Types of motorcycles
There are many systems for classifying types of motorcycles, describing how the motorcycles are put to use, or the designer's intent, or some combination of the two. Six main categories are recognized: cruiser, touring, dual-purpose, dirt bike. Sometimes sport touring motorcycles are recognized as a seventh category. Strong lines are sometimes drawn between motorcycles and their smaller cousins, mopeds and underbones, but other classification schemes include these as types of motorcycles. There is no universal system for classifying all types of motorcycles. There are strict classification systems enforced by competitive motorcycle sport sanctioning bodies, or legal definitions of a motorcycle established by certain legal jurisdictions for motorcycle registration, road traffic safety rules or motorcyclist licensing. There are informal classifications or nicknames used by manufacturers and the motorcycling media; some experts do not recognize sub-types, like naked bike, that "purport to be classified" outside the six usual classes, because they fit within one of the main types and are recognizable only by cosmetic changes.
Street motorcycles are motorcycles designed for being ridden on paved roads. They have smooth tires with a light tread pattern and engines in the 125 cc and over range. Most are capable of speeds up to 100 mph, many of speeds in excess of 125 mph. Standards called naked bikes or roadsters, are versatile, general-purpose street motorcycles, they are recognized by their upright riding position, partway between the reclining rider posture of the cruisers and the forward leaning sport bikes. Footpegs are below the rider and handlebars are high enough to not force the rider to reach too far forward, placing the shoulders above the hips in a natural position; because of their flexibility, lower costs, moderate engine output, standards are suited to motorcycle beginners. Standards do not come with fairings or windscreens, or if they have them, they are small. Standard is a synonym for naked bike, a term that became popular in the 1990s in response to the proliferation of faired sport bikes; the standard seemed to have disappeared, fueling nostalgia for the return of the Universal Japanese Motorcycle, which were admired for their simplicity and versatility.
Muscle bike is a nickname for a motorcycle type, derived from either a standard or sport bike design, that puts a disproportionately high priority on engine power. Roadster is naked. Cruisers are styled after American machines from the 1930s to the early 1960s, such as those made by Harley-Davidson and Excelsior-Henderson. Harley-Davidsons define the cruiser category, large-displacement V-twin engines are the norm, although other engine configurations and small to medium displacements exist, their engines are tuned for low-end torque, making them less demanding to ride because it is not necessary to shift as to accelerate or maintain control. The riding position places the feet forward and the hands are up high, so that the spine is erect or leaning back slightly. At low to moderate speeds, cruisers are more comfortable than other styles, but riding for long periods at freeway speeds can lead to fatigue from pulling back on the handlebars to resist the force of the wind against the rider's chest.
Cruisers have limited cornering ability due to a lack of ground clearance. Choppers are a type of cruiser, so called because they are a "chopped", or cut-down, version of a production cruiser. Choppers are custom projects that result in a bike modified to suit the owner's ideals, and, as such, are a source of pride and accomplishment. Stereotypically, a chopper may have small fuel tanks and high handlebars. Choppers were popularised in the Peter Fonda film Easy Rider. Being designed for visual effect, choppers will not be the most efficient riding machines. Related to the chopper motorcycle is the bobber, created by "bobbing" a factory bike by removing dead weight and bodywork from a motorcycle to reduce mass and increase performance. A common element of these motorcycles is a shortened rear fender. A distinguishing feature between a chopper and a bobber is that bobbers reuse the factory motorcycle frame, whereas choppers use custom frames with increased rake; the more conservative steering geometry of a bobber will in most cases lead to superior cornering performance relative to a chopper.
Power cruiser is a name used to distinguish bikes in the cruiser class that have higher levels of power. They come with upgraded brakes and suspensions, better ground clearance, premium surface finishes, as well as more exotic or non-traditional styling. Sport bikes emphasize top speed, braking and grip on paved roads at the expense of comfort and fuel economy in comparison to less specialized motorcycles; because of this, there are certain design elements. Sport bikes have comparatively high performance engines resting inside a lightweight frame. Inline-four engines dominate the sport bike category, with V-twins having a significant presence, nearly every other engine configuration appearing in small numbers at one time or another; the combination of these elements helps maintain chassis rigidity. Braking systems combine higher performance brake pads and multi-piston calipers that clamp onto oversized vented rotors. Suspension systems are advanced in terms of adjustments and materials for increased stability and durability.
Most sport bikes have fairings
A motorcycle's suspension serves a dual purpose: contributing to the vehicle's handling and braking, providing safety and comfort by keeping the vehicle's passengers comfortably isolated from road noise and vibrations. The typical motorcycle has a pair of fork tubes for the front suspension, a swingarm with one or two shock absorbers for the rear suspension; the most common form of front suspension for a modern motorcycle is the telescopic fork. Other fork designs are girder forks, suspended on sprung parallel links and bottom leading link designs, not common since the 1960s; some manufacturers used a version of the swinging arm for front suspension on their motocross designs. A single-sided version of the idea is used in motor scooters such as the Vespa; the Hub-center steering as developed by Ascanio Rodorigo, on a concept associated to Massimo Tamburini is a complex front swingarm alternative system that entails suspension and steering, as seen in projects such as Bimota Tesi and Vyrus motorcycles.
Scott produced a motorcycle with telescopic forks in 1908, would continue to use them until 1931. In 1935 BMW became the first manufacturer to produce a motorcycle with hydraulically damped telescopic forks. Most motorcycles today use telescopic forks for the front suspension; the forks can be most understood as large hydraulic shock absorbers with internal coil springs. They allow the front wheel to react to imperfections in the road while isolating the rest of the motorcycle from that motion; the top of the forks are connected to the motorcycle's frame in a triple tree clamp, which allows the forks to be turned in order to steer the motorcycle. The bottom of the forks is connected to the front wheel's axle. On conventional telescopic forks, the lower portion or fork bodies, slide up and down the fork tubes; the fork tubes must be mirror-smooth to seal the fork oil inside the fork. Some fork tubes on early roadsters and off-road motorcycles, are enclosed in plastic protective "gaiters. "Upside-down" forks known as inverted forks, are installed inverted compared to conventional telescopic forks.
The slider bodies are at the top, fixed in the triple clamps, the stanchion tubes are at the bottom, fixed to the axle. This USD arrangement has two advantages: it decreases the unsprung weight of the motorcycle. Two disadvantages of USD forks are: they are more expensive than conventional telescopic forks. USD forks are found on sportbikes, though the Honda Valkyrie featured USD forks. Motorcycle suspensions are designed so that the springs are always under compression when extended. Pre-load is used to adjust the initial position of the suspension with the weight of the motorcycle and rider acting on it; the difference between the extended length of the suspension and the length compressed by the weight of the motorcycle and rider is called "total sag" or "race sag". Total sag is set to optimize the initial position of the suspension to avoid bottoming out or topping out under normal riding conditions. "Bottoming out" occurs when the suspension is compressed to the point where it mechanically cannot compress any more.
Topping out occurs when the suspension extends and cannot mechanically extend any more. Increasing pre-load increases the initial force on the spring thereby reducing total sag. Decreasing pre-load decreases the initial force in the spring thereby increasing total sag; some motorcycles allow adjustment of pre-load by changing the air pressure inside the forks. Valves at the top of the forks allow air to be released from the fork. More air pressure gives more pre-load, vice versa. Basic fork designs use a simple damper-rod system, in which damping is controlled by the passage of fork oil through an orifice. Though cheap to manufacture, it is hard to tune such forks, as they tend to give too little damping at low slider speeds, yet too much damping at higher slider speeds. Any adjustment setting will always be a compromise, giving both over-stiff damping. Since forks act as hydraulic dampers, changing the weight of the fork oil will alter the damping rate; some telescopic forks have external adjustments for damping.
A more sophisticated approach is the cartridge fork, which use internal cartridges with a valving system. Damping at low slider speeds is controlled by a much smaller orifice, but damping at higher slider speeds is controlled by a system of flexible shims, which act as a bypass valve for the fork oil; this valve has a number of such shims of varying thicknesses that cover the orifices in the valve to control the damping of the fork on high and medium speed bumps. Some of the shims lift with little force allowing fluid to flow through the orifice. Other springs require greater force to allow flow; this gives the fork digressive damping, allowing it to be stiff over small bumps, yet softer over larger bumps. The springs only allow flow in one direction, so one set of springs controls compression damping, another rebound damping; this allows the dampings to be set separately. Cartridge emulators are aftermarket parts that make damper-rod forks behave as cartridge forks; the damping orifice in the damper-rod is made so large that it has no effect on damping, instead an "emulator" takes over the damping function.
The emulator has a small orifice for low fork-speed damping, an adjustable shim-stack for high fork-speed damping. Gas-charged cartridge forks, w
Motorcycle testing and measurement
Motorcycle testing and measurement includes a range of more than two dozen statistics giving the specifications of the motorcycle, the actual performance, expressed by such things as the output of the engine, the top speed or acceleration of the motorcycle. Most parameters are uncontroversial and claims made by manufacturers are accepted without verification; these might include simple measurements like rake, trail, or wheelbase, or basic features, such as the type of brakes or ignition system. Other measurements are doubted or subject to misunderstandings, the motorcycling press serves as an independent check on sometimes unrealistic sales and marketing claims. Many of these numbers are subject to variable methods of measurements, or disagreement as to the definition of the statistic; the parameters most in contention for motorcycles are the weight, the engine output, the overall performance acceleration, top speed, fuel economy. With electric motorcycles and scooters, the range between charges is a pivotal measurement.
Motorcycle speed tests at high speeds, are prone to variation due to human error, limitations in equipment, atmospheric factors like wind and altitude. The published results of two otherwise identical tests could vary depending on whether the result is reported with or without industry standard correction factors calculated to compensate for test conditions. Rounding errors are possible as well when converting to/from kilometers per hour. With power being the product of force and speed, a motorcycle's power and torque ratings will be indicative of its performance. Reported numbers for power and torque may however vary from one source to another due to inconsistencies in how testing equipment is calibrated, the method of using that equipment, the conditions during the test, the location that force and speed are being measured at; the power of the engine alone called crankshaft power, or power at the crankshaft, will be greater than the power measured at the rear wheel. The amount of power lost due to friction in the transmission depends on the details of the design and construction.
Generalizing, a chain drive motorcycle may have some 5-20% less power at the rear wheel than at the crankshaft, while a shaft drive model may lose a little more than that due to greater friction. While the crankshaft power excludes these transmission losses, still the measurement is made elsewhere in the drive-train at the rear wheel. A correction for the transmission losses is applied to the measured values to obtain the crankshaft values. For motorcycles, the reported power and torque numbers pertain to the crankshaft. In directive 92/61/EEC of 30 June 1992 relating to the type-approval of two or three-wheel motor vehicles, it is referred to as "maximum engine power", manufacturers use similar terms; this convention may have come from the pre-unit construction, wherein the crankshaft was directly accessible for measurements, the gearbox might have come from a different manufacturer. However, when the engineering details of the transmission are known, the losses therein can be quantified & corrected for.
Explicit guidance on the homologation measurements and transmission corrections is given in directive 95/1/EC. A main source of ambiguity and differences comes from the conditions; these conditions include details like atmospheric conditions, tire pressure, but most importantly: the conditions of the motorcycle itself. Examples thereof are: was the alternator fitted?. One would hope that manufacturers would test their motorcycles in normal running order, so the condition that they are sold in, for which they obtained type-approval, but this is not always the case. Ducati, for instance, has chosen to publish more positive values, stating that "Technical data referring to power and torque was measured on an engine test stand at Ducati", their published values are 5% higher than the homologation values, in normal running order. Motorcycle weight is expressed in three ways: gross vehicle weight rating, dry weight and wet weight. GVWR is the maximum total weight of the motorcycle including all consumables, the rider, any passenger, any cargo.
It is well-understood and standardized, being defined by law and overseen by agencies such as the US Department of Transportation. In contrast and dry weight are unstandardized measurements that refer to the weight of the motorcycle without rider, passengers or cargo, either with or without a varying set of fluids such as fuel or lubricants, the battery. Wet and dry weight are used to make comparisons between different motorcycles, because all else being equal, a lighter motorcycle will perform and handle better than a heavier one; the difference between GVWR and wet weight is how much the motorcycle can safely carry, including the rider and other load. As its weight changes during riding, the dry weight of a motorcycle excludes the gasoline. Dry weight, in this sense, can directly be used for comparison with weight limits, which pertain to the motorcycle in operating condition, it is part of the homologation tests, it is found on the EC Certificate of Conformity as unladen mass. This dry weight could be useful in comparing different models, with different fuel tank capacities.
However, manufacturers may exclude some or all of the following: engine oil, coolant, or brake fluid, this makes such a comparison difficult. When any of these is exclu
A disc brake is a type of brake that uses calipers to squeeze pairs of pads against a disc or "rotor" to create friction. This action slows the rotation of a shaft, such as a vehicle axle, either to reduce its rotational speed or to hold it stationary; the energy of motion is converted into waste heat. Hydraulically actuated disc brakes are the most used form of brake for motor vehicles, but the principles of a disc brake are applicable to any rotating shaft. Development of disc-type brakes began in England in the 1890s. In 1902, the Lanchester Motor Company designed brakes that looked and operated in a similar way to a modern disc-brake system though the disc was thin and a cable activated the brake pad. Other designs were not practical or available in cars for another 60 years. Successful application began in airplanes before World War II, the German Tiger tank was fitted with discs in 1942. After the war, technological progress began to arrive in the 1950s, leading to a critical demonstration of superiority at the 1953 24 Hours of Le Mans race, which required braking from high speeds several times per lap.
The Jaguar racing team won, using disc brake equipped cars, with much of the credit being given to the brakes' superior performance over rivals equipped with drum brakes. Mass production began with the 1955 Citroën DS. Compared to drum brakes, disc brakes offer better stopping performance because the disc is more cooled; as a consequence discs are less prone to the brake fade caused when brake components overheat. Disc brakes recover more from immersion. Most drum brake designs have at least one leading shoe. By contrast, a disc brake has no self-servo effect and its braking force is always proportional to the pressure placed on the brake pad by the braking system via any brake servo, braking pedal, or lever; this helps to avoid impending lockup. Drums are prone to "bell mouthing" and trap worn lining material within the assembly, both causes of various braking problems; the disc is 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 the axle. To slow down the wheel, friction material in the form of brake pads, mounted on the brake caliper, is forced mechanically, pneumatically, or electromagnetically against both sides of the disc. Friction attached wheel to slow or stop. Development of disc brakes began in England in the 1890s; the first caliper-type automobile disc brake was patented by Frederick William Lanchester in his Birmingham factory in 1902 and used on Lanchester cars. However, the limited choice of metals in this period meant that he had to use copper as the braking medium acting on the disc; the poor state of the roads at this time, no more than dusty, rough tracks, meant that the copper wore making the system impractical. Successful application began in airplanes and tanks before and during World War II. In Britain, the Daimler Company used disc brakes on its Daimler Armoured Car of 1939, the disc brakes, made by the Girling company, were necessary because in that four-wheel drive vehicle the epicyclic final drive was in the wheel hubs and therefore left no room for conventional hub-mounted drum brakes.
At Germany's Argus Motoren, Hermann Klaue had patented disc brakes in 1940. Argus supplied wheels fitted with disc brakes e.g. for the Arado Ar 96. The German Tiger I heavy tank, was introduced in 1942 with a 55 cm Argus-Werke disc on each drive shaft; the American Crosley Hot Shot is given credit for the first production disc brakes. For six months in 1950, Crosley built a car with these brakes returned to drum brakes. Lack of sufficient research caused reliability problems, such as sticking and corrosion in regions using salt on winter roads. Drum brake conversions for Hot Shots were quite popular; the Crosley disc was a Goodyear development, a caliper type with ventilated disc designed for aircraft applications. Chrysler developed a unique braking system, offered from 1949 to 1953. Instead of the disc with caliper squeezing on it, this system used twin expanding discs that rubbed against the inner surface of a cast-iron brake drum, which doubled as the brake housing; the discs spread apart to create friction against the inner drum surface through the action of standard wheel cylinders.
Because of the expense, the brakes were only standard on the Chrysler Crown and the Town and Country Newport in 1950. They were optional, however, on other Chryslers, priced around $400, at a time when an entire Crosley Hot Shot retailed for $935; this four-wheel disc brake system was built by Auto Specialties Manufacturing Company of St. Joseph, under patents of inventor H. L. Lambert, was first tested on a 1939 Plymouth. Chrysler discs were "self energizing," in that some of the braking energy itself contributed to the braking effort; this was accomplished by small balls set into oval holes leading to the brake surface. When the disc made initial contact with the friction surface, the balls would be forced up the holes forcing the discs further apart and augmenting the braking energy; this made for lighter braking pressure than with calipers, avoided brake fade, promoted cooler running, provided one-third more friction surface than standard Chrysler twelve-inch drums. Today's owners consider the Ausco-Lambert reliable and powerful, but admit its grabbiness and sensitivity.
The first use of disc brakes in racing was in 1951, one of the BRM Type 15s using a Girling-produced set, a first for a Formula One car. Reliable caliper-type
A motorcycle fork connects a motorcycle's front wheel and axle to its frame via a yoke known as a triple clamp, which consists of an upper yoke joined to a lower yoke via a steering stem, a shaft that runs through the steering head, creating the steering axis. Most forks incorporate the front suspension and front brake, allow the front wheel to rotate about the steering axis so that the bike may be steered. Most handlebars attach to the top clamp in various ways, while clip-on handlebars clamp to the fork tubes, either just above or just below the upper triple clamp; the fork and its attachment points on the frame establish the critical geometric parameters of rake and trail, which play a major role in defining how a motorcycle handles and dives during braking. While the standard telescopic fork arrangement is found with few major differences among mainstream street motorcycles since the 1970s there have been many variations, including trailing or leading link, Earles and others, as well as non-fork steering such as hub-center steering.
A variety of fork arrangements have been tried during more than one hundred years of motorcycle development, several of which remain available today. A telescopic fork uses fork tubes; this is the most common form of fork commercially available. It may or may not include gaiters for protection against abrasive elements on the suspension cylinders; the main advantages of the telescopic fork are that it is simple in design and cheap to manufacture and assemble. Conventionally, the fork stanchions are at the top, secured by a yoke, the sliders are at the bottom, attached to the front wheel spindle. On some modern sport bikes and most off-road bikes, this system is inverted, with "sliders" at the top, clamped to the yoke, while the stanchions are at the bottom; this is done to reduce unsprung weight by having the heavier components suspended, to improve the strength and rigidity of the assembly by having the strong large-diameter "sliders" clamped in the yokes. The inverted system is referred to "USD" for short.
A disadvantage of this USD design is that the entire reservoir of damping oil is above the slider seal so that, if the slider seal were to leak, the oil could drain out, rendering any damping ineffective. A trailing link fork suspends the wheel on a link with a pivot point forward of the wheel axle. Most famously used by Indian Motocycle. A leading link fork suspends the wheel on a link with a pivot point aft of the wheel axle. Russian Ural motorcycles still use leading link forks on sidecar equipped motorcycles, aftermarket leading link forks are installed today on motorcycles when they are outfitted with sidecars, they are very popular with trikes, improving the handling while steering or braking. The most common example of a leading link fork is; the springer fork is an early type of leading link fork. A springer fork does not have the suspension built into the fork tubes, but instead has it mounted externally, where it may be integrated into the triple clamp; this style of fork may be found on antique motorcycles or choppers, is available today on Harley-Davidson's Softail Springer.
While it may have an exposed spring near the triple clamp, a springer fork is distinguishable from a girder fork by its two parallel sets of legs. The rear is fixed to the bottom triple clamp. A short leading link holds the forward leg which actuates the springs; the Earles fork is a variety of leading link fork where the pivot point is behind the front wheel, the basis of the Earles' patent. Patented by Englishman Ernest Earles in 1953, the design is constructed of light tubing, with conventional'shock absorbers' mounted near the front axle; the Earles fork has a small wheelbase change under braking or under compression, unlike telescopic forks. Their construction is much stronger than teleforks against lateral deflection caused by hard cornering, or when cornering with a sidecar; this triangulated fork causes the front end of a motorcycle to rise when braking hard, as the mechanical braking forces rotate'downward' relative to the fork's pivot point — this action can be disconcerting to riders used to telescopic forks, which have the opposite reaction to braking forces.
Several motorcycle manufacturers licensed the Earles patent forks for racing motorcycles in 1953, such as MV Agusta and BMW Motorcycle, while other companies used the Earles design on their roadsters or off-road machines. BMW used Earles forks on all their motorcycles between 1955 and 1968. One of the earliest types of motorcycle front suspension, the girder fork consists of a pair of uprights attached to the triple clamp by linkages with a spring between the top and bottom triple clamps; the design reached a peak in the "Girdraulics" used on the Vincent motorcycle. Girdraulic forks featured forged alloy blades for hydraulic damping. While both may have an exposed spring near the triple clamp, a girder fork is distinguishable from a springer fork by the wheel being fixed to the upright; the pivot points are short links mounted to bottom triple clamps. The spring is mounted to the gird
Engine balance refers to those factors in the design, engine tuning and the operation of an engine that benefit from being balanced. Major considerations are: Balancing of structural and operational elements within an engine Longevity and performance Power and efficiency Performance and weight/size/cost Environmental cost and utility Noise/vibration and performanceThis article is limited to structural and operational balance within an engine in general, balancing of piston engine components in particular. Piston engine balancing is a complicated subject that covers many areas in the design, production and operation; the engine considered to be well balanced in a particular usage may produce unacceptable level of vibration in another usage for the difference in driven mass and mounting method, slight variations in resonant frequencies of the environment and engine parts could be big factors in throwing a smooth operation off balance. In addition to the vast areas that need to be covered and the delicate nature, terminologies used to describe engine balance are incorrectly understood and/or poorly defined not only in casual discussions but in many articles in respected publications.
Internal combustion piston engines, by definition, are converter devices to transform energy in intermittent combustion into energy in mechanical motion. A slider-crank mechanism is used in creating a chemical reaction on fuel with air, converting the energy into rotation; the intermittent energy source combined with the nature of this mechanism make the engine vibration-prone. Multi-cylinder configuration and many of the engine design elements are reflections of the effort to reduce vibrations through the act of balancing; this article is organized in six sections: Items to be balanced: lists the balancing elements to establish the basics on the causes of imbalance. Types of vibration: lists different kinds of vibration as the effects of imbalance. Primary balance: discusses the term "Primary balance". Secondary balance: explains what Secondary balance is, how the confusing terminologies'Primary' and'Secondary' came into popular use. Inherent balance: goes into engine balance discussions on various multi-cylinder configurations.
Steam locomotives: an introduction to the balancing of 2-cylinder locomotives and includes the wheel hammer effect unique to steam locomotives. There are many factors that can contribute to engine imbalance, there are many ways to categorize them; the following categories will be used for the purposes of this discussion. In the category descriptions,'Phase' refers to the timing on the rotation of crankshaft,'Plane' refers to the location on the crankshaft rotating axis, and'CG' refers to the center of gravity. Static balance refers to the location of the CG on moving parts. 1. Reciprocating mass - e.g. Piston and connecting rod weight and CG uniformity. 2. Rotating mass - e.g. Crank web weight uniformity and flywheel eccentricity In order for a mass to start moving from rest or change direction, it needs to be accelerated. A force is required to accelerate a mass. According to Newton's 3rd law of motion, there will be a counter force in the opposite direction of equal size. Dynamic balance refers to the balancing of these forces due to friction.
All accelerations of a mass can be divided into two components in opposite directions. For example, in order for a piston in a single cylinder engine to be accelerated upward, something must receive the downward force, it is the mass of the entire engine that moves downward a bit as there is no counter-moving piston; this means one cause of engine vibration appears in two opposing directions. The movement or deflection in one direction appears on a moving mass, the other direction appears on the entire engine, but sometimes both sides appear on moving parts, e.g. a torsional vibration in a crankshaft, or a push-pull cyclic stress in a chain or connecting rod. In other cases, one side is a deflection of a static part, the energy of, converted into heat and dissipated into the coolant. Piston mass needs to be decelerated, resisting a smooth rotation of a crankshaft. In addition to the up-down movement of a piston, a connecting rod big-end swings left and right and up and down while it rotates.
In order to simplify the motion of a crank/slider mechanism, the connecting rod/piston assembly is divided into two mass groups, a reciprocating mass, a rotating mass. The big-end of the rod is said to be rotating while the small end is said to be reciprocating. In truth, both ends both reciprocate and rotate. 3. Phase balance - e.g. Pistons on 60 or 90° V6 without an offset crankshaft reciprocate with unevenly spaced phases in a crank rotation 4. Plane balance - e.g. Boxer Twin pistons travel on two different rotational planes of the crankshaft, which creates forces to rock the engine on Z-axis 5. Phase balance - e.g. Imbalance in camshaft rotating mass can generate a vibration with a frequency equal to once in 2 crank rotations in a 4 cycle engine 6. Plane balance - e.g. Boxer Twin crankshaft without counterweights rocks the engine on Z-axis 7. Torsional balance - If the rigidity of crank throws on an inline 4 cylinder engine is uniform, the crank throw farthest from the clutch surface shows the biggest torsional deflection.
It is impossible to make these deflections uniform across multiple cylinders except on a radial engine. See Torsional vibration 8. A single cylinder 10 HP engine weighing a ton is smooth, because the forces that comprise its imbalance in operation must move a large mass to create a vibration; as pow
Aluminium or aluminum is a chemical element with symbol Al and atomic number 13. It is a silvery-white, soft and ductile metal in the boron group. By mass, aluminium makes up about 8% of the Earth's crust; the chief ore of aluminium is bauxite. Aluminium metal is so chemically reactive that native specimens are rare and limited to extreme reducing environments. Instead, it is found combined in over 270 different minerals. Aluminium is remarkable for its low density and its ability to resist corrosion through the phenomenon of passivation. Aluminium and its alloys are vital to the aerospace industry and important in transportation and building industries, such as building facades and window frames; the oxides and sulfates are the most useful compounds of aluminium. Despite its prevalence in the environment, no known form of life uses aluminium salts metabolically, but aluminium is well tolerated by plants and animals; because of these salts' abundance, the potential for a biological role for them is of continuing interest, studies continue.
Of aluminium isotopes, only 27Al is stable. This is consistent with aluminium having an odd atomic number, it is the only aluminium isotope that has existed on Earth in its current form since the creation of the planet. Nearly all the element on Earth is present as this isotope, which makes aluminium a mononuclidic element and means that its standard atomic weight equates to that of the isotope; the standard atomic weight of aluminium is low in comparison with many other metals, which has consequences for the element's properties. All other isotopes of aluminium are radioactive; the most stable of these is 26Al and therefore could not have survived since the formation of the planet. However, 26Al is produced from argon in the atmosphere by spallation caused by cosmic ray protons; the ratio of 26Al to 10Be has been used for radiodating of geological processes over 105 to 106 year time scales, in particular transport, sediment storage, burial times, erosion. Most meteorite scientists believe that the energy released by the decay of 26Al was responsible for the melting and differentiation of some asteroids after their formation 4.55 billion years ago.
The remaining isotopes of aluminium, with mass numbers ranging from 21 to 43, all have half-lives well under an hour. Three metastable states are known, all with half-lives under a minute. An aluminium atom has 13 electrons, arranged in an electron configuration of 3s23p1, with three electrons beyond a stable noble gas configuration. Accordingly, the combined first three ionization energies of aluminium are far lower than the fourth ionization energy alone. Aluminium can easily surrender its three outermost electrons in many chemical reactions; the electronegativity of aluminium is 1.61. A free aluminium atom has a radius of 143 pm. With the three outermost electrons removed, the radius shrinks to 39 pm for a 4-coordinated atom or 53.5 pm for a 6-coordinated atom. At standard temperature and pressure, aluminium atoms form a face-centered cubic crystal system bound by metallic bonding provided by atoms' outermost electrons; this crystal system is shared by some other metals, such as copper. Aluminium metal, when in quantity, is shiny and resembles silver because it preferentially absorbs far ultraviolet radiation while reflecting all visible light so it does not impart any color to reflected light, unlike the reflectance spectra of copper and gold.
Another important characteristic of aluminium is its low density, 2.70 g/cm3. Aluminium is a soft, lightweight and malleable with appearance ranging from silvery to dull gray, depending on the surface roughness, it is nonmagnetic and does not ignite. A fresh film of aluminium serves as a good reflector of visible light and an excellent reflector of medium and far infrared radiation; the yield strength of pure aluminium is 7–11 MPa, while aluminium alloys have yield strengths ranging from 200 MPa to 600 MPa. Aluminium has stiffness of steel, it is machined, cast and extruded. Aluminium atoms are arranged in a face-centered cubic structure. Aluminium has a stacking-fault energy of 200 mJ/m2. Aluminium is a good thermal and electrical conductor, having 59% the conductivity of copper, both thermal and electrical, while having only 30% of copper's density. Aluminium is capable of superconductivity, with a superconducting critical temperature of 1.2 kelvin and a critical magnetic field of about 100 gauss.
Aluminium is the most common material for the fabrication of superconducting qubits. Aluminium's corrosion resistance can be excellent due to a thin surface layer of aluminium oxide that forms when the bare metal is exposed to air preventing further oxidation, in a process termed passivation; the strongest aluminium alloys are less corrosion resistant due to galvanic reactions with alloyed copper. This corrosion resistance is reduced by aqueous salts in the presence of dissimilar metals. In acidic solutions, aluminium reacts with water to form hydrogen, in alkaline ones to form aluminates—protective passivation under these conditions is negligible; because it is corroded by dissolved chlorides, such as common sodium chloride, household plumbing is never made from aluminium. However, because