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Golden Age of Aviation Engine Designs.

Golden Age of Aviation Engine Designs.

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Engine Design Revolution (continued)

Brief history highlights of The Golden Age of Aviation and how air racing furthered Engine Development

  • The Pratt & Whitney Engines.


    Frederick Brant Rentschler,graduated from Princeton in 1909, and went to work as a molder and mechanic in his family's manufacturing plant. When World War I started, Rentschler enlisted in the Army. Because of his manufacturing know-how, he was assigned to oversee production of aircraft engines for the Army's New York district. So began his life-long interest and commitment to flight.

    After the War, Rentschler helped organize Wright Aeronautical Corporation in New Jersey, assumed its presidency, and shaped it into a leading producer of aero engines.

    Despite Wright's success, Rentschler was frustrated because its board of directors had little interest in experimental engineering and the development of products of the future.

    Rentschler left Wright in the summer of 1924. Over the next few months, he crystallized his vision and made plans to create a new engine company from scratch. In the spring of 1925, at the suggestion of an influential business contact, Rentschler took a train to Hartford looking for backing for his venture from the Pratt and Whitney Company, a machine-tool manufacturer. The tool company not only provided startup money, but also gave Rentschler's new company its name and the use of idle plant space.

    Rentschler had no contracts or customers. But he had learned from a high-ranking officer that the U.S. Navy would be interested in an engine of the type he had in mind -- an air-cooled engine in the 400-to-500 horsepower range, weighing no more than 650 pounds. He was proposing a power-to-weight ratio unheard of at a time when heavier, liquid-cooled engines were in favor.

    The first Pratt & Whitney engine, the Wasp, was completed on Christmas Eve 1925. The Wasp engine ran clean and true on test, reaching about 425 horsepower. Roaring through its Navy qualification trials, it stunned naval aviators with a dazzling performance that surpassed anything they had ever seen in an aero engine.

    In 1926, little more than a year old, Pratt & Whitney booked its first production order, a Navy contract for 200 Wasps. Work also moved ahead on the design of a more powerful engine, the Hornet, initially rated at 525 horsepower and a weight of 750 pounds.

  • The company was on its way.

    Pratt & Whitney engines became engines of choice for the big Thompson racers. Because the company chose to use the racing sport as a laboratory for durability development and as a show case for public relations. Pratt & Whitney offered custom modifications and convenient lend/lease accomodations for specific racing teams. The factory supplied two factory technicians at each major pylon racing event across the country from 1930 through 1939.

  • Early Pratt & Whitneys

    The Pratt & Whitney Wasp Junior production engine No. 2. which came off the assembly line in the summer of 1930. It was a brand new design and Pratt & Whitney wanted to get one in service as soon as possible for observation, so the company agreed to loan the new engine to Matty Laird in Chicago for his new Solution racing Biplane which was under constrution for the first Thompson race coming up in September. "Speed" Holman pilot of the Laird biplane won the 1930 Thompson race at record speed. The engine never missed a beat. This was the beginning, that same engine was rebuilt and used in the Gee Bee Z for the 1931 Thompson race in which the Gee Bee Z won it with ease. This same engine was also used in the Gee Bee R2 in 1932 and because the R2 only took fourth place in the Bendix race and fifth in the Thompson race the engine ended up with stock specs and installed in Martin and Osa Johnson's Sikorsky amphibian exploring Africa for their travel lecture circuit. Pratt & Whitney made their engines available where they would do the company the most good. By the time this same engine was prepared for the Gee Bee Z in 1931, the new standardized fuel specifications were in force and the top 87 octane grade with 3 cc of lead seemed adequate for a boost in compression ratio to 6:1 and blower gear ratio to 10:1. this raised full throttle out to 535 hp at 2400 rpm at 43 in. manifold pressure.


    The Pratt & Whitney nine-cylider radial engine. The main source of power for the large engine Thompson racers of the 1930s. Capable of putting out 800 hp.

    For the 1932 Thompson races, Pratt & Whitney loaned the Granville brothers a larger Wasp R-1340 engine for the Gee Bee R1. This big engine had 6:1 compression ratio and 12:1 blower gears, a combination not yet ATC rated, and developed about 770 hp at 2350 RPM. This output required doped gas and considerably richened carburetion to let the fuel do some internal cooling. The famous engine not only won the Thompson Trophy, but pushed the landplane speed record to 294.38 mph. Then Jim Wedell used it a year later to up that record to 304.98 mph in his Wedell 44.

    Another interesting custom Wasp engine was built for Benny Howard's Mr. Mulligan cabin monoplane in 1933-1936.They made a one-of-a-kind set of 13:85:1 blower gears for this engine,so that it could deliver a continuous 500 hp at 2200 rpm clear up to 11,000 ft altitude,running on the usual 87 octane fuel.This was intended to give fast,economical cruising at high altitudes for the cross country bendix races.

    The problem was that these high ratio gears were inefficient at sea level, causing excessive mixture heating and blower power loss.This compromised the power available for pylon racing.Since two speed chargers had not yet been developed,Pratt & Whitney had no choice but two reduce the limit of the manifold pressure to 34 in. manifold pressure at 2200 rpm with 87 octane gasoline.This reduced the engines power to around 500 hp.Pilot Harold Neumann tried to exceed this with doped up fuel when qualifying for the 1935 Thompson race,but he didn't use more than 480 hp.

  • Pratt & Whitney Hornet R-1690

    In 1934 Roscoe Turner installed the Hornet engine in his Wedell racer. Roscoe called the Hornet a 1000h.p. engine, but the huge cowl and extra drag cancelled out any increase in speed. Because of the fuels available in 1934 it is doubtful that the Hornet engine operated at 1000 hp. Pratt & Whitney engineers rated the original version at 825 h.p.

    The last two known prewar examples of custom Pratt & Whittney race engines were the fourteen cylinder Twin Wasp and Twin Wasp Junior for use in the late thirties by Roscoe Turner and Earl Ortman. These were basically miltary engines at the time and were not yet ATC rated.

    Earl Ortman's R-1535 Twin Wasp Junior was rated at 1000 hp at 2675 rpm on 48 in. of manifold pressure. For the big R-1830 Twin Wasp for Roscoe Turners Meteor, they quoted 1,200 hp at 2650 rpm on 47 in. of manifold pressure. It is doubtful if either pilot used the full potential of these engines until 100 octane fuel was released in 1938. For the most part the race pilots were more conservative than the factory engineers about pushing their engines to the limits, finishing the race meant money or in some cases life and death. All these engine setups were by no means all the Pratt & Whitney engines that raced in the Prewar Thompson races. There were many others, mostly Wasp and Wasp Junior models.

    The Wasp

    The Wasp was a radial engine with 1,340 cubic inches of displacement.It weighed less than 650 pounds.The Wasp achieved 425 horsepower. The Wasp remained in production until 1960, with later models producing up to 600 horsepower. Wasp engines built before 1930 are still flying today.

  • The Hornet

    The Hornet, initially rated at 525 horsepower,

  • the Wasp Jr.,
  • The R-985 air-cooled engine was first used by the Air Corps in 1932. At that time, it was rated at 300 horsepower. By 1934 it had been sufficiently improved so that it delivered 350 horsepower and two years later it was rated at 400 horsepower. Further refinements were made and during World War II it produced 450 horsepower. Through the years the R-985 was used in thousands of military aircraft of various types in addition to being installed in numerous civilian types of aircraft.

    Model: R-987-AN-14B
    Type: 9-cylinder, air-cooled, supercharged radial
    Displacement: 985
    Max. RPM: 2,300
    Max. HP: 450
    Cost: $6,000

    it was designed for light transports, trainers, sports aircraft and helicopters.

  • The R1830 Twin Wasp
  • The Pratt and Whitney R-1830 Twin Wasp engine was one of the most efficient and reliable engines of the 1930s. It was introduced in 1932 with either a 6.1 or 6.5 compression ratio and 775 or 825 horsepower respectively, at 2,400 rpm. To reach its designed power the R-1830 needed the highest octane gasoline available. Using improved fuel the R-1830 reached 1,000 hp and later 1,200 hp. It has 14 cylinders in two banks of seven. The R-1830 was used on B-24s, C-47s and the Grumman F4F-4 Wildcat, until it was phased out by Grumman. Pratt and Whitney built 13,464 R-1830-90C engines for the C-47 aircraft. It was also used in a variety of British aircraft including the Royal Air Force Catalinas, Short Sunderland Vs, Maryland bombers, and Bristol Beauforts

    Model: R-1830-90C
    Type: 14-cylinder, air-cooled, twin row radial
    Displacement: 1830
    Max. RPM: 2,400
    Max. HP: 1,200
    Weight: 1,467 lbs.
  • To learn more about Pratt & Whitney and their marvelous engines.(Click here to visit their web site

  • Other Engines of Historical Significance.

  • The Jacobs Engine
  • The Jacobs Engine Company began in Camden, New Jersey, in 1930 with a 55-hp F-head three and a 150-hp seven.

    The 3-cylinder engine had a short production life, but the seven founded a long-lived line. Its output rose to 170 hp in 1931, and, enlarged as the LA-2 model, to 195 hp in 1932. The LA series Jacobs used exposed z-type rocker arms; they were the only U.S. engines to employ this dubious design feature. This was eliminated in the 1934 L-4, which used enclosed fore-and-aft rocker arms of classic design. The L-4 developed 225 hp from 757 cu in. (12.4 L). The 285-hp L-5 was added 2 years later. At 831 cu in. (13.6L) the L-5 was the largest American seven until the post-war Cyclone Seven was built, and it is easy to understand why its World War II nickname was the "Shaky Jake."

    In the market as in design, the Jacobs was a late bloomer. While used to some extent during the late thirties the Beech Staggerwing and the very advanced Spartan Executive were Jacobs-powered it did not come into its own until the Second World War. Cessna used two in the "Bamboo Bomber" UC-71 and evidently became a convert to Jacobs power, since those exemplary airplanes, the Cessna 190 and 195, were Jacobs-powered (the 190 was actually Continental powered - ed.). One peculiarity showed up in the Cessna installations. The Jakes used coil ignition instead of magneto, and the distributor caps were prone to cracking. When this happens, the spark travels to the wrong cylinders and the engine runs rough. The cure was to have the cap undergo a bakeout in a vacuum oven and them impregnate the crack with insulating varnish, after which it would run forever without giving further trouble. The only difficulty was that this was illegal. What the government wanted you to do was replace the cracked cap with a new crack-prone cap.

    Jacobs R-755B2193472752200757 cu. in.415 lb15 GPH

  • Wright Engines

  • Wright T-3 Engine

  • The Wright T-3 is a liquid-cooled V-12 engine derived from the Wright T-2. It represents the continuation of a line of development that originated with the Liberty V-12 of WWI. Developed primarily as a racing engine, it was adopted by the U.S. Navy for several types of scouting, torpedo, and bombing airplanes as well as the Navy's two Wright F2W racing airplanes that competed in the Pulitzer Trophy Race of 1923. The T-3 engine also powered the Wright XO-3 aircraft evaluated in 1925 by the Army Air Service at McCook Field in Dayton, Ohio. The XO-3 was not selected for production.

    Model: Wright T-3
    Type: 12-cylinder, liquid-cooled, Vee
    Displacement: 1,947
    Rated RPM: 2,000 (2,500 RPM for racing)
    Rated HP: 675 (780 HP for racing)
    Weight (Dry): 1,160 lbs.

  • The Wright Cyclone R-1820 Engine

    The Wright Aeronautical Corp. introduced the first R-1820 in 1931. Developed from earlier "Cyclone" engines of the 1925-1930 era, the R-1820 was larger and more powerful than its predecessors. Originally rated at 575 hp., the engine's performance was dramatically improved during its many years of production, with several later versions being rated at 1,525 hp. Although the R-1820 was used in thousands of military and civilian aircraft of various types, it is probably best known as the engine that powered the B-17 of WW II fame.

    (for R-1820-33 used on the Martin B-10)
    Model: R-1820-33
    Type: 9-cylinder, air-cooled, radial
    Displacement: 1,823
    Max. RPM: 2,100
    Max. HP: 775
    Cost: $10,000

  • Wright R-790

    Wright R-790 engines powered the Fokker trimotor The Bird of Paradise during its flight from the U.S. to Hawaii in 1927. The R-790, rated at 225 hp., was a standard radial engine used by the Air Corps in several types of airplanes during the 1920s and 1930s. The civilian version of the R-790, designated the Wright J-5 "Whirlwind", was used to power the Spirit of St. Louis flown by Charles A. Lindbergh from New York to Paris in 1927.

  • Curtiss K-12 Engine
  • The Curtiss K-12 was a milestone in the development of liquid-cooled aircraft engines and was regarded as one of the most advanced in the world for its time. Designed by Charles B. Kirkham and first tested in 1916, the K-12 featured a cast aluminum upper crankcase and integral cylinder blocks, four valves per cylinder, and "wet sleeve" construction for improved cooling. It relied upon high RPM and reduction gearing to develop the same power as larger engines. Although technologically advanced, many of the K-12's innovations challenged the state-of-the-art and created serious reliability problems. The K-12 design, however, led to the development of the very successful Curtiss D-12 (1922) engine used in fighters and racing planes. By 1926, the D-12 design had evolved into the more powerful Curtiss V-1570 "Conqueror," noted for its use in military aircraft. That evolution was continued in the powerful liquid-cooled, V-12 aircraft engines of WWII that owed so much to design concepts pioneered in the K-12 engine of 1916.

    Model: K-12
    Type: 12 cylinder, liquid-cooled, Vee
    Displacement: 1,145 cu. in.
    Rated Horsepower: 375
    Rated RPM: 2,250

  • Allison V-1710

    The V-1710 engine was the first product of an extensive Army program to develop a high-power, liquid-cooled engine. Derived from a model designed in 1930 for airship use, the V-1710 was first used by the Air Corps in 1932. Rated at 1,000 horsepower, it was installed in the Consolidated XA-11A, an experimental attack version of the Consolidated P-25. By 1938, the engine's output had been increased to 1,150 horsepower and was used to power the Bell X/YFM-1 multiplace fighters. The V-1710 was continually improved and during World War II its output was increased to 1,475 horsepower in some series engines. During the war it was used primarily in the Curtiss P-40 "Warhawk", the Bell P-39 "Airacobra", and the twin-engine Lockheed P-38 "Lightning". It was also used in early versions of the North American P-51 "Mustang".

    Model: V-1710-51 (right-hand drive)
    Type: 12 cylinder, supercharged
    Displacement: 1,710
    Weight: 1,345 lbs.
    Maximum RPM: 3,000
    Maximum Horsepower: 1,325
    Cost: $19,000 (engine only)

  • Ranger L-440 Engine

  • The L-440 air-cooled, six-cylinder, inverted, in-line engine was manufactured by the Ranger Aircraft Engine Division of Fairchild Engine and Airplane Corp. Built in several versions ranging from 175 hp. to 200 hp., L-440 series engines were used to power the more than 6,000 Fairchild PT-19 and PT-26 trainers built during WW II. This engine was donated by Mr. David Blakeney, Hoxie, Arkansas, and Mr. Edgar E. Adams, Garland, Texas.

    Model: L-440-1
    Type: 6 cylinder, in-line
    Displacement: 441
    Max. RPM: 2,450
    Max. HP: 175
    Cost: $2,600

    Curtiss R-600 Engine

  • The Curtiss R-600 "Challenger" air-cooled engine , rated at 180 hp., was used in experimental versions of the PT-5 and PT-11 trainers during the 1929-1931 period. Although the R-600 was installed in only two military airplanes, it is historically significant because it was the Air Corps' first twin-row radial engine.

  • Curtiss V-1570 "Conqueror" Engine

  • The Curtiss Aeroplane and Engine Co. began producing its famous Conqueror engine in 1926. Although similar in general principles of design to the earlier Curtiss D-12 engine, the Conqueror was larger and more powerful. Originally rated at 600 hp., the engine's performance in several later versions was improved to 675 hp. In the late 1920s and early 1930s, the V-1570 Conqueror was selected to power the Curtiss P-6 series "Hawk" aircraft as well as various other Air Corps types including the A-8, B-2, B-7, O-25, and P-16. After 1935, the Conqueror was superseded by more advanced liquid-cooled engines.

    Model: V-1570-59
    Type: 12 cylinder, liquid-cooled, Vee
    Displacement: 1,570 cu. in.
    Maximum Horsepower: 675
    Max. RPM: 2,450
    Cost: $7,500

    PACKARD MODEL DR-980 OF 1928
  • Packard Diesel Engine


    Fuel injection

    Bore and stroke
    Compression ratio
    Weight-horsepower ratio
    Where manufactured
    Fuel consumption
    Fuel consumption
    Oil consumption
    Outside diameter
    Overall length
    Optional accessories
    4-stroke cycle diesel
    9---static radial configuration
    Directly into cylinders at a pressure of 6000 psi
    Poppet type, one per cylinder
    Compression---glow plugs for starting---air compression 500 psi at 1000 F.
    Distillate or "furnace oil"
    225 at 1950 rpm
    4 13/.16 x 6 in.
    16:1---maximum combustion pressure 1500 psi
    982 cu in.
    510 lb without propeller hub
    2.26 lb hp
    .46 lb per hp/hr at full speed
    .40 lb per hp/hr at cruising
    .04 lb per hp/hr
    45 11/16 in.
    36 3/4 in.
    Starter---Eclipse electric inertia; 6 volts. Special series no. 7
    Generator---Eclipse type G-1; 6 volts

    Instruction Book for the Packard-Diesel Aircraft Engine (Detroit: Packard Motor Car Company, 1931), p. 3.

    The specifications from SMITHSONIAN ANNALS OF FLIGHT,
    The First Airplane Diesel Engine
    Packard Model DR-980 of 1928 - Robert B. Meyer 1964

  • The Jet Engine

    Sir Frank Whittle demonstrated for the first time on April 12,1937 the world's first turbojet engine designed specifically for aircraft propulsion. Essentially a heat engine,using air as a working fluid to provide thrust. The more accurate term is: "Gas Turbine Engine".

  • Note:

    This site is for informational purposes only and I recognize that some words,logo,models,names and designations,mentioned and used on this site are the property of the trademark holder.I use them for identification purposes only.

    Source: A History of Aircraft Piston Engines by Herschel Smith


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