Bühler hook
The Bühler hook is a so-called "glued" bolt to secure climbing routes . It consists of stainless V2A steel and is bent in one piece. The two ends are welded together and cemented into the compact rock.
The development of the Bühler hook has made a significant contribution to safety in sport climbing.
Historical
The Bühler hook is named after its inventor Oskar Bühler . Bühler has secured many climbing routes in Franconian Switzerland and in the Wilder Kaiser . For this voluntary work he received the Federal Cross of Merit on ribbon in 1988 .
At the end of the 1950s, there were already many climbing routes in the Northern Franconian Jura that were at least 30 years old. The hooks that were supposed to secure these routes had been stuck in the rock for decades, were exposed to water and frost, mostly rusty and no longer seemed to be reliable.
pipe chisels, hammers, cement mortar , narrow spatulas and tin cans for mixing the mortar. In addition, toothbrushes and paintbrushes were needed to remove the drilling dust from the drill hole and a "Steggerle" (thin stick) to plug in the mortar.
On the left of the picture you can see some old hooks that have been removed.
When Bühler began to take his daughters with him to climb more often, he also began to change hooks. As a trained bricklayer and civil engineer , he did not rely on the hook, but looked for a safer and more permanent solution. In 1960 he began cementing galvanized hooks into drilled holes. In nights of work he developed a concept and implemented it with his comrade Wilhelm Messner. From 1965 he was able to replace the galvanized hooks with cold-bent hooks made of V2A stainless steel, which he called "silver coins". They were soon referred to as “Bühler” in climbers' jargon. He set around 2,000 pieces with a drill bit and another 500 with a cordless drill. He kept a record of about 7,000 hooks that comrades drilled in.
construction
Oskar Bühler designed the Bühler hook in its characteristic shape based on the following considerations:
- The stainless V2A steel , which was relatively new in the construction industry at the time , offered a material that, in contrast to the metals previously used, was corrosion-resistant . The cold bendable V2A steel is characterized by its special elasticity and thus holding power. The steel could be purchased cheaply as waste from construction.
- The shape of the hook should enable a climber who feels insecure to hold onto the hook eye with two fingers and at the same time attach a carabiner to secure it.
- The hook should be constructed so that the climber can safely step on the hook.
- The ends of the steel rod should be welded together so that none can be pulled out of the drill hole independently of the other and the hook eye opens.
- The notches on the ends of the steel bar mean that the hook is better held by the cement around it. This prevents them from slipping out of the borehole.
The shape of the Bühler hook has been discussed again and again over the years. One argument in favor of a smaller eyelet opening was the "education" of climbers to free climbing . On the other hand, Oskar Bühler left it open to every climber whether he used a hook solely for securing or as a step or grip.
The loop shape of the Bühler hook can be disadvantageous in the case of an unfavorable carabiner position, which can result from rope movement, because the carabiner could unhook itself when it is subsequently loaded. This applies not only to the Bühler hook, but also to all other hooks that offer a support for the carabiner in the upper eye area. This danger does not exist with the triangular shape.
safety
On the occasion of the construction of a climbing tower for the Bavarian riot police , the Bühler hook was tested by TÜV Bavaria at the end of the 1980s . The tests were all successful until the concrete block in which the hook was cemented was torn from its anchorages. No safety-critical changes were found on the hook itself.
In 1995 the Bavarian State Ministry published:
“The Bühler hook is the first secure bolt to be widely used. ... Load tests on both cemented and glued-in Bühler hooks with a minimum shaft length of 70 mm (material thickness 8 mm, other thicknesses are not used) in concrete (B50) and in limestone in the radial direction (main load direction, transverse pull) resulted in pull-out forces of 35 to over 56 kN (approx. 3500 to over 5600 kp). "
Legal
Patent freedom
Bühler has been approached several times about patenting its hook. He did without it because the hook, which is relatively easy to manufacture, should be available to everyone. Careful handling and the greatest sense of responsibility when ticking the boxes was essential to him.
Instruction obligation
According to the Equipment Safety Act (GSG §3), when selling composite hooks (adhesive hooks), an operating manual must be supplied. The operating instructions must contain instructions on how and with which mortar the hook can be correctly set.