Vertical caving terminology and methods > Personal SRT gear
A lower jammer, knee jammer or foot jammer which has a footloop or is attached to the foot directly, with some bungee cord pulling the top of the ascender upwards, so that it moves up the rope when the foot is lifted. Used as part of the double bungee or Howie rig variations of rope walking, as well as the another prusiking system. It could also be used for any other system that has a relevant ascender, such as the Texas system and singe system. This is done to remove the need for manually lifting the top of the ascender using a hand, allowing that hand to be used for other purposes. If the bungee cord pulls upwards on the body of a lever cam ascender that is not spring loaded, this can also help the ascender to engage and grip the rope more easily, without needing to be sharply pulled downwards. Also helps to keep the ascender pulled upwards so that it is easier to reach, when it is diconnected from the rope at a rebelay. Usually needs a fairly long bungee to get the required elastic power, so unless a pulley is used to lengthen it in some other way, the ascender will need to be placed quite low on the leg, with the other end of the bungee attached high up on the chest harness. This can make it very difficult to reverse prusik, since the ascender cannot be reached. This also 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, and ascending can prove very difficult if the bungee snaps.
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. It was first used for the Howie rig variation of rope walking.
This history section only covers floating cams. 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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