This article is about the eight-cylinder engine. For the filmmaking event, see Straight 8. For the 8 mm motion picture film format (STRAIGHT EIGHT), see Filmo §History.
Although an inline six-cylinder engine can also be timed for inherent primary and secondary balance, a straight-eight develops more power strokes per revolution and, as a result, will run more smoothly under load than an inline six. Also, due to the even number of power strokes per revolution, a straight-eight does not produce unpleasant odd-order harmonic vibration in the vehicle's driveline at low engine speeds.
The smooth running characteristics of the straight-eight made it popular in luxury and racing cars of the past. However, the engine's length demanded the use of a long engine compartment, making the basic design unacceptable in modern vehicles.[1] Also, due to the length of the engine, torsional vibration in both crankshaft and camshaft can adversely affect reliability and performance at high speeds. In particular, a phenomenon referred to as "crankshaft whip," caused by the effects of centrifugal force on the crank throws at high engine rpm, can cause physical contact between the connecting rods and crankcase walls, leading to the engine's destruction. As a result, the design has been displaced almost completely by the shorter V8 engine configuration.
Early period (1903–1918)
The first straight-eight was conceived by Charron, Girardot et Voigt (CGV) in 1903, but never built.[2][pageneeded] Great strides were made during World War I, as Mercedes made straight-eight aircraft engines like the Mercedes D.IV. Advantages of the straight-eight engine for aircraft applications included the aerodynamic efficiency of the long, narrow configuration, and the inherent balance of the engine making counterweights on the crankshaft unnecessary. The disadvantages of crank and camshaft twisting were not considered at this time, since aircraft engines of the time ran at low speeds to keep propeller tip speed below the speed of sound.
Unlike the V8 engine configuration, examples of which were used in De Dion-Bouton, Scripps-Booth, and Cadillac automobiles by 1914, no straight-eight engines were used in production cars before 1920.
Straight-eight engines were used in expensive luxury and performance vehicles until after World War II. Bugattis and Duesenbergs commonly used double overhead cam straight-eight engines. Other notable straight-eight-powered automobiles were built by Daimler, Mercedes-Benz, Isotta Fraschini, Alfa Romeo, Stutz, Stearns-Knight and Packard. One marketing feature of these engines was their impressive length — some of the Duesenberg engines were over 4ft (1.2m) long, resulting in the long hoods (bonnets) found on these automobiles.
Premium automobiles in the United States
In the United States in the 1920s, automobile manufacturers, including Hupmobile (1925), Chandler (1926), Marmon (1927), Gardner (1925), Kissel (1925), Locomobile (1925) and Auburn (1925) began using straight-eight engines in cars targeted at the middle class. Engine manufacturer Lycoming built straight-eight engines for sale to automobile manufacturers, including Gardner, Auburn, Kissel, and Locomobile. Hupmobile built their own engine. Lycoming was purchased by Auburn owner Errett Lobban Cord, who used a Lycoming straight-eight in his front-drive Cord L-29 automobile,[7] and had Lycoming build the straight-eight engine for the Duesenberg Model J, which had been designed by the Duesenberg brothers for the Cord-owned Duesenberg Inc.[8] The automobile manufacturers within the Cord Corporation, comprising Auburn, Cord, and Duesenberg, were shut down in 1937. Lycoming continues to this day as an aircraft engine manufacturer.
In the late 1920s, volume sellers Hudson and Studebaker introduced straight-eight engines for the premium vehicles in their respective lines. They were followed in the early 1930s by Nash (with a dual-ignition unit), REO, and the Buick, Oldsmobile, and Pontiac divisions of General Motors.
The Buick straight-eight was an overhead valve design, while the Oldsmobile straight-8 and Pontiac straight-8 straight-eights were flathead engines. Chevrolet, as an entry-level marque, did not have a straight-eight. Cadillac, the luxury brand of General Motors, stayed with their traditional V8 engines. In order to have engines as smooth as the straight-eights of its competitors, Cadillac introduced the crossplane crankshaft for its V8, and added V12 and V16 engines to the top of its lineup.
Ford never adopted the straight-eight; their entry-level Ford cars used flathead V8 engines until the 1950s while their Lincoln luxury cars used V8 from the 1930s to the 1980s and V12 engines in the 1930s and 1940s. Chrysler used flathead straight-eights in its premium Chrysler cars, including the Imperial luxury model.
Airships
The British R101 rigid airship was fitted with five Beardmore Tornado Mk I inline eight-cylinder diesel engines. These engines were intended to give an output of 700bhp (520kW) at 1,000 rpm but in practice had a continuous output rating of only 585bhp (436kW) at 900 rpm.[9]
Post-war
After World War II, changes in the automobile market resulted in the decline and final extinction of the straight-eight as an automobile engine. The primary users of the straight-eight were American luxury and premium cars that were carried over from before the war. A Flxible inter-city bus used the Buick straight-eight.
During World War II, improvements in the refinery technology used to produce aviation gasoline resulted in the availability of large amounts of inexpensive high octane gasoline. Engines could be designed with higher compression ratios to take advantage of high-octane gasoline. This led to more highly stressed engines which amplified the limitations of the long crankshaft and camshaft in the straight-eight engines.
Oldsmobile replaced their straight-eight flathead engine with an overhead valve V8 engine in 1949, at which time Cadillac's V8 was changed to one with overhead valves. Chrysler replaced its straight-eight with its famous Hemi V-8 for 1951. Hudson retired its straight-eight at the end of the 1952 model year. Buick introduced a (4.0" bore × 3 13⁄64" stroke = 322 in³ (5.277L)) V8 in 1953, with similar displacement as their (3 7⁄16" bore × 4 5⁄16" stroke = 320.2 in³ (5.247L)) straight-8, the latter being produced until the end of the 1953 model year. Pontiac maintained production on their straight-eight, as well as a L-head inline six, through the end of the 1954 model year, after which a V8 became standard. Packard ended production of their signature straight-eight at the end of 1954, replacing it with an overhead valve V8.[10][11]
By the end of the 1970s overhead valve V8s powered 80% of automobiles built in the US, and most of the rest had six-cylinder engines.[6]:pp99-103,116–117
In Europe, many automobile factories had been destroyed during World War II, and it took many years before war-devastated economies recovered enough to make large cars popular again. The change in the design of cars from a long engine compartment between separate fenders to the modern configuration with its shorter engine compartment quickly led to the demise of the straight-8 engine. As a result of this, and of gasoline prices several times as expensive as in the U.S., four- and six-cylinder engines powered the majority of cars in Europe, and the few eight-cylinder cars produced were in the V8 configuration.[6]:pp99-113,119–135
Military use
The British Army selected Rolls-RoyceB80 series of straight-eight engines in the Alvis FV 600 armoured vehicle family. The Alvis Saladin armoured car was a 6x6 design with the engine compartment in the rear, a 76.2mm low pressure gun turret in the centre and the driver in front. The Saracen armoured personnel carrier had the engine in front with the driver in the centre and space for up to nine troops in the rear. The Stalwart amphibious logistics carrier has the driver's compartment over the front wheels, the larger B81 engine in the rear and a large load compartment over the middle and rear. The Salamander firefighting vehicle was unarmoured, and resembled the Stalwart with a conventional fire engine superstructure.
The Rolls-Royce B80 series of engines were also used in other military and civilian applications, such as the Leyland Martian military truck, the winch engine in the Centurion ARV, and various Dennis fire engines.
Despite the shortcomings of length, weight, bearing friction, and torsional vibrations that led to the straight-eight's post-war demise, the straight-eight was the performance engine design of choice from the late 1920s to the late 1940s, and continued to excel in motorsport until the mid-1950s. Bugatti, Duesenberg, Alfa Romeo, Mercedes-Benz, and Miller built successful racing cars with high-performance dual overhead camshaft straight-eight engines in the 1920s and 1930s.
The Duesenberg brothers introduced the first successful straight-eight racing engine in 1920, when their 3L engine placed third, fourth, and sixth at the Indianapolis 500. The following year one of their cars won the French Grand Prix, while two others placed fourth and sixth in the race. Based on work the company had done on 16-cylinder aircraft engines during World War I, the overhead camshaft, three-valve-per-cylinder engine produced 115 brake horsepower (86kW) at 4,250rpm, and was capable of revving to an astonishing (at the time) 5,000rpm. No Grand Prix engine before the war had peaked at more than 3,000rpm.[12]:pp22–25
Bugatti experimented with straight-eight engines from 1922, and in 1924, he introduced the 2L Bugatti Type 35, one of the most successful racing cars of all time, which eventually won over 1000 races. Like the Duesenbergs, Bugatti got his ideas from building aircraft engines during World War I, and like them, his engine was a high-revving overhead camshaft unit with three valves per cylinder. It produced 100bhp (75kW) at 5,000rpm and could be revved to over 6,000rpm. Nearly 400 of the Type 35 and its derivatives were produced, an all-time record for Grand Prix motor racing.[12]:pp26–29
Alfa Romeo were the first to react to the engineering problems of the straight-eight: in their racing car engines for the P2 and P3 and in their Alfa Romeo 8C 2300/2600/2900 sports cars of Mille Miglia and Le Mans fame the camshaft drive had been moved to the engine centre, between cylinders four and five, thus reducing the aforementioned limitations. The straight-eight was actually built as a symmetrical pair of straight-four engines joined in the middle at common gear trains for the camshafts and superchargers. It had two overhead camshafts, but only two valves per cylinder.[12]:pp34–37
The Alfa Romeo straight-eight would return after World War II to dominate the first season of Formula One racing in 1950, and to win the second season against competition from Ferrari's V12-powered car in 1951. The Alfa Romeo 158/159 Alfetta was originally designed in 1937 and won 47 of 54 Grands Prix entered between 1938 and 1951 (with a six-year gap in the middle caused by the war). By 1951, their 1.5L supercharged engines could produce 425bhp (317kW) at 9,300rpm, and could rev as high as 10,500rpm. However, the engines were at the end of their potential, and rule changes for the 1952 season made the Alfettas obsolete.[12]:pp67–69
Mercedes-Benz would create the last notable straight-eight racing cars in 1955, with the championship-winning W196 Formula One racing car and the 300SLR sports racing car. The 300SLR was famous for Stirling Moss and Denis Jenkinson's victory in the 1955 Mille Miglia, but notorious for Pierre Levegh's deadly accident at the 1955 24 Hours of Le Mans. The 300SLR was the final development of the Alfa Romeo design of the early 1930s as not only the camshaft, but now also the gearbox was driven from the engine's centre. Engineers calculated that torsional stresses would be too high if they took power from the end of the long crankshaft, so they put a central gear train in the middle (which also ran the dual camshafts, dual magnetos, and other accessories) and ran a drive shaft to the clutch housing at the rear.[12]:pp94-97
A V6 engine is a six-cylinder piston engine where the cylinders share a common crankshaft and are arranged in a V configuration.
A V16 engine is a sixteen-cylinder piston engine where two banks of eight cylinders are arranged in a V configuration around a common crankshaft. V16 engines are less common than engines with fewer cylinders, such as V8 and V12 engines. Each bank of a V16 engine can be thought of as a straight-eight, a design that can be inherently balanced. Most V16 engines have a 45° bank angle.
A straight-four engine is a four-cylinder piston engine where cylinders are arranged in a line along a common crankshaft.
The inline-six engine is a piston engine with six cylinders arranged in a straight line along the crankshaft. A straight-six engine has perfect primary and secondary engine balance, resulting in fewer vibrations than other designs of six or fewer cylinders.
Duesenberg Automobile & Motors Company, Inc. was an American racing and luxury automobile manufacturer founded in Indianapolis, Indiana, by brothers Fred and August Duesenberg in 1920. The company is known for popularizing the straight-eight engine and four-wheel hydraulic brakes. A Duesenberg car was the first American car to win a Grand Prix race, winning the 1921 French Grand Prix. Duesenbergs won the Indianapolis 500 in 1922, 1924, 1925 and 1927. Transportation executive Errett Lobban Cord acquired the Duesenberg corporation in 1926. The company was sold and dissolved in 1937.
A U engine is a piston engine made up of two separate straight engines placed side-by-side and coupled to a shared output shaft. When viewed from the front, the engine block resembles the letter "U".
An overhead camshaft (OHC) engine is a piston engine in which the camshaft is located in the cylinder head above the combustion chamber. This contrasts with earlier overhead valve engines (OHV), where the camshaft is located below the combustion chamber in the engine block.
In automotive engineering a multi-valve or multivalve engine is one where each cylinder has more than two valves. A multi-valve engine has better breathing and may be able to operate at higher revolutions per minute (RPM) than a two-valve engine, delivering more power.
The Ford flathead V8 is a V8 engine with a flat cylinder head designed by the Ford Motor Company and built by Ford and various licensees. During the engine's first decade of production, when overhead-valve engines were used by only a small minority of makes, it was usually known simply as the Ford V‑8, and the first car model in which it was installed, the Model 18, was often called simply the "Ford V-8", after its new engine. Although the V8 configuration was not new when the Ford V8 was introduced in 1932, the latter was a market first in the respect that it made an 8-cylinder affordable and a V engine affordable to the emerging mass market consumer for the first time. It was the first independently designed and built V8 engine produced by Ford for mass production, and it ranks as one of the company's most important developments. A fascination with ever-more-powerful engines was perhaps the most salient aspect of the American car and truck market for a half century, from 1923 until 1973. The engine was intended to be used for big passenger cars and trucks; it was installed in such until 1953, making the engine's 21-year production run for the U.S. consumer market longer than the 19-year run of the Ford Model T engine for that market. The engine was on Ward's list of the 10 best engines of the 20th century. It was a staple of hot rodders in the 1950s, and it remains famous in the classic car hobbies even today, despite the huge variety of other popular V8s that followed.
Alfa Romeo Twin Spark (TS) technology was used for the first time in the Alfa Romeo Grand Prix car in 1914. In the early 1960s it was used in their race cars (GTA, TZ) to enable it to achieve a higher power output from its engines. And in the early and middle 1980s, Alfa Romeo incorporated this technology into their road cars to enhance their performance and to comply with stricter emission controls.
The Alfa Romeo Twin Cam engine is an all-alloy inline-four engine series produced by Alfa Romeo from 1954 to 1994. In Italian it is known as the "bialbero" ("twin-shaft"), and has also been nicknamed the "Nord" (North) engine in reference to its being built in Portello, Milan, in the North of Italy and to distinguish it from the Alfa Romeo Boxer engine built in the South (Sud) for the Alfasud.
Frederick Samuel Duesenberg was a German-born American automobile and engine designer, manufacturer and sportsman who was internationally known as a designer of racecars and racing engines. Duesenberg's engineering expertise influenced the development of the automobile, especially during the 1910s and 1920s. He is credited with introducing an eight-cylinder engine, also known as the Duesenberg Straight-8 engine, and four-wheel hydraulic brakes, a first for American cars, in addition to other mechanical innovations. Duesenberg was also patentholder of his designs for a four-wheel hydraulic brake, an early automatic transmission, and a cooling system, among others. Fred and his younger brother, August "Augie" Duesenberg, shared the patents, filed in 1913 and renewed in 1918, for their "walking beam" four-cylinder engine and the Duesenberg Straight 8.
A V8 engine is an eight-cylinder piston engine in which two banks of four cylinders share a common crankshaft and are arranged in a V configuration.
The Duesenberg straight-8 engine was produced from 1921 to 1937 and sold in Duesenberg automobiles. Fred and August Duesenberg got their start building experimental racing engines which achieved a great deal of success. Among their accomplishments are wins at the Indianapolis 500, the 1921 French Grand Prix and speed records at the Bonneville Salt Flats. They used the expertise they had gained to start building production engines and cars which were renowned for their performance and luxury.
The Bugatti U-16 was a 16-cylinder water-cooled double-8 vertical in-line "U engine", designed by Ettore Bugatti in 1915 to 1916 and built in France in small numbers. The US Bolling Commission bought a license to build the engine in the US, and small numbers of a slightly revised version were built by the Duesenberg Motor Corporation as the King-Bugatti. Probably about 40 King-Bugattis were made before the end of World War I caused building contracts to be canceled.
The Chevrolet Cosworth Vega is a subcompact four-passenger automobile produced by Chevrolet for the 1975 and 1976 model years. It is a limited-production version of the Chevrolet Vega, with higher performance.
The Duesenberg Model A was the first automobile in series production to have hydraulic brakes and the first automobile in series production in the United States with a straight-eight engine. Officially known as the Duesenberg Straight Eight, the Model A was first shown in late 1920 in New York City. Production was delayed by substantial changes to the design of the car, including a change in the engine valvetrain from horizontal overhead valves to an overhead camshaft; also during this time, the company had moved its headquarters and factory from New Jersey to Indiana. The Model A was manufactured in Indianapolis, Indiana, from 1921 to 1925 by the Duesenberg Automobiles and Motors Company and from 1925 to 1926 at the same factory by the restructured Duesenberg Motor Company. The successors to the company began referring to the car as the Model A when the Model J was introduced. With a top speed of 71mph.
Leo William Goossen was a draftsman, mechanical engineer and automobile designer. He is known for his work with Harry Miller and his long involvement in the design and ongoing development of the four-cylinder Offenhauser ("Offy") racing engine.
Bugatti made a series of Grand Prix, and later Formula One, straight-8 racing engines; between 1922 and 1939, and once again in 1956.
References
↑ Moore, Stephen J. (2020). A Detailed History of the Straight-Eight Automobile Engine. Self-published on USB. ISBN978-0-473-54810-0.
↑ Georgano, G. N. (1985). Cars: Early and Vintage, 1886–1930. London: Grange-Universal.
↑ Posthumus, Cyril (1977) [1977]. "War and Peace". The story of Veteran & Vintage Cars. John Wood, illustrator (Phoebus 1977ed.). London: Hamlyn / Phoebus. p.70. ISBN0-600-39155-8.
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