Post by Tim White on Jan 18, 2007 11:19:29 GMT -5
There has been discussion and questions in the Team Thor: Thor Expedition 2006 thread regarding the spelean shunt. So, I thought I’d start another thread. Here is what I know...
To my knowledge the first widely published information on the spelean shunt was in the book Single Rope Techniques by N.R. Montgomery – 1977 and an article by W.B. Toomer and Bruce Welch in the Nylon Highway Issue No. 9 – 1978.
Toomer and Welch did not describe using the spelean shunt to stop a rapeller who gets out of control, by the extra drag on the ascender overcoming the weight of the carabiner, and the locking the gibbs cam as Off Rope stated in his post. But their system had the spelean shunt attaching to a chest harness via a length of webbing or rope. Their theory was that if a rapeller were to be rendered unconscious they would lean back and their weight would lock the device.
This technique required the rappeller to wear a chest harness. Then around 1984 or so Bill Cuddington and Mike Fischesser came up with the idea of running the attachment webbing behind the chest harness of a rope walker system and attaching it to the seat harness. A much better idea, if I were to be hanging on rope unconscious! I’d much rather be hanging from my seat harness than from a chest harness.
Over the years I’ve heard of testing done using the spelean shunt where the device simply did not catch but rather followed the rapeller and rack down the rope. According to Bruce Smith in On Rope, “the spelean shunt is a device that requires positive action to engage”. He states the efficiency of the shunt was tested by 1978 by Web in Australia by getting a blindfolded victim to rappel off the end of a rope and try to engage the spelean shunt. In most cases this was unsuccessful.
Would the use of a spelean shunt have saved Philip Robinson life on Mt. Thor? I don’t know. But I do know this event has prompted me and Berta to so some intense testing using the spelean shunt. I am not convinced that the spelean shunt should be overlooked as a rappel backup device. There are drawbacks such inadvertently locking up and there is the real risk if enough velocity is achieved, the cam of the gibbs can cut or damage the rope. We will repot on our results.
To my knowledge the first widely published information on the spelean shunt was in the book Single Rope Techniques by N.R. Montgomery – 1977 and an article by W.B. Toomer and Bruce Welch in the Nylon Highway Issue No. 9 – 1978.
Toomer and Welch did not describe using the spelean shunt to stop a rapeller who gets out of control, by the extra drag on the ascender overcoming the weight of the carabiner, and the locking the gibbs cam as Off Rope stated in his post. But their system had the spelean shunt attaching to a chest harness via a length of webbing or rope. Their theory was that if a rapeller were to be rendered unconscious they would lean back and their weight would lock the device.
This technique required the rappeller to wear a chest harness. Then around 1984 or so Bill Cuddington and Mike Fischesser came up with the idea of running the attachment webbing behind the chest harness of a rope walker system and attaching it to the seat harness. A much better idea, if I were to be hanging on rope unconscious! I’d much rather be hanging from my seat harness than from a chest harness.
Over the years I’ve heard of testing done using the spelean shunt where the device simply did not catch but rather followed the rapeller and rack down the rope. According to Bruce Smith in On Rope, “the spelean shunt is a device that requires positive action to engage”. He states the efficiency of the shunt was tested by 1978 by Web in Australia by getting a blindfolded victim to rappel off the end of a rope and try to engage the spelean shunt. In most cases this was unsuccessful.
Would the use of a spelean shunt have saved Philip Robinson life on Mt. Thor? I don’t know. But I do know this event has prompted me and Berta to so some intense testing using the spelean shunt. I am not convinced that the spelean shunt should be overlooked as a rappel backup device. There are drawbacks such inadvertently locking up and there is the real risk if enough velocity is achieved, the cam of the gibbs can cut or damage the rope. We will repot on our results.
