Bicycle pedal
Bicycle pedals are pedals attached to the free ends of the two cranks on the bicycle . The driving force exerted with the legs of the cyclist, who alternately presses the rotating cranks with his feet, acts through them. The bike is driven by the rotating chainring via the chain .
history
The invention of the pedal was an important step in the evolution of the bicycle to its current form. Up until the 1860s there were bicycles in the form of running bikes (draisines) or as three- and four-wheelers that were driven by pedal levers. Pedal cranks were first available directly on the wheel of Pierre Michaux's velocipede and on the high wheel . Michaux only used a shaft instead of a rotatable pedal. The Frenchman Pierre Lallement put wooden spools on the shafts in 1863 and is thus considered the inventor of the rotating bicycle pedal. "Another novelty of the bicycle, which was further developed in 1861, was the material used. The wood was replaced by malleable iron and the saddle was spring-loaded, which significantly increased riding comfort."
Almost 30 years later, at the World Exhibition in Paris in 1889 , this innovation was presented to a wider audience. There the bicycle as we know it today received its new name: "Vélocipède bicycle", which freely translated means "two-wheeled fast foot".
It was not until 1878 that roller chains were fitted to bicycles as standard, which enabled a much more efficient power transmission using pedals. Until then, the bicycle pedals were attached to the front axle with a rigid hub.
So it came about that today's standard pedal with ball bearings and rubber treads was probably first used around 1884.
In 1885 the American Charles Hanson invented the first clipless pedals and applied for a patent. Then as now, a special bicycle shoe was necessary to use this type of pedal.
A pedal with a sophisticated leather strap construction was invented in 1947 by the Italian racing cyclist Alfredo Binda and was subsequently used by most professional cyclists.
Around 100 years after the invention of the first clipless pedal by Charles Hanson, the French Bernard Hinault won the most famous cycle race in the world, the Tour de France , with clipless pedals from LOOK - which were launched the year before, in 1994 . Since then, clipless pedals have been the standard pedals in road cycling .
construction
The main components of a bicycle pedal are a pedal body and an axle . As a rule, the pedal body is supported by two ball bearings on the axle, which has an external thread at the inner end, so that it can be screwed into the threaded hole of the crank.
The force of the foot is absorbed by the pedal body. It generates a torque via the pedal on the crank , which is sent via the chain drive to the rear wheel of the bicycle and drives it .
The bearings must be able to withstand the pedaling force and the weight of the rider when getting on and off, and they must also be small. Their diameter determines the minimum thickness of the pedal body. The sleeve of the pedal body in which they are installed should remain below the contact surfaces with the foot. Because of these conflicting requirements, double ball bearings, roller bearings or high-quality plain bearings are used in addition to ball bearings .
An older type of pedal body consists of several metal parts and two rubber rods. The rubber parts are connected at their ends with two metal sheets to form a four-part frame. In the middle of the sheets there are short sleeves to hold the ball bearings. These two sleeves are also connected to a sleeve of smaller diameter that surrounds the pedal axis. Pedal bodies of modern design have a compact cast part ( aluminum alloy or carbon fiber reinforced plastic ) as a base body, to which only parts for contact or connection with the shoe are attached.
With sophisticated, modern pedals, the axle is made of titanium or high-quality steel. Very cheap pedals have no roller bearings, they only consist of a plastic body and a simple steel axle. The friction between the pedal body and the axle is considerable and the bearings wear out quickly.
Mounting on the cranks
The pedal axis is traditionally flattened between the thread and the inner roller bearing seat so that a wrench can be attached. Most this flattening is for a conventional combination wrench too narrow, therefore, a special, thinner pedal-end wrench (jaw width 15 mm, when BMX 9 / 16 inches ) is used.
Today the pedal axles often have an 8 mm hexagon socket ( Allen ). The Allen key is applied from the inside of the crank; A commercially available torque wrench can be used and the pedal axles can be tightened evenly. In general, a tightening torque of 35 Nm is recommended.
Protection against self-loosening from the cranks
The direction of rotation of the thread is different on the right and left pedals. It is selected in such a way that the pedal axles are protected from the pedal cranks from loosening themselves.
In order to meet a loosening torque which is caused by the bearing friction in the pedal, should actually be the left pedal shaft with right-hand threads with, and the right pedal shaft left-hand thread be provided. In fact, it's the other way around. The reason for this is a second effect that opposes and dominates the bearing friction torques. It occurs when a pedal axle is not properly tightened. The in principle unavoidable radial play in the thread leads under these circumstances to the fact that the pedal axis is always tilted slightly downwards by the foot force. The tilt runs relative to the crank, the pedal axis wobbles (see also Nutation ) in its threaded hole. Its tumbling causes it to spin on its own axis. This is because it rolls at both ends of the internal thread in the crank (picture on the left). This process becomes particularly clear with a simple experiment with a pencil (figure on the right).
The direction of rotation of the wobble is clockwise on the left pedal (same as the negligible bearing friction torques). The rolling causes the pedal shaft to rotate counterclockwise. It gets a left-hand thread so that it will tighten sooner if it should become loose. The situation is reversed for the right pedal, its axis has a right-hand thread.
Designs
Block pedal
The block pedal is both the oldest design and the bicycle pedal used as a standard pedal. Its pedal body traditionally consists of sheet steel and two profiled rubber blocks , today often made of a single profiled hard plastic block.
Hook pedal
In cycling , the hook pedal was widespread until the early 1990s , in which the shoe is held by a hook-shaped bracket attached to the pedal and lying on the instep at the front over the toes of the shoe. In addition, the foot can also be fixed on the pedal to prevent it from slipping sideways with a strap that connects the end of the bracket to the pedal in a ring shape. The straps are designed in such a way that they can loosen themselves when the foot moves sideways, but fix the upward movement. Pedal straps can be loosened or fastened with a handle.
The device on the pedal is also known as a racing hook . Road racers only tightened the pedal straps shortly before a sprint, as driving for hours with your feet buckled up is very tiring. For decades, dull-ground hacksaw blades were nailed into racing shoes to prevent feet from falling asleep, taking the strain off the tips of the toothed pedals. In track cycling the feet were strapped in principle.
The material used for the hook was initially metal, mostly spring steel, later also plastic. The belt was originally made of leather, later synthetic fabric was used. There are also versions that only consist of a hook without a strap or a harness. The latter models were popular with the emerging mountain bikes, they were not used on racing bikes.
With the help of hook pedals you can step down as well as pull up. This enables the so-called round kick , with which the athlete can perform more evenly and protect his joints. Most importantly, the front leg does not lift the weight of the rear. In order to enable a round step, shoes were strapped to pedals early on without the pedals being specially designed for this.
Clipless pedal
Clipless pedals enable the feet to be firmly connected to the pedals, similar to a modern ski binding . For this purpose, special cycling shoes must be used, under which a metal or plastic plate ( cleat ) is screwed, which engages in the pedal when the rider puts his foot on the pedal with enough pressure. To release the connection, the foot must be turned a little to the side.
The first system of this kind was developed by the LOOK company. The SPD (Shimano Pedaling Dynamics) system is now widely used on mountain bikes , recumbent bikes and touring. The look system and SPD-SL are mainly used for racing bikes . There are also about a dozen other systems. The two systems SPD (for mountain bikes) and SPD-SL (for racing bikes) are not compatible with each other and require different pedals, pedal plates and shoes.
A characteristic of racing bike shoes is that the cleats are screwed under a smooth sole, which makes walking difficult. The sole is usually very stiff in order to reduce pressure points on the foot by distributing the pressure over a large area. SPD cleats, on the other hand, are countersunk and the soles of mountain bike shoes are not so stiff that they can be worn.
The pedals are available in different versions. Some have a locking mechanism on both sides, others only on one side for reasons of weight. So-called combination pedals have a locking mechanism on one side and a cage ("bear paw") on the other to provide sufficient support for non-cycling shoes. Or the multi-purpose pedals are used to increase flexibility in order to enable comfortable getting on and off in short inner-city passages, while the advantages of a fixed shoe are used over longer distances. There are also pedals that have a metal frame around the click mechanism to increase the contact surface for the shoes. In most systems, the locking mechanism is in the pedal, in a few systems it is in the cleats. Some systems do not have a complex mechanism, but the cleats are locked in the pedal with a kind of bayonet lock.
When the clipless pedals appeared, they were misleadingly referred to as “safety pedals” because they supposedly come off the shoe in every emergency. Practice has shown that this is not always the case.
Clipless pedals (System Look)
Clipless pedal (Shimano SPD system)
Clipless pedal (Shimano SPD-R system)
PD7700
eggbeater pedal with cleat by crank brothers, for mountain bikes
Magnetic pedal
Norbert Sadler and Wolfgang Dürr applied for a patent for this development in 2004. Very strong magnets are built into the pedals , while steel plates are screwed under the shoes. The magnetic pedal system allows a freely selectable foot position on the pedal that can be changed at any time while driving. This helps some drivers with knee or joint problems. Loosening is done by tilting the feet or with a strong jerk. In the event of a fall, the shoes come off the pedals; getting caught is impossible.
Large area pedal
Large-area pedals were first developed in 1920 under the name "Modell Marcel Berthet ". Later they came into fashion again and again. A more recent development is a pedal, patented in 2008, which is intended to noticeably improve the power transmission from the foot to the crank arm. It is almost three times as long (16 cm) as a normal pedal. It should also use the strong pressure that comes from the metatarsus, but this design prevents a round kick because the foot is too far forward on the pedal. Large-area pedals have practically no market significance these days (as of September 2011). From a technical point of view, racing pedals with the almost rigid connection between pedal and shoe are also large-area pedals.
Platform pedal is another name for large and sturdy pedals. Usually the pedal body is made from one piece. Grub screws protrude from both sides of the pedal body, which results in a very high level of adhesion. This can be maximized by using special shoes. Due to the protruding screws, the risk of injury is quite high. Since this type of pedal is mainly used in downhill and freeride , and shin guards are usually worn here, the higher risk of injury is largely offset.
Bear paws originally come from BMX bikes, are made of metal and are larger than other pedals. The grip of the sheet metal frame, together with the treaded soles, makes it easier to hold onto dirty shoes off-road, which is why they were mainly used in dirt jump and downhill. Today they are mainly found on inexpensive bicycles.
Folding pedal
The protruding pedals can be a nuisance when transporting or pushing the bike; there are folding pedals that protrude less when folded. In order to prevent accidental folding, they are locked and secured in the unfolded state.
Folding pedal, off- ...
... and folded up
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Pedal adapter
A pedal adapter makes cycling easier for people with knee problems. The pedal adapter is attached to the pedal arm. The pedal is screwed onto it. This pedal adapter can be used to reduce the radius on the pedal arm. As a result, the diameter changes from the top to the bottom dead center of the pedal rotation. These adapters are also called handicapped cranks, pedal assistance, pedal shorteners or pedal arm shorteners.
photos
Block pedal, old design
Block pedal with reflectors
Bear paw
Combination pedals
Magnetic pedal
Large area pedal
Manufacturer
In addition to the market leader Shimano, there are a number of other manufacturers specializing in bicycle pedals: BBB Cycling, Zéfal (until the early 1980s), Crank Brothers, LOOK , Mavic , Ritchey , SKS, Syntace, Wellgo (the pedals are sold under a number of other brands ), XLC and others.
literature
- Fritz Winkler, Siegfried Rauch: Bicycle technology repair, construction, production. 10th edition, BVA Bielefelder Verlagsanstalt GmbH & Co. KG, Bielefeld, 1999, ISBN 3-87073-131-1
- Peter de Leuw: Choose the right bicycles, ride safely. 1st edition, Beuth Verlag GmbH, Berlin-Vienna-Zurich, 2006, ISBN 3-410-16487-1
- Frank Lewerenz, Martin Kaindl, Tom Linthaler: Das Rennrad Technikbuch. 1st edition, Pietsch Verlag, Stuttgart, 2005, ISBN 3-613-50486-3
- Pryor Dodge: the fascination of bicycles. History, technology, development . (Foreword by Hans-Erhard Lessing .) (Original title: The Bicycle ). German by Renate Bauer-Lessing. Delius Klasing , Bielefeld 2007, ISBN 978-3-7688-5253-1 (previously with Moby Dick, Kiel 1997, ISBN 3-89595-118-8 ).
Individual evidence
- ↑ www.speedplay.com: Bicycle Pedal Timeline
- ↑ The invention of the bicycle pedals: a long development. Retrieved October 27, 2019 (German).
- ^ Siegfried Wetzel: Right and left-hand threads on pedals and in the bottom bracket
- ↑ www.smolik-velotech.de: Pedal
- ↑ Cyclist fell down the bank of the Rhine : dead. In: Rhein-Zeitung. March 3, 2011, accessed March 23, 2017 .
