V-twin 32661 220587980 2008-06-20T16:11:34Z 71.113.162.36 /* Transverse mounting */ {{otheruses3|V2 (disambiguation)}} {| align="right" |- |[[Image:Harley Davidson.jpg|thumb|[[Harley-Davidson]] [[Harley-Davidson FL#Unfaired Glides - Electra Glide Sport and Road King|Road King]] 45° transversely mounted V-twin.]] |- |[[Image:Moto Guzzi V-twin.JPG|right|thumb|[[Moto Guzzi]] Jackal with a longitudinally mounted 90° V-twin.]] |- |[[Image:Honda v-twin.jpg|right|thumb|[[List of Honda motorcycles|Honda]] 90° transversely mounted V-twin.]] |- |[[Image:DSC09063.sized.jpg|right|thumb|[[Ducati]] 90-degree transversely mounted V-twin.]] |- |[[Image:Honda Longitudinal V-twin.JPG|right|thumb|[[Honda GL500|Honda GL500 Silver Wing]] with a longitudinally mounted V- twin.]] |- |[[Image:Sokol 995 cc zijklep v-twin.jpg|right|thumb|[[Sokół motorcycles|Sokół]] transversely mounted V-twin.]] |} A '''V-twin''' is a two cylinder [[internal combustion engine]] where the cylinders are arranged in a [[V engine|V]] configuration. == Configurations == === "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 engine|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 engine]]s use shared crank pins for cylinder pairs, they are not referred to as "V-octuplet"s. 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.<ref> {{cite web | url = http://powersports.honda.com/the_story/heritage/heritage_milestone.asp?Decade=1980&TargetUrl=Milestone/Milestone_Model_0102.asp&PrevPageTitle=TimeLine | title = Honda: 1983 Shadow 750 | accessdate = 2008-05-20}}</ref> === V angles === The most obvious configuration for a V-twin is a 90°, in which [[counterweight]]ing can balance the engine, in odd-firing 90 degree Vees. This is seen in the [[Moto Guzzi]], [[Ducati]] and [[Suzuki]] [[SV650]], but other angles can be seen like the 45° of the classic Harley-Davidson engine, the 75° [[Suzuki]], the 52° [[Honda]], the 80° [[Honda CX-500]], the 47° [[Vincent Motorcycles|Vincent]], the 42° [[Indian (motorcycle)|Indian]], the 60° [[Aprilia]], the 45° [[S&S Cycle|S&S]], and the 56.25° S&S X-Wedge. The signature Ducati engine, a transverse 90° twin with the front cylinder approximately parallel to the ground and the rear cylinder vertical, is sometimes referred to as an "L" twin. == Orientations == The terms [[longitudinal engine]] and [[transverse engine]] are used to refer to the crankshaft orientation. A common mistake with V-2 engines is to refer to the cylinder orientation.<ref>{{cite web|url=http://www.bmwmotorcycles.com/pdfs/history/design_tech.pdf|publisher=BMW Motorcycles|title=Heritage/History: Design/Technology}}</ref> However referring to the crankshaft gives a correct method to engine orientations as it gives the same orientation for all V-engine types like V-2, V-4 (which would be difficult to describe with cylinder orientation) and V-8. === Transverse mounting === Both two-cylinder V engines are common on [[motorcycle]]s. The engine can be mounted in transverse position like on [[Harley-Davidson]]s, [[Ducati]]s 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 mounting === The longitudinal two-cylinder V as seen on [[Moto-Guzzi]]s and some [[Honda]]s is less common. This position is well adapted to transmission shafting. When used in motorcycles, this approach has the slight disadvantage 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. ==Non-V twin configurations== === Flat twin === The flat twin, or [[Flat engine|boxer]] configuration, has a longitudinal crankshaft with the cylinders protruding horizontally from either side of the engine. BMW is the best-known manufacturer of this configuration, which has two advantages: the cylinders are squarely in the airstream and run cooler; and in the event of an accident the cylinders will help protect the rider. Disadvantages of this design are the torque reaction mentioned above in the section on longitudinal mounting, and the engine must be mounted higher in the frame to keep the cylinders from scraping the road in sharp curves. According to the American Motorcyclist Association's ''Motorcycle Hall of Fame Museum'', regarding the World-War-II-vintage Harley-Davidson XA, which has an opposed twin engine &mdash; ''"Mechanically, the large cooling fins stuck straight out in the breeze, reportedly keeping the XA’s oil temperature 100 degrees cooler than a standard Harley 45."''<ref>{{cite web|url=http://www.motorcyclemuseum.org/classics/bike.asp?id=71|title=Classic Bikes: 1942 Harley-Davidson XA|publisher=[[Motorcycle Hall of Fame|Motorcycle Hall of Fame Museum]]|accessdate=2008-01-25}}</ref> The latter was a transversely mounted V-twin, in which the airstream cannot reach the rear cylinder as efficiently as on a longitudinally mounted flat twin. [[Douglas (motorcycles)|Douglas Motorcycles]] made a flat-twin with fore-and-aft cylinders, which allowed the engine to be mounted lower in the frame. The disadvantage was that the rear cylinder tended to overheat. Currently there are no motorcycles with this configuration in mass production. === Vertical twin === The [[Straight-two|vertical twin or parallel twin]] is another logical alternative to the V-twin. It was made famous by such British motorcycles as [[Triumph Motorcycles|Triumph]], [[Ariel (vehicle)|Ariel]], [[AJS]], [[List of BSA motorcycles|BSA]], [[Matchless]], [[Norton (motorcycle)|Norton]] and [[Enfield (motorcycles)|Royal Enfield]]. The parallel twin has also been used by [[BMW motorcycles#F series twins|BMW]] , [[Benelli]], [[List of Honda motorcycles#650cc|Honda]], [[Ninja 650|Kawasaki]], [[Laverda#The big twins|Laverda]], [[Suzuki GS500|Suzuki]], and [[Yamaha XTZ 750|Yamaha]]. ==See also== *[[Engine balance]] *[[Flat-twin]] ==References== {{reflist}} {{Piston engine configurations}} [[Category:Piston engine configurations|V- ]] [[Category:Motorcycle engines]] [[it:Motore V2]] [[ja:V型2気筒]] [[nl:V-twin]] [[pl:V2 (silnik)]] [[pt:Motor V2]]