Thursday, December 27, 2007

Harley-Davidson engines

The classic Harley-Davidson engines are two-cylinder, V-twin engines with the pistons mounted in a 45° "V". The crankshaft has a single pin, and both pistons are connected to this pin through their connecting rods.

This design causes the pistons to fire at uneven intervals, the consequence of an engineering tradeoff to create a large, powerful engine in a small space. This design choice is entirely vestigial from an engineering standpoint, but has been sustained because of the strong connection between the distinctive sound and the Harley-Davidson brand. This design, which is covered under several United States patents, gives the Harley-Davidson V-twin its unique choppy "potato-potato" sound. To simplify the engine and reduce costs, the V-twin ignition was designed to operate with a single set of points and no distributor, which is known as a dual fire ignition system, causing both spark plugs to fire regardless of which cylinder was on its compression stroke, with the other spark plug firing on its cylinder's exhaust stroke, effectively "wasting a spark." The exhaust note is basically a throaty growling sound with some popping.

The 45 degree design of the engine thus creates a plug firing sequencing as such: The first cylinder fires, the second (rear) cylinder fires 315° later, then there is a 405° gap until the first cylinder fires again, giving the engine its unique sound.

Harley Davidson has used various ignition systems throughout its history - be it the early points/condenser system, (Big Twin up to 1978 and Sportsters 1970 to 1978), magneto ignition system used on 1958 to 1969 Sportsters, early electronic with centrifugal mechanical advance weights, (all models 1978 and a half to 1979), or the late electronic with transistorized ignition control module, more familiarly known as the black box or the brain, (all models 1980 to present).

With the implementation of Electronic Fuel Injection (EFI), Harley Davidson uses a single fire ignition system on the models equipped with EFI, which now includes 100% of their product line with the introduction of the 2007 models.

In 1991, Harley-Davidson began to participate in the Sound Quality Working Group, founded by Orfield Labs, Bruel and Kjaer, TEAC, Yamaha, Sennheiser, SMS and Cortex. This was the nation's first group to share research on psychological acoustics. Later that year, Harley-Davidson participated in a series of sound quality studies at Orfield Labs, based on recordings taken at the Talladega Superspeedway, with the objective to lower the sound level for EU standards while analytically capturing the "Harley Sound." This research resulted in the bikes that were introduced in compliance with EU standards for 1998.

On 1 February 1994, the company filed a trademark application for the distinctive sound of a Harley-Davidson motorcycle engine: "The mark consists of the exhaust sound of applicant's motorcycles, produced by V-twin, common crankpin motorcycle engines when the goods are in use". Nine of Harley-Davidson's competitors filed comments opposing the application, arguing that cruiser-style motorcycles of various brands use a single-crankpin V-twin engine which produce a similar sound. These objections were followed by litigation. After six years, Harley-Davidson withdrew their trademark application.

When Honda first began making a motorcycle with a 45° V-2 design, the Honda Shadow, it used a more advanced engineering approach with an offset crank design featuring dual crankpins, which allows for even firing pulses and higher horsepower because of the reduced vibrational stresses on the engine. Responding to customer demands for a more traditional V-twin, in 1995 Honda rolled out the Shadow A.C.E., a single-crankpin design, with a more traditional exhaust note and feel, but more vibration and less maximum power.


The beginning

The company considers 1903 to be its year of founding, though the Harley-Davidson enterprise could be considered to have started in 1901 when William S. Harley, age 21, drew up plans for a small engine that displaced 7.07 cubic inches (116 cc) and had four-inch flywheels. The engine was designed for use in a regular pedal-bicycle frame.

Over the next two years Harley and his boyhood friend Arthur Davidson labored on their motor-bicycle using the northside machine shop of their friend Henry Melk. It was finished in 1903 with the help of Arthur's brother, Walter Davidson. Upon completion the boys found their power-cycle unable to conquer Milwaukee's modest hills without pedal assistance. Will Harley and the Davidsons quickly wrote off their first motor-bicycle as a valuable learning experiment.

Work was immediately begun on a new and improved machine. This first "real" Harley-Davidson motorcycle had a bigger engine of 24.74 cubic inches (405 cc) with 9-3/4 inch flywheels weighing 28 pounds. The machine's advanced loop-frame was similar to the 1903 Milwaukee Merkel motorcycle. They also got help with their new engine from outboard motor pioneer Ole Evinrude. Elder brother William A. Davidson also lent a hand.

The prototype of the new improved loop-frame model was assembled in a 10 by 15-foot (3 by 5 meter) shed in the Davidson family backyard. The machine was functional by 8 September 1904 when it was entered in a Milwaukee motorcycle race, the first known appearance of a Harley-Davidson motorcycle.

In January 1905 small advertisements were placed in the "Automobile and Cycle Trade Journal" that offered bare Harley-Davidson engines to the do-it-yourself trade. By April, complete motorcycles were in production on a very limited basis. In 1905 no more than a dozen machines were built in the backyard shed. (Some years later the original shed was taken to the Juneau Avenue factory where it would stand for many decades as a tribute to the Motor Company's humble origins. Unfortunately, the first shed was accidentally destroyed by contractors in the early 1970s during a clean-up of the factory yard.)

In 1906 Harley and the Davidsons built their first factory on Chestnut Street (later Juneau Avenue). This location remains the Motor Company's corporate headquarters today. The first Juneau Avenue plant was a modest 40 by 60-foot single-story wooden structure. That year around 50 motorcycles were produced.

In 1907 William S. Harley graduated from the University of Wisconsin-Madison with a degree in mechanical engineering. That year additional factory expansion came with a second floor and later with facings and additions of Milwaukee pale yellow ("cream") brick. With the new facilities production increased to 150 motorcycles in 1907. That September a milestone was reached when the fledgling company was officially incorporated. They also began selling their motorcycles to police departments around this time, a tradition that continues today.

Production in 1905 and 1906 were all single-cylinder models with 26.84 cubic inch (440 cc) engines but as early as February of 1907 a prototype model with a 45-degree V-Twin engine was displayed at the Chicago Automobile Show. Although shown and advertised, very few dual cylinder V-Twin models were built between 1907 and 1910. These first V-Twins displaced 53.68 cubic inches (880 cc) and produced about 7 horsepower (5 kW). This gave about double the hill-climbing power of the first singles. Top speed was about 60 mph (97 km/h). Production jumped from 450 motorcycles in 1908 to 1,149 machines in 1909.

The success of Harley-Davidson (along with Indian's success) had attracted many imitators. By 1911 some 150 makes of motorcycles had already been built in the United States -- although just a handful would survive the 1910s.

In 1911 an improved V-Twin model with mechanically operated intake valves was introduced. (Earlier V-Twins had used "automatic" intake valves that opened by engine vacuum). Displacing 49.48 cubic inches (810 cc), the 1911 V-Twin was actually smaller than earlier twins, but gave better performance. After 1913 the majority of bikes produced by Harley-Davidson would be V-Twin models.

By 1913 the yellow brick factory had been demolished and on the site a new 5-story structure of reinforced concrete and red brick had been built. Begun in 1910, the red brick factory with its many additions would take up two blocks along Juneau Avenue and around the corner on 38th Street. Despite the competition, Harley-Davidson was already pulling ahead of Indian and would dominate motorcycle racing after 1914. Production that year swelled to 16,284 machines.


Harley-Davidson Motor Company (NYSE: HOG) is an American manufacturer of motorcycles based in Milwaukee, Wisconsin. The company emphasizes heavyweight (over 750 cc) bikes designed for cruising on the highway. Harley-Davidson motorcycles (popularly known as "Harleys") have a distinctive design and exhaust note, and are especially noted for the tradition of heavy customization that gave rise to the chopper-style of motorcycle.

Harley-Davidson attracts a loyal brand community, with licensing of the Harley-Davidson logo accounting for almost 5% of the company's net revenue ($41 million in 2004).

The Motor Company supplies many American police forces with their motorcycle fleets.

The Buell Motorcycle Company became a wholly-owned subsidiary of Harley-Davidson in 2003, the same year that the Motor Company celebrated its 100th birthday.