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Harley-Davidson Road King 45° transversely mounted V-twin.
Moto Guzzi Jackal with a longitudinally mounted 90° V-twin.
Honda 90° transversely mounted V-twin.
Ducati 90-degree transversely mounted V-twin.
Honda GL500 Silver Wing with a longitudinally mounted V- twin.
Sokół transversely mounted V-twin.

A V-twin is a two cylinder internal combustion engine where the cylinders are arranged in a V configuration.

Contents

Configurations

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"True V-twin" vs V-2

There is some ambiguity regarding what defines a V-twin which arose from 180 degree "V" engines (see Flat engine). When the cylinders are arranged in a V pattern, it is generally accepted as being a V engine. However, some people differentiate using "V-twin" to mean the classic V design of a shared crank pin for each pair of cylinders and "V-2" to indicate a boxer-style crank with a separate crank pin for each cylinder. This convention is not common, and applies only to two cylinder engines. For example, while most V8 engines use shared crank pins for cylinder pairs, they are not referred to as "V-octuplets". Most engine manufacturers do not use this convention and the 1983 Honda Shadow 750 is known as being the first V-twin with an offset-dual-pin crankshaft.[1]

V angles

Generally, any two-cylinder motorcycle engine with its two cylinders at an equidistant opposite angles from the center rotation of the crankshaft is referred to as a V-twin. The V-twin engine is not designated by a specific angle, but people associate the 45° Harley-Davidson engine with the classic V-twin configuration. While any motorcycle can have a v-twin engine, cruiser style motorcycles most commonly use this configuration. For example, Honda offers a 52° engine in several of their cruiser motorcycles. But other angles can be seen such as the 75° Suzuki and KTM, the 80° Honda CX-500, the 47° Vincent, and the 60° Aprilia. The engine manufacturer S&S offers a 45° and a 56.25° engine for use in custom choppers.

A 90° twin engine, such as the signature Ducati engine and recent Aprilia engines — with the front cylinder approximately parallel to the ground and the rear cylinder vertical — is generally referred to as a L-twin engine. There is no technical distinction between V-twin and L-Twin engines. These are merely names used by convention. From an engineering perspective, the 90° angle is preferred as it acts as a counterweight to balance the engine.

Orientations

The terms longitudinal engine and transverse engine are most often used to refer to the crankshaft orientation,[2][3] however, some sources, most prominently Moto Guzzi, use the terminology in the opposite way.

A Moto Guzzi Technical Services representative tried to explain to LA Times columnist Susan Carpenter that Moto Guzzi engines are "called 'transverse' because the engine is mounted with the crankshaft oriented front to back instead of left to right."[4] In spite of this, it it could be assumed that those who call V-twin motorcycle engines "transverse" when they are mounted with the crankshaft front-to-back and the cylinders sticking out the sides are saying that to them, the engine's axis is the line passing from one cylinder to the other, at a right angle to the crankshaft, rather than going by the crankshaft's axis.[5][6][7][8][9][10][11] Highly technical sources, such as V. Cossleter's Motorcycle Dynamics,[2] or Gaetaeno Cocco's Motorcycle Design and Technology[12] are careful to not simply use the terms "longitudinal engine" or "transverse engine," but rather to specify that they mark the engine's orientation based on the crankshaft, and so they will say "transverse crankshaft engine" or "longitudinal crankshaft engine."

Transverse crankshaft mounting

The engine can be mounted in transverse crankshaft position as on Harley-Davidsons, Ducatis and many recent Japanese motorcycles. This transverse position gives the motorcycle a reduced frontal area. The main disadvantage of this configuration is that the rear cylinder and the front cylinder will receive different air-flows making air cooling somewhat problematic especially for the rear cylinder. Cooling problems are somewhat mitigated by having all "four" sides of each cylinder exposed to air flow. This differs from a parallel-twin cylinder engine which has a distinct front, back, and sides, but the inside of each cylinder is not exposed to airflow as the cylinders are typically joined together with a cam chain running up through the block in-between the cylinders.

Longitudinal crankshaft mounting

The longitudinal crankshaft two-cylinder V as seen on Moto-Guzzis and some Hondas is less common. This orientation is well suited for shaft drive by eliminating the need for a 90° bevel gear at the transmission end of the shaft. In motorcycles, a longitudinal engine fits well inside the frame, and aids cooling because both heads protrude out into the air. [5] However this approach has the slight disadvantage in motorcycles of causing a torque reaction that tends to lean the motorcycle slightly to one side as the angular rate of the crankshaft increases or decreases. The faster the change, the larger the torque it produces. However, many motorcycle manufacturers have corrected for torque reaction by rotating the transmission input shafts and/or the balance and drive shafts opposite that of the crankshaft so that there is approximately equal mass turning clockwise and counterclockwise at any time, thereby physically canceling the effect.

Automobile use

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V-twin engines, adapted from motorcycles, were featured in 3-wheeled Morgans made from 1911 to 1939.

Mazda made 356cc and 571cc V-twins beginning in 1960 for the Mazda R360.

The Triking Cyclecar uses a Moto-Guzzi V-twin.

The Ace Cycle Car features a V-twin Harley-Davidson engine.[13]

See also

References

  1. ^ "Honda: 1983 Shadow 750". http://powersports.honda.com/the_story/heritage/heritage_milestone.asp?Decade=1980&TargetUrl=Milestone/Milestone_Model_0102.asp&PrevPageTitle=TimeLine. Retrieved 2008-05-20.  
  2. ^ a b Cossalter, Vittore (2006). Motorcycle Dynamics (Second Edition ed.). Lulu.com. pp. 291–294. ISBN 978-1-4303-0861-4.  
  3. ^ Foale, Vittore (Tony). Motorcycle Handling and Chassis Design: the art and science (Second Edition ed.). Tony Foale. pp. 11–6. ISBN 978-8493328634.  
  4. ^ Carpenter, Susan, "Chaps aren't de rigueur, but a helmet, yes", ASK THROTTLE JOCKEY, http://www.latimes.com/classified/automotive/highway1/la-hyw-qa25jul25,1,2706840.story, "According to my source at Moto Guzzi Technical Services, "The Guzzi engine is a 90-degree 'L' twin, actually, because the cylinders are oriented at 90 degrees, instead of a typical V twin that has a smaller angle ( 60-degree, 77-degree, etc.). It is called 'transverse' because the engine is mounted with the crankshaft oriented front to back instead of left to right. Because of this you cannot run a chain or belt drive directly to the rear wheel like in most motorcycles. This is why you have a separate gearbox that bolts to the engine and transfers the power to the rear wheel via the drive shaft. This is how it is done on the Moto Guzzi and a BMW."  
  5. ^ a b Coombs, Matthew; Haynes, John; Shoemark, Pete (2002), Motorcycle Basics (2nd ed.), Haynes, p. 1•31, http://books.google.com/books?id=D0DhHAAACAAJ, "The transversely mounted [cylinder] V-twin, as used to good effect for many years by Moto Guzzi, slots easily into the frame, and has excellent cooling as both heads are stuck out into the wind. It also provides the perfect set-up for using shaft drive."  
  6. ^ Holmstrom, Darwin (2001), The Complete Idiot's Guide to Motorcycles, Alpha Books, ISBN 0028642589, 9780028642581, http://books.google.com/books?id=VGrp5Pjsf4UC&pg=PA82, "Ducati's engines, which are longitudinal (they are positioned lengthwise in the frame) most obviously display the "L" configuration, but Moto Guzzi's engines, which are transverse (arranged croswise in the frame), are also at 90 degrees."  
  7. ^ New 2009 Moto Guzzi V7 Classic Honors Historic Roots, Moto Guzzi Spa, http://www.motoguzzi-us.com/servonline/news/dettaglio.asp?indice=271, retrieved 2009-04-29, "Just as importantly, the V7 became an instant technology trendsetter thanks to its innovative transverse, air-cooled V-twin engine with shaft drive."  
  8. ^ New 2009 Moto Guzzi V7 Classic Honors Historic Roots, Moto Guzzi Spa, http://www.motoguzzi-us.com/servonline/news/dettaglio.asp?indice=271, retrieved 2009-04-29, "We could, of course write a book about Moto Guzzi’s transverse V-Twin."  
  9. ^ Breva V 1100, Moto Guzzi Spa, http://www.motoguzzi-us.com/Nuovi_modelli/breva1100/specifiche4.asp?pagina=spec&modello=breva1100&pag=4, retrieved 2009-04-29, "Just as importantly, the V7 became an instant technology trendsetter thanks to its innovative transverse, air-cooled V-twin engine with shaft drive."  
  10. ^ A walk around the Breva V 1100, Moto Guzzi Spa, http://www.motoguzzi-us.com/Nuovi_modelli/breva1100/specifiche4.asp?pagina=spec&modello=breva1100&pag=4, retrieved 2009-04-29, "The transverse 90° V-Twin engine and its shaft drive were chosen not as limitations on the freedom of design, but as the very heart of the design concept."  
  11. ^ Grubb, Jake (March 1975), "Easy Riders Grand Touring Motorcycles for '75 url=http://books.google.com/books?id=aeMDAAAAMBAJ&pg=PA82", Popular Mechanics (Hearst Magazines) 143 (3): 82, ISSN 0032-4558, "Ducati 750 Sport with its clip-on handlebars and racing setup, is for those who want to do their touring stretched out prone! Engine is a longitudinal V-twin. ..The unique 90∘longitudinal engine produces enormous low and mid-range torque...Moto Guzzi 850T...An 850-cc 90 V-twin engine..."  
  12. ^ Cocco, Gaetano (2004), Motorcycle design and technology, pp. 117 ff, ISBN 0760319901, 9780760319901  
  13. ^ "Ace Cycle Car". http://www.cycle-car.com. Retrieved 2008-11-27.  

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