text: (Redirected from Bike frame)
  Historically, women's bicycle frames had a top tube that connected in the middle of the seat tube instead of the top, resulting in a lower standover height. This was to allow the rider to dismount while wearing a skirt or dress. The design has since been used in utility bikes to facilitate easy mounting and dismounting for both genders, and is also known as a step-through frame or an open frame.[3] Another style that accomplishes similar results is the mixte.
  The recumbent bicycle moves the cranks to a position forward of the rider instead of underneath, generally improving the slipstream around the rider without the characteristic sharp bend at the waist used by racers of diamond-frame bicycles. Banned from bicycle racing in France in 1934 to avoid rendering diamond-frame bicycles obsolete in racing,[5] manufacturing of recumbents remained depressed for another half century, but many models from a range of manufacturers were available by 2000.
  Frames that use cables for members that are only under tension,[9][10] such as the Dursley Pedersen pictured.
  Frames with hoops replacing the seat tube, chain stays and seat stays: called "roundtail"s.[11][12]
  The top tube,[13] or cross-bar,[14] connects the top of the head tube to the top of the seat tube.
  In a traditional-geometry diamond frame, the top tube is horizontal (parallel to the ground). In a compact-geometry frame, the top tube is normally sloped downward toward the seat tube for additional standover clearance. In a mountain bike frame, the top tube is almost always sloped downward toward the seat tube. Radically sloped top tubes that compromise the integrity of the traditional diamond frame may require additional gusseting tubes, alternative frame construction, or different materials for equivalent strength.[15][16][17] (See Road and triathlon bicycles for more information on geometries.)
  Step-through frames usually have a top tube that slopes down steeply to allow the rider to mount and dismount the bicycle more easily. Alternative step-through designs may include leaving out the top tube out completely, as in monocoque mainframe designs using a separated or hinged seat tube, and twin top tubes that continue to the rear fork ends as with the Mixte frame. These alternatives to the diamond frame provide greater versatility, though at the expense of added weight to achieve equivalent strength and rigidity.[15][16]
  Many alternatives to the traditional seat stay design have been introduced over the years. A style of seat stay that extends forward of the seat tube, below the rear end of the top tube and connects to the top tube in front of the seat tube, creating a small triangle, is called a Hellenic stay after the British frame builder Fred Hellens, who introduced them in 1923.[18] Hellenic seat stays add aesthetic appeal at the expense of added weight. This style of seat stay was popularized again in the late 20th century by GT Bicycles (under the moniker "triple triangle"), who had incorporated the design element into their BMX frames, as it also made for a much stiffer rear triangle (an advantage in races); this design element has also been used on their mountain bike frames for similar reasons.
  Recently, a variation of the traditional seat stay that bypasses the seat tube and connects further into the top tube was patented by Volagi Cycles.[19] This frame element added length to the traditional design of seat stays, making a softer ride at the sacrifice of frame stiffness.
  Another common seatstay variant is the wishbone, single seat stay, or mono stay,[20] which joins the stays together just above the rear wheel into a monotube that is joined to the seat tube. A wishbone design adds vertical rigidity without increasing lateral stiffness, generally an undesirable trait for bicycles with unsuspended rear wheels.[21] The wishbone design is most appropriate when used as part of a rear triangle subframe on a bicycle with independent rear suspension.
  Fastback seat stays meet the seat tube at the back instead of the sides of the tube.[22]
  There are a few traditional standard shell widths (68, 70 or 73 mm).[23] Road bikes usually use 68 mm; Italian road bikes use 70 mm; Early model mountain bikes use 73 mm; later models (1995 and newer) use 68 mm more commonly. Some modern bicycles have shell widths of 83 or 100 mm and these are for specialised downhill mountain biking or snowbiking applications. The shell width influences the Q factor or tread of the bike. There are a few standard shell diameters (34.798 – 36 mm) with associated thread pitches (24 - 28 tpi).
  saddle height, the distance from the center of the bottom bracket to the point of reference on top of the middle of the saddle.[24]
  stack, the vertical distance from the center of the bottom bracket to the top of the head tube.[25]
  reach, the horizontal distance from the center of the bottom bracket to the top of the head tube.[26]
  bottom bracket drop, the distance by which the center of the bottom bracket lies below the level of the rear hub.[27]
  handlebar drop, the vertical distance between the reference at the top of the saddle to the handlebar.[28]
  saddle setback, the horizontal distance between the front of the saddle and the center of the bottom bracket.[29]
  standover height, the height of the top tube above the ground.[30]
  front center, the distance from the center of the bottom bracket to the center of the front hub.[31]
  toe overlap, the amount that the feet can interfere with steering the front wheel.[32]
  Track frames have much in common with road and time trial frames, but come with rear-facing, horizontal fork ends,[33] rather than dropouts,[34] to allow one to adjust the position of the rear wheel horizontally to set the proper chain tension. Also the seat tube angle is steeper than on road racing bikes.
  The elevated chainstay bicycle was popular in the early 90s. It featured a rear triangle with elevated bottom frame stays, negating the need for the chain to be drawn through the rear frame. This allowed for a shorter wheelbase and improved handling during technical ascents, at the cost of compromised integrity and resultant increased bottom bracket flex (unless reinforced) compared to a frame with traditional chainstays.[35]
  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. Conversely, this very argument calls the claim of aluminum frames having greater vertical stiffness into question.[38] On the other hand, lateral and twisting (torsional) stiffness improves acceleration and handling in some circumstances.
  Frame tubes are almost always joined by Gas Tungsten Arc Welding (GTAW or TIG) welding, although vacuum brazing has been used on early frames.[39] Some earlier titanium frames were made with titanium tubes bonded to aluminum lugs, as e.g. the Miyata Elevation 8000 and the Raleigh Technium Titanium.
  Carbon fiber composite is an increasingly popular non-metallic material commonly used for bicycle frames.[40][41][42][43] 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.[44] 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 can be lightweight and strong, they have much lower impact resistance than traditional materials and consequently are prone to damage or failure if crashed or mishandled.[45][46] Cracking and failure can result from a collision, but also from over tightening or improperly installing components.[47] These materials are also vulnerable to fatigue failure, a process which occurs with use over a long period of time.[48] It is possible for broken carbon frames to be repaired, but because of safety concerns it should be done only by professional firms to the highest possible standards.[49]
  Other materials besides carbon fiber, such as metallic boron, can be added to the matrix to enhance stiffness further.[50] Some newer high end frames are incorporating Kevlar fibers into the carbon weaves to improve vibration damping and impact strength, particularly in downtubes and seat- and chainstays.
  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.[51] The small number of modern magnesium frames in production are constructed conventionally using tubes.[52]
  American Bicycle Manufacturing of St. Cloud, Minnesota, briefly offered a frameset made of beryllium tubes (bonded to aluminum lugs). Given the toxic nature of the material and the pricing ($26,000 for frame and fork), they never caught on. Reports were that the ride was very harsh, but the frame was also very laterally flexible.[53]
  Several bicycle frames have been made of bamboo tubes connected with metal or composite joinery. Aesthetic appeal has often been as much of a motivator as mechanical characteristics.[54][55]
  Several bicycle frames have been made of wood, either solid or laminate. Although one survived 265 grueling kilometers of the Paris–Roubaix race, aesthetic appeal has often been as much of a motivator as ride characteristics.[56] Wood is used to fashion bicycles in East Africa.[57] Cardboard has also been used for bicycle frames.[58]
  Combining different materials can provide the desired stiffness, compliance, or damping in different areas better than can be accomplished with a single material. The combined materials are usually carbon fiber and a metal, either steel, aluminum, or titanium. One implementation of this approach includes a metal down tube and chain stays with carbon top tube, seat tube, and seat stays.[59] Another is a metal main triangle and chain stays with just carbon seat stays.[60] Carbon forks have become very common on racing bicycles of all frame materials.[61]
  A variety of small features — bottle cage mounting holes, shifter bosses, cable stops, pump pegs, cable guides, etc. — are described as braze-ons because they were originally, and sometimes still are, brazed on.[62]
  ^ a b Sheldon Brown. "Glossary: Diamond Frame". Retrieved 16 February 2013. ^ "Sheldon Brown's Bicycle Glossary E - F". sheldonbrown.com. Retrieved 6 February 2017. ^ "Nimrod road tests the Jack Taylor touring bicycle". Cycling. March 16, 1960. Retrieved 2013-04-02. their range of seventeen models includes a woman's open frame bicycle ^ Sheldon Brown. "Sheldon Brown's Bicycle Glossary: Cantilever Frame". Archived from the original on 10 June 2011. Retrieved 2011-07-24. ^ Arnfried, Schmitz (June 1990). "Why your bicycle hasn't changed for 106 years". Cycling Science. ^ Sheldon Brown. "Glossary: Cross Frame". Archived from the original on 13 May 2011. Retrieved 2011-05-04. ^ Herbert Kuner. "Cross Frames". Archived from the original on 24 July 2011. Retrieved 2011-08-18. Other names for bicycles with an extra reinforcing tube were girder frame or truss frame. ^ Sheldon Brown. "Glossary: Cross Frame". Archived from the original on 14 May 2011. Retrieved 2011-05-04. ^ Evans, Paul (March 9, 2009). "Wire Bike uses carbon fiber and Kevlar cables". GizMag. Retrieved 2010-03-14. ^ "The Wire 2009 Viva Bike". Cool Material. Retrieved 2010-03-14. ^ "Tortola Roundtail – A bicycle frame with a twist". BikeRadar. 11 Apr 2011. Retrieved 2011-04-11. ^ Jason Viau (December 7, 2011). "Windsor-bred bike hits big time". The Windsor Star. Retrieved 2011-12-07. The RoundTail bicycle is featured on the front of the January issue of Road Bike Action Magazine — one of the largest international bike publications with a global circulation of 90,000. [permanent dead link]
  Retrieved from "https://en.wikipedia.org/w/index.php?title=Bicycle_frame&oldid=771658042"	Categories: Bicycle partsHidden categories: All articles with dead external linksArticles with dead external links from November 2016Articles with permanently dead external links	Navigation menu
  العربيةCatalàDanskDeutschEspañolFrançaisGalego한국어ItalianoעבריתNederlands日本語Norsk bokmålPolskiPortuguêsРусскийසිංහලУкраїнська	Edit links	This page was last modified on 22 March 2017, at 20:18.