Bicycle pedal
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A bicycle pedal provides the connection between the cyclist's foot or shoe and the crankarm allowing the leg to be used to turn the crank. Pedals usually consist of a spindle that threads into the crankarm and a body, on which the foot rests or is attached, that is free to rotate on bearings with respect to the spindle.
The Velocipede, a predecessor to the bicycle, lacked pedals but allowed the crank to be operated by means of a treadle. Pedals were initially attached to crankarms connecting directly to the driven (usually front) wheel. The safety bicycle as we know it today came into being when the pedals were attached to a crankarm driving a ring gear that transmitted power to the driven wheel by means of a chain.
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[edit] Flat & Platform
Traditionally, platform pedals were pedals with a relatively large flat area for the foot to rest on, in contrast to the quill pedal which had very little surface area.
One form of the platform pedal had a large flat top area and flat bottom with large "flip-up" tabs for use with toe clips and toe straps designed for greater cornering clearance, which was often needed on the track. The pedals were designed with a larger topside for better leverage and a smaller underside for less potential contact with the track.
Today, platform pedals refer to any flat pedal (typically for mountain biking and BMX) without a cage. MTB and BMX riders alike prefer platforms to cage pedals because they offer more grip using short metal studs, are rounder and do less damage to a rider's shins and ankles during an accident. Cage pedals will often scrape skin and flesh off the shin if the rider stops short and loses footing of the pedal.
Platform pedals are available in a wide variety of types and price ranges, ranging from disposeable plastic units used for test rides on new bicycles to high-end downhill models. Budget models may be made of steel or aluminum and incorporate reflectors for safer riding on streets at night. Less expensive platform pedals are generally considered disposeable and cannot be rebuilt when worn out.
More expensive platform pedals for the mountain bike market are available with replaceable metal traction pins and cartridge bearings. In recent years lightweight pedals intended for Freeride and downhill cycling have been made from exotic alloys such as magnesium.
Toe clips typically aren't installed on this type of pedal because they are considered unsafe by some MTB and BMX riders.
[edit] Cages & Toe clips
Very early pedals were simply platforms (with a rotating axis) on which the cyclist could press downward with the foot. Then cages called toe clips were added to help keep the foot in place.
Cages now refer to pedals that can accommodate toe clips and not necessarily the clips themselves, they are more specifically called quill pedals. The actual cage is the outer part of a conventional pedal, the part that comes into contact with the rider's shoe and has holes where toe clips can be secured by screws. Toe straps used with clips further secure the foot to the pedal and to allow the cyclist to apply power on the upstroke by pulling against the pedal. Traditionally toe straps could be used with toe clips in conjunction with slotted cycling shoes. The clip is generally made of metal or high impact plastic. The strap is generally made of leather or nylon.
The main difference between track, road, and touring quill pedals is width. Track pedals are narrow and the front and back plates of the cage are separate, road being a little wider with a one piece cage in a shape of a sideways "U", and touring being the widest to allow for comfort when used with wider, non-racing shoes during longer rides.
While quill pedals can be used for mountain biking, they are not ideal since use of clips for MTB is dangerous and they do not offer substantial grip. Cage pedals built for mountain biking are typically serrated so that even when muddied, the pedals can be gripped well by any flat shoe.
Although quill pedals can be used with smoothed-soled cycling shoes or ordinary shoes, they were designed to be used with cycling shoes which had a slotted shoeplate attached to its sole. The slot in the shoeplate fits into the rear plate of the pedal, and together with the toe strap and to a lesser extend the toeclip, the shoe is held firmly to the pedal. The disadvantage with this system is that to remove the shoe from the pedal a rider had to reach down and loosen the toestrap by hand--or, more commonly with casual riders, leave the toe strap loose and thus give up some efficiency. This type of pedal and shoe were used by all racing cyclists until the mid to late 1980s.
[edit] Clipless pedals
Clipless pedals (also clip-in or step-in) require a special cycling shoe with a cleat fitted to the sole, which interfaces with a locking mechanism on the pedal. Clipless refers to not using an external toe clip.
The clipless pedal was invented by Charles Hanson in 1895. It allowed the rider to twist the shoe to lock and unlock, and had rotational float. [1]
The first modern clipless pedal was designed by Cino Cinelli and produced by his company in 1971. The M71, as it was known, utilized a plastic shoe cleat which slid into grooves in the pedal and locked in place with a small lever located on the back side of the pedal body. While this system attached the foot of the cyclist to the pedal very securely, it was in some ways unsafe because the shoe could not be released from the pedal without manually actuating the locking lever. This meant that in a situation where a cyclist would have to quickly put a foot down with little or no warning, they would likely fall over because they would not have the time or necessarily be in a position to reach down and pull the unlocking lever.
In 1984, the French company LOOK applied downhill snow skiing binding or cleat technology to pedals producing the first practical clipless pedals. Bernard Hinault's victory in Tour de France in 1985 helped secure the acceptance of quick-release clipless pedal systems by cyclists. Those pedals, and compatible models by other manufacturers, remain in widespread use today. The cleat is engaged by simply pushing down and forward on the pedal, or, with some designs, by twisting the cleat in sideways. Then, instead of pulling a lever, the cyclist releases a foot from the pedal by twisting the heel outward. First time clipless users may forget to unclip when coming to a stop, which usually results in an embarrassing sideways fall at very low speed and some bruises. Some practice in a forgiving environment is advisable, especially as new pedals (and cleats) can be stiff and require a considerably degree of force to release.
Cycling shoes have stiff or rigid soles to maximize power transfer and efficiency. They may be specific to road or mountain biking, or usable for both. Shoes designed for mountain biking typically have recessed cleats that do not protrude beyond the sole of the shoe, and have treads for walking on trails, as walking the bike is frequently necessitated. This slightly compromises the design, and power transfer and efficiency can be adversely affected. Road cycling shoes are designed with the assumption that the cyclist will remain riding always, and they normally have a protruding cleat – which makes them awkward for walking and is prone to damage – and a completely rigid sole.
Mountain bike cleats can generally be mounted without difficulty to road shoes although sometimes an adapter is required. The inverse is not normally true as the cleats used with road pedals are normally too large. The smaller mountain bike cleats are attached to the sole of the shoe by two bolts; larger road-specific cleats are attached by three.
Various other manufacturers have produced their own design of clipless pedal systems over the years, most notably BeBop, LOOK, Speedplay, Time, and Shimano.
[edit] Attachment to crank arm
The pedal spindle is threaded to match a threaded hole at the outboard end of the crank arms. Adult or multi-piece cranks have a 9/16 inch hole with 20 TPI (a diameter/pitch combination fairly unique to this application). One-piece or kids cranks use a 1/2 inch hole.
The right-side (usually the drive-side) pedal spindle is right-hand threaded, and the left-side (usually the non-drive-side) pedal spindle is left-hand (reverse) threaded to help prevent it from becoming loose by an effect called precession.
Although the left pedal turns clockwise on its bearing relative to the crank arm (and so would seem to tighten a right-hand thread), the force from the rider's foot presses the spindle against the crank arm thread at a point which rolls around clockwise with respect to the crank arm, thus slowly pulling the outside of the pedal spindle anticlockwise (counterclockwise) because of friction and thus would loosen a right-hand thread.
[edit] Manufacturers of Pedals
[edit] See also
[edit] References
- ^ The History of the Bicycle Pedal. Retrieved on May 28, 2006.
