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In the earlier days of skiing, the skis were in a design somewhat similar to snowshoes, roughly a walking motion, although they were slid over the snow instead of lifted with each stride. During this era, the binding was also similar to those of a contemporary snowshoe, generally consisting of a leather strap fastened over the toe of the boot.
During the 1800s, skiing evolved into a sport and great advances in technique and equipment design followed. Generally the skiing motion was much closer to skating, using long gliding strides. This technique required bindings that followed the skier's foot through a wider range of motion, but loosening the toe strap simply made it fall off. To address this, a second strap was added that looped from the toe around the heel of the boot, pulling it forward into the toe strap.
Over time, both portions of the binding evolved. Early on, the toe strap was replaced by a metal clip under the toe that folded up on the sides to cup the toe of the boot. This provided much greater grip on the boot, allowing the ski to be pushed sideways. The heel strap also changed over time; in order to allow a greater range of motion, a spring was added to allow the strap to lengthen when the boot was rotated up off the ski. This buckled strap was later replaced by a metal cable, or in some cases a single large metal spring. By this point the bindings were generally known as cable bindings.
The introduction of the cable binding allowed the Christie turn to become a standard on downhill runs, and to further support this style of skiing the Swiss racer Guido Reuge in 1929 invented a cable binding with steel clips below the boot heel to enable clamping the heel down for downhill portions. He named the product "Kandahar" for the international Kandahar Cup ski races. In use in alpine races, the Kandahar binding led to serious leg injuries, and by 1939 experimentation began in earnest on bindings that would release the boot in a fall.
The evolution of bindings for alpine skiing wasn't complete until the introduction of plastic ski boots (beginning in 1966) permitted the development of industrial standards for binding function. Injury rates began to fall with the gradual introduction of the Teflon anti-friction pad around 1972.
Cable bindings remained in use for some time for cross-country, and are today popular for telemark skiing. However, the Rottafella design from the 1930s became more popular for cross country skiing through the 1950s and into the 1970s, and the Salomon Nordic System (SNS) binding re-invented this field entirely. Today cross-country binding systems have become as customized as their downhill counterparts of the 1960s.
The vast majority of bindings for Alpine skiing work by fixing the ski boot to the ski at the toe and heel. The binding attaches the boot to the ski, but to reduce injury also allows the boot to release in case of a fall. Generally, the toe piece is designed to allow the boot to rotate to the sides, while the heel piece rotates up. In modern bindings a wide variety of motions is available from both toe and heel pieces.
The boot is released by the binding if a certain amount of torque is applied, usually created by the weight of a falling skier. The amount of torque required to release the boot is adjusted by turning a screw on the toe and heel piece. This is called (colloquially) the DIN setting, because the standards for Alpine ski binding settings are issued by Deutsches Institut für Normung. The correct DIN setting is based on height, weight, ski boot sole length, the skiing style of the skier (cautious, average, or aggressive) and, age (if the skier is younger than 10 years old, or 50 years old or older).
Normally, torque itself does not cause injury, not until a natural limit of the human skeleton is reached. For instance, a very strong vertical torque, twisting the knee, will not cause damage unless the knee is forced to travel beyond a certain angle. Some bindings move relatively short distances before releasing, leading to the possibly of "pre-release", where the ski releases long before the motion could have caused damage. Bindings with longer "float" may hold on during events that require those with shorter motion would require higher DIN settings.
Bindings may be sold alone to be mounted to "flat" skis, or can be integrated systems. Integrated systems have declined in popularity due primarily to their higher weight and difficulty of adjusting the balance of a skier since cants and shims are difficult or impossible to use. Some racing skis have plates on them which allow a binding to be attached and afford the possibility of changing the balance through cants and shims.
Alpine ski bindings employ the use of a snow brake to prevent the ski from moving while it is not attached to a boot. Snow brakes work by the use of a sprung square 'C' shape, typically made of metal, which makes contact with the snow. When a ski boot is put in the ski binding, the brake pivots under the downward pressure and runs parallel with the ski allowing free movement. When the boot comes out of the ski, the brakes spring out perpendicular to the ski and stop the ski from sliding.
There are three common Nordic binding systems:
Like Nordic bindings, Telemark bindings fix only the toe leaving the heel free to move. The main difference is that Telemark bindings are more heavy-duty to withstand the increased forces encountered in high speed descents. The cable binding (aka Kandahar binding), where the toe section of the boot is anchored, and an adjustable cable around the heel (for which there is a groove in the heel of the shoe) secures the boot. Used for cross-country (to a certain extent), Telemark and ski jumping.
While binding designs vary, before 2007 almost all dedicated Telemark models had been designed to fit boots with 75mm Nordic Norm "duckbill" toes. However, in late 2007 Rottefella introduced the New Telemark Norm (NTN) binding which uses a different boot sole, co-developed with the Crispi and Scarpa boot companies.
Also known as Randonee, an Alpine Touring ski is a special ski binding that allows the heel to be clipped down to the ski when skiing downhill, but which allows it to be released when climbing.
Traditionally, skiboards and Salomon's Snowblade have used non-release plate bindings. The reason being that skiboards and snowblades have traditionally been 100 cm in length or less, so the torque during a fall was assumed to be small enough that a releasable binding was not necessary. However, in recent years, as skiboarding has become a more established niche sport, releasable bindings have become a viable option to decrease the chances of injury. Spruce Ski created a riser which adapts between the standard 4 cm by 4 cm four-hole skiboard binding and standard ski bindings; furthermore, Spruce began selling their 120 cm skiboard in the 2005-06 season which are only available with their releasable setup. Additionally, Salomon now offers most of their Snowblades with releasable ski bindings as well. Some riders still prefer the plate-style bindings.
One of the first recorded advances in binding design was made by Sondre Norheim, the "father" of modern skiing. His binding included a leather toe strap that was fastened tightly with a buckle, and a heel strap of small birch roots twisted into a rope. The heel strap started at the toe, looped around the heel, and forward again to the toe. The heel strap pulled the boot forward into the toe strap, so the ski would not fall off when pressure was released on the toe. The strap had to be flexible and elastic in order to allow it to keep tension on the heel as the skier strode forward and the heel lifted from the ski.
First introduced in 1850, Norheim's binding allowed a much longer striding motion that greatly increased cross-country speeds, and this quickly became widespread. It also allowed the ski to be directed by twisting the foot, transmitting the torsion to the ski through the toe strap. Techniques based on this ability were developed over the next few years, replacing the former technique of dragging a large pole in the snow on one side or the other to drag the skier in that direction. These new techniques spread throughout Telemark and would later be named for the region. Norheim made a splash when he introduced this publicly at an 1868 ski jump meet, where the contestants were required to ski up the hill, down the hill to the top of the jump, and then jump, with their style being marked on all phases. Norheim's smooth linked turns stunned the crowds, and he won the competition.
Fritz R. Huitfeldt drove the evolution of the ski binding over the next 20 years. In 1894 he introduced the use of semi-circular metal hooks at the toe to attach the straps. The hooks were positioned to tightly fit to the sides of the boot, keeping the ski centred and eliminating any "flop" that the formerly loose straps allowed. The heel strap was also attached to the same hooks, but because of their rounded shape, the required range of motion was provided by the straps sliding up and down on the hooks. This allowed the heel strap to be replaced by a less flexible leather strap. Together, these changes dramatically tightened the binding, greatly increasing control.
In 1897, Huitfeldt further improved the design by changing the toe piece. Instead of hooks, he drilled a rectangular hole through the ski from side to side, and passed an iron bar through it. The bar was then bent up on either side, locking it in place, and then formed to fit the toe of the boot. This improvement once again dramatically improved the firmness of the fit. Finally, in 1904 he adopted the Hoyer-Ellefsen toggle, a lever that replaced the buckles. This not only greatly improved mechanical advantage, further improving the strength of the binding, but also made the system much easier to put on and remove. Better yet, the geometry of the attachment points meant the heel strap was mechanically attached below that of the toe strap, which provided a constant "diagonal downpull" that naturally returned the heel to the ski.
Huitfeldt style bindings were by far the most popular system for decades, with the only major change being Marius Eriksen's 1920 introduction of pre-formed plates that were screwed on top of the ski. Other binding systems did exist, in particular a class of bindings originally introduced by Mathias Zdarsky that replaced the heel strap with a long metal plate under the sole of the boot, hinged at the front to allow the heel to rise. The heel was held to the plate by a short strap attaching at the back. These gave even better control than the Huitfeldt design, but so firmly attached the leg that injury was a real problem.
The final major improvement to the Huitfeldt "free heel" designs was the replacement of the heel strap with a metal cable and springs. Invented in 1929 by the Swiss ski racer Guido Reuge, patented by him and marketed in 1932, the spring-loaded cable binding was named for the Lord Roberts of Kandahar Cup ski races. Kandahar-style cable bindings would be almost universal into the early 1960s.
The Kandahar design offered two advantages over the earlier designs. The use of a spring to provide tension allowed fine control over the mechanics, and a smooth action that did not suddenly increase tension at the end of the stroke. It also allowed the skier to adjust the tension by moving the spring or turning a control knob, allowing for different conditions and skiing style and stride. More important was the addition of two small hooks on either side of the ski near the heel. When skiing downhill, the skier could clip the cable under the hooks, locking down the heel and providing much greater control. Now the ski could be turned by rotating the leg, forcing the ski to stem. When it was time to climb back up the hill, the cable was unhooked and returned to being a normal cross-country binding.
The introduction of dedicated ski lifts in 1908 led to an evolution of skiing as a sport. In the past, skiers would have to ski or walk up the hills they intended to ski down. With the lift, the skiers could leave their skis on, and would be skiing downhill all the time. The need to unclip the heel for cross-country use was eliminated, at least at resorts with lifts. As lifts became more common, especially with the introduction of the chairlift in 1936, the ski world split into cross-country and downhill, a split that remains to this day.
For pure downhill skiing, the Kandahar was a problem. In particular, the metal toe clip so tightly clamped the front of the boot that even small sideways motions of the tip of the ski could twist the lower leg, and spiral fractures of the calf were common. The death grip led to the nickname "bear trap bindings", and it was estimated that 1% of skiers suffered an injury on any given day.
During the 1930s it was discovered that an improvement could be made by removing the toe strap from a typical Kandahar binding. Instead, the metal cup was bent inward to slightly wrap over the top of the boot, or at least the top of the sole. Although the resulting clip was much less solid than the strap, in the case of a forward fall the boot would rotate up and out of the cup, releasing the leg. Although this was an improvement, it was a small one.
In 1937 Hjalmar Hvam broke his leg skiing, and while recuperating from surgery, invented the Saf-Ski toe binding. This was a metal clip with a pyramidal top that fit into a slot cut into the sole of the ski boot. When the boot was rotated forward, the slot on the toe eventually rose above the metal pyramid, allowing the toe to release from the ski. The system was considered with suspicion by professional skiers, especially when Olaf Rodegaard released during a race. However, Rodegaard credits the release with saving him from a broken leg. In the post-war era, Hvam sold several thousand pairs of Saf-Ski's, in an era when downhill skiing was in its infancy. Hvam continued to sell the Saf-Ski into the 1960s, but in 1966 his insurance rates increased so dramatically that he was forced from the market.
A dramatic advance was introduced as the Look Nevada in 1950. The Nevada held the toe centred over the ski using two metal fingers shaped into an upside-down V. The fingers were pivoted to allow motion to the sides, and centred with a spring. During a fall, sideways torsion could overcome the force of the spring and allow the boot to release directly to the side. This design was quickly copied by other vendors, notably Marker, and had the first real impact on the dominance of the classic fixed-toe bindings. By the late 1950s, there were about 35 different release toe bindings on the US market, most of which used a normal Kandahar-style heel cable.
The first modern heel-and-toe binding was the Cubco binding, first introduced in 1950 but not popular until about 1960. A heel-release binding faced the problem that there was no obvious place to attach to on the heel, so the Cubco solved this by screwing small metal clips into the sole of the boot. This also eliminated the changes in performance as the sole of the boot wore down, or the geometry of the sole changed as the boot wore into the skiers foot. Marker introduced the Rotomat, which gripped onto the sole where it extended past the heel, and Look quickly followed suit with their Grand Prix design. By the mid-1960s, release bindings that worked on both the heel and the toe were common, and by the late 1960s the cable binding had disappeared from downhill.
One problem with 1960s release bindings was that the boots were not standardized, and a binding that worked well on one boot might be dangerous on another, or might become dangerous over time as the boot shifted about. This led to the introduction of plate bindings, which used a metal plate firmly clipped to the sole of the boot, and bindings that clamped onto the plate. The plate could be easily removed for walking about. Plate bindings were popular in the US in the 1970s, notably the BURT Retractable Bindings and Spademan binding, but never caught on in any major way in Europe. As more and more of the downhill ski market came under control of European companies, the plate bindings disappeared, in spite of their excellent safety records.
The disappearance of the plate and alternate systems was due to a combination of factors, notably the introduction of standardized hard plastic boots. Plastic was first introduced by Lange as a way of improving existing leather designs. As the new material spread through the industry, the sole piece was standardized to allow toe-and-heel bindings to clip on. Plastic had the advantages of being much firmer than leather, not changing shape over time, and having predictable friction characteristics wet or dry. Although plate bindings of the era had much better safety records, notably the Spademan design, the new boots and bindings could be easily adapted to any ski for any skier.
The cable binding remained in use, and even increased in popularity, throughout this period as cross-country skiing developed into a major sport of its own. In this field the speeds were generally not high enough that the release was a serious concern, and the freedom of the free-heel design was perfect for the sport.
Change eventually came though the evolution of the Rottefella binding, first introduced in 1927. The original Rottefella eliminated the heel strap, which held the boot forward in the binding, by drilling small holes in the sole of the boot which fit into pins in the toe piece. This would only work if the sole was held very firmly down on the pins, so the binding also introduced a metal clip that was forced down onto the top of the sole of the boot, forcing it onto the pins. When the inventor, Bror With, won a race on the new design, Norwegian Crown Prince Olav ask him what they were, and he responded "Oh, they're just a couple of rat traps I picked up at the hardware store". "Rottefella" is Norwegian for "rat trap".
Problems with the geometry of the boot sole, which meant only certain boots would work, meant the Rottafella was not widely used. This problem was eventually solved through the same evolution of plastic components that changed the downhill market. In this case the use of highly flexible plastics allowed for a sole that was very strong torsionally and side-to-side, but still had excellent flexibility lengthwise, allowing the heel to rise as with a cable binding. This was standardized as the 3-pin system, which was widespread by the 1970s.