Vertical caving terminology and methods > Prusiking systems, prusiking methods > Step or rope walking systems, sit on the heels systems
A step system for prusiking which is based on the Mitchell system. The main benefit is that it frees up one hand. The name "floating cam system" refers to the foot jammer being configured as a floating cam. As a result, the name could be applied to any number of prusiking systems, if an ascender is used in this way. That name originally referred to the Howie rig version of rope walking, for example. Therefore the original British name of the system is used here, whether the system is used with a floating cam or not. Cannot be used for prusik loops.
Most of the limitations of the Mitchell system still exist, including the inconvenience when passing rebelays and deviations. It can be used for passing a knot while abseiling or prusiking, but the position of the foot jammer makes this awkward. When using a more powerful foot jammer, reverse prusiking is exceptionally difficult, verging on impossible, due to the positions of the ascenders. Bottom weighting is done by looping the rope under one foot and pulling the rope upwards with the free hand, if using a more powerful foot jammer that initially prevents the rope moving easily. Mid-rope changeovers are relatively easy when using a lower jammer or knee jammer, but very clumsy when using a foot jammer since the entire manoeuvre needs to be done while standing upright, hugging the rope. This system is closer to rope walking than the frog system, in terms of energy transfer efficiency. It is less awkward than the Mitchell system for sloping pitches, since one hand is free to push away from a wall. When not using a chest jammer, taking a rest requires one leg to be bent, so that the top jammer can be lifted. Can be tiring for the arms on long pitches, but at least one arm can take a rest while the other works.
The configuration is similar to the Mitchell system but instead of a lower jammer, it uses a floating cam foot jammer, connected via a bungee cord to the chest harness. This brings a very serious risk of a malfunction causing a fully stretched bungee cord to hurl a metal clip at high speed towards your face. Uses a top jammer with a footloop and safety cord. A chest roller is used for the rope, and for the footloop. It may optionally be swapped for a chest jammer, which adds more friction and makes the body position less convenient, but allows the foot jammer to be a more easily removable type since it does not need to be rated. When using a chest jammer in this way, the another prusiking system essentially becomes identical to the frog system when used with a foot jammer. The sit harness plays a secondary role for safety only when using a chest roller, but plays an essential role as a main support when using a chest jammer. The chest harness is essential for support when using a chest roller and for pulling up the foot jammer, and improves efficiency when using a chest jammer. Only the top jammer can have a functional safety cord, so if the top jammer fails when using a chest roller, the chest roller becomes a piece of safety equipment that holds you to the rope. As a result, the chest harness also has to be load bearing when using a chest roller.
As a variation, the foot jammer can be replaced with a knee jammer and footloop, with a strap holding it to the knee, removing the need for the bungee cord. The safety cord of the top jammer can also be tied part way down the top jammer's footloop, instead of being tied to the top jammer itself. This is the original variation. The original description of this system acknowledged that it is not convenient for passing rebelays, deviations and awkward Y-hangs. The suggestion was to add a chest jammer that could be engaged when needed instead of the knee jammer or foot jammer, turning the system into the frog system. A better suggestion is to simply use the frog system with a more easily removable foot jammer.
The idea of a floating cam was developed by Kirk MacGregor in Toronto, Canada some time around 1970 (it set a speed record at the start of 1971), using surgical tubing instead of bungee cord to pull an ascender upwards, originally used for rope walking. The another prusiking system was developed and named by British caver Mike Cowlishaw, replacing the Mitchell system's lower jammer with the knee jammer from the three Gibbs ropewalker variation of rope walking, with the knee jammer strapped to the knee. This was first described in Descent 36, 1977, but was probably developed at least a year before that. It used a chest roller. The floating cam approach was then used with the Mitchell system's lower jammer, essentially turning it into a floating knee jammer, described by British caver Nick Thorne in Cambridge Underground, 1978, without giving it a name. The another prusiking system still did not have a floating cam when described in 1982 in BCRA Cave Science volume 9 number 4. In 1989, American Bill Farr independently recreated the another prusiking system using components from rope walking and the frog system, as something that could be converted as needed from a frog system, which he called the rope hopper. It used a chest roller which could be swapped for a chest jammer when needed, and a fixed foot jammer instead of a knee jammer, without using the floating cam approach. The top jammer could be used with both feet in the footloop when using it as the frog system. However, the floating cam idea won, and the system was referred to as "a floating cam system" by 2007, as described in Vertical by Al Warild. In that publication, the lower jammer or knee jammer had been replaced by a floating cam foot jammer, to get more strength from the bungee cord, or a fixed foot jammer. The description implies that Nick Thorne's variation, the rope hopper, and the frog system with a foot jammer had been used as inspiration. The original version of the another prusiking system was not mentioned. Once again, it could be used with a chest jammer instead, turning it into a frog system.
This history section only covers the another prusiking system. 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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