Vertical caving terminology and methods > Personal SRT gear
The most common descender, made by Petzl. Has an automatic locking system, where a handle is used to allow descent. Locking off can be relatively easily done with both a hard and soft lock, although the 2019 model makes soft locks impossible unless a braking carabiner is also being used.
The handle is not supposed to be used to control the speed of descent. The automatic locking feature is intended only to help avoid serious outcomes if mistakes are made, so that if the caver accidentally lets go of the down rope and the handle, it can hopefully save them. It will not be able to help if they press the handle further in when panicking. The automatic lock is supposed to be fully disengaged when abseiling, and the Stop is supposed to be locked off before letting go of the down rope. It can lead to a false sense of security and cavers sometimes intentionally let go of both the down rope and the stop handle, assuming that it will stop them like it normally does. However, this should not be relied on, since catching the handle by mistake can cause it to disengage, resulting in a very rapid descent. It also does not always engage fully if it is released during a fast descent, or if the rope is a thin diameter or very fast. This can be worse for lighter cavers as their weight may not be sufficient to cause the locking cam to pinch the rope hard enough. Creeping or slipping slowly down a rope is normal, and sometimes the handle needs to be manually forced out to increase the locking strength. This risk, and the fact that worn bobbins eventually cause the automatic locking system to become less reliable, led to them being affectionately known as a "Petzl Go" (a name that Petzl have given officially to one of their maillons).
The bobbins become very hot in use, and can easily singe a rope, especially on longer descents. Ropes may be intentionally wetted in order to reduce this risk. Difficult to use on very long hangs (over 100 metres), because the weight of the rope adds too much friction. Difficult to use with tight pitches, where there may not be space to reach a hand in front in order to use the handle. Models prior to 2019 allowed the handle to be clipped fully in with a carabiner (the small metal loop opposite the handle), making the Stop act like a Simple, allowing it to be used with tight pitches. Models after 2019 do not have this facility.
Many early descenders featured levers that could be used to control the descent speed, but most of them needed a force to be applied to make them slow down, rather than speed up. The first known descender to feature an automatic slowing mechanism which required a lever to be moved to allow motion was created by American Thomas C. Rice in 1871, for use as a fire escape. It functioned in a very similar way to the Stop, with the weight causing an eccentric cam to rotate, and apply force to the rope. A carabiner with an integrated pulley and braking lever was designed in 1882 by the German Lohner brothers, made for the fire brigades. It would automatically add friction when released, and reduce friction when a lever was pulled. This was described as being used either as a descender, or for lowering people, the way a modern Petzl GriGri is. The inventors complained about the pulleys falling off existing designs (which were not integrated within a carabiner), which seemed to also have a similar lever. No existing devices were described in a comprehensive manual from that region 5 years earlier. In 1884, American Marcus Henry Robb created a fire escape descender where the weight pulled on a lever, applying friction to a pulley. It could be adjusted to the point that it would automatically stop until the lever was moved, or the user applied pressure to the top of the descender. In 1888, Americans Lenious D. Smith and Wilson Albert Olds created a fire escape descender where the weight pulled two levers onto the rope, creating enough friction to slow or stop the descent. Handles could be pulled to control the speed.
The first descender used for caving, the Frein de Descente, had a safety brake that would immediately automatically lock the rope, if a handle was not held open. It was created by Henri "Kiki" Brenot in about 1930, and was described in Henry P. Guérin's 1944 book "Spéléologie, manuel technique; Le matériel et son emploi Les explorations". This descender was the ancestor of the Simple and the Stop. Cavers then learned that by using the bars in the wrong order, and therefore wrapping the rope further around each bar, they could reduce the requirement down to 2 thicker bars, which became the bobbins of the Simple. French caver Bruno Dressler made the first Simple in the Grenoble region of France in the 1960s, before giving the design to the founder of Petzl, who released their Simple in 1968 (before Petzl existed as a company). Several companies then created descenders that used a rotating cam to automatically lock the rope. In 1972, British caver Guy Talbot and Cambridge University Caving Club researchers developed and tested a fall arrester which used the exact same fixed bobbin and rotating cam arrangement as the Stop. The intention was that the lever could be used to disengage it after a fall, and turn it into a descender. However, because it did not function well as a fall arrester, they abandoned the idea, without realising that they had just invented what would have been the most popular European descender. B. D. Butkovič (country unknown, but the name is typically Slovenian or Slovakian) apparently presented the approach of interlocking bobbins at an Italian caving conference in 1974. Italians Costantino Bottoli and Mauro Venier created the BO.VE Diabolo in 1977, which looked almost exactly like the Stop, but was quite poor at automatic locking, and wore out very quickly. Kong released the Giuseppe & F.lli Bonaiti branded descender in 1977, which used a separate cam to automatically lock the rope. Bruno Dressler's automatic locking descender, called the DAD, had a moving front cover as a handle, and was patented 1979, one month before Petzl patented the Stop. The first version of the Petzl Stop was originally developed in 1979, and was barely changed until 2019. It had the auto-lock based on a rotating cam that pinched the rope in exactly the same way as the BO.VE Diabolo, but it worked far more reliably due to small differences in the cam shape. In 2019, a new model was released that used steel bobbins instead of aluminium, and a flip-out handle. The bobbins could no longer be replaced, and there was no facility to lock the Stop into acting like a Simple.
This history section only covers the Stop. This article also has a detailed history of many of the other devices and techniques that are used for vertical caving.
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