The early '60s produced a period of unique and optimistic automotive engineering. Rival powerplants were engaged in another horsepower race, gasoline remained cheap, and automakers were relatively free from governmental regulation.

Automotive researchers received the corporate interest, funding, and freedom to take seriously radical alternatives with regards to future automotive and truck platform powerplants. Though several options to the piston engine were studied, one of the most promising was the gas turbine engine.

American manufacturers, including Caterpillar, Chrysler, Detroit Diesel, Ford, and International, were engaged in the development of turbines, regarded then as the future alternative for the gasoline-powered piston engine. Each of these corporations had a series of running prototypes in production test beds for ongoing evaluation. All shared common internals but varied in size and weight depending on market application, platform type, and torque and horsepower output. General Motors had developed several operational turbine concept platforms in the early '50s, Chrysler began the research and market interest in 1939, and Chevrolet, Ford, and International directed productive efforts toward the fullsize truck and heavy-duty market.

The industries' shared opinion was that this new powerplant would provide performance and control equal or superior to the piston powerplants, be notably smoother at all rpms, have greater operational range with less component fatigue, start easier in colder climates, and provide instant heat and window defrosting on colder days. Turbines, it was also thought, would deliver equal or superior fuel mileage, provide longer unit life at less cost, require less maintenance, reduce or eliminate periodic oil changes, and make the antique cooling system, with its accompanying annual antifreeze replacement, obsolete. In short, a futuristic powerplant providing greater efficiency, using a variety of common liquid fuels, free from expensively refined petro-octane varieties, combined with cleaner exhaust.

Back Ground
In July of 1965, Chevrolet announced its Turbo-Titan III, an operational prototype combining advanced truck styling with novel features, including major design improvements within its fifth generation gas turbine engine. Installed on an existing production truck chassis, and including a specially produced 40-foot stainless trailer, the entire platform had a 50-foot overall length and an operating gross combination weight of 76,800 pounds.

The GT-309 turbine engine was based on more than 15 years of continued development. Its operating heritage included units used in the experimental Firebirds, the Turbo-Cruiser bus, two Chevrolet Turbo-Titan production truck platforms, and 15 operational Allison Prototypes. The 309 produced 280 hp with an upper shaft speed of 4,000 rpm, reduction geared downward from 35,000 rpm. Because turbine engines deliver their highest torque levels at stall, the 309 developed a maximum torque rating of 875 lb-ft at idle. Thus, the colder the climate, the more instant power was available.

The 309 used the uniform basic internal components as its cousins, including a compressor, a gasifier, a power turbine, and a regenerator. The gasifier was mounted on the same shaft as the compressor. The power turbine gear was connected to the output shaft. Incoming air was drawn in by the compressor, compressed, and directed to the combustion chamber. This compressed air, combined with fuel sprayed into the chamber, generated combustion with operating temperatures of 1,700 degrees Fahrenheit. These gases, under high pressure and temperature, flowed through nozzles against the vanes in the gasifier unit, driving both the turbine and compressor at 35,700 rpm. This power turbine, though located at the rear of the gasifier, was not connected to it.

After moving through the gasifier unit, the nozzles directed the gases toward the turbine blades, moving them from stall to 35,000 rpm. All of the above internals were fitted into two divided chambers: the high-pressure plenum, containing the combustion chamber in front, with the lower pressure exhaust plenum in the rear. Located in the passage between these cavities were the turbines. The heated air passed through the combustion chamber, was combined with the fuel, which drove the turbine units, and exhausted into the low-pressure unit. The gases were cooled as they made their way through the regenerator, which transferred the heat combined with fresh incoming air to the high-pressure plenum. In short, a continued process.

The gas temperature emitted by the 309 averaged 1,200 degrees. The regenerator absorbed the heat and dropped these temperatures in half to the 300-500 degree range, about half of a conventional diesel unit. More than 90 percent of the exhaust system heat was salvaged, which reduced the amount of fuel needed to produce the high velocity gas needed to drive the turbines. The regenerator also eliminated the need for mufflers and a conventional exhaust system, serving as an insulating blanket for heat and noise.

The unique power transfer unit was added to the 309, which made use of a gear train to couple the gasifier turbine and compressor to the output shaft. A clutch, or variable coupling, engaged or disengaged this drive to allow the transfer for the right amount of power. With platform deceleration, this power transfer provided double to triple the amount of braking power than conventional piston powerplants. This power transfer also allowed incessant engine braking without adverse effect. With the extended power transfer available to both the front and rear of the unit, both a front and rear accessories could also be used. A pulley up front handled the alternator, power-steering pump, and fan drawing outside air through the transmission-engine oil cooler. The rear PTO powered the interior air-conditioning unit.

Transmission
A conventional Allison automatic transmission was coupled to the 309 with a special aluminum adapter. The transmission also had its torque converter and hydraulic retarder components removed. Because the 309 could operate with both the turbine and output shaft stalled, the unit itself was an onboard torque converter. The production six-speed ratios were retained.

Chassis
A conventional truck chassis was selected using two 10-1/16x31/2x5/16-inch heat-treated frame side rails with standard crossmembers. Up front, a 15,000-pound I-beam was used. At the rear, a 34,000-pound tandem bogie was used. Spiral bevel two-speed units with 7.17 and 9.77x1 ratios were used with the 7.17 ratio geared specifically for 309. Rear leaf springs were rated at 17,000 pounds. The air brake units consisted of a 17-1/4x3-1/2-inch units up front, combined with 15x7-inch units at the rear axles. Sixteen ply belted 18x19.5-inch tires were mounted at the rear, with 10.00x20s on the front.

Electricals
The platform tractor contained a modified conventional electrical system. The battery-powered starter driving through the power transfer gear activated both the gasifier turbine and the compressor to 4,000 rpm when the fuel and single spark plug ignited. The cranking continued until the turbine reached an idling speed of 15,000 rpm. The minimum operational unit speed was 18,000 rpm. A continuous spark was used with the 309 to burn off inadvertent fuel accumulation.

Styling
The Turbo-Titan III used a pearlescent white fiberglass and steel cab combo with its styling theme extended to the chassis, which was completely concealed by molded fiberglass panels. Doors mounted just ahead of the rear wheels on both sides of the skirt provided access to dual batteries and the turbine engine when the cab was electrically tilted. Power-operated wing-type side windows with top hinges provided operator entry when the key was inserted in the door. Retractable square headlamps were mounted within functional air intakes in two banks of three lamps each. The front turn signals were retractable, with the rears operating in sequence, flashing inward. A flat exhaust stack exited through the roof.

Inside, "Astronaut Seats" with full headrests were mounted on each side of a center console. A wing-topped handle controlling the six-speed automatic transmission was mounted on the console. Full interior carpeting was included along with retractable seatbelts, air-operated windshield wipers, full tinted glass, and air conditioning/warm air heating. A four-speaker FM stereo radio and a two-way telephone were used for the first time.

The most novel feature, though, was the GM designed and engineered "dial steering system." This unit was mounted on a pedestal in front of the driver, replacing the conventional steering column and wheel. Twin dials mounted on a padded vinyl panel operated the platforms power steering. An auxiliary pump driven from the propeller shaft provided emergency usage if the main pump failed for any reason when the platform was in motion. The automatic transmission quadrant was also mounted on this panel along with the turn signals. The pedestal pivoted forward and back along with the panel for the most comfortable driving position.

Government regulations, manufacturing costs, and continued refinement killed all of the turbine programs. The Clean Act of 1970 also got in the way. The strict legislative control of NOX also was a factor. Piston power was easier to regulate, and no one was ready to speculate on radical powerplant manufacturing funding. The 309 and Titan III were proof that there was, and is, a place for radical, multi-fuel engines with reduced emissions. The features and styling weren't bad either.

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