Bicycle pedal
Bicycle pedals are at the free ends of the two pedal cranks of the bicycle pedal attached. About it affects the force exerted by the legs driving force of the cyclist, which presses the rotating cranks alternately down. The bike is powered by the co-rotating sprocket on the chain.
History
The invention of the pedal was an important step in the development of the bicycle to its present form. Until the 1860s there were into bicycles in the form of wheels ( track inspection vehicles) or as three-and four-wheeler, which were driven with pedal levers. Cranks were first directly on the impeller of the velocipede by Pierre Michaux and the penny-farthing. Michaux used only one spindle shaft instead of a rotary pedal. The Frenchman Pierre Lallement put 1863 wooden spools on the shaft shafts and thus is considered the inventor of the rotary bicycle pedal. The current standard pedal with ball bearings and rubber treads was probably first used in 1884. Around 1895, the first clipless pedal was used. A pedal with sophisticated leather strap design has been known since 1947 by the Italian cyclist Alfredo Binda.
Construction
Main components of a bicycle pedal is a pedal body and an axle. In general, the pedal body via a pair of ball bearings is mounted on the axis at the inner end has an external thread for screwing it into the threaded hole of the pedal crank.
The force of the foot is taken off the pedal body. It generates on the pedal to the pedal crank, a torque, which is passed over the chain drive to the rear wheel of the bicycle, and the drive effected.
The bearings must both pedaling and when getting on and off and the rider's weight to withstand, as also be small. Their diameter determines the minimum thickness of the pedal body. The sleeve of the pedal body, in which they are incorporated, is to remain below the contact surfaces with the foot. Because of these conflicting demands come next ball bearings, double ball bearings, roller bearings or plain bearings quality used.
A pedal body older design consists of several metal parts and two rods made of rubber. The rubber parts are connected at their ends with two metal sheets for a four- piece frame. In the middle of sheets short sleeves for receiving the ball bearings are mounted. These two tubes are additionally connected to a sleeve of smaller diameter, which surrounds the pedal shaft. Pedal body of modern design have a compact casting ( aluminum alloy or carbon fiber reinforced plastic) as the main body, are attached to the only parts for the contact or connection with the shoe in addition.
With sophisticated, modern pedals is the axis of titanium or steel. Very cheap pedals have no bearings, they only consist of a plastic body and a steel axle simple quality. The friction between the pedal body and the axle is significant, the bearings wear quickly.
Mounting on the cranks
The pedal shaft is flattened traditionally between the thread and the inner roller bearing seat for attaching a wrench. Most of these flattening is too narrow for a standard open-end wrench, which is why a special, thinner pedal spanner ( jaw width 15 mm, for the BMX 9/16 inches) should be used.
Today the pedal axes often with an 8- mm hex (Allen) are provided. The Allen key is recognized by the crank inside out. In this solution, a standard torque wrench can be used and the pedal axes can be uniformly strongly attracted. Generally, a tightening torque of 35 Nm is recommended.
Privilege against self- loosening of the cranks
The direction of rotation of the screw is on the right and on the left pedal is not the same. It is in each case chosen such that the pedal axles are protected against self- loosening of the cranks.
To meet a loosening torque, which is caused by the bearing friction in the pedal, the left pedal spindle with right-hand thread and the right pedal axle should be provided with left-hand thread. Actually the situation is reversed.
The reason for this is a second effect, which is opposite to the bearing friction torque and this dominates. It occurs when a pedal axle should not be tightened. The principle of unavoidable radial play in the thread leads in these circumstances mean that the pedal axis is tilted by the force of the foot always slightly downward. The tilt relative to runs to the foot pedals, the pedal axis wobbles (see also nutation ) in its threaded hole. Your tumbling causes them to rotate about its own axis. She rolls namely at the two ends of the internal thread in the crank (pictured left). This process is in a simple experiment with a pencil particularly clear (pictured right).
The direction of rotation of the wobble is on the left pedal clockwise (same as the negligible bearing friction torques ). The rollers causes the pedal shaft to rotate in the counterclockwise direction. She gets a left-hand thread, so that they do more to tighten, if they should become loose. When the right pedal, the situation is reversed, its axis is provided with right-hand thread.
Designs
Block pedal
The block pedal is both the oldest design and the bicycle pedal used as a standard pedal. His pedal body is traditionally made of sheet steel and two profiled rubber blocks, now often made of a single profiled hard plastic block.
Hook pedal
In cycling was until the early 1990s, spread the hook pedal, in which the shoe is held by a hook-shaped bracket which is attached to the pedal and front running is on the instep of the shoe lace. In addition, the foot having a strap that connects the ring-shaped end of the strap to the pedal can be fixed against lateral slipping on the pedal. The belts are designed so that they are at a lateral movement of the foot can resolve itself, but fix the high motion. One can solve or fix pedal straps with a handle.
The device on the pedal is also referred to as a racing hook. Tightening the pedal straps took place at street racers just before a sprint, since hours of driving with unbelted feet is very tiring. Against " eingeschlafene feet " for decades blunt cut Eisensägeblätter were nailed into the racing shoes who took the burden from the tips of the serrated pedals. In track cycling 's feet were strapped in principle.
As the material for the hook initially was metal, usually steel spring, and later plastic used. The belt was originally made of leather, and later synthetic fabric was widespread. In addition, there are designs that consist only of the hook without straps or a belt harness. The latter models were popular with the newly emerging mountain bikes, racing bikes, they were not used.
With the help of hooks pedals can be both stepped down as also pulled upwards. This allows the so-called round kick with which the athlete can provide his service uniform and protect his joints. To make this possible, shoes were early strapped to pedals without the pedals were specifically designed for this.
Clipless pedal
Clipless pedals allow a firm connection of the feet to the pedals, similar to a modern ski binding. These special bike shoes have to be used, is screwed under a metal plate ( Cleat ), which locks in the pedal when the driver puts his foot with enough pressure on the pedal. To disconnect the walk a bit to the side must be rotated.
The first system of this type was developed by the company look. High rates has meanwhile also the SPD system ( Shimano Pedaling Dynamics ) for mountain bikes, recumbent bikes and tour the area. In racing wheels, the look- system and SPD -SL are mainly used. In addition, there are about a dozen other systems.
Characteristic of road bike shoes is that the cleats are screwed with a smooth sole which makes walking difficult. The sole is usually very rigid, to reduce pressure points on the foot, by distributing the pressure over a large area. SPD cleats, however, are sunk and the sole of mountain bike shoes is not so stiff to make carrying sections possible.
The pedals are offered in different designs. Some on both sides have a latching mechanism, other reasons of weight on one side only. So -called combination pedals have on one side with the latch and on the other a cage to provide non- bike shoes sufficient support. There are pedals having a metal frame by the click mechanism around, in order to increase the bearing surface for the shoes. In most systems, the locking mechanism in the pedal, with a few in the cleat instead. Some systems do not have a complex mechanism, but the cleats can be locked with a bayonet type in the pedal.
With the appearance of clipless pedals they were misnamed " Security pedal ", since they supposedly dissolve in any emergency situation from the shoe. In practice, it has been shown that this is not always the case.
Magnetic pedal
This development was submitted by Norbert Sadler and Wolfgang Dürr 2004 patent. This very powerful magnets are built into the pedals while under the shoes steel plates are screwed. The magnetic pedal system allows an arbitrary and changed at any time while driving foot position on the pedal. That helps some riders with knee or joint problems. Solving is carried out by a tilting of the feet or with a firm tug. In a fall, the shoes released from the pedals; entanglement is excluded.
Large area Pedal
Large Area pedals were first developed in 1920 under the name " Marcel Berthet model ". Later, they came every now and then in vogue. A relatively new development is a 2008 patented pedal, which aims to improve the power transfer from the foot to the crank arm felt. It is almost three times as long (16 cm) as a normal pedal. It should also take advantage of the strong pressure exerted by the metatarsal, however, this design prevents a round kick, because the foot rests too far forward on the pedal. Large Area pedals nowadays (as of September 2011) virtually no market significance. Technically, racing pedals with the almost rigid connection between pedal and shoe too large surface pedals.
Platform pedal is another name for large and sturdy pedals. Most of the pedal body is made of one piece. From both sides of the pedal body protrude screws, whereby a very high level of adhesion is achieved. This can be maximized by the use of special shoes on. By the protruding screws the risk of injury is relatively high. Since these Pedalart but is used mainly in downhill and freeride and shin guards are worn here as a rule, the increased risk of injury is largely balanced.
Bear paws are originally from BMX bikes are made of metal and larger than other pedals. The grip of the sheet metal frame facilitates along with treaded soles to grip even in dirty shoes in the terrain, which is why they were used in the dirt jump and downhill mostly. Today they are found primarily on inexpensive bikes.
Pictures
Block pedal with reflectors
Bear Paw
Combined pedals
Magnetic pedal
Large area Pedal