Motorcycle construction
Encyclopedia
Motorcycle components and systems for a motorcycle
are engineered, manufactured, and assembled in order to produce motorcycle models with the desired performance, aesthetics, and cost. The key components of modern motorcycles are presented below.
or steel
(or alloy
) struts, with the rear suspension
being an integral component in the design. Carbon fibre and titanium
are used in a few very expensive custom frames.
The frame includes the head tube
that holds the front fork
and allows it to pivot. Some motorcycles include the engine as a load-bearing (or stressed) member; this has been used all through motorcycle history but is now becoming more common.
Oil-in-Frame (OIF) chassis, where the lubricating oil is stored in the frame of the motorcycle, was used for Vincent motorcycles
of the 1950s, and for a while during the 1970s on some NVT British motorcycles. It was widely unpopular and generally regarded as a bad idea at the time. Today it is a used on some "thumpers" (single-cylinder four-strokes) that usually have dry-sump lubrication requiring an external oil tank. It has since gained some cachet in the modern custom bike world too because of the space savings it can afford and the reference to an earlier era.
Buell
motorcycles employ a similar design — the oil is held in the swingarm
, while the fuel is held in the frame.
Modern designs have the two wheels of a motorcycle connected to the chassis by a suspension arrangement, however 'chopper
' style motorcycles often elect to forgo rear suspension, using a rigid frame.
The front suspension is usually built into the front fork
and may consist of telescoping tubes called fork tubes which contain the suspension inside or some multibar linkage that incorporate the suspension externally.
The rear suspension supports the swingarm
, which is attached via the swingarm pivot bolt to the frame and holds the axle
of the rear wheel. The rear suspension can consist of several shock arrangements:
A fork generally consists of two fork tubes (sometimes also referred to as forks), which hold the front wheel axle, and a triple tree, which connects the fork tubes and the handlebars
to the frame with a pivot that allows for steering.
Almost all commercially available motorcycles are driven by conventional gasoline internal combustion engine
s, but some small scooter-type models use an electric motor
, and a very small number of diesel
models exist (e.g., the USMC
M1030 M1 version of the Kawasaki KLR650
and the Dutch-produced Track T-800CDI).
The displacement
is defined as the total volume of air/fuel mixture an engine can draw in during one complete engine cycle. In a piston engine, this is the volume that is swept as the pistons are moved from top dead centre to bottom dead centre. To the layperson this is the "size" of the engine. Motorcycle engines range from less than 50 cc (cubic centimetre
s), commonly found in many small scooters, to 5735 cc, a Chevrolet V8 engine
, currently used by Boss Hoss in its cruiser style motorcycle.
Motorcycles have mostly, but not exclusively, been produced with one to four cylinders
, and designers have tried virtually every imaginable layout. The most common engine configurations today are the single and twin
, the V-twin
, the opposed twin
(or boxer
), and the in-line triple
and in-line four
. A number of others designs have reached mass production, including the V-4
, the flat 6-cylinder
, the flat 4-cylinder
, the in-line 6-cylinder
, and the Wankel engine
. Exotic engines, such as a radial piston
engine, sometimes appear in custom built motorcycles, though two firms Megola
and Redrup put radial engined motorcycles into production.
Engines with more cylinders for the same displacement feel smoother to ride. Engines with fewer cylinders are cheaper, lighter, and easier to maintain. Liquid-cooled motorcycles have a radiator
which is the primary way their heat is dispersed. Coolant or oil is constantly circulated between this radiator and the cylinder when the engine is running. Air-cooled motorcycles rely on air blowing past fins on the engine case to disperse heat. Liquid-cooled motorcycles have the potential for greater power at a given displacement, tighter tolerances, and longer operating life, whereas air-cooled motorcycles are potentially cheaper to purchase, less mechanically complex and lighter weight.
An air-cooled engine contracts and expands with its wider temperature range, requiring looser tolerances, and giving shorter engine life. The temperature range of an air-cooled two-stroke is even more extreme and component life even shorter than in an air-cooled four-stroke.
As applied to motorcycles, two-stroke engines have some advantages over equivalent four-strokes: they are lighter, mechanically much simpler, and produce more power when operating at their best. But four-stroke engines are cleaner, more reliable, and deliver power over a much broader range of engine speeds. In developed countries, two-stroke road-bikes are rare, because—in addition to the reasons above—modifying them to meet contemporary emissions standards is prohibitively expensive. Almost all modern two-strokes are single-cylinder, liquid-cooled, and under 600 cc.
In November 2006, the Dutch
company E.V.A. Products BV Holland announced that its diesel-powered motorcycle, the Track T-800CDI, achieved production status.
The Track T-800CDI uses a 800 cc three-cylinder Daimler Chrysler diesel engine. Other manufacturers, including Royal Enfield
, had been producing diesel-powered bikes since at least the 1980s.
Also, Intelligent Energy, a British alternative-fuel company, is developing a motorcycle powered by a detachable hydrogen
-powered fuel cell
, which it calls an Emissions Neutral Vehicle (ENV
).
According to reports, the vehicle can sustain speeds of 50 mph (80 km/h) while making virtually no noise, and can run for up to four hours without refueling.
Most modern motorcycles have a sequential manual transmission
shifted by a foot lever. Some motorcycles, and many scooters, use a continuously variable transmission
. Other types of automatic transmission and semi-automatic transmission are also in use.
Engine power can be engaged or interrupted through the clutch
, typically an arrangement of plates stacked in alternating fashion, one geared on the inside to the engine and the next geared on the outside to the transmission input shaft.
Chain drive
uses sprocket
s and a roller chain
, which requires both lubrication and adjustment for elongation (stretch) that occurs through wear. The lubricant is subject to being thrown off the fast-moving chain and results in grime and dirt build up. Chains do deteriorate, and excessive wear on the front and rear sprockets can be dangerous. In a chain drive the power is transmitted into the real wheel via a cush drive
. Conventional roller chain drives suffer the potential for vibration, as the effective radius of action in a chain and sprocket combination constantly changes during revolution. If a drive sprocket rotates at constant RPM, then the chain (and the driven sprocket) must accelerate and decelerate constantly. Most chain-driven motorcycles are fitted with a rubber bushed rear wheel hub to eliminate this vibration issue. Virtually all high-performance racing motorcycles use chain drive.
A belt drive
is still subject to stretch but operates very quietly, cleanly, and efficiently. However, belt drives are limited in the amount of power they can transmit. A toothed belt
is frequently used.
A shaft drive
is usually completely enclosed; the visual cue is a tube extending from the rear of the transmission to a bell housing on the rear wheel. Inside the bell housing a bevelled gear on the shaft mates with another on the wheel mount. This arrangement is superior in terms of noise and cleanliness and is virtually maintenance free, with the exception of occasional fluid changes. However, the additional gearsets are a source of power loss and added weight. A shaft-equipped motorcycle may also be susceptible to shaft effect
.
The wheel
rims are usually steel or aluminium (generally with steel spokes and an aluminium hub) or mag-type cast
or machined
aluminium. Cast magnesium
disks, produced by one-step hot forging from magnesium alloys ZK60 and MA-14, are also used for many motorcycle wheels.
At one time, motorcycles used spoke wheels built up from separate components
, but, except for dirtbikes, one-piece wheels are more common now. Performance racing motorcycles often use carbon-fibre wheels, but the expense of these wheels is prohibitively high for general usage.
Wire wheels
have a central hub connected to the rim of the wheel via spokes made of wire. These spokes are generally quite solid and will not easily bend as would typical wire cord. Nevertheless, they mechanically function as wires under tension
, holding the rim true and providing strength to the wheel.
s), the tires are filled with a "mousse" which is unpunctureable. Both types of tire come in many configurations. The most important characteristic of any tire is the contact patch
, the small area that is in contact with the road surface while riding. There are tires designed for dirtbikes, touring, sport and cruiser bikes.
Dirtbike tires have knobbly, deep treads for maximum grip on loose dirt, mud, or gravel; such tires tend to be less stable on paved surfaces. Touring tires are usually made of harder rubber for greater durability. They may last longer, but they tend to provide less outright grip than sports tires at optimal operating temperatures. The payoff is that touring tires typically offer more grip at lower temperatures, meaning they can be more suitable for riding in cold or winter conditions whereas a sport tire may never reach the optimal operating temperature.
Sport/performance tires provide amazing grip but may last 1,000 miles (1,600 km) or less. Cruiser and "sport touring" tires try to find the best compromise between grip and durability. There is also a type of tire developed specifically for racing. These tires offer the highest of levels of grip for cornering. Because of the high temperatures at which these tires typically operate, use on the street is unsafe because the tires will typically not reach optimum temperature before a rider arrives, thus providing almost no grip en route. In racing situations, racing tires would normally be brought up to temperature in advance by the use of tire warmers.
There are generally two independent brake
s on a motorcycle, one set on the front wheel and one on the rear. However, some models have "linked brakes" whereby both can be applied at the same time using only one control.
Front brakes are generally much more effective than rear brakes: roughly two thirds of stopping power comes from the front brake—mainly as a result of weight transfer being much more pronounced compared to longer or lower vehicles, because of the motorcycle's short wheelbase relative to its center of mass height. This can result in brake dive.
Brakes can either be drum
or disc
based, with disc brakes being more common on large, modern or more expensive motorcycles for their far superior stopping power, particularly in wet conditions. There are many brake-performance-enhancing aftermarket parts available for most motorcycles, including brake pads of varying compounds and steel-braided brake lines.
In 1981, BMW introduced an antilock braking system (ABS) on a motorcycle. Other manufacturers have since also adopted this technology, although Harley Davidson only offers it on some police motorcycles and not on civilian motorcycles. ABS is normally found on motorcycles of 500 cc or greater engine capacity, although it is available on motor scooters down to 49 cc.
, usually consisting of speedometer
, odometer
and tachometer
.
Fuel gauge
s are becoming more common, but traditionally a reserve tank arrangement is used with a petcock
(petrol tap) on the side of the motorcycle allowing the rider to switch to a reserve fuel supply
when the main fuel supply is exhausted. There is not actually a separate reserve tank: The intake for the petcock has two pipes, one extending higher into the fuel tank than the other. When fuel no longer covers the longer pipe the engine will lose power/splutter and the rider switches the petcock to the "reserve" setting, which accesses the shorter pipe. Riders whose bikes lack a fuel gauge (most machines prior to the past few years) usually learn how far they can go with a full tank of fuel, and then use a trip meter if available to judge when they must refill the tank.
Motorcycle
A motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...
are engineered, manufactured, and assembled in order to produce motorcycle models with the desired performance, aesthetics, and cost. The key components of modern motorcycles are presented below.
Chassis
The chassis of a motorcycle includes the frame and suspension, along with the front forks, of the vehicle.Frame
The frame is typically made from welded aluminiumAluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
or steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
(or alloy
Alloy
An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...
) struts, with the rear suspension
Suspension (vehicle)
Suspension is the term given to the system of springs, shock absorbers and linkages that connects a vehicle to its wheels. Suspension systems serve a dual purpose — contributing to the car's roadholding/handling and braking for good active safety and driving pleasure, and keeping vehicle occupants...
being an integral component in the design. Carbon fibre and titanium
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
are used in a few very expensive custom frames.
The frame includes the head tube
Head tube
Most bicycles, tricycles and motorcycles have a tubular frame. The front fork pivots within the head tube . On a motorcycle, the "head tube" is normally called the steering head...
that holds the front fork
Motorcycle fork
A motorcycle fork connects a motorcycle's front wheel and axle to its frame, typically via a pair of triple clamps. It typically incorporates the front suspension and front brake, and allows the bike to be steered via handlebars attached to the top clamp....
and allows it to pivot. Some motorcycles include the engine as a load-bearing (or stressed) member; this has been used all through motorcycle history but is now becoming more common.
Oil-in-Frame (OIF) chassis, where the lubricating oil is stored in the frame of the motorcycle, was used for Vincent motorcycles
Vincent Motorcycles
Vincent Motorcycles was a British manufacturer of motorcycles from 1928 to 1955. Their 1948 Black Shadow was at the time the world's fastest production motorcycle...
of the 1950s, and for a while during the 1970s on some NVT British motorcycles. It was widely unpopular and generally regarded as a bad idea at the time. Today it is a used on some "thumpers" (single-cylinder four-strokes) that usually have dry-sump lubrication requiring an external oil tank. It has since gained some cachet in the modern custom bike world too because of the space savings it can afford and the reference to an earlier era.
Buell
Buell Motorcycle Company
The Buell Motorcycle Company was an American motorcycle manufacturer based in East Troy, Wisconsin and founded in 1983 by ex-Harley-Davidson engineer Erik Buell.Harley-Davidson acquired 49% of Buell in 1993, and it became a wholly owned subsidiary by 2003....
motorcycles employ a similar design — the oil is held in the swingarm
Swingarm
A swingarm, or "swinging arm" is the main component of the rear suspension of most modern motorcycles and ATVs...
, while the fuel is held in the frame.
Suspension
Chopper (motorcycle)
A chopper is a type of motorcycle that was either modified from an original motorcycle design or built from scratch to have a hand-crafted appearance. The main features of a chopper that make it stand out are its longer frame design accompanied by a stretch front end...
' style motorcycles often elect to forgo rear suspension, using a rigid frame.
The front suspension is usually built into the front fork
Motorcycle fork
A motorcycle fork connects a motorcycle's front wheel and axle to its frame, typically via a pair of triple clamps. It typically incorporates the front suspension and front brake, and allows the bike to be steered via handlebars attached to the top clamp....
and may consist of telescoping tubes called fork tubes which contain the suspension inside or some multibar linkage that incorporate the suspension externally.
The rear suspension supports the swingarm
Swingarm
A swingarm, or "swinging arm" is the main component of the rear suspension of most modern motorcycles and ATVs...
, which is attached via the swingarm pivot bolt to the frame and holds the axle
Axle
An axle is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to its surroundings, with the wheels rotating around the axle. In the former case, bearings or bushings are provided at the mounting points where the axle...
of the rear wheel. The rear suspension can consist of several shock arrangements:
- Dual shocks, which are placed at the far ends of the swingarm
- Traditional monoshock, which is placed at the front of the swingarm, above the swingarm pivot bolt
- SoftailSoftailThe term softail refers to motorcycles and bicycles that feature a rear suspension system with springs or shock absorbers to absorb bumps. On Softail motorcycles, the shock absorbers or springs are often hidden underneath out of view to give the appearance of a hard-tail or rigid frame, however...
style suspension, where the shock absorbers are mounted horizontally in front of the swingarm, below the swingarm pivot bolt and operate in extension.
Front fork
A motorcycle fork is the portion of a motorcycle that holds the front wheel and allows one to steer. For handling, the front fork is the most critical part of a motorcycle. The combination of rake and trail determines how stable the motorcycle is.A fork generally consists of two fork tubes (sometimes also referred to as forks), which hold the front wheel axle, and a triple tree, which connects the fork tubes and the handlebars
Motorcycle handlebar
Motorcycle handlebar refers to the steering mechanism for motorcycles. Handlebars often support part of the rider's weight, and provide a mounting place for controls such as brake, throttle, clutch, horn, light switch, and rear view mirrors....
to the frame with a pivot that allows for steering.
Engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...
s, but some small scooter-type models use an electric motor
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...
, and a very small number of diesel
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...
models exist (e.g., the USMC
United States Marine Corps
The United States Marine Corps is a branch of the United States Armed Forces responsible for providing power projection from the sea, using the mobility of the United States Navy to deliver combined-arms task forces rapidly. It is one of seven uniformed services of the United States...
M1030 M1 version of the Kawasaki KLR650
Kawasaki KLR650
The Kawasaki KLR650 is a dual-sport motorcycle intended for use on both paved and unpaved roads. It has been a long-standing model in Kawasaki's lineup, having been introduced in 1987 and remaining almost unchanged through the 2007 model. The 2008 model was the first significant redesign of the...
and the Dutch-produced Track T-800CDI).
The displacement
Engine displacement
Engine displacement is the volume swept by all the pistons inside the cylinders of an internal combustion engine in a single movement from top dead centre to bottom dead centre . It is commonly specified in cubic centimeters , litres , or cubic inches...
is defined as the total volume of air/fuel mixture an engine can draw in during one complete engine cycle. In a piston engine, this is the volume that is swept as the pistons are moved from top dead centre to bottom dead centre. To the layperson this is the "size" of the engine. Motorcycle engines range from less than 50 cc (cubic centimetre
Cubic centimetre
A cubic centimetre is a commonly used unit of volume extending the derived SI-unit cubic metre, and corresponds to the volume of a cube measuring 1 cm × 1 cm × 1 cm...
s), commonly found in many small scooters, to 5735 cc, a Chevrolet V8 engine
V8 engine
A V8 engine is a V engine with eight cylinders mounted on the crankcase in two banks of four cylinders, in most cases set at a right angle to each other but sometimes at a narrower angle, with all eight pistons driving a common crankshaft....
, currently used by Boss Hoss in its cruiser style motorcycle.
Motorcycles have mostly, but not exclusively, been produced with one to four cylinders
Cylinder (engine)
A cylinder is the central working part of a reciprocating engine or pump, the space in which a piston travels. Multiple cylinders are commonly arranged side by side in a bank, or engine block, which is typically cast from aluminum or cast iron before receiving precision machine work...
, and designers have tried virtually every imaginable layout. The most common engine configurations today are the single and twin
Straight-two
A straight-two engine, is a two-cylinder piston engine that has its cylinders arranged side by side....
, the V-twin
V-twin
A V-twin engine is a two-cylinder internal combustion engine where the cylinders are arranged in a V configuration.- Crankshaft configuration :Most V-twin engines have a single crankpin, which is shared by both connecting rods...
, the opposed twin
Flat-twin
A flat-twin is a two cylinder internal combustion engine with the cylinders arranged on opposite sides of the crankshaft. It is part of the class of flat engines, sub-type "boxer", and shares most characteristics of those engines.-Motorcycle use:...
(or boxer
Flat-twin
A flat-twin is a two cylinder internal combustion engine with the cylinders arranged on opposite sides of the crankshaft. It is part of the class of flat engines, sub-type "boxer", and shares most characteristics of those engines.-Motorcycle use:...
), and the in-line triple
Straight-3
A straight-three engine, also known as inline-three engine, or a triple, is a reciprocating piston internal combustion engine with three cylinders arranged in a straight line or plane, side by side....
and in-line four
Straight-4
The inline-four engine or straight-four engine is an internal combustion engine with all four cylinders mounted in a straight line, or plane along the crankcase. The single bank of cylinders may be oriented in either a vertical or an inclined plane with all the pistons driving a common crankshaft....
. A number of others designs have reached mass production, including the V-4
V4 engine
A V4 engine is a V form engine with four cylinders and three main bearings.-Automobile use:Lancia produced several narrow-angle V4 engines from the 1920s through 1960s for cars like the Lambda, Augusta, Artena, Aprilia, Ardea, Appia, and Fulvia....
, the flat 6-cylinder
Flat-6
A flat-6 or horizontally opposed-6 is a flat engine with six cylinders arranged horizontally in two banks of three cylinders on each side of a central crankcase...
, the flat 4-cylinder
Flat-4
A flat-4 or horizontally opposed-4 is a flat engine with four cylinders arranged horizontally in two banks of two cylinders on each side of a central crankcase...
, the in-line 6-cylinder
Straight-6
The straight-six engine or inline-six engine is a six-cylinder internal combustion engine with all six cylinders mounted in a straight line along the crankcase...
, and the Wankel engine
Wankel engine
The Wankel engine is a type of internal combustion engine using an eccentric rotary design to convert pressure into a rotating motion instead of using reciprocating pistons. Its four-stroke cycle takes place in a space between the inside of an oval-like epitrochoid-shaped housing and a rotor that...
. Exotic engines, such as a radial piston
Radial engine
The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders point outward from a central crankshaft like the spokes on a wheel...
engine, sometimes appear in custom built motorcycles, though two firms Megola
Megola
The Megola was a German motorcycle produced between 1921 and 1925 in Munich. Like Bimota, the name is a portmanteau derived loosely from the names of its designers Meixner, Cockerell, and Landgraf.-An Unusual Design:...
and Redrup put radial engined motorcycles into production.
Radiator
Radiators are heat exchangers used to transfer thermal energy from one medium to another for the purpose of cooling and heating. The majority of radiators are constructed to function in automobiles, buildings, and electronics...
which is the primary way their heat is dispersed. Coolant or oil is constantly circulated between this radiator and the cylinder when the engine is running. Air-cooled motorcycles rely on air blowing past fins on the engine case to disperse heat. Liquid-cooled motorcycles have the potential for greater power at a given displacement, tighter tolerances, and longer operating life, whereas air-cooled motorcycles are potentially cheaper to purchase, less mechanically complex and lighter weight.
An air-cooled engine contracts and expands with its wider temperature range, requiring looser tolerances, and giving shorter engine life. The temperature range of an air-cooled two-stroke is even more extreme and component life even shorter than in an air-cooled four-stroke.
As applied to motorcycles, two-stroke engines have some advantages over equivalent four-strokes: they are lighter, mechanically much simpler, and produce more power when operating at their best. But four-stroke engines are cleaner, more reliable, and deliver power over a much broader range of engine speeds. In developed countries, two-stroke road-bikes are rare, because—in addition to the reasons above—modifying them to meet contemporary emissions standards is prohibitively expensive. Almost all modern two-strokes are single-cylinder, liquid-cooled, and under 600 cc.
In November 2006, the Dutch
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
company E.V.A. Products BV Holland announced that its diesel-powered motorcycle, the Track T-800CDI, achieved production status.
The Track T-800CDI uses a 800 cc three-cylinder Daimler Chrysler diesel engine. Other manufacturers, including Royal Enfield
Royal Enfield
Royal Enfield was the name under which the Enfield Cycle Company made motorcycles, bicycles, lawnmowers and stationary engines. This legacy of weapons manufacture is reflected in the logo, a cannon, and their motto "Made like a gun, goes like a bullet". Use of the brand name Royal Enfield was...
, had been producing diesel-powered bikes since at least the 1980s.
Also, Intelligent Energy, a British alternative-fuel company, is developing a motorcycle powered by a detachable hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
-powered fuel cell
Fuel cell
A fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent. Hydrogen is the most common fuel, but hydrocarbons such as natural gas and alcohols like methanol are sometimes used...
, which it calls an Emissions Neutral Vehicle (ENV
ENV
The ENV is an electric motorcycle prototype powered by an hydrogen fuel cell. It is being developed by Intelligent Energy, a British company.-Specifications:...
).
According to reports, the vehicle can sustain speeds of 50 mph (80 km/h) while making virtually no noise, and can run for up to four hours without refueling.
Transmission
Most modern motorcycles have a sequential manual transmission
Sequential manual transmission
A sequential manual transmission is a type of manual transmission used on motorcycles and high-performance cars for auto racing, where gears are selected in order, and direct access to specific gears is not possible....
shifted by a foot lever. Some motorcycles, and many scooters, use a continuously variable transmission
Continuously variable transmission
A continuously variable transmission is a transmission that can change steplessly through an infinite number of effective gear ratios between maximum and minimum values. This contrasts with other mechanical transmissions that offer a fixed number of gear ratios...
. Other types of automatic transmission and semi-automatic transmission are also in use.
Engine power can be engaged or interrupted through the clutch
Clutch
A clutch is a mechanical device which provides for the transmission of power from one component to another...
, typically an arrangement of plates stacked in alternating fashion, one geared on the inside to the engine and the next geared on the outside to the transmission input shaft.
Final drive
Power transfer from the gearbox to the rear wheel is accomplished by different methods.Chain drive
Chain drive
Chain drive is a way of transmitting mechanical power from one place to another. It is often used to convey power to the wheels of a vehicle, particularly bicycles and motorcycles...
uses sprocket
Sprocket
A sprocket or sprocket-wheel is a profiled wheel with teeth, cogs, or even sprockets that mesh with a chain, track or other perforated or indented material. The name 'sprocket' applies generally to any wheel upon which are radial projections that engage a chain passing over it...
s and a roller chain
Roller chain
Roller chain or bush roller chain is the type of chain drive most commonly used for transmission of mechanical power on many kinds of domestic, industrial and agricultural machinery, including conveyors, wire and tube drawing machines, printing presses, cars, motorcycles, and simple machines like...
, which requires both lubrication and adjustment for elongation (stretch) that occurs through wear. The lubricant is subject to being thrown off the fast-moving chain and results in grime and dirt build up. Chains do deteriorate, and excessive wear on the front and rear sprockets can be dangerous. In a chain drive the power is transmitted into the real wheel via a cush drive
Cush drive
A cush drive is a part of a motorcycle or scooter drive-train that is designed to reduce stress from engine torque damaging other components during gear or throttle changes. A common design used by almost all street motorcycles, it has three major pieces: the wheel, the sprocket assembly, and the...
. Conventional roller chain drives suffer the potential for vibration, as the effective radius of action in a chain and sprocket combination constantly changes during revolution. If a drive sprocket rotates at constant RPM, then the chain (and the driven sprocket) must accelerate and decelerate constantly. Most chain-driven motorcycles are fitted with a rubber bushed rear wheel hub to eliminate this vibration issue. Virtually all high-performance racing motorcycles use chain drive.
A belt drive
Belt (mechanical)
A belt is a loop of flexible material used to link two or more rotating shafts mechanically. Belts may be used as a source of motion, to transmit power efficiently, or to track relative movement. Belts are looped over pulleys. In a two pulley system, the belt can either drive the pulleys in the...
is still subject to stretch but operates very quietly, cleanly, and efficiently. However, belt drives are limited in the amount of power they can transmit. A toothed belt
Gilmer belt
Gilmer belt is a trade name for a type of belt used for transferring power between axles in a machine. The belt itself has ribs on the inner side to engage special pulleys mounted to the axles....
is frequently used.
A shaft drive
Driveshaft
A drive shaft, driveshaft, driving shaft, propeller shaft, or Cardan shaft is a mechanical component for transmitting torque and rotation, usually used to connect other components of a drive train that cannot be connected directly because of distance or the need to allow for relative movement...
is usually completely enclosed; the visual cue is a tube extending from the rear of the transmission to a bell housing on the rear wheel. Inside the bell housing a bevelled gear on the shaft mates with another on the wheel mount. This arrangement is superior in terms of noise and cleanliness and is virtually maintenance free, with the exception of occasional fluid changes. However, the additional gearsets are a source of power loss and added weight. A shaft-equipped motorcycle may also be susceptible to shaft effect
Shaft effect
The shaft effect, also known as elevator effect or shaft jacking, is a phenomenon occurring in shaft-drive motorcycles. This effect occurs because the acceleration being applied to the rear wheel creates a reactive force on the drive shaft. This in turn lifts the rider and the body of the bike,...
.
Wheels
Wheel
A wheel is a device that allows heavy objects to be moved easily through rotating on an axle through its center, facilitating movement or transportation while supporting a load, or performing labor in machines. Common examples found in transport applications. A wheel, together with an axle,...
rims are usually steel or aluminium (generally with steel spokes and an aluminium hub) or mag-type cast
Casting
In metalworking, casting involves pouring liquid metal into a mold, which contains a hollow cavity of the desired shape, and then allowing it to cool and solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process...
or machined
Machining
Conventional machining is a form of subtractive manufacturing, in which a collection of material-working processes utilizing power-driven machine tools, such as saws, lathes, milling machines, and drill presses, are used with a sharp cutting tool to physical remove material to achieve a desired...
aluminium. Cast magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
disks, produced by one-step hot forging from magnesium alloys ZK60 and MA-14, are also used for many motorcycle wheels.
At one time, motorcycles used spoke wheels built up from separate components
Wheelbuilding
Wheelbuilding is the art and science of assembling a wheel from its component rim, spokes, nipples and hub.-Goals:...
, but, except for dirtbikes, one-piece wheels are more common now. Performance racing motorcycles often use carbon-fibre wheels, but the expense of these wheels is prohibitively high for general usage.
Wire wheels
Wire wheels
The rims of wire wheels are connected to their hubs by wire spokes. Although these wires are generally stiffer than a typical wire rope, they function mechanically the same as tensioned flexible wires, keeping the rim true while supporting applied loads.Wire wheels are used on most bicycles and...
have a central hub connected to the rim of the wheel via spokes made of wire. These spokes are generally quite solid and will not easily bend as would typical wire cord. Nevertheless, they mechanically function as wires under tension
Tension (mechanics)
In physics, tension is the magnitude of the pulling force exerted by a string, cable, chain, or similar object on another object. It is the opposite of compression. As tension is the magnitude of a force, it is measured in newtons and is always measured parallel to the string on which it applies...
, holding the rim true and providing strength to the wheel.
Tires
Motorcycles mainly use pneumatic tires. However, in some cases where punctures are common (some enduroEnduro
Enduro is a form of motorcycle sport run on courses that are predominantly off-road. Enduro consists of many different obstacles and challenges...
s), the tires are filled with a "mousse" which is unpunctureable. Both types of tire come in many configurations. The most important characteristic of any tire is the contact patch
Contact patch
Contact patch is the portion of a vehicle's tire that is in actual contact with the road surface. It is most commonly used in the discussion of pneumatic tires, , where the term is strictly used to describe the portion of the tire’s tread that touches the road surface...
, the small area that is in contact with the road surface while riding. There are tires designed for dirtbikes, touring, sport and cruiser bikes.
Dirtbike tires have knobbly, deep treads for maximum grip on loose dirt, mud, or gravel; such tires tend to be less stable on paved surfaces. Touring tires are usually made of harder rubber for greater durability. They may last longer, but they tend to provide less outright grip than sports tires at optimal operating temperatures. The payoff is that touring tires typically offer more grip at lower temperatures, meaning they can be more suitable for riding in cold or winter conditions whereas a sport tire may never reach the optimal operating temperature.
Sport/performance tires provide amazing grip but may last 1,000 miles (1,600 km) or less. Cruiser and "sport touring" tires try to find the best compromise between grip and durability. There is also a type of tire developed specifically for racing. These tires offer the highest of levels of grip for cornering. Because of the high temperatures at which these tires typically operate, use on the street is unsafe because the tires will typically not reach optimum temperature before a rider arrives, thus providing almost no grip en route. In racing situations, racing tires would normally be brought up to temperature in advance by the use of tire warmers.
Brakes
Brake
A brake is a mechanical device which inhibits motion. Its opposite component is a clutch. The rest of this article is dedicated to various types of vehicular brakes....
s on a motorcycle, one set on the front wheel and one on the rear. However, some models have "linked brakes" whereby both can be applied at the same time using only one control.
Front brakes are generally much more effective than rear brakes: roughly two thirds of stopping power comes from the front brake—mainly as a result of weight transfer being much more pronounced compared to longer or lower vehicles, because of the motorcycle's short wheelbase relative to its center of mass height. This can result in brake dive.
Brakes can either be drum
Drum brake
A drum brake is a brake in which the friction is caused by a set of shoes or pads that press against a rotating drum-shaped part called a brake drum....
or disc
Disc brake
The disc brake or disk brake is a device for slowing or stopping the rotation of a wheel while it is in motion.A brake disc is usually made of cast iron, but may in some cases be made of composites such as reinforced carbon–carbon or ceramic matrix composites. This is connected to the wheel and/or...
based, with disc brakes being more common on large, modern or more expensive motorcycles for their far superior stopping power, particularly in wet conditions. There are many brake-performance-enhancing aftermarket parts available for most motorcycles, including brake pads of varying compounds and steel-braided brake lines.
In 1981, BMW introduced an antilock braking system (ABS) on a motorcycle. Other manufacturers have since also adopted this technology, although Harley Davidson only offers it on some police motorcycles and not on civilian motorcycles. ABS is normally found on motorcycles of 500 cc or greater engine capacity, although it is available on motor scooters down to 49 cc.
Instruments
Most road motorcycles have an instrument panelDashboard
A dashboard is a control panel placed in front of the driver of an automobile, housing instrumentation and controls for operation of the vehicle....
, usually consisting of speedometer
Speedometer
A speedometer is a gauge that measures and displays the instantaneous speed of a land vehicle. Now universally fitted to motor vehicles, they started to be available as options in the 1900s, and as standard equipment from about 1910 onwards. Speedometers for other vehicles have specific names...
, odometer
Odometer
An odometer or odograph is an instrument that indicates distance traveled by a vehicle, such as a bicycle or automobile. The device may be electronic, mechanical, or a combination of the two. The word derives from the Greek words hodós and métron...
and tachometer
Tachometer
A tachometer is an instrument measuring the rotation speed of a shaft or disk, as in a motor or other machine. The device usually displays the revolutions per minute on a calibrated analogue dial, but digital displays are increasingly common...
.
Fuel gauge
Fuel gauge
A fuel gauge is an instrument used to indicate the level of fuel contained in a tank. Commonly used in cars, these may also be used for any tank including underground storage tanks.As used in cars, the gauge consists of two parts:...
s are becoming more common, but traditionally a reserve tank arrangement is used with a petcock
Petcock
A petcock is a small valve used to control the flow of liquid or gas.- Use on motorcycles :Most older motorcycles have a fuel petcock valve mounted on or nearby the fuel tank to control the supply of gasoline....
(petrol tap) on the side of the motorcycle allowing the rider to switch to a reserve fuel supply
Fuel reserve
In motorcycles and cars, fuel reserve is the extra fuel reserved by the manufacturer in the fuel tank of a car or motorcycle before the main fuel capacity runs out....
when the main fuel supply is exhausted. There is not actually a separate reserve tank: The intake for the petcock has two pipes, one extending higher into the fuel tank than the other. When fuel no longer covers the longer pipe the engine will lose power/splutter and the rider switches the petcock to the "reserve" setting, which accesses the shorter pipe. Riders whose bikes lack a fuel gauge (most machines prior to the past few years) usually learn how far they can go with a full tank of fuel, and then use a trip meter if available to judge when they must refill the tank.
See also
- Bicycle and motorcycle dynamicsBicycle and motorcycle dynamicsBicycle and motorcycle dynamics is the science of the motion of bicycles and motorcycles and their components, due to the forces acting on them. Dynamics is a branch of classical mechanics, which in turn is a branch of physics. Bike motions of interest include balancing, steering, braking,...
- Motorcycle accessoriesMotorcycle accessoriesMotorcycle accessories are features and accessories selected by a motorcycle owner to enhance safety, performance, or comfort, and may include anything from mobile electronics to sidecars and trailers...
- Motorcycle saddleMotorcycle saddleA motorcycle saddle is a term for a motorcycle seat in some parts of the world. It is a seat for carrying a rider and, possibly, a passenger, and which is attached to a motorcycle often but not exclusively, behind the fuel tank....
- Shaft effectShaft effectThe shaft effect, also known as elevator effect or shaft jacking, is a phenomenon occurring in shaft-drive motorcycles. This effect occurs because the acceleration being applied to the rear wheel creates a reactive force on the drive shaft. This in turn lifts the rider and the body of the bike,...
- Outline of motorcycles and motorcyclingOutline of motorcycles and motorcyclingThe following outline is provided as an overview of motorcycles and motorcycling:Motorcycle – single-track, engine-powered, two-wheeled motor vehicle...
External links
- How Motorcycles Work by Bill Harris
- Motorcycle Glossary - definitions of motorcycle terms