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Material Selection For A Bicycle

Material Selection For A Bicycle



Material Selection For A Bicycle

Material Selection For A Bicycle



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    Material Selection For A Bicycle Material Selection For A Bicycle Presentation Transcript

      • 2008-2009
      • Erasmus Student
      • Prepared by Hasan YARICI
    • Contest
      • Cover………………………………………………………………………..3
      • Part of bicycles …………………………………………………………….4
      • Bicycle Frame ……………………………………………………………5
      • Frame materials ……………………………………………………………7
      • Steel …………………………………………………………………………9
      • Aluminium alloys …………………………………………………………..11
      • Titanium …………………………………………………………………….13
      • Magnesium …………………………………………………………………13
      • Carbon Fiber …………………………………………………………..........14
      • Bicycle fork ………………………………………………………………….15
      • Bicyle suspansion……………………………………………………………17
      • Bicycle Chain…………………………………………………………………18
      • Bicycle Gearing ………………………………………………………………19
      • Reference Page ………………………………………………………………20
    • Material Selection For A Bcycle *1
    • Part of Bcycles *3
    • Bicycle Frames A bicycle frame is the main component of a bicycle, onto which wheels and other components are fitted. The modern and most common frame design for an upright bicycle is based on the safety bicycle, and consists of two triangles, a main triangle and a paired rear triangle. This is known as the diamond frame . In the diamond frame, the main triangle consists of the head tube, top tube, down tube and seat tube. The rear triangle consists of the seat tube, and paired chain stays and seat stays. The head tube contains the headset, the interface with the fork. The top tube connects the head tube to the seat tube at the top, and the down tube connects the head tube to the bottom bracket shell. The rear triangle connects to the rear dropouts, where the rear wheel is attached. It consists of the seat tube and paired chain stays and seat stays. The chain stays run parallel to the chain, connecting the bottom bracket to the rear dropouts. The seat stays connect the top of the seat tube (often at or near the same point as the top tube) to the rear dropouts *1
    • Bcycle Frames There are different kind of Bcycle Frame.We can use for a frame carbon fiber ,aleminium alloys or pure steel.but for some racing bcycle titanium can be used.but that material is really expensive.now ı will search these materials BMX Mountain Bicycle Touring Bicycle Racing Bicycle *4 *7 *5 *6
    • Frame Materials
      • Generally, the tubes of the frame are made of steel. Steel frames can be very inexpensive carbon steel to highly specialised using high performance alloys. Frames can also be made from aluminum alloys, titanium, carbo n fiber, and even wood or bamboo . Occasionally, diamond (shaped) frames have been formed from sections other than tubes. These include I-beams and monocoque. Materials that have been used in these frames include wood (solid or laminate), magnesium (cast I-beams), and thermoplastic. Several properties of a material help decide whether it is appropriate in the construction of a bicycle frame:
      • Density (or specific gravity) is a measure of how light or heavy the material per unit volume.
    • Frame Materials
      • Stiffness (or elastic modulus) can in theory affect the ride comfort and power transmission efficiency. In practice, because even a very flexible frame is much more stiff than the tires and saddle, ride comfort is in the end more a factor of saddle choice, frame geometry, tire choice, and bicycle fit. Lateral stiffness is far more difficult to achieve because of the narrow profile of a frame, and too much flexibility can affect power transmission, primarily through tire scrub on the road due to rear triangle distortion, brakes rubbing on the rims and the chain rubbing on gear mechanisms. In extreme cases gears can change themselves when the rider applies high torque out of the saddle.
      • Yield strength determines how much force is needed to permanently deform the material (for crash-worthiness).
      • Elongation determines how much deformity the material allows before cracking (for crash-worthiness).
      • Fatigue limit and Endurance limit determines the durability of the frame when subjected to cyclical stress from pedaling or ride bumps.
      • Tube engineering and frame geometry can overcome much of the perceived shortcomings of these particular materials.
    • STEEL
      • Steel frames are often built using various types of steel alloys including chromoly. They are strong, easy to work, and relatively inexpensive, but denser (heavier) than many other structural materials. Steel tubing in traditional standard diameters is often less rigid than oversized tubing in other materials; this flex allows for some shock absorption giving the rider a slightly less jarring ride compared to other more rigid tubings such as oversized aluminum.
      • A classic type of construction for both road bicycles and mountain bicycles uses standard cylindrical steel tubes which are A high-quality steel frame is lighter than a regular steel frame. This lightness makes it easier to ride uphill, and to accelerate on the flat. Also many riders feel thin-walled lightweight steel frames have a "liveliness" or "springiness" quality to their ride.
      • If the tubing label has been lost, a high-quality (chromoly or manganese) steel frame can be recognized by tapping it sharply with a flick of the fingernail. A high-quality frame will produce a bell-like ring where a regular-quality steel frame will produce a dull thunk. They can also be recognized by their weight (around 2.5 kg for frame and forks) and the type of lugs and dropouts used
      • connected with lugs . Lugs are fittings made of thicker pieces of steel. The tubes are fitted into the lugs, which encircle the end of the tube, and are then brazed to the lug. Historically, the lower temperatures associated with brazing (silver brazing in particular) had less of a negative impact on the tubing strength than high temperature welding, allowing relatively light tube to be used without loss of strength
      • . Recent advances in metallurgy ("air hardening ’’) have created tubing that is not adversely affected, or whose properties are even improved by high temperature welding temperatures, which has allowed both TIG & MIG welding to sideline lugged construction in all but a few high end bicycles. More expensive lugged frame bicycles have lugs which are filed by hand into fancy shapes - both for weight savings and as a sign of craftsmanship. Unlike MIG or TIG welded frames, a lugged frame can be more easily repaired in the field due to its simple construction. Also, since steel tubing can rust, the lugged frame allows a fast tube replacement with virtually no physical damage to the neighbouring tubes.
      • A more economical method of bicycle frame construction uses cylindrical steel tubing connected by TIG welding, which does not require lugs to hold the tubes together. Instead, frame tubes are precisely aligned into a jig and fixed in place until the welding is complete. Fillet brazing is another method of joining frame tubes without lugs. It is more labor intensive, and consequently is less likely to be used for production frames. As with TIG welding, Fillet frame tubes are precisely notched or mitred and then a fillet of brass is brazed onto the joint, similar to the lugged construction process. A fillet braze frame can achieve more aesthetic unity (smooth curved appearance) than a welded frame.
      • Among steel frames, using butted tubing reduces weight and increases cost. Butting means that the wall thickness of the tubing changes from thick at the ends (for strength) to thinner in the middle (for lighter weight).
      • Cheaper steel bicycle frames are made of mild steel, such as might be used to manufacture automobiles or other common items. However, higher-quality bicycle frames are made of high strength steel alloys (generally chromium-molybdenum, or "chromoly" steel alloys) which can be made into lightweight tubing with very thin wall gauges. One of the most successful older steels was Reynolds "531", a manganese-molybdenum alloy steel. More common now is 4130 ChroMoly or similar alloys. Reynolds and Columbus are two of the most famous manufacturers of bicycle tubing. A few medium-quality bicycles used these steel alloys for only some of the frame tubes. An example was the Schwinn Le tour (at least certain models), which used chromoly steel for the top and bottom tubes but used lower-quality steel for the rest of the frame.
    • Aluminum Alloys
      • Aluminum alloys have a lower density and lower strength compared with steel alloys, but what interests us here, is the better strength-to-weight ratio of aluminum giving it significant weight savings over steel. Early aluminum structures have shown to be more vulnerable to fatigue, such as due to vibrations, either due to ineffective alloys, or imperfect welding technique being used. This contrasts to some steel and titanium alloys, which have clear fatigue limits and are easier to weld or braze together. However, this has changed, with more skilled labor capable of producing better quality welds, automation (especially in Taiwan where they have developed an expertise for this), and the greater accessibility of the same modern aluminum alloys as used in commercial airliners' structures, assuring strength and reliability comparable to any steel frame. Aluminum's attractive strength to weight ratio as compared to steel, and certain mechanical properties, assure it a place among the favored frame-building materials (for example, a very strong rider, who does lots of hill-climbing, may prefer the stiffness of aluminum). Its disadvantages are that an aluminum frame doesn't have the same "feel" to an experienced cyclist as a steel frame, and there is a new trend, among bicycling enthusiasts and advanced riders, to going back to steel, trading the dead feel of aluminum for the live, springy responsiveness of steel (or that of titanium, for those who can afford it).
      • Shaped aluminum downtube with keyhole cross-section. It is connected to a dual chain stay made from carbon fiber. The aluminum parts were TIG-welded, and the carbon fiber parts are glued onto the aluminum sections.
      • The most popular type of construction today uses aluminum alloy tubes that are connected together by Tungsten Inert Gas (TIG) welding. Welded aluminum bicycle frames started to appear in the marketplace only after this type of welding became economical in the 1970s.
      • Aluminum has a different optimal wall thickness to tubing diameter than steel. It is at its strongest at around 200:1 (diameter:wall thickness), whereas steel is a small fraction of that. However, at this ratio, the wall thickness would be comparable to that of a beverage can, far too fragile against impacts. Thus, aluminum bicycle tubing is a compromise, offering a wall thickness to diameter ratio that is not of utmost efficiency, but gives us oversized tubing of more reasonable aerodynamically acceptable proportions and good resistance to impact. This results in a frame that is significantly stiffer than steel. While many riders claim that steel frames give a smoother ride than aluminum because aluminum frames are designed to be stiffer, that claim is of questionable validity: the bicycle frame itself is extremely stiff vertically because it is made of triangles, the sides of which do not change in length under stress. [10] On the other hand, lateral and twisting (torsional) stiffness improves acceleration and handling in some circumstances.
      • Aluminum frames are generally recognized as having a lower weight than steel, although this is not always the case. An inexpensive aluminum frame may be heavier than an expensive steel frame. Butted aluminum tubes—where the wall thickness of the middle sections are made to be thinner than the end sections—are used by some manufacturers for weight savings. Beware of marketing-motivated "innovations" which include the shaping of the cross-section of the tubes, especially that of the (large diagonal main) down tube, such as oval or teardrop shapes, to reduce wind resistance. The down tube is considered the "backbone" of the bicycle, and resists strong torsional forces from the rider while keeping everything together. Turbulence from the front wheel and head tube, plus the fact that a tube at an angle already looks like an oval into the direction of the wind, shed serious doubt on any important benefits of using such mechanically unsound shapes to cheat the wind. Indeed, an ovalized, teardrop, or triangular shaped tube is much easier to buckle or collapse under extreme torsional stress testing and will fail far before a perfectly round one shows any signs of flinching. The (almost vertical) seat tube is also often ovalized to cheat the wind. This again, is marketing motivated, as the rider pays as some of the pedaling energy is lost as it is diverted into flexing this tube from side to side. The seat tube is already in the wind-shadow of the front wheel and downtube, thus, aerodynamic benefits are very limited. Some very expensive bicycles, costing in the thousands of dollars, can be found on the market, where marketing instead of sound engineering principles lead the way.
    • Titanium
      • Titanium is perhaps the most exotic and expensive metal commonly used for bicycle frame tubes. It combines many desirable characteristics, including a high strength to weight ratio and excellent corrosion resistance. Reasonable stiffness (roughly half that of steel) allow for many titanium frames to be constructed with "standard" tube sizes comparable to a traditional steel frame, although larger diameter tubing is becoming more common for more stiffness. As many titanium frames can be much more expensive than similar steel alloy frames, cost can put them out of reach for many cyclists. Many common titanium alloys and even specific tubes were originally developed for the aerospace industry.
      • Titanium frame tubes are almost always joined by Tungsten inert gas (TIG) welding , although vacuum brazing has been used on early frames. It is more difficult to machine than steel or aluminum, which sometimes limits its uses and also raises the effort (and cost) associated with this type of construction.
      • Magnesium
      • A handful of bicycle frames are made from magnesium which has around 64% the density of aluminum. In the 1980s, an engineer, Frank Kirk, devised a novel form of frame that was die cast in one piece and composed of I beams rather than tubes. A company, Kirk Precision Ltd, was established in Britain to manufacture both road bike and mountain bike frames with this technology. However, despite some early commercial success, there were problems with reliability and manufacture stopped in 1992.The small number of modern magnesium frames in production are constructed conventionally using tubes.
      • Reportedly, a major problem with these frames is corrosion caused by the chemical reactivity of magnesium. Unless care is taken during assembly of the bicycle, there is likely to be galvanic corrosion at points where steel or aluminum components attach to the frame.
    • Carbon Fiber
      • Carbon fiber, a composite material, is an increasingly popular non-metallic material commonly used for bicycle frames.Although expensive, it is light-weight, corrosion-resistant and strong, and can be formed into almost any shape desired. The result is a frame that can be fine-tuned for specific strength where it is needed (to withstand pedaling forces), while allowing flexibility in other frame sections (for comfort). Custom carbon fiber bicycle frames may even be designed with individual tubes that are strong in one direction (such as laterally), while compliant in another direction (such as vertically). The ability to design an individual composite tube with properties that vary by orientation cannot be accomplished with any metal frame construction commonly in production
      • Some carbon fiber frames use cylindrical tubes that are joined with adhesives and lugs, in a method somewhat analogous to a lugged steel frame. Another type of carbon fiber frames are manufactured in a single piece, called monocoque construction. While these composite materials provide light weight as well as high strength, they have much lower impact resistance and consequently are prone to damage if crashed or mishandled. It has also been suggested that these materials are vulnerable to fatigue failure, a process which occurs with use over a long period of time.
      • Many racing bicycles built for individual time trial races and triathlons employ composite construction because the frame can be shaped with an aerodynamic profile not possible with cylindrical tubes, or would be excessively heavy in other materials. While this type of frame may in fact be heavier than others, its aerodynamic efficiency may help the cyclist to attain a higher speed and consequently outweigh other considerations in such events.
      • Other materials besides carbon fiber, such as metallic boron, can be added to the matrix to enhance stiffness further.
    • Bcycle Fork
      • A bicycle fork is the portion of a bicycle that holds the front wheel and allows the rider to steer and balance the bicycle. A fork consists of two dropouts which hold the front wheel axle, two blades which join at a fork crown , and a steerer or steering tube to which the handlebars attach (via a stem) allowing the user to steer the bicycle. The steerer of the fork interfaces with the frame via a set of bearings known as a headset mounted in the head tube.
      • Forks have been made from steel, aluminum, carbon fiber, titanium, magnesium, and various combinations. For example, a fork may have carbon fiber blades with an aluminum crown, steer tube, or dropouts.
      • In rigid forks the material, shape, weight, and design of the forks can noticeably affect the feel and handling of the bicycle. Carbon fiber forks are popular in road bicycles because they are light, and also because they can be designed to lessen and absorb vibrations from the road surface.
      • Forks may have attachment points for brakes, racks, and fenders. These may be located in the crown, along the blades, and near the dropouts. These are often holes, threaded or not, and may be located on tabs that protrude.
      • On most mountain bicycles, the fork contains a set of shock absorbers, in which case the blades typically consist of upper and lower telescoping tubes and are called "legs." The suspension travel and handling characteristics vary depending on the type of mountain biking the fork is designed for. For instance, manufacturers produce different forks for cross-country (XC), downhill, and freeride riding. Forks designed for XC racing are typically lighter, less robust and have less suspension travel than those designed for rougher terrain and more extreme conditions.
      • Bicycle forks usually have an offset, or rake ( not to be confused with a different use of the word rake in the motorcycle world ), that places the dropouts forward of the steering axis. This is achieved by curving the blades forward, angling straight blades forward, or by placing the dropouts forward of the centerline of the blades. The latter is used in suspension forks that must have straight blades in order for the suspension mechanism to work. Curved fork blades can also provide some shock absorption.
      • Shape of a bicycle fork
      • The purpose of this offset is to reduce 'trail', the distance that the front wheel ground contact point trails behind the point where the steering axis intersects the ground. Too much trail makes a bicycle feel difficult to turn.
      • Virtually all road racing bicycle forks have an offset of 43-45mm due to the almost-standard frame geometry and 700c wheels, so racing forks are widely interchangeable. For touring bicycles and other designs, the frame's head angle and wheel size must be taken into account when determining offset, and there is a narrow range of acceptable offsets to give good handling characteristics. The general rule is that a slacker head angle requires a fork with more offset, and small wheels require less offset than large wheels.
      • Fork offset influences geometric trail, which affects a bicycle's handling characteristics. Increasing offset results in decreased trail, while decreasing offset results in increased trail.
    • Bicycle Suspansion
      • Bicycle suspension refers to the system or systems used to suspend the rider and all or part of the bicycle in order to protect them from the roughness of the terrain over which they travel. Bicycle suspension are used primarily on mountain bicycles, but are also common on hybri d bicycles, and can even be found on some road bicycles.
      • Bicycle suspension can be implemented in a variety of ways:
      • Suspension front fork
      • Suspension stem (although these have fallen out of favor)
      • Suspension seatpost
      • Rear suspension
      • or any combination of the above. Bicycles with suspension front forks and rear suspensions are referred to as full suspension bikes . Additionally, suspension mechanisms can be incorporated in the seat or saddle, or the hubs.
      • Besides providing obvious rider comfort, suspensions improve both safety and efficiency by keeping one or both wheels in contact with the ground and allowing the rider's mass to move over the ground in a flatter trajectory.
      • There are two kind of bicycle suspansion.rear suspansion and fron suspansion
      • Especially we can see it in mountains bicycles.
    • Bicycle chain
      • A bicycle chain is a roller chain that transfers power from the pedals to the drive-wheel of a bicycle, thus propelling it. Most bicycle chains are made from plain carbon or alloy steel, but some are chrome-plated or stainless steel to prevent rust, or simply for aesthetics.
      • How best to lubricate a bicycle chain is a commonly debated question among cyclists. [2] Liquid lubricants penetrate to the inside of the links and are not easily displaced, but quickly attract dirt. "Dry" lubricants, often containing wax or Teflon, are transported by an evaporating solvent, and stay cleaner in use.
      • In order to reduce weight, chains have been manufactured with hollow pins and with cut-outs in the links. A few titanium chains have also been made, but while much lighter they are vastly more expensive, perhaps 10x the cost, and the titanium bearing surfaces reportedly wear quickly, leading to shortened life and reduced efficiency.
      • Bicycle chains are made by companies such as Campagnolo Rohloff AG KM C Shimano SRAM
      • Sizes; t he chain in use on modern bicycles has a 1/2" pitch, which is ANSI standard #40, where the 4 indicates the pitch of the chain in eighths of an inch, and metric #8, where the 8 indicates the pitch in sixteenths of an inch.
      • Meanwhile there re some chainless bicycle which is a bicycle that transmits power to the driven wheel through a mechanism other than a chain directly driven "ordinary" bicycle ,shaft-driven bicycle belt-driven bicycle ,hydraulic bicycle,(and pneumatic bicycle) hybrid vehicle)
    • Bicycle gearing
      • The gearing on a bicycle is the selection of appropriate gear ratios for optimum efficiency or comfort. Different gears and ranges of gears are appropriate for different people and styles of cycling. Multi-speed bicycles allow gear selection to suit the circumstances, e.g. it may be comfortable to use a high gear when cycling downhill, a medium gear when cycling on a flat road, and a low gear when cycling uphill.
      • On a bicycle, power is transmitted from the rider's legs to the rear wheel via the pedals, crankset, chain or shaft, and rear hub. A cyclist's legs produce power optimally within a narrow pedalling speed range. Gearing is optimized to use this narrow range as best as possible. As in other types of transmissions, the gear ratio is closely related to the mechanical advantage of the drivetrain of the bicycle. On single-speed bicycles and multi-speed bicycles using derailleur gears, the gear ratio is the ratio of the number of teeth on the chainring of the crankset to the rear cog or sprocket, or the ratio of bevel gears on a shaft-driven bicycle. In the case of a derailleur-equipped bicycle, this sprocket is one of several composing the cogset. On hub gears, the ratio is determined by the internal planetary gears within the hub.
      • For a bicycle to travel at the same speed, set to a lower gear (larger mechanical advantage) it will require the rider to pedal at a faster cadence, but with less force. Conversely, a higher gear (smaller mechanical advantage) provides a higher speed for a given cadence, but requires the driver to exert greater force. Different cyclists may have different preferences for cadence and pedaling force. Prolonged exertion of too much force in too high a gear at too low a cadence can increase the chance of knee damage, whereas extremely great cadence and little force maintained at too a low gear also is not advised.
    • Reference Page
      • http://www.amazon.com/BBB-Fiberscraper-MTB-Bicycle-Seatpost/dp/B000PKMHGA/ref=acc_glance_sg_ai_-2_2_img
      • http://en.wikipedia.org/wiki/Bicycle
      • web.nchu.edu.tw/~jillc/me/Ch20%20-%20 Materials %20 Selection .pdf
      • http://www.corratec.com/content/en-gb/products/bikes/mtb/bow/?model=superbow_trail&offset=0px&x=67&y=25
      • http://www.bikeschool.com/frame.htm
      • http://www.ransbikes.com/ITR41.htm
      • http://www.torelli.com/tech/material.shtml