material selection for a bicycle

Download Material Selection For A Bicycle

Post on 12-May-2015

10.813 views

Category:

Design

3 download

Embed Size (px)

DESCRIPTION

Material Selection For A Bicycle

TRANSCRIPT

  • 1.MATERAL SELECTON FOR A BICYCLE
    • 2008-2009
  • Erasmus Student
  • Prepared by Hasan YARICI

2. Contest

  • Cover..3
  • Part of bicycles .4
  • Bicycle Frame5
  • Frame materials 7
  • Steel 9
  • Aluminium alloys ..11
  • Titanium .13
  • Magnesium 13
  • Carbon Fiber ..........14
  • Bicycle fork.15
  • Bicyle suspansion17
  • Bicycle Chain18
  • Bicycle Gearing 19
  • Reference Page 20

3. Material Selection For A Bcycle *1 4. Part of Bcycles *3 5. Bicycle Frames Abicycle frameis 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 thediamond 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 6. Bcycle Frames There are different kind of Bcycle Frame.We can use for a framecarbon fiber ,aleminium alloys or pure steel.but for some racing bcycle titanium can be used.but that material is really expensive.now will searchthese materials BMX Mountain Bicycle Touring Bicycle Racing Bicycle *4 *7 *5 *6 7. 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 nfiber, and evenwood 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.

8. 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.

9. 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 2.5kg for frame and forks) and the type of lugs and dropouts used
  • connected withlugs . 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

10.

  • . 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, usingbuttedtubing reduces weight and increases cost.Buttingmeans 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 SchwinnLe 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.

11. 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