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    Guest Message by DevFuse

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    The GMC Astro 95 and Astro SS Gas-Turbine Tractors

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    13 replies to this topic

    #1 OFFLINE   kscarbel


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    Posted 16 July 2013 - 03:03 AM

    The future for gas turbines appeared bright in the 1970s, particularly with the introduction of the Detroit Diesel Allison GT-404-4.


    Information on these trucks is extremely limited, a but I’d like to share what I know.


    The Astro 95 gas-turbine was powered by the General Motors developed GT-309 gas turbine.


    It was equipped with GM’s 34,000 pound "Astro-Aire" rear air suspension, available from 1971 and offering up to 1,000 pounds in weight savings.

    Throughout its 18-year production run, the Astro’s grille opening was never enlarged, and the gas-turbine Astro was no exception. GMC made the grille appear larger by using a painted section that matched the pattern of the truck's custom grille.

    The truck's chassis equipment, including battery boxes, steps, fuel tanks, suspension, and even wheels, were all painted white, complimented by a chrome front bumper.


    The truck’s enlarged dual exhaust stacks were painted white to draw attention to the clean-burning nature of the truck’s gas-turbine powerplant.

    Like many GM concept trucks such as the Turbo Titan III, the Astro gas-turbine had its own trailer for display and load testing.


    The U.S. Department of Energy (DOE) initiated a program in the mid-1970s at the Detroit Diesel Allison Division of General Motors to design ceramic components into the GT- 404-4 gas turbine truck engine. Testing included powering a truck on highways, city roads and the GM proving grounds, where the engine was exposed to extreme vibrational and shock loading on the Belgian-block and truck-durability road courses. Testing clearly demonstrated that properly designed ceramic components could survive under the most severe conditions for a typical vehicle.


    GM said the emergence of low-cost, high-temperature ceramic components could allow the potential of gas turbines to be realized. Operating with ceramic components at turbine inlet temperatures up to 2350 F to 2500 F, GM said the GT-404 engine had the potential to offer fuel economy equal or superior to current diesel engines.


    From 1974 to late 1977, Detroit Diesel Allison installed nearly one hundred GT-404 and GT-505 series gas turbines in trucks, inter-city coaches (Greyhound), municipal buses (Baltimore – RTS-II), fire apparatus (American LaFrance), marine and industrial applications to conduct field evaluation. Consolidated Freightways, Greyhound, Ruan Transportation, Terminal Transport, GM Truck and Coach and Freightliner participated.


    Later in 1979, an “Astro SS” was built equipped with a General Motors GT-404-4 split-shaft regenerative gas turbine incorporating newly developed high temperature resistant ceramic materials. At 1,750 pounds, the GT-404 was approximately 650 pounds lighter than a comparable Detroit Diesel 8V-71. On a vehicle-installed basis, a 1,000 pound weight savings was realized, once reason being the lack of an engine cooling system.


    • GT-404 300/310/325 horsepower
    • GT-505 390/400 horsepower
    • GT-606 475 horsepower

    Attached Files

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    #2 OFFLINE   kscarbel


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    Posted 16 July 2013 - 03:07 AM

    Dept. of Energy/Dept. of Transportation

    Gas Turbine Transit Bus

    Demonstration Program

    Program Plan

    April 1978



    One of the most promising advanced propulsion systems is the gas turbine engine. The gas turbine not only offers potential for reductions in noxious emissions and fuel consumption, but also could provide operators with improvements.


    Development of the gas turbine engine as a potential power source for automotive vehicles began in the early 1950's. In1976, only three manufacturers in the United States, Chrysler Corporation, the Detroit Diesel Allison (DDA) Division of General Motors Corporation, and Industrial Turbines International (Garrett, Mack Trucks and KHD) were actively engaged in the development of small (150 HP to 650 HP) gas turbines that could realistically be considered engines for automobile, truck and bus use.


    The Chrysler engine evolved as a passenger car engine. In 1962 this engine was extensively field-tested in 50 prototype automobiles. The development of this engine is continuing with U.S. Government financial aid, in areas that can best be described as "advanced technology."


    The ITI consortium (Garrett, Mack Trucks and KHD) engine is in the 450 HP to 650hp range and is being designed as an eventual replacement for truck diesel engines. It is in the initial, unproven stages of development and prototype engines will not be available for 2 to 3 years. Production engines could not be available for several years after the prototypes.


    Activities Involved in Developing Improved Gas Turbine Engines


    Chrysler Corporation - ERDA Baseline Engine (150 HP) and Upgraded Engine (123 HP) under active development, 2-shaft regenerative


    Detroit Diesel Allison - 300 HP, 400 HP and 500 HP, 2-shaft regenerative engine under active development for bus, truck, industrial application


    ITI (Garrett/Mack/KHD) - Comprehensive program for truck and industrial applications 450-650hp range


    The DDA gas turbine engine has been designed as an alternative for the diesel engines manufactured by that firm, and is currently developed to a state where volume production can be seriously considered. In addition to research and development engines, nearly 100 DDA gas turbines have been field-tested in trucks, transit coaches, intercity coaches, marine craft, and industrial electrical generator sets and air compressors.


    Since 1972, test engines in 24 trucks of ten different brands have operated in widely divergent service in all parts of the country. In addition, eight Greyhound inter-city coaches powered by GT-404 gas turbines have operated throughout the country. In the most recent of these applications, the turbine engine has demonstrated greatly improved reliability and fuel consumption rates compared with earlier turbines. In fact, the fuel consumption in the inter-city coaches was nearly competitive with that of the diesel engine.


    In the early 1970's, under the Urban Mass Transportation Administration (UMTA) Transbus Engineering Test Program, three DDA gas turbine engines were installed in the Transbus prototype coaches manufactured by the Truck and Coach Division of General Motors. This engine was selected for testing in Transbus because of the gas turbine's apparent advantages and demonstrated potential in heavy trucks. During this program the turbine engine demonstrated its potential as a viable transit coach powerplant by exhibiting the following advantages over the conventional diesel engine in transit coach application:


    • Reduction of installed weight and volume
    • Elimination of cooling radiator, fan, and
    • attendant piping
    • Cleaner exhaust emissions
    • Lower noise level
    • Reduced or low vibration operation
    • Reduced lubricating oil consumption
    • Good reliability
    • Improved vehicle performance for power rating
    • Greater engine braking capability
    • Superior cold weather starting


    Fuel consumption demonstrated in the program was higher than contemporary diesel engines. The extended periods of idle and extensive part-load operations, both inherent to transit coach service, accounted for a measure of the high fuel consumption.


    However, improvements have been made since these coaches were evaluated and further improvements are scheduled for reducing brake specific fuel consumption (BSFC) in the transit coach duty cycle.


    Because of the gas turbine's apparent advantages and demonstrated success in heavy trucks, an in-depth survey of gas turbine engine manufacturers was conducted to determine the suitability of the turbine engine for transit coach application.


    The following sections trace the development of the only gas turbine engine found to be sufficiently developed to be considered for near-term volume production and subsequent application to transit coach service.


    Gas Turbine Engine Development at Detroit Diesel Allison


    For over 20 years, Detroit Diesel Allison both independently and with government assistance has been energetically developing gas turbine engines to compete in many commercial applications with piston diesel engines. Specifically, they have concentrated on applications in large trucks and buses, although field evaluation has included construction equipment, marine equipment, and electrical power generation units.


    DDA's goals were to develop a practical, cost-effective turbine engine to meet the requirements of heavy vehicles. This program has resulted in a family of three engines covering the power range from 300 HP to 500 HP (SAE rating): The smallest of these engines is designated GT-404, and engines incorporating the latest design changes with improved performance have the -4 suffix.


    The GT-404 gas turbine is a two-shaft, regenerative gas engine featuring a power transfer system. A rigid block assembly, constructed of cast iron, serves as the main structural support member for the engine. It houses, in a modular fashion, the burner, gasifier section, power section, regenerators, and the reduction and accessory drive gearing. The modular design allows easy service and unit replacement of the various sections. The engine controls are electronic and are remotely mounted from the engine block itself. The engine is available with a rated maximum output shaft speed of 2880 rpm.


    The GT-404 engine's normal dry weight of 1750 pounds is approximately 650 pounds lighter than a comparable diesel engine, the DDA 8V-71, and its basic size is very similar. On an average vehicle-installed basis, this weight savings advantage is about 1,000 pounds, and the GT-404 can be installed in virtually any vehicle accommodating the 8V-71.


    The GT-404-4 will have similar performance but with improved fuel economy and durability. Maximum torque is produced at power turbine (output shaft) stall (0 rpm) condition. With the high torque rise characteristic, fewer number of transmission gear ranges are required-generally five or less in trucks, and four or less in buses. With an automatic transmission, a torque converter is not required and a fluid-coupling can be used. The dynamic braking capability of the engine is equal to the rated power at maximum output shaft speed and is effective in each transmission gear range.


    The GT-404 engine displays a considerable cost savings, consuming just one quart of lubricating oil per 20,000 to 30,000 miles compared with about 1 quart per 800 miles for a diesel engine in transit coach service . In addition, the turbine engine oil requires changing every 250,000 miles compared with 9,000 miles for the transit coach diesel engine.


    The GT-404 engine emits less noise than a comparable diesel engine. Results of an exterior noise test on trucks, conducted to the SAE test standards, demonstrated that the noise level of the GT-404 engine is 11 dBA lower than a standard diesel powered truck. This 11 dBA lower reading represents nearly a 75 percent reduction in sound pressure over a diesel engine. Development effort is continuing toward a still further reduction of the noise level to meet future noise attenuation requirements.


    Major pollution elements in transit coaches would be minimized with the GT-404 engine through highly efficient, low-pressure, continuous burning with large amounts of excess air resulting in almost 100 percent combustion.


    The gas turbine’s exhaust odor is virtually undetectable, exhibiting only as light kerosene odor a t engine idle, and exhaust smoke is virtually undetectable. And it’s ability to start quickly at low temperature is superior to any conventional diesel powerplant. The GT-404 has demonstrated its ability to start, without aids, in temperatures well below 0º F. However, batteries must be reasonably well-charged and #1 diesel fuel must be used (since #2 diesel fuel begins to gel around +20º F).


    The GT-404 does not require a water-based cooling system because it is internally cooled by the excess air passing through the engine and by the lubricating oil which is cooled through a small oil-to-air heat exchanger. The elimination of a water-based cooling system greatly decreases engine maintenance and downtime, thereby reducing a major maintenance cost area in transit coaches.


    The gas turbine engine, in general, requires less maintenance than a diesel engine because of fewer wearing parts and almost vibration-free operation. All moving elements in the basic turbine engine are rotary in motion, compared with reciprocating components in diesel engines.


    No water hoses or pipes, drive belts or other elements that tend to be unreliable are used. Use of self-cleaning inertial air filters, absence of a liquid cooling system and manifold exhaust system, extended brake life, and expected extended life of components will contribute to reduced maintenance costs and significantly increase vehicle availability.


    The fuel system of the GT-404 engine can operate on a wide range of petroleum-based fuels including: #1 diesel, #2 diesel, heating oil, JP fuels, kerosene and gasoline. The diesel fuels are most commonly used because of their higher energy content and current ready availability. Gasoline is the least preferred fuel because the lead additive tends to deposit and foul the turbine, nozzles, and regenerators, thereby reducing engine performance. When synthetic or other fuels become available in quantity, the fuel handling and control system of the GT-404 can be modified to accommodate these fuels.



    Detroit Diesel Allison Field Tests


    DDA has manufactured approximately 100 GT series gas turbines for field evaluation in trucks, buses, boats, electrical power generation units and other applications. These engines include the GT-404 and GT-505 in both the -2 and -3 versions. Pilot models of the engine began going into service in 1972 for extensive field evaluation. The engines have been tested in 24 trucks from ten manufacturers, eight motor coaches from MCI-Greyhound, coaches from GMC Truck and Coach Division, Transbus prototypes, various watercraft and industrial applications.


    Consignment engines were operational with Greyhound on the East Coast and West Coast, Binswanger Trucking in Los Angeles, Freightliner Corporation and Consolidated Freightways in Portland, Acadian Marine Rentals in New Orleans, Terminal Transport in Atlanta, Gardner-Denver in Quincy, Illinois, a Hatteras yacht operating in the waters of New Jersey, GMC Truck and Coach Division of General-Motors in Pontiac, Michigan, and Detroit Diesel Allison in its Indianapolis-based field-test vehicles.


    The major effort at DDA in the development of the GT-404 engine has been directed toward heavy trucks. The field experience with turbine engines in transit coaches has been the Transbus prototypes, and several transit coach engineering models assembled by the Truck and Coach Division of General Motors. The most extensive coach experience with turbine engines is in the Greyhound fleet. However, it must be recognized that the duty cycle and service requirements for intercity coaches, such as those operated by Greyhound, are substantially different from transit coaches.


    The eight GT-404 turbine powered Greyhound coaches, four MC-7s and four MC-8s, have logged well over one million miles since mid-1975 and several have been refitted with -3 engines. These particular -3 engines were capable of operating at 0.51 BSFC as compared with 0.54 BSFC of the -2 engines used in the Transbus prototypes. The last of the -3 engines with the latest burner improvements, and other developments, lowered the BSFC to 0.45. Even without the latest engine modifications, the fuel penalty sustained by Greyhound has averaged slightly over 1 mpg for the turbine engine compared with the diesel. The gas turbine engine also virtually eliminated engine overheating and other cooling system-related problems, which account for 50 percent of Greyhound's road failures with diesel engines. Brake life on the turbine powered Greyhound coaches was extended by more than 50 percent due to the engine's regenerative braking system. Elimination of engine vibration-induced cracks in refrigerant lines and fittings improved air conditioning system reliability in turbine powered coaches, and elimination of engine vibrations and reduction of the powerplant weight improved coach structural integrity. The largest number of engine problems Greyhound experienced with the turbine engines were with the various electrical controls.


    Eleven Allison GT 404-4 gas turbine engines, and five HT740CT and six V730CT Allison automatic transmissions, were supplied to Greyhound for testing in 1981.


    The turbine engine in the early years of production is projected to cost 20 to 25 percent more than the 8V-71 diesel engine. The projected production cost of a turbine engined transit coach, however, is projected to be $70,000 in 1976 dollars, or only 2.9 percent more than $68,224 for the typical diesel-powered coach currently in production.


    DDA Engine Survey Conclusions


    The operational cost impact analysis indicates that transit coaches equipped with the production improvement 'gas turbine engines (GT-404-4 PI) will be essentially equal in total operating cost to current diesel-powered transit coaches, without including any added value for:

    • BSFC performance gain potential beyond 1983
    • Multi-fuel capability
    • Ability to accommodate future synthetic or
    • alternative fuels
    • Improved operational performance
    • Conformance with environmental standards
    • Perceived environmental improvement
    • Reduced noise
    • Reduced gaseous emissions
    • Elimination of exhaust odor and smoke.


    The tangible and intangible value/benefit of these attributes can, based on currently proposed regulations, lower the operating cost of a turbine-powered transit bus by well over 1 cent/mile.


    If the current government regulatory trends continue into the 1980's, the above factors will become increasingly important and realistic monetary value could be assigned to these benefits offered by the gas turbine engine. The current higher fuel consumption of the gas turbine could continue to be a disadvantage of 'the engine, particularly if the cost of fuel continues to escalate at a faster rate than other costs. The multi-fuel capability and the ability to burn less expensive lower grade middle-distillate fuels may offset this disadvantage, especially if non-petroleum based fuels become readily available.


    Beyond 1983, the fuel consumption of the gas turbine engine will continue to improve relative to the diesel engine. Increasing emission controls for diesel engines will result in a more complex engine, with escalating cost and declining fuel economy, while development of improved technologies in all gas turbine component areas indicate that gas turbine fuel economy will continue to improve. In fact, by the mid-1980's gas turbine fuel economy should equal that of the diesel engine at most speed/load ranges (with the exception of idle).


    The major factors indicated by the cost impact analysis are the improved reliability and reduced maintenance costs of the gas turbine engine, offsetting the increased fuel consumption. The turbine engine used in the analysis was the DDA GT-404-4 PI model. This improved engine, with a rated MTBO of 10,000 hours, is tentatively scheduled for

    volume production in 1983, which is the earliest reasonable date to expect widespread use of turbine engines in transit coaches.


    The procurement cost of the turbine engine, as stated previously, will initially be about 20 percent higher than the contemporary diesel engine. As the production volume of the engine is increased, the cost of the engine should be reduced and may be comparable with the diesel engine. Cost of the diesel, moreover, may be adversely affected by additional equipment required as a result of environmental regulations. The anticipated fuel consumption improvements will be attained by increasing the TIT and possibly variable inlet geometry. The higher TIT will necessitate incorporating improved materials in the nozzles and turbine blades and may also require blade cooling. These changes and the additional complexity of the variable inlet mechanism will increase the cost of the engine somewhat, but it must be presumed that the competitive nature of the engine market will maintain the selling price of the gas turbine within a range commensurate with the advantages it has to offer for vehicular power.

    Attached Files

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    #3 OFFLINE   kscarbel


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    Posted 16 July 2013 - 03:08 AM

    Ford Motor Company also experimented with gas turbine powered inter-city coaches in cooperation with Continental Trailways. In Detroit, Ford installed a gas turbine in a 1969 Model 05 Eagle operated by American Bus Lines (unit 29511). In 1970, it went into regular service running from New York City to Los Angeles via St. Louis.


    Unlike the Greyhound gas turbine buses where were paid for under grants from the US Dept. of Energy (Greyhound just supplied the MCI buses), the Trailways gas turbine Eagle was entirely privately funded by Continental and Ford.


    The Continental-Ford project went better than expected. The initial engine actually proved too powerful, and a smaller gas turbine was subsequently installed.


    How often do you see the signage "Turbine Power By Ford" on the rear of a Trailways bus? 

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    #4 OFFLINE   kscarbel


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    Posted 16 July 2013 - 03:08 AM

    In 1976, Allison began development of a generator powered by the GT-404 gas turbine to supply power to the radar set and engagement control station of the U.S. Army Patriot Missile System. The program’s goal included placement of two 150 kW generator sets providing 100 percent backup in a single container to be carried on an Army 5-ton truck. Other goals included minimizing fuel consumption by the use of twin, rotating ceramic-disk regenerators and developing a reliable, multi-fuel capability without adjustment.


    In 1978, Allison began the design, development and construction of five military specification gas turbine-powered generator sets. The completed generator sets were tested at the Aberdeen, Belvoir, Elgin and White Sands facilities with these results:


    • Fuel consumption was reduced from 48 to 16 gallons per hour as compared with previous generators.
    • A 0.1 percent frequency stability at rated load was obtained.
    • Free-shaft starting to minus 50 F was accomplished without heaters.
    • Multi-fuel capability was demonstrated on diesel, JP and gasoline.
    • All reliability requirements were met.
    • Sound level standards of less than 90 dBA were met.


    In December 1981, Allison delivered an initial order of 200 generator sets to the U.S. Army. Thru 1997, over 2,000 GT-404 powered generator sets were delivered to-date for the Patriot system, which was employed during the Gulf War.


    These generators have logged over 1 million hours of operation without any major problems.

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    #5 OFFLINE   ap40rocktruck


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    Posted 16 July 2013 - 05:56 AM

    Well Kevin,

    That is quite the bit of history.  Hats off to you for typing all this out for all of us to learn more heavy truck technology history.  


     If memory serves, Ford installed at least 1 in a W series COE & quickly learned to point the exhaust up as the engine idling burned & melted the asphalt road way.


    International also performed tests & evaluations of a turbine powered Transtar 2 COE, the unit had a distinctive solid panel covering up the grille.


    In the 1960's Kenworth also experimented with a turbine powered 524 conventional.  The press releases touted a 200 pound turbine powered the unit.  



    Richard Mark

    Owner / Master Model Maker 

    Industrial Model Design

    #6 OFFLINE   mackniac


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    Posted 16 July 2013 - 06:46 AM

    wow what a nice piece of history , thank you for sharing

    Makniac , collector and customizer of die-cast model in 1/50th scale

    #7 OFFLINE   Vladislav


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    Posted 16 July 2013 - 03:55 PM

    Too interesting to read those facts.

    Thanks alot for posting it.

    Никогда не бывает слишком много грузовиков!  leversole 11.2012

    #8 OFFLINE   bullhusk


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    Posted 16 July 2013 - 06:31 PM

    GMC big truck's!!! Once a great company with great class 8 trucks!!!....................... Then came Volvo and BANG!!! all gone now..White motors as well!!.......Mack???


    #9 OFFLINE   ap40rocktruck


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    Posted 17 July 2013 - 08:40 AM

    GMC big truck's!!! Once a great company with great class 8 trucks!!!....................... Then came Volvo and BANG!!! all gone now..White motors as well!!.......Mack???


    The writing is on the wall, In fact it has been there before the ink was dry the day V took ownership of Mack........ :pat:  :pat:

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    #10 OFFLINE   kscarbel


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    Posted 18 July 2013 - 07:04 PM

    Two more GM gas turbine testbeds, and this time they are Chevrolet brand Titan 90s.


    Attached Files

    #11 OFFLINE   farmer52


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    Posted 18 July 2013 - 07:15 PM

    Caterpillar tested a few gas turbine powered on-highway trucks.

    HOF City, PRR Country, and Charter member of the "Mack Pack"

    #12 OFFLINE   kscarbel


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    Posted 18 July 2013 - 11:36 PM



    By H. E. Helms

    Chief Project Engineer

    Industrial Gas Turbine

    Detroit Diesel Allison Division

    Genera! Motors Corporation

    Indianapolis, Indiana 46206


    Prepared for: NAlO/CCMS Fourth International Symposium on Automotive Propulsion Systems

    Washington, D.C., April 17-22, 1977


    Reference Contract: "Improved Heavy Duty Gas Turbine Engine" – National Aeronautical and Space Administration (NASA) Contract No. NAS 3-20064

    NASA Lewis Research Center

    Cleveland, Ohio


    Mr. D. Beremond, Technical Manager

    Mr. W. Goette, Technical Manager

    Mr. M. Krasner, Chief, Transportation Propulsion Division


    Program Sponsors: United States Energy Research and Development Administration, Washington, D.C. 20545

    Mr. George Thur, Chief Heat Engine Systems Branch, Energy Conservation



    An improved heavy duty gas turbine engine program plan has resulted from a study contract issued by NASA Lewis Research Center, Cleveland, Ohio using funds supplied by the Energy Research and Development Administration (ERDA).


    Program objectives are to demonstrate improved fuel economy [(213 mg/W-h (0. 35) specific fuel consumption by 1981], conformance to current and projected Federal noise and emission standards and to demonstrate a commercially viable gas turbine engine.


    Study results show that increased turbine rotor and regenerator inlet temperatures, using ceramic materials contribute the greatest amount to achieving fuel economy goals. Furthermore, improved component efficiencies (for the compressor, gasifier turbine, power turbine and regenerator disks) can also show significant gains in fuel economy.


    Fuel saved in a 500,000 mile engine life, risk levels involved in development, and engine related life cycle costs for fleets (100 units) of trucks and buses were used as criteria to select work goals for the planned program.



    Gas turbine engines offer an alternate power plant selection for trucks, buses and other heavy duty engine applications. The diesel engine now is the prime powerplant in these heavy duty vehicles and has established an impressive record for reliability, economy of operation and flexibility of operation. The gas turbine must also achieve a similar level of performance, durability and economy to become a complimentary power plant for heavy duty applications.


    An industrial gas turbine (IGT) (Figure 1) has been under development at General Motors Corporation for more than fifteen years and is rapidly approaching a stage of production readiness.


    This gas turbine engine is being developed in two power sizes:

    • GT-404 series engine rated at 300hp (224kW) at 29. 4°C (85°F) and 500ft (152) altitude.
    • GT-505 series engine is rated at 390hp (291kW).


    A third member of this turbine engine family is planned, the 605, to be rated at 465hp (347kW).


    Several million miles of bus, truck, boat and other field service has now been accumulated on the GT-404/505 all metal engines (See installations in Figure 3). Valuable lessons on performance, durability and operating costs have been learned as introduction to production of this family of engines is considered.


    Recent emphasis on fuel economy has produced improvements in fuel consumption for all types of highway and off-highway vehicles. Gasoline and diesel engines have incorporated new features leading to improvements in fuel economy, and the IGT 404/505 gas turbine engines must also be improved to meet target fuel economies in-the late 1970's and the 1980's. This consideration has led to the "Improved Heavy Duty Gas Turbine Engine" program initiated with NASA Lewis Research Center, Cleveland, and the Energy Research and Development Administration (ERDA) in 1976.


    This Phase I study program has three definite objectives:

    • Improve specific fuel consumption (SFC) from 274 mg/W-h (0.45) to 213 mg/W-h (0. 35) by the year 1981
    • Satisfy current and projected government noise and emission regulations
    • Develop a commercially viable engine for use in trucks and buses


    The suggested method to achieve improved fuel economy in the IGT is to increase turbine and regenerator inlet temperatures and improve component efficiencies of the compressor, turbines, and regenerator. The increased turbine and regenerator temperatures are to be achieved by the introduction of ceramic materials (non-cooled). An inherent advantage of the gas turbine is lower noise and emission characteristics than diesel and gasoline engines.


    Meeting current and projected noise and emission standards should be easily achieved. Demonstrating a commercially viable engine can only be achieved by future demonstrations of required performance, durability and costs. This first study phase has the objective of quantifying levels of improvement to be pursued, to plan technical activities, and establish a feasible program schedule to achieve these improvements.


    In the Phase I study program many factors were considered. Utilizing existing engines and capitalizing on the availability of spare parts was important. This would promote early acceptance for production of new ceramic components and minimize program cost. Selection of work to be performed had to be established recognizing time, funding, and feasibility of technical accomplishment. The final selection of work had to be based upon reduced fuel consumption and life cycle costs (engine related) for a customer of the gas turbine engines. Evaluation of these life cycle costs involves assumptions relative to fabricability, reliability and costs of ceramic parts which introduce an unknown 'risk' to the final assessments made in the study.




    Approach to Study

    The approach to establishing a viable program was to make design assessments of candidate engine improvements, evaluate reductions in fuel consumption, assign production and maintenance costs for candidate engines and establish fuel saved and life cycle costs for a fleet of buses or trucks for each level of engine improvement. If fuel saved was significant and life cycle costs improved, the individual developments would be worthwhile and new components should receive serious consideration for early introduction to production engines.


    Assessment of Candidate Improvements

    An assessment of sensitivity to change in component efficiencies, engine pressure losses, engine heat rejection, cooling air requirements, engine operating temperature, regenerator inlet temperature, engine pressure ratio and leakages was conducted. Table 1 summarizes the sensitivities compiled showing the change in parameter required to obtain 1% improvement in specific fuel consumption. Having these sensitivities, technical analysis was applied to establish which parameters could be improved with development and improved materials.


    Two basic routes for improvement were selected as follows:

    • Improved component efficiencies

    • Higher turbine inlet temperature (through use of ceramic materials)


    Changing pressure ratio would not be effective because lower pressure ratio leads to compromised part power engine operation. Only very small improvement in heat and power losses relative to the current engine can be achieved. Small reductions in cooling air flows and leakages will be strived for although increasing turbine inlet temperature will make it difficult to keep cooling air flows at the same level as in the current engine. Pressure losses are largely a function of overall engine geometry (turns, expansions, heat exchanger matrix and inlet and exhaust) and it is desirable to maintain maximum geometric similarity with the current engine because of costs and time to accomplish changes in the basic block, covers and gearbox.


    Specific components selected for improvement were the compressor, turbine (compressor drive), the power turbine and the regenerator. It was known that increasing turbine inlet temperature would require lower engine airflow for a given engine horsepower output. Further, lower engine airflow leads to smaller compressor and turbine sizes with the associated loss in component efficiency from decreasing size.


    Figure 4 shows a projection of loss in compressor, turbine (compressor drive) and power turbine efficiencies with decreasing airflow. Also shown are the projected improvements achievable in these components with a rigorous development program. Two to three years will be required to fully develop these advanced technology components.


    Figure 5 shows a regenerator effectiveness plot. Improved effectiveness is achieved by decreasing airflow while maintaining the same frontal airflow area in the current regenerator matrix. The lower curve represents the current metal matrix, the center curve is a current thin wall (0.0889 mm [0.0035 in.] to 0. 1143 mm [o. 0045 in.]) triangular ceramic (AS) matrix, and the upper curve represents a thin wall rectangular matrix (projected to require two to three years to develop) which has the potential of both higher effectiveness and lower matrix pressure drop.


    A prime benefit achieved in the change from metal to ceramic regenerators is the increased temperature capability of the ceramic. The current metal regenerator is limited to a maximum steady state temperature of 774°C (1425°F) and a transient temperature of 913°C (1675°F). The ceramic regenerator can achieve a 982 °F (1800°F) steady state temperature and a transient temperature of 1093°C (2000°F). This increased temperature capability is particularly important at part power operation of the engine since the best specific fuel consumption is achieved by maintaining turbine inlet temperature constant over the power range of the engine and letting the regenerator inlet temperature increase as power level decreases. In the current engine, turbine inlet temperature is reduced starting at approximately 80% power (to accommodate the 774°C [1425°F] metal limit), whereas the ceramic regenerator with a 982°C (1800°F) capability will not require reduced part power turbine inlet temperature until a level of near 1260°C (2300°F) is obtained. In addition, the lower conduction loss of the ceramic provides a favorable part power effectiveness.


    In summary, improvements in component efficiencies and regenerator effectiveness can substantially improve the engine fuel consumption and should be vigorously worked on in the proposed program.



    The current engine turbine inlet temperature is 1002°F (1835°F). Table 1 shows that a 12°C (22°F) increase will give a 1% improvement in specific fuel consumption at this level of turbine inlet temperature. This is not a linear function, but increasing temperature does provide improved specific fuel consumption over a considerable range of temperature. Changing this parameter yields the greatest single improvement in specific fuel consumption so long as it is not necessary to change another parameter (such as cooling air from the compressor).


    The incorporation of ceramic materials in the high temperature components offers the means for achieving the improved specific fuel consumption. Silicon carbide and silicon nitride are the two leading candidate ceramic materials for the high temperature vanes, blades, combustor, turbine inlet plenum and the stationary turbine tip shroud rings.


    Analysis of metal high temperature parts was performed to establish limiting turbine inlet temperatures which render the metal no longer usable. In metal components it was found that either chemical stability (oxidation, sulfidation), creep strength or tensile strength were a limiting factors at given operating temperatures.


    Figure 6 shows limits for components plotted against gasifier turbine inlet temperature, regenerator inlet temperature and power turbine inlet temperature. The metal regenerator, gasifier turbine inlet vanes and tip shrouds are the initial metal components that should be replaced with ceramic materials.


    Table 2 shows the turbine inlet temperatures at which other metal components must be replaced.


    Figure 7 shows these ceramic components in the IGT engine.


    Table 2 identifies logical engine development temperature levels for advancing to the target specific fuel consumption levels. These engine temperature levels (1038°C [l900°F], 1132°C [2070°F], 1204°C [2200°F] andl271°C [2500 °F]) were used in the balance of the study to calculate engine performance, design of components and for cost analysis.



    Initial planning specified use of the current engine with the introduction of ceramic components and improved component efficiencies as they became available. Assessment of component efficiency improvements suggest a two to three year development period for compressor, turbine and regenerator efficiency development. A thin wall ceramic regenerator can be introduced into the current engine along with ceramic vanes, tip shrouds, turbine blades and a ceramic turbine inlet plenum. Thus, the current engine can be used for development at turbine inlet temperatures to 1132°C (2070°F). (At this temperature level, the power turbine must be replaced because of limiting blade creep strength and turbine aerodynamic loading.) This permits two to three years development before a significant flow path change can be accomplished. A new compressor and turbine flow path would then be introduced with improved component efficiencies at the 1204°C (2200 °F) gas turbine operating temperature and this technology would be applicable to 1371°C (2500°F). This timing dictated that a technology discontinuity occur between the 1132°C (2070°F) and 1204°C (2200°F) engines.


    For comparison of fuel savings and life cycle costs, the engine horsepower selected for engine sizing was 300hp (224kW), the same as the 404-3 engine. Performance calculations were then made using the preceding turbine inlet temperatures, component efficiency improvements and constant horsepower.


    Table 3 shows the airflow for constant horsepower, specific fuel consumption at the various turbine inlet temperatures, and other engine component parameters. It is noted that the target 213 mg/W-h (0. 35) specific fuel consumption is achieved at a-temperature level between 1204°C (2200°F) and 1371 °C (2500°F).


    Figure 8 shows how specific fuel consumption varies for the baseline engine and the increased cycle operating temperatures over a complete operating power range from 0 to 300hp (224kW). It is noted that the ceramic regenerator temperature limit yields a much flatter specific fuel consumption curve in the 50% (150hp [112kW]) to 100% (300hp [224kW]) power range where most heavy duty engine usage occurs. Also, it is worthy of note that the turbine is very stable to low power levels and yields a torque-speed curve that is ideal for many off-design operating conditions.


    Figure 9 shows this torque characteristic (compared to a diesel engine) which experience has shown to be very valuable on icy roads, wet roads, for use on grades and for selecting a less complex transmission when compared to a diesel engine.


    An engine feature maintained in all the engines analyzed is the power transfer unit. This device has several advantages as follows:

    • Engine braking capability equal to maximum engine horsepower
    • Single shaft operation capability (particularly valuable in gen set installations)
    • Power turbine overspeed control
    • Lower transient turbine temperature excursions compared to most turbine engines


    This power transfer feature is considered to be important to helping the turbine successfully compete against current heavy duty diesel powerplants. All engine performance presented is shown for an SAE standard day rating of 29.4°C (85°F) and 152 (500 ft) altitude. Gas turbines are sensitive to ambient inlet temperatures as shown in Figure 10. Attention is directed to the feature that lower ambient inlet temperatures produce increased power and lower specific fuel consumption for a given turbine engine. The average United States temperature is 13.3°C (56°F).* This lower average ambient air temperature (compared to the SAE Rating temperature) means an average improvement in fuel economy of approximately 5% above the values shown herein.



    Current and projected regulations on noise and emissions for heavy duty vehicles/engines are shown in Table 4. These regulations are subject to change, but can materially affect the current gasoline and diesel heavy duty power plants if they are not changed. The production diesel engine will find it difficult to meet the 1980 and 1983 California standards without compromising fuel economy. However, it is believed that Federal standards may override state standards and may continue to be much less stringent than state standards.


    The noise standards may become restrictive for the diesel with encapsulation a possible solution to the truck noise problem. This will cause increased acquisition and maintenance costs.


    Noise and emission values were calculated for each of the four study engine cycles [1O38°C (1900°F), 1132°C (2070°F), 1204°C (2200cF) and 1371 °C (2500°F)]. Because of reduced airflow and lower exhaust velocities, noise was found to be reduced below current turbine engine noise values of 75-77 dBA at 15.2 m (50 ft) sideline measuring locations. The exhaust noise will be reduced by over 5 dBA at the 1371°C (2500°F) turbine inlet temperature. Even the 75 dBA noise at 50 foot (15.2 meter) sideline regulations of some cities and states can be met by these improved turbine engines (with no special noise insulation or encapsulation). It is noted that the normal air inlet filter and regenerator disks are very effective noise suppressors for compressor and turbine noise.


    Emission values obtained at each of the improved engine cycle temperatures are shown in Table 5.


    These emission levels were obtained for the 13 mode Federal Heavy Duty Diesel Cycle. HC, CO and smoke all reduce at; a result of higher cycle temperatures. The primary pollutant of concern is NOx. This would only be of concern if a Federal Standard of less than 10. 0 is legislated in 1979 and will only very slightly exceed the projected 1980 California standard. Work for pollutant (NOX) reduction will be performed in the proposed program to achieve a minimum NOx margin of 25% to accommodate deviations obtained in production combustors.



    Having performance established for the improved engines, typical truck and bus usage with these power plants was evaluated.


    The tractor-trailer selected was a 70,000lb (31,751kg) gross weight unit with 102 square foot (9.5 m2) frontal area, 480 revolutions per mile (0. 2983 tire revolutions per meter), a 4.886 axle ratio and a Fuller RT9509A nine speed transmission.


    The bus was a typical Greyhound unit of 36,000lb (16,329kg) gross vehicle weight, 74 square foot (6. 9 m2) frontal area, 497 revolutions per mile (0.3088 tire revolutions per meter), an axle ratio of 4.330 and a DDA HT-740CT four speed automatic transmission.


    In each vehicle, appropriate accessory loads and driveline losses were assigned for various vehicle speeds. Each vehicle was then run through the General Motors vehicle computer analysis for typical runs from Los Angeles to Salt Lake City and from Chicago to Boston.


    Figure 11 shows the plots of miles per gallon (kilometers per liter) versus rotor turbine inlet temperature for both the truck and the Greyhound bus. Note is made of the discontinuity in the curves between 1132°C (2070°F) and 1204 °C (2200° F) as predicted earlier in the paper. Particular note is made in the improvement made in fuel consumption.


    Figure 12 shows fuel used in a typical 500,000 mile (804,672 kilometer) engine life for the baseline engine and fuel savings for the study engines.


    The gallons saved for one truck with a 1204°C (2200°F) engine multiplies to 3,060,000 gallons (72, 857 barrels) for a 100 truck fleet. It is believed that fuel savings shown are extremely significant and will have a meaningful impact on conservation of petroleum products.



    Engine drawings were generated for each engine cycle temperature (1038°C [l900°F] , 1132°C [2070oF] , 1204°C [2200°F] and 1371°C [2500°Fj ) with emphasis placed on ceramic components and supporting metal parts. Figure 13 is a general arrangement drawing showing the 1371°C (2500°F) configuration study engine. Sketches of each unique part were made and pricing for ceramic components was performed by the Carborundum Company, Niagara Falls, New York. Costs for ceramic parts to produce 6000 engines per month were supplied.


    The Harrison Radiator Division of General Motors Corporation supplied quantity costs for regenerators and seals and Detroit Diesel Allison priced all other engine parts required. These prices were then used to generate engine acquisition and maintenance costs in the life cycle cost study.


    Life cycle costs were calculated for both trucks and buses. A 100 tractor truck fleet and a 100 coach bus fleet were chosen for these studies. A 500,000 mile (804,672km) engine life was used. An average of 9,000 miles per month (14,484km per month) was used for the trucks and 16,500 miles per month (26,554km per month) for the buses.


    A mature engine schedule of maintenance was applied for each engine. In this maintenance schedule it was assumed that ceramic and metal parts would have the same reliability since no data base is available for ceramic parts in production gas turbine engines. Road applied maintenance included oil and fuel. Shop applied maintenance included predicted items (oil change, oil filter, fuel filter, and other predicted component parts). Sixty percent of shop maintenance was in-frame, forty percent was out-of-frame. Of the 40% out-of-frame, 10% was overhaul and 5% was major repair. Fuel costs were calculated based upon $0. 40 per gallon (current price) and $0.60 per gallon (projected 1980 price).


    Data gathered for vehicle performance, maintenance material and labor and engine acquisition costs were then entered into a life cycle cost computer program and actual life cycle costs calculated. The current all metal 404 engine was used as a baseline engine for comparison purposes with the improved engines.


    Figure 14 shows a plot of life cycle costs relative to the baseline engine life cycle costs. This figure is for the line haul truck fleet.


    Figure 15 is for the Greyhound bus fleet.


    Note the effect that $0.40 and $0. 60 fuel has on relative costs. Note the discontinuity between 1132°C (2070°F) and 1204°C (2200°F) caused by the introduction of components with improved efficiencies.


    Figure 16 summarizes gains in fuel savings and costs for the study engines.


    The most obvious conclusion drawn from the life cycle cost analysis was that only 1% improvement is achieved in going from a 1204°C (2200°F) turbine rotor inlet temperature to a 1371°C (2500°F) turbine rotor inlet temperature. This is caused by fuel cost being the primary cost driver and the fact that so little improvement in specific fuel consumption is achieved in this change in operating temperature level.


    It is observed that high risk is introduced by the use of ceramic materials at the 1371°C (2500°F) cycle temperature level. At this temperature level, the single stage gasifier turbine rotor blades, two stages of power turbine rotor blades and all three stator vane rows (one gasifier and two power turbine stages) are made of ceramic materials.


    Also, variations in costs of ceramic components can severely impact the acquisition costs and thus total life cycle costs. Analysis was performed where ceramic components were priced 10% to 25% over those levels used in the basic analysis and it was found that total life cycle costs at 1371°C (2500°F) actually increased over the baseline engine costs. Costs are very important and must be closely monitored as engine development proceeds.

    (It is acknowledged that ceramic component prices could also be less than the base prices obtained.)


    Based upon the low improvement in life cycle costs and high risk with today's technology with ceramic materials in going from 1204°C (2200°F) to 1371°C (2500°F) it was decided that the program recommended would have a maximum cycle temperature that would produce the target specific fuel consumption of 213 mg/W-h (0. 35) at 100% power. It is also recommended that flexibility be maintained in the program to permit re-evaluation of this conclusion as progress is made toward meeting program objectives and experience is gained in working with ceramic flow path components.



    Two primary means of improving fuel economy evolved from the study conducted:


    1. Improved component efficiencies are feasible and can achieve approximately one-third the specific fuel consumption improvement desired. Improved efficiency in the compressor, both gasifier and power turbines and in the regenerator should receive emphasis in the program.


    2. Increased engine cycle and regenerator inlet temperatures are feasible using ceramic materials and can achieve approximately two-thirds the specific fuel consumption improvement desired. This is achieved by increasing turbine rotor inlet temperature from 10C2°C (1835°F) to 1241°C (2265°F) and regenerator inlet temperature from 774°C (1425°F) to 982°C (1800°F).


    Naturally, it is desirable to initiate this program using the engine being prepared for production and introduce improvements as soon as possible. Steps to achieve engine fuel consumption improvements as soon as possible are suggested. The first step is to introduce ceramic regenerators, ceramic gasifier turbine vanes and ceramic stationary tip shrouds into the engine and increase turbine rotor inlet temperature to 1038°C (1900°F).


    The second step is to introduce additional ceramics into the current engine for the turbine inlet plenum and ceramic gasifier turbine rotor blades and increase turbine rotor inlet temperature to 1132°C (2070°iT) (the current power turbine temperature limit for minimum demonstration testing).


    While these two steps are in progress, improved efficiencies for the compressor, turbine and regenerator disks should receive emphasis with rig testing and engine evaluations as practical. Estimates of time required to achieve these steps is two to three years. (This recognizes funding and technical constraints.) The highest risk element is considered to be the rotating gasifier turbine rotor with ceramic blades. It is recommended that an alternate air-cooled rotor be carried as a parallel program in case development problems with the ceramic bladed rotor assembly are not solved in time to meet the proposed schedule.


    The third step in the program will be an advanced engine with new, improved compressor, turbine and regenerator components and maximum use of ceramics. This engine would demonstrate the target specific fuel consumption of 213 mg/W-h (0. 35).


    Table 6 summarizes the steps for introduction of ceramic components.


    Table 7 summarizes the temperature steps, engine airflow, horsepower and specific fuel consumption that will be obtained. Test stand and vehicle demonstrations will be made with each of the last three steps in the program.


    Figure 17 shows the predicted specific fuel consumption versus power to be achieved by the recommended engines in the proposed program. The timing required for the third step is recommended to be three years. However, it is desirable to perform the design and initial fabrication of the advanced engine during the third year of the program thus giving a five year overall program.


    Figure 18 shows a schedule with various steps identified for reference. On this schedule, the vehicle demonstrations with the improved engines will be made either in a line-haul truck or a bus as appropriate.



    This study program has identified a program plan which should meet the objectives of improving specific fuel consumption from 274 mg/W-h (0. 45) to 213 mg/W-h (0. 35) by 1981, and should produce demonstration engines meeting Federal noise and emission regulations.


    Sufficient durability running of engines is planned in the program to demonstrate components that can progress to a commercially viable engine for use in trucks and buses.


    Technology generated in this program will be applicable to automotive turbines and will represent a significant step forward for commercial gas turbine engines.



    The work summarized in this paper has been prepared by a large team of experts at Detroit Diesel Allison Division of General Motors Corporation. These persons have contributed skills in engineering, materials, fabrication, cost analysis, service and maintenance, marketing, accounting and management. A complete listing of contributors would be lengthy, however, the following individuals have been the largest contributors to material presented herein.


    Beuford C. Hall            Technical Director for Phase I Study Program

    Roger C. Dycus          Project Direction and Coordination

    Samuel R. Thrasher   Regenerator Design and Analysis

    James R. Wooten       Performance Analysis

    Terry Knickerbocker   Performance Analysis

    Carlton Curry              Life Cycle Cost Analysis

    John Wertz                 Design Analysis

    James Lunsford          Design Analysis

    John Hayes                 Design Analysis

    David Decker              Design Analysis

    Dr. Peter Heitman       Materials


    Acknowledgement is directed to personnel from the Energy Research and Development Administration for their conceptual program planning, efforts to seek and provide program funding and continuous monitoring of program progress.

    Specific recognition is directed to:

    Mr. John Brogan - Assistant Director, Highway Systems, Transportation Energy Conservation

    Mr. Goerge Thur - Chief, Heat Engine Systems Branch Energy Conservation

    Mr. Thomas Sebasteyn - Program Engineer, Heat Engine Systems Branch

    Mr. Robert Mercure - Program Engineer, Heat Engine Systems Branch


    Acknowledgment is given to NASA Lewis Research Center personnel for their assistance in defining the Phase I study work and their technical and administrative assistance in sponsoring this work at Detroit Diesel Allison.

    Specific recognition is directed to:

    Mr. Mort Krasner Chief - Transportation Propulsion Division

    Mr. Don Beremond - NASA Technical Program Manager - "improved Heavy Duty Gas Turbine Engine" Contract No. NAS3-20064

    Mr. William Geotte - Technical Program Manager - (Replaced Mr. Beremond 12/1/76)

    Attached Files

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    #13 OFFLINE   kscarbel


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    Posted 18 July 2013 - 11:47 PM

    Caterpillar tested a few gas turbine powered on-highway trucks.


    My understanding is the CAT gas turbines were for off-highway dump trucks and construction machinery.


    Noel Penny Turbines (NPT) of Coventry, UK designed, developed and built 350 horsepower gas turbine engines for Caterpillar, for off-highway applications.


    CAT built an experimental model 621 turbine scraper in 1968, a model 992 turbine rubber tired loader in 1973, and I heard they also built a gas turbine grader.


    Penny had been managing director of Leyland Gas Turbines, which had developed two-shaft gas turbine engines with regenerative heat exchangers from 1968 to 1974 for experimental Leyland gas turbine trucks.


    Leyland Gas Turbines was the successor to Rover Gas Turbines, a small UK company that had worked with Sir Frank Whittle during World War II on England’s first jet engines. Rover was the earliest company to consider gas turbines for vehicles and built the world’s first gas turbine car in 1950.

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    #14 OFFLINE   farmer52


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    Posted 19 July 2013 - 04:49 AM

    Caterpillar had at least two (2) on-highway tractors in the early 70s.  They along with John Deere also experimented with gas turbines in off-highway equipment.  CAT had a dedicated "turbine R&D building" at the Techical Center in Mossville.

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