Difference between revisions of "Bicycle"
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== Shifters ==
== Shifters ==
Revision as of 15:24, 14 February 2008
Frame type: Mt. Fury Mountain bike
Frame materials: Handcrafted, women's-style, high-tensity steel frame
Gearing/Shifters: 15-speed, rear-index shifting with torque drive
Brakes: Front and rear steel caliper brakes
Wheels: 24" x 1.95" MTB all-terrain tires
Anatomically-padded sport saddle
Element Brand MTB all-terrain bar and stem
Oversized, high-tensity, steel rigid fork
Element brand MTB all-terrain bar and stem
High-impact, resin brake levers
Anatomically-padded sport saddle
Silver, powder-coated, 36-spoke rims One-piece, hot-forged, steel crank set 5-speed 14-28T index freewheel
Click here to download the full CAD Assembly model of the bicycle (unzip the two files in the same folder):
The rear derailleur is the parallel linkage at the back of the bike which uses springs and wheels to change gears. The mechanism works by "derailling" or forcing the chain sideways from one sprocket to the next. For more details on the derailleur, click here: Bicycle_Derailleur
The chain is used to propell the bicycle by tranferring power from the pedals to the rear wheel. For more details on the chain, click here: Bicycle_Chain
Brakes can be any mechanism used to slow the progress of a bicycle. They are important safety and control features. There are many varieties of brake systems, the most common being front and rear rim brakes on modern production bicycles. For more details on the brakes, click here Bicycle_Brakes
Rear Hub & Gears
With the addition of gears on bicycles, people could maintain higher speeds while keeping wheel sizes small. For more details on the gears, click here Bicycle_Gears
The Bottom Bracket is the piece that connects the two crank arms which are connected to the pedals to the bottom of the frame. The bottom bracket contains threads which securely hold them into the frame. For more details on the bottom bracket, click here: Bicycle_Bottom_Bracket
Pedals and Crank Arms
The Pedals are the part of a Bicycle that the rider drives with their feet to propel the bicycle.
The crank arm is the component of the bicycle that transfers the force exerted on the pedals to the crankset. There are two main types of Crank_Arms.
Fork and Handlebar
The front wheel of the bike is connected to the fork, which is in turn connected to the frame of the bike via the head tube. Different mechanisms are used to attach the wheel to the fork, but the most commonly used method is by a quick release system. The handle bar is connected to the fork inside the head tube to allow rotation of the fork/front wheel for steering. A number of configurations for the handle bar and fork have been developed to accommodate the needs of different riders.
For more information on the fork click here: Bicycle_Fork
For more information on the fork/head tube/handle bar assembly click here: Bicycle_Front_Assembly
The seat supports most of the bicycle rider's weight. For more details on the seat, click here: Bicycle_Seat
Bicycle wheels connect to the frame and fork via dropouts. Front hub, spokes, rim, tires, and the quick release mechanism form the wheel. For more details on the wheels, click here: Bicycle_Wheels
The Rover "Diamond Frame" Safety was invented in 1885 by John Starley in England. The most popular materials used in the construction of the diamond frame are steel, aluminum, titanium, or carbon fiber. For more details on the frame, click here: Bicycle_Frame
http://gicl.cs.drexel.edu/wiki/Shifters Friction shifters
Friction shifters use levers mounted on the top, down, or head tube of a bicycle frame. The levers are connected via steel cables to derailleurs, which are mechanisms that switch the chain from gear to gear. Pulling the lever puts the cable into tension or relaxation, which either pulls or releases the derailleur and pushes the chain to a different gear. Friction shifters do not have set stops in the shift point. The rider has to manually adjust the lever so that the chain is centered on the gear. Lining up the chain and gear is more difficult on this type of shifter, but it is easier to set up initially because it does not require much fine tuning. This lever system started with just two or three gears and eventually went up to five and six gears. Friction shifters were generally considered harder to use, and had problems such as unwanted shifts and noisy operation. The use of friction shifters has been eased with the invention of things such as ramped gears and idler or floating gears on the derailleurs.
Index shifters are not a separate type of shifter but an innovation in shifting technology. Indexed shifters can be levers like friction shifters, or handlebar mounted triggers or twisters. These shifters function differently than friction shifters in that they have set shift points for each gear. This means that each gear has a set position on the shifter. Once in position, the position cannot be fine tuned by using the shifter. The position of each preset shift point is determined by setup and tuning of the derailleurs. The positions need to be set perfectly from a static position since they are not adjustable while being ridden. This type of operation is preferred over friction shifters because of the ease of shifting while riding. Major drawbacks include a more difficult set up and incompatibility with other brands. Most index shifters work with specific parts, unlike friction shifters which worked with almost any part brand.
Brifter or dual control levers
While index shifters were an improvement to friction shifters the rider still lost some riding stability when shifting gears. This issue was resolved with the introduction of the Brifter. The system combines an index shifter into each brake lever and for this reason became known as a Brifter. This system allows the rider to shift quickly and accurately without sacrificing stability which is important during a race. Brifters are often combined with cassette modifications which allow the chain to transfer power during a shift which utilizes the Brifters rapid shifting capabilities. The downside to Brifters are there cost and complexity. Due to the large number of moving parts they can be less reliable because there functionality depends of cable tension. Over time cables stretch and require routine tightening to ensure adequate performance. Finally some brands are almost impossible to be rebuilt; Shimano STI levers in particular are notorious for this resulting in a large expense to be replaced if one fails.
Rear spring-damper suspension systems were not widely commercially available on mountain bikes until the early 1990's. In combination with front shocks the bikes were coined with the term "full suspension frames". However, the concept was developed more than a century before. Evolution_Rear_Shock