockpit and the engine. The entire car weighs close to the 650 kg. minimum for 3-litre prototypes. (The turbine is so light, the car could have been built a lot lighter but since they had to meet the minimum weight Heppenstall and McKee took advantage of the situation to build in greater strength and balance.)
Two of these cars have been built and it was originally planned to run at Daytona, Sebring and Le Mans. However, when the ruled recently that turbine cars could compete for manufacturers' points, instead of just on an exhibition basis, Howmet decided to add the B.O.A.C. 500 at Brands Hatch to its schedule.—D. G.