Most V-twin engines have a single crankpin, which is shared by both connecting rods. The connecting rods may sit side-by-side with offset cylinders, or they may be "fork & blade" items with cylinders in the same plane without an offset.
Some notable exceptions include the Moto Guzzi 500cc (with 120° V angle and 180° crank pin offset) that Stanley Woods rode to win the 1935 Isle of Man TT; the 1983 Honda Shadow 750, claimed as being the first V-twin with an offset-dual-pin crankshaft; and the 1987 Suzuki VX 800, 45° V angle with 45° crank pin offset in USA and 75° crank pin offset for the rest of the world.
Generally, any two-cylinder motorcycle engine with its two cylinders arranged more than 0° and less than 180° apart is referred to as a V-twin. Although Ducati use the name "L-twin" for their 90° twin engine (with its front cylinder nearly horizontal and the rear cylinder almost vertical), there is no technical distinction between V-twin and L-twin engines; and these are merely names used by convention.
A 90° V-twin will, with a correct counterweight, yield perfect primary and secondary balance, and although its firing intervals are uneven, they are not unpleasant.Template:Citation needed A V-twin with an angle of less than 90° is more compact and has more even firing intervals, but has significantly poorer mechanical balance. Offset crankpins are sometimes used to reduce the resulting vibration.
The terms longitudinal engine and transverse engine are most often used to refer to the crankshaft orientation, 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." In spite of this, it is 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. Highly technical sources, such as V. Cossleter's Motorcycle Dynamics, or Gaetaeno Cocco's Motorcycle Design and Technology are careful not simply to 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", or, conversely, "transversely mounted cylinders" in referenced to the classic BMW orientation, with a longitudinal crankshaft and cylinders at a right angle to the axis of the frame.
Transverse crankshaft mounting
Template:Unreferenced section The engine can be mounted in transverse crankshaft position as on Harley-Davidsons, Ducatis and many recent Japanese motorcycles. This layout produces a twin cylinder motorcycle engine that is little or no wider than a single. A narrower engine can be mounted lower in the frame with handling benefits. A significant disadvantage of this configuration for air-cooled engines is that the two cylinders receive different air-flows and cooling of the rear cylinder tends to be restricted. 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.
Some transverse V-twins create further cooling problems for themselves by placing the hot exhaust port (and pipe) of the rear cylinder towards the back of the motorcycle. The advantage of this arrangement is that the two cylinders can share their carburettor, further contributing to the essentially low power nature of this set-up.
- Ducati Monster 620 Dark.jpg
This air-cooled Ducati Monster 620 has a transverse crankshaft 90° V-twin with one cylinder lying horizontally, and one vertically, so that the rearward, vertical cylinder's air flow is less obstructed by the one in front.
- Honda VTR250 2009 Engine Radiator.JPG
Honda's VTR250 is similar, but the engine is not leaning forward, thus each cylinder is about 45° from vertical. The rear cylinder's air flow is blocked, but note this is a water-cooled engine, so what most matters is that the radiator is out in front with good air flow.
- Ducati Monster S4R Testastretta.jpg
As the Ducati models get larger engines, they gain oil-, and then water-cooling, as in this Monster S4R S. Like the VTR250, the radiators are out in front, but the basic engine orientation retains the cooling advantages of the Monster 620.
Longitudinal crankshaft mounting
The longitudinal crankshaft two-cylinder V as seen on Moto-Guzzis and some Hondas is less common. This orientation is suited to shaft drive, eliminating the need for a 90° bevel gear at the transmission end of the shaft. A longitudinal crankshaft engine fits neatly into a typical motorcycle frame, leaving ample room for the transmission, and cooling is facilitated by cylinder heads and exhausts protruding into the air stream. Longitudinal crankshaft mounting is associated with a torque reaction that tends to twist the motorcycle to one side on sharp acceleration or when opening the throttle in neutral and in the opposite direction on sharp deceleration. Many modern motorcycle manufacturers correct for this effect by rotating flywheels or alternators in the opposite direction to that of the crankshaft.
V-twin engines, adapted from motorcycles, were featured in Morgan three-wheelers made from 1911 to 1939. A number of Morgan-inspired models are produced today including the Triking Cyclecar, which uses a Moto-Guzzi V-twin; the Ace Cycle Car, which uses a V-twin Harley-Davidson engine; and the JZR which uses engines from the Honda CX series.
Commercial equipment such as pressure washers, lawn and garden tractors, tillers, generators and water pumps use V-twin engines when that equipment is large enough to need more power, usually in excess of 16 horsepower, than can be provided by a single-cylinder engine. These V-twin engines have horizontal or vertical crankshafts, usually have 90-degree crankshaft angles, and are usually forced-air–cooled. The V-twin configuration gives these engines a smaller footprint and less vibration, in the absence of balancing shafts, than other two-cylinder configurations.
Manufacturers of such engines include Honda with its V-twin series engines; Kawasaki with its FD, FH, FS, and FX series; Subaru with its EH series; Briggs & Stratton with its Professional and Intek V-twin Series; Tecumseh with its OV691EA and TVT691 engines; and Kohler.
- ↑ "I Coulda Had a V-8.... so I Did". http://www.motorcycle.com/events/i-coulda-had-a-v8-so-i-did-12730.html. Retrieved 2010-04-18. "By 1934 Guzzi offered a range of 175, 250 and 500cc models including full touring machines. The next year they raised the ante once again, challenging the all-vanquishing Norton at the legendary Isle of Man TT, basically a course the British racer owned lock, stock and single barrel thanks to a phenomenal rider, Scotsman Jim Guthrie. Moto Guzzi went to a Brit for riding skills, one Stanley Woods. They gave him a new racer featuring a 120-degree V-twin with offset cranks firing at 180 degrees with bevel gears and shafts driving the SOHC, good enough for 44 hp at 7500 rpm and 112 mph, on equal standing with the Norton. It had an ace up its sleeve so to speak in that it incorporated a type of pivoted-fork rear suspension while the frontend was a springer, a design that had never won a Senior TT due to its handling deficiencies, or so was thought. Guzzi had done some tweaking in that department as well. It also came equipped with a massive twin-leading shoe front brake, a 4-speed gearbox, and alloy wheels, another innovation to cut down unsprung weight. When the dust had settled and the calculations determined, the wreath of victory went to Woods and Moto Guzzi, leaving Norton as they say, gobsmacked. Not only that, the Guzzi had smashed the track lap record. The next day Moto Guzzi was world famous."
- ↑ "Honda: 1983 Shadow 750". Archived from the original on May 19, 2008. http://web.archive.org/web/20080519233200/http://powersports.honda.com/the_story/heritage/heritage_milestone.asp?Decade=1980&TargetUrl=Milestone/Milestone_Model_0102.asp&PrevPageTitle=TimeLine. Retrieved 2008-05-20.
- ↑ "Suzuki VX800". Cycle World: 36–37. July 1990. "At some point in the motorcycle's development, the company changed the crankpin offset from 45 to 75 degrees in hope of creating a smoother-running motor. But just as production began, American Suzuki engineers decided that the new offset resulted is less mid-range power as well as a too-sanitized exhaust note, one that didn't sound very V-Twin-like. Presto, now the US models come with the 45-degree offset, while the rest of the world gets the 75-degree staggered crankpins."
- ↑ 4.0 4.1 Vittore Cossalter. "Shaking forces of twin engines". http://www.sense.net/~blaine/twin/twin.html. Retrieved 2010-07-25.
- ↑ "Moto Morini V-Twin Engine Diagram". http://www.cybermotorcycle.com/gallery/morini/Moto_Morini_v-twin_engine_diagram.htm. Retrieved 2011-04-22.
- ↑ 6.0 6.1 Cossalter, Vittore (2006). Motorcycle Dynamics (Second Edition ed.). Lulu.com. pp. 291–294. ISBN 978-1-4303-0861-4.
- ↑ Foale, Vittore (Tony). Motorcycle Handling and Chassis Design: the art and science (Second Edition ed.). Tony Foale. pp. 11–6. ISBN 978-8493328634.
- ↑ Carpenter, Susan (2007-07-25), "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."
- Coombs, Matthew; Haynes, John; Shoemark, Pete (2002), Motorcycle Basics (2nd ed.), Haynes, p. 1•31, ISBN 9781859605158, 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."
- Holmstrom, Darwin (2001), The Complete Idiot's Guide to Motorcycles, Alpha Books, ISBN 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."
- New 2009 Moto Guzzi V7 Classic Honors Historic Roots, Moto Guzzi Spa, archived from the original on May 27, 2009, http://web.archive.org/web/20090528073549/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."
- Out of history, on to the road., Moto Guzzi Spa, archived from the original on March 26, 2009, http://web.archive.org/web/20090326002937/http://www.motoguzzi-us.com/Nuovi_modelli/breva1100/specifiche4.asp?pagina=spec&modello=breva1100&pag=4, retrieved 2009-04-29, "We could, of course write a book about Moto Guzzi’s transverse V-Twin."
- Grubb, Jake (March 1975), "Easy Riders Grand Touring Motorcycles for '75", Popular Mechanics (Hearst Magazines) 143 (3): 82, ISSN 0032-4558, http://books.google.com/books?id=aeMDAAAAMBAJ&pg=PA82, retrieved 2009-04-29, "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..."
- ↑ Cocco, Gaetano (2004), Motorcycle design and technology, pp. 117 ff, ISBN 9780760319901
- ↑ (PDF) Heritage/History: Design/Technology, BMW Motorrad, archived from the original on September 27, 2007, http://web.archive.org/web/20070927231254/http://www.bmwmotorcycles.com/pdfs/history/design_tech.pdf, "...the boxer had three unique innovations that would remain throughout its years in development:The engine design included transversely mounted cylinders, which were cooled by exposure to the passing air."
- ↑ Coombs, Matthew; Haynes, John; Shoemark, Pete (2002), Motorcycle Basics (2nd ed.), Haynes, p. 1•31, ISBN 9781859605158, http://books.google.com/books?id=D0DhHAAACAAJ
- ↑ Friedman, Art; Trevitt, Andrew; Cherney, Andrew; Elvidge, Jamie; Brasfield, Evans (April 2000). "Sport Cruisers Comparison - Seven Sport-Cruiser Motorcycles". Motorcycle Cruiser. Source Interlink Media. "Take a Spin" section, paragraph 4. http://www.motorcyclecruiser.com/roadtests/sport_cruisers_comparison/index.html. Retrieved 2010-09-10. ""Though the Valkyrie also has a longitudinal crankshaft, this torque reaction has been eliminated by making some of the components, such as the alternator, spin the opposite direction of the engine.""
- ↑ Battisson, Stephen (1997). "Developing the V6 - Taming The Beast". The Laverda V6. Stephen Battisson. p. 3. Archived from the original on 2011-07-08. http://web.archive.org/web/20110708092245/http://www.breganzane.com/vm/history/v6/page3.html. Retrieved 2010-09-10. ""By arranging the rest of the engine internals to rotate in the opposite direction to the crankshaft their forces are cancelled out without having to resort to the weight, complexity and friction associated with two crankshafts. ""
- ↑ Bobbitt, Malcolm (2004). Three Wheelers - Those were the days. Veloce Publishing Ltd. p. 16. ISBN 9781903706817.
- ↑ "Triking". 3wheelers.com. http://www.3wheelers.com/triking.html. Retrieved 2010-08-21.
- ↑ "Ace Cycle Car". http://www.cycle-car.com. Retrieved 2008-11-27.
- ↑ "JZR Vehicles". 3wheelers.com. http://www.3wheelers.com/jzr.html. Retrieved 2010-09-10.
- ↑ Adolphus, David Traver. "Hemmings Motor News: 1964 Mazda R360". Hemmings Motor News. http://www.hemmings.com/hsx/stories/2007/07/01/hmn_feature20.html. Retrieved 2010-08-21.
- ↑ "1962 Mazda R-360 Coupe "De Luxe"". The Bruce Weiner Microcar Museum. http://microcarmuseum.com/tour/mazda-r360.html. Retrieved 2010-08-21.
- ↑ "Honda V-TWIN SERIES ENGINES". http://engines.honda.com/models/series/v-twin. Retrieved 2011-04-21.
- ↑ "Kawasaki ENGINE SERIES". http://www.kawpowr.com/engines/type.aspx?shaft=0. Retrieved 2011-04-21.
- ↑ "Subaru Robin". http://robinamerica.com/engines.aspx. Retrieved 2011-04-21.
- ↑ "Briggs & Stratton Riding Mower Engines". http://www.briggsandstratton.com/engines/riding-mower/. Retrieved 2011-04-21.
- ↑ "Tecumseh Power". http://www.tecumsehpower.com/CustomerService/ServiceEnginesandAccessories.pdf. Retrieved 2011-04-21.
- ↑ "Kohler Engines". http://www.kohlerengines.com/onlinecatalog/productMatrix.htm. Retrieved 2011-04-21.