Transmission
The transmission is controlled by a clutch lever under the left hand in standard configurations, a twistgrip throttle on the right handlebar and a gear lever at the left foot.
The gear lever operates by shifting gears when it is pressed or lifted. A normal street motorcycle is put in first gear by pressing the gear lever, while second and all further gears are reached by lifting it. Downshifting is done by pressing the gear lever. Neutral sits between first gear and second, so a small lift out of first causes the gearbox to change into neutral, but a large movement causes the gearbox to change into second gear. In contrast, racing motorcycles have all gears arranged "below" the first gear, thus pressing the gear lever always shifts up, while lifting it shifts down.
Modern motorcycles normally have five or six forward gears. Only the largest touring motorcycles (most prominently, the Honda Goldwing) and a few models that are routinely used with a sidecar are fitted with a reverse gear.
The clutch is typically an arrangement of plates stacked in alternating fashion, one geared on the inside to the engine, and next geared on the outside to the transmission input shaft. Whether wet (rotating in engine oil) or dry, the plates are squeezed together by a spring, causing friction buildup between the plates until they rotate as a single unit, driving the transmission directly. A lever on the handlebar, through a cable or hydraulic arrangement, uses mechanical advantage to release the clutch spring, allowing the engine to freewheel with respect to the transmission.
The most commonly used transmission is a sequential gearbox. From neutral, you may select either first or second gear, but higher gears may only be accessed in order - you may not shift from second gear to fourth gear, without shifting through third gear. Internally, a rotating cam on the shift lever operates cogs on two counter-rotating shafts carrying a variety of gears. One shaft is geared to the final drive mechanism, and the other to the clutch. Operating the shift lever slides individual gears on one shaft, to intersect with a matching gear on the other. The small mass of the whole arrangement allows for extremely quick gear changes. Also, gear synchronizers typically found in passenger cars with manual transmissions are not necessary. The two shafts are always geared together (except in neutral), always spinning at a speed nearly approximating the next higher or lower gear ratio. Aided by beveled edges on the gears, shifting gears is simple for novices - no double clutching or grinding of gears. Advanced drivers can perform "full-throttle upshifts" on racing mounts, but this risks both the warranty and mechanical integrity.
Final drive from the gearbox to the rear wheel is typically accomplished with a chain, which requires both lubrication and adjustment for elongation (stretch) through wear. The lubricant is subject to being thrown off the fast-moving chain and results in grime and dirt buildup. Chains do deteriorate, and excessive wear on the front and rear sprockets can be dangerous. Many motorcyclists replace the chain and both sprockets as a set to maintain efficiency and safety. Many manufacturers offer cruiser models with final drive options of a belt, or a shaft. 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. The belt is frequently toothed. A shaft drive is 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, cleanliness, and is virtually maintenance free. However, the additional gearsets are a source of power loss and add to bike weight.
Sunday, December 25, 2005
Chassis stability
Chassis stability
There could be three kinds of stability problems with motorbikes:
Capsizing is well known in low speeds, and easy to overcome by going a bit faster. Wobbling (AVI movie) is a high frequency (7-9 Hz) oscillation of the front wheel. It is often relatively harmless but annoying (and quite frightening if previously inexperienced). It can appear at moderate speeds. Weaving (AVI movie) is a low frequency (2-3 Hz) oscillation of the whole vehicle. It can become unstable at higher speeds with fatal results. Based on The control and stability analysis of two-wheeled road vehicles:
The weave oscillations damp out once the rider reduced the roll angle. Tyre (tire) characteristics and inflation pressures are important variables in the behaviour of the motorcycle at high speeds. From a stability point of view it is desirable to make the lateral stiffness as large as possible, with the possibility of an optimum value for the torsional stiffness of the rear frame. Common levels of lateral stiffness at the wheel spindle deteriorates the wobble mode damping substantially with significant changes in the wobble frequency as well, and slight reduction in the weave mode damping at high speeds. Lateral distortion should be opposed as much as possible by locating the front fork torsional axis as low as possible. The largest contribution to the weave damping came from the cornering and camber stiffnesses and relaxation length of the rear tyre and not so much from the same parameters of the front tyre. Amongst others, stiff frames, a long wheelbase, a long trail and a flat steering head angle were found to increase weave mode damping. Degraded damping of the rear suspension, rear loading and increased speed amplifies cornering weave tendencies. Rear load assemblies with appropriate stiffness and damping were successful in damping out weave and wobble oscillations. Motorcyclists on a Honda CB600F Hornet.SuspensionModern designs have the two wheels of a motorcycle connected to the chassis by a suspension arrangement, however 'chopper' style motorcycles often elect to forego rear suspension ("rigid frame").
The front suspension generally consists of sliding steel tubes with long springs inside called forks which use hydraulic fluid for damping shock absorbers. The front fork is the most critical part of a motorcycle. The angle of rake determines how controllable the steering is. The rake should be chosen so that precessive force from countersteer and body steering slightly overbalance the leaning forces from the weight of the bike, at a speed near the running speed of a person. This is the speed at which the rider's feet can no longer be safely used to balance the bike.
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:
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 'Softail' style monoshock, which is mounted horizontally in front of the swingarm, below the swingarm pivot bolt
BrakesThere are generally two independent brakes on a motorcycle, one set on the front wheel, controlled by the right hand lever, and one on the rear controlled by the right foot. In older motorcycles the rear may be on the left foot. However, several models have "linked brakes" which apply both at the same time, although one more than the other. The front brake is generally much more powerful than the rear as roughly 2/3rds of stopping power can come from the front brake when properly applied and in some cases 100% depending on the model of motorcycle and operator; rear wheels can generally lock and skid much more easily than the front due to weight distribution dynamics. Brakes can either be drum or disc based, with disc brakes being more common on large, modern or 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. Some manufacturers have created Antilock braking systems (ABS).
In virtually all cases, 70% to 90% of total braking force should be applied by the front brake when operated on a hard surface such as tarmac, with the remainder being simultaneously applied to the rear brake. Riders fear that aggressive use of the front brake will stop rotation of the tire and cause loss of control, or a skid, and therefore often fail to use the front brake to its full potential. Another common misconception is that application of the rear brake will cause motorcycle instability. The phenomenon known as a "stoppie" may only be achieved if the front brake is used aggressively with no application of the rear brake; if sufficient force is applied to the front brake, the rear of the motorcycle chassis will lift off the roadway, while the bike continues to move forward on the still-rotating front wheel. This is a highly skilled (and generally illegal) maneuver which requires practice to perfect. Trailbraking is a term used to describe carrying the braking action of a vehicle past the turn entry, allowing the rider to adjust speed all the way through a turn to the apex. Another variation of brake use can be seen at top level motorcycle roadracing and motorcross events. The technique of steering the motorcycle in a high speed turn (or lower speeds on a dirt course) using the rear brake is called "backing it in" (or "turning" on dirt). Racers while hard on the front brake will feather the rear brake just enough to start a controlled rear slide, thus rendering a sharper turn angle. Note: This technique is not recommended for public road use.
There could be three kinds of stability problems with motorbikes:
Capsizing is well known in low speeds, and easy to overcome by going a bit faster. Wobbling (AVI movie) is a high frequency (7-9 Hz) oscillation of the front wheel. It is often relatively harmless but annoying (and quite frightening if previously inexperienced). It can appear at moderate speeds. Weaving (AVI movie) is a low frequency (2-3 Hz) oscillation of the whole vehicle. It can become unstable at higher speeds with fatal results. Based on The control and stability analysis of two-wheeled road vehicles:
The weave oscillations damp out once the rider reduced the roll angle. Tyre (tire) characteristics and inflation pressures are important variables in the behaviour of the motorcycle at high speeds. From a stability point of view it is desirable to make the lateral stiffness as large as possible, with the possibility of an optimum value for the torsional stiffness of the rear frame. Common levels of lateral stiffness at the wheel spindle deteriorates the wobble mode damping substantially with significant changes in the wobble frequency as well, and slight reduction in the weave mode damping at high speeds. Lateral distortion should be opposed as much as possible by locating the front fork torsional axis as low as possible. The largest contribution to the weave damping came from the cornering and camber stiffnesses and relaxation length of the rear tyre and not so much from the same parameters of the front tyre. Amongst others, stiff frames, a long wheelbase, a long trail and a flat steering head angle were found to increase weave mode damping. Degraded damping of the rear suspension, rear loading and increased speed amplifies cornering weave tendencies. Rear load assemblies with appropriate stiffness and damping were successful in damping out weave and wobble oscillations. Motorcyclists on a Honda CB600F Hornet.SuspensionModern designs have the two wheels of a motorcycle connected to the chassis by a suspension arrangement, however 'chopper' style motorcycles often elect to forego rear suspension ("rigid frame").
The front suspension generally consists of sliding steel tubes with long springs inside called forks which use hydraulic fluid for damping shock absorbers. The front fork is the most critical part of a motorcycle. The angle of rake determines how controllable the steering is. The rake should be chosen so that precessive force from countersteer and body steering slightly overbalance the leaning forces from the weight of the bike, at a speed near the running speed of a person. This is the speed at which the rider's feet can no longer be safely used to balance the bike.
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:
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 'Softail' style monoshock, which is mounted horizontally in front of the swingarm, below the swingarm pivot bolt
BrakesThere are generally two independent brakes on a motorcycle, one set on the front wheel, controlled by the right hand lever, and one on the rear controlled by the right foot. In older motorcycles the rear may be on the left foot. However, several models have "linked brakes" which apply both at the same time, although one more than the other. The front brake is generally much more powerful than the rear as roughly 2/3rds of stopping power can come from the front brake when properly applied and in some cases 100% depending on the model of motorcycle and operator; rear wheels can generally lock and skid much more easily than the front due to weight distribution dynamics. Brakes can either be drum or disc based, with disc brakes being more common on large, modern or 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. Some manufacturers have created Antilock braking systems (ABS).
In virtually all cases, 70% to 90% of total braking force should be applied by the front brake when operated on a hard surface such as tarmac, with the remainder being simultaneously applied to the rear brake. Riders fear that aggressive use of the front brake will stop rotation of the tire and cause loss of control, or a skid, and therefore often fail to use the front brake to its full potential. Another common misconception is that application of the rear brake will cause motorcycle instability. The phenomenon known as a "stoppie" may only be achieved if the front brake is used aggressively with no application of the rear brake; if sufficient force is applied to the front brake, the rear of the motorcycle chassis will lift off the roadway, while the bike continues to move forward on the still-rotating front wheel. This is a highly skilled (and generally illegal) maneuver which requires practice to perfect. Trailbraking is a term used to describe carrying the braking action of a vehicle past the turn entry, allowing the rider to adjust speed all the way through a turn to the apex. Another variation of brake use can be seen at top level motorcycle roadracing and motorcross events. The technique of steering the motorcycle in a high speed turn (or lower speeds on a dirt course) using the rear brake is called "backing it in" (or "turning" on dirt). Racers while hard on the front brake will feather the rear brake just enough to start a controlled rear slide, thus rendering a sharper turn angle. Note: This technique is not recommended for public road use.
Construction
Construction
VariationsVariations exist:
There are two basic forms of motorcycles: offroad and street. Some motorcycles have floorboards instead of footpegs. Some motorcycles can be fitted with a sidecar, this converting it into a 3-wheeler or "hack". There are other 3-wheeled variations, commonly referred to as a trike or motortricycle. Motorcycle manufacturers often also produce All-terrain vehicles or ATVs. These have two or more back wheels, usually two front wheels, an open driver's seat and a motorcycle-type handlebar. (Early models had a single front wheel, but these were prone to rollovers.) ATVs are used off-road for utility and recreation. However, a proper motorcycle has fewer than four wheels in contact with the ground.
ChassisThe chassis (or frame) of a motorcycle is typically made from welded aluminium or steel (or an alloy) struts, with the rear suspension being an integral component in the design. Carbon-fiber is used in a few very expensive custom frames.
Some motorcycles include the engine as a load-bearing (or stressed) member; this has been used all through bike history but is now becoming more common.
The fuel tank is usually mounted above the engine. This tank is generally made of stamped, brazed or welded sheet metal, or blow molded high-density polyethylene. At least one motorcycle manufacturer (Buell) offer models that use a hollow frame as the fuel tank, and various manufacturers offer designs which use part of the frame as an oil reservoir. The wheel rims are usually steel (generally with steel spokes and an aluminium hub) or 'mag' type cast or machined aluminum. Performance racing motorcycles often use carbon-fiber wheels, but the expense of these wheels is prohibitively high for general usage.
A plastic or fiberglass shell, known as a fairing, is placed over the frame in some models to shield the rider from the wind. Drag is the major factor that limits motorcycle speed, as it increases at the square of the velocity, with the resultant required horsepower increasing with the cube of velocity. As can be seen from the streamlined appearance of new performance motorcycles, there is much aerodynamic technology included in the design, but unfortunately no one has been able to overcome the effect from the turbulence caused by the spinning front wheel which disallows the motorcycle from cutting a clean path through the air. Another problem is the fact that no designs have been discovered that can improve aerodynamic performance without unacceptably compromising the rider's ability to control the machine. In the absence of a fairing or windshield, a phenomenon known as the windsock effect occurs at speeds above 100 km/h, where the rider becomes a major source of drag and is pushed back from the handlebars, tiring the rider. However, these motorcycles still effectively push their way through the atmosphere with brute force.
Cabin cycle solved the problem of aerodynamics by isolating driver from outside air.
VariationsVariations exist:
There are two basic forms of motorcycles: offroad and street. Some motorcycles have floorboards instead of footpegs. Some motorcycles can be fitted with a sidecar, this converting it into a 3-wheeler or "hack". There are other 3-wheeled variations, commonly referred to as a trike or motortricycle. Motorcycle manufacturers often also produce All-terrain vehicles or ATVs. These have two or more back wheels, usually two front wheels, an open driver's seat and a motorcycle-type handlebar. (Early models had a single front wheel, but these were prone to rollovers.) ATVs are used off-road for utility and recreation. However, a proper motorcycle has fewer than four wheels in contact with the ground.
ChassisThe chassis (or frame) of a motorcycle is typically made from welded aluminium or steel (or an alloy) struts, with the rear suspension being an integral component in the design. Carbon-fiber is used in a few very expensive custom frames.
Some motorcycles include the engine as a load-bearing (or stressed) member; this has been used all through bike history but is now becoming more common.
The fuel tank is usually mounted above the engine. This tank is generally made of stamped, brazed or welded sheet metal, or blow molded high-density polyethylene. At least one motorcycle manufacturer (Buell) offer models that use a hollow frame as the fuel tank, and various manufacturers offer designs which use part of the frame as an oil reservoir. The wheel rims are usually steel (generally with steel spokes and an aluminium hub) or 'mag' type cast or machined aluminum. Performance racing motorcycles often use carbon-fiber wheels, but the expense of these wheels is prohibitively high for general usage.
A plastic or fiberglass shell, known as a fairing, is placed over the frame in some models to shield the rider from the wind. Drag is the major factor that limits motorcycle speed, as it increases at the square of the velocity, with the resultant required horsepower increasing with the cube of velocity. As can be seen from the streamlined appearance of new performance motorcycles, there is much aerodynamic technology included in the design, but unfortunately no one has been able to overcome the effect from the turbulence caused by the spinning front wheel which disallows the motorcycle from cutting a clean path through the air. Another problem is the fact that no designs have been discovered that can improve aerodynamic performance without unacceptably compromising the rider's ability to control the machine. In the absence of a fairing or windshield, a phenomenon known as the windsock effect occurs at speeds above 100 km/h, where the rider becomes a major source of drag and is pushed back from the handlebars, tiring the rider. However, these motorcycles still effectively push their way through the atmosphere with brute force.
Cabin cycle solved the problem of aerodynamics by isolating driver from outside air.
Motorcycle
Motorcycle
A motorcycle is a two-wheeled vehicle powered by an engine. The wheels are in-line, and at higher speed the motorcycle remains upright and stable by virtue of gyroscopic forces; at lower speeds continual readjustment of the steering by the rider gives stability. The rider sits astride the vehicle on a seat, with hands on a set of handlebars which are used to steer the motorcycle, in conjunction with the rider shifting his weight through his feet, which are supported on a set of footpegs which stick out from the frame.
History The inspiration for the earliest motorcycles, and arguably the first motorcycle, was designed and built by the German inventors Gottlieb Daimler and Wilhelm Maybach in Bad Cannstatt (a city district of Stuttgart) in 1885. It was the first petroleum-powered vehicle ever and, but for the provision of a pair of stabilizing wheels, a motorized bicycle, although they called their invention the Reitwagen ("riding car"). They had not set out to create a vehicle form but to build a simple carriage for the engine which was the focus of their endeavours. However,if one counts two wheels with steam propulsion as being a motorcycle, then the first one may have been American. One such machine was demonstrated at fairs and circuses in the eastern US in 1867, built by one Sylvester Howard Roper of Roxbury, Massachusetts. There is an existing example of a Roper machine, dated 1869. It's powered by a charcoal-fired two-cylinder engine, whose connecting rods directly drive a crank on the rear wheel. This machine predates the invention of the safety bicycle by many years, so its chassis is also based on the "bone-crusher" bike.
In 1894, the Hildebrand & Wolfmüller was the first motorcycle that was available for purchase.
In the early period of motorcycle history there were many manufacturers as producers of bicycles adapted their designs for the new internal combustion engine. As the engines became more powerful and designs outgrew the bicycle origins, the number of motorcycle producers reduced.
Up until the First World War, the largest motorcycle manufacturer was Indian. After that, this honour went to Harley Davidson, until 1928 when DKW took over as the largest manufacturer. After the Second World War, in 1951, the BSA Group became the largest producer of motorcycles in the world. The German NSU was the largest manufacturer from 1955 until the 1970s when Honda became the most prominent manufacturer, a title it retains to this day. British manufacturers held a dominant position in some markets until the rise of the Japanese manufacturers (led by Honda) in the late 60s and early 70s who were able to produce designs faster, cheaper and of better quality. Today, the Japanese manufacturers Honda, Kawasaki, Suzuki and Yamaha dominate the motorcycle industry, although Harley-Davidson still maintains a high degree of popularity in America.
Recent years have also seen a resurgence in the popularity of many other brands, including BMW, Triumph and Ducati.
A motorcycle is a two-wheeled vehicle powered by an engine. The wheels are in-line, and at higher speed the motorcycle remains upright and stable by virtue of gyroscopic forces; at lower speeds continual readjustment of the steering by the rider gives stability. The rider sits astride the vehicle on a seat, with hands on a set of handlebars which are used to steer the motorcycle, in conjunction with the rider shifting his weight through his feet, which are supported on a set of footpegs which stick out from the frame.
History The inspiration for the earliest motorcycles, and arguably the first motorcycle, was designed and built by the German inventors Gottlieb Daimler and Wilhelm Maybach in Bad Cannstatt (a city district of Stuttgart) in 1885. It was the first petroleum-powered vehicle ever and, but for the provision of a pair of stabilizing wheels, a motorized bicycle, although they called their invention the Reitwagen ("riding car"). They had not set out to create a vehicle form but to build a simple carriage for the engine which was the focus of their endeavours. However,if one counts two wheels with steam propulsion as being a motorcycle, then the first one may have been American. One such machine was demonstrated at fairs and circuses in the eastern US in 1867, built by one Sylvester Howard Roper of Roxbury, Massachusetts. There is an existing example of a Roper machine, dated 1869. It's powered by a charcoal-fired two-cylinder engine, whose connecting rods directly drive a crank on the rear wheel. This machine predates the invention of the safety bicycle by many years, so its chassis is also based on the "bone-crusher" bike.
In 1894, the Hildebrand & Wolfmüller was the first motorcycle that was available for purchase.
In the early period of motorcycle history there were many manufacturers as producers of bicycles adapted their designs for the new internal combustion engine. As the engines became more powerful and designs outgrew the bicycle origins, the number of motorcycle producers reduced.
Up until the First World War, the largest motorcycle manufacturer was Indian. After that, this honour went to Harley Davidson, until 1928 when DKW took over as the largest manufacturer. After the Second World War, in 1951, the BSA Group became the largest producer of motorcycles in the world. The German NSU was the largest manufacturer from 1955 until the 1970s when Honda became the most prominent manufacturer, a title it retains to this day. British manufacturers held a dominant position in some markets until the rise of the Japanese manufacturers (led by Honda) in the late 60s and early 70s who were able to produce designs faster, cheaper and of better quality. Today, the Japanese manufacturers Honda, Kawasaki, Suzuki and Yamaha dominate the motorcycle industry, although Harley-Davidson still maintains a high degree of popularity in America.
Recent years have also seen a resurgence in the popularity of many other brands, including BMW, Triumph and Ducati.
Monday, December 05, 2005
Property
Anthropology studies the diverse systems of ownership, rights of use and transfer, and possession under the term "theories of ". Western legal theory is based, as mentioned, on the owner of being a legal individual. However, not all systems are founded on this basis.
Communal systems describe ownership as belonging to the entire social and political unit, while corporate systems describe ownership as being attached to an identifiable group with an identifiable responsible individual: generally a family. The Roman law was based on such a corporate system, for example.
Different societies may have different theories of for differing types of ownership, as the above paragraph makes clear: land is collectivelyowned, improvements are individually owned, but may not be transferred outside of the community. Currently, anthropological theory relates the kind of kinship system - whether through one or both parents - with certain theories, though this idea is in dispute. Essentially, it is very common among systems to have the community own where kinship is reckoned both through patrilineal and matrilineal systems, but is owned by the family if only one method of reckoning is used. Exceptions to this rule have been documented, but it remains the prevailing assumption of tribal ownership.
Pauline Peters argued that Auction systems are not isolable from the social fabric, and notions of may not be stated as such, but instead may be framed in negative terms: for example the taboo system among Polynesian peoples.
Communal systems describe ownership as belonging to the entire social and political unit, while corporate systems describe ownership as being attached to an identifiable group with an identifiable responsible individual: generally a family. The Roman law was based on such a corporate system, for example.
Different societies may have different theories of for differing types of ownership, as the above paragraph makes clear: land is collectivelyowned, improvements are individually owned, but may not be transferred outside of the community. Currently, anthropological theory relates the kind of kinship system - whether through one or both parents - with certain theories, though this idea is in dispute. Essentially, it is very common among systems to have the community own where kinship is reckoned both through patrilineal and matrilineal systems, but is owned by the family if only one method of reckoning is used. Exceptions to this rule have been documented, but it remains the prevailing assumption of tribal ownership.
Pauline Peters argued that Auction systems are not isolable from the social fabric, and notions of may not be stated as such, but instead may be framed in negative terms: for example the taboo system among Polynesian peoples.
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