Bicycle pedal
From Free net encyclopedia
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. 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.
The left-hand pedal has a left-hand thread, to prevent it becoming loose from an effect called precession. Although the pedal turns clockwise in its bearing relative to the crankarm, the force from the rider's foot presses the bearing against the crankarm thread at a point which rolls around clockwise, thus slowly pulling the outside of the bearing anticlockwise because of friction.
Toe clips
Early pedals were simply platforms (with a rotating axis) on which the cyclist could press downward with the foot. Later, cages called toe clips were added to help keep the foot in place. Then toe straps were added to both further secure the foot to the pedal and to allow the cyclist to apply power on the upstroke by pulling against the pedal. The clip is generally made of metal or high impact plastic. The strap is generally made of leather or nylon.
Clipless pedals
Image:But rowerowy SPD.jpg 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.
It is generally acepted that the first 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. Instead of pulling a lever, the cyclist releases a foot from the pedal by twisting the heel outward.
Cycling shoes have inflexible soles to maximize power transfer and efficiency. They may be specific to road or mountain biking, or usable for both. Shoes designed for mountain bicycling typically have recessed cleats that do not protrude beyond the sole of the shoe, and have treads for walking on trails. Road bicycling shoes normally have a protruding cleat that makes them somewhat less suited for walking.
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 (bicycles), Time, and Shimano.