In reply to:
Research was done by Mike Gibbs of Rigging for Rescue in Ouray Colorado on the results of shock loading daisy chains and other commonly used positioning lanyards. In addition to being the owner of one of the premier rescue training organizations in the country (R4R), Mike is an active climbing guide as well as a member of the Ouray Mountain Rescue team. Mike performed dynamic testing on daisy chains as well as a number of positioning lanyards commonly used in climbing and rope rescue. The results of this testing were informative, to say the least. After reading this post, many of you may want to reconsider your choice in positioning lanyards.
Mike designed a drop test representative of what could take place in the field that would provide some indications as to the capabilities and/or limitations of positioning lanyards. A common example in canyoneering would be slipping from a stance when starting a rappel with the anchor at your feet resulting in dynamically loading your safety lanyard. The purpose was to examine the magnitude of peak forces as well as the integrity of the connections on certain commercially and user-created lanyards in a dynamic event. The drops were conducted with 80 kg and 100 kg mass simulating the weight of a climber or climber with a heavy pack and fall factors from 0.5 to 2.0. The surprise was how easily daisy chains and some other lanyards resulted in catastrophic failure on relatively short drops.
Test results were sobering at best. Particularly considering how many canyoneers still insist on using the daisy chain (almost 30% of poll responders) as their primary positioning lanyard. Daisy chains failed in short falls (FF 0.5-1.0) and slings made of Spectra/Dyneema webbing exhibited alarmingly high impact forces (>12kN) and catastrophic failure at surprisingly low fall factors. In canyoneering this could easily happen at any rap anchor below chest level. One slip and bang, you've dynamically loaded the anchor.
Nylon slings (not nylon daisy chains) and the Purcell Prusik came out on top as a result of their shock absorbing abilities. Typically, nylon slings held falls with reasonable impact forces (<10kN). The Purcell Prusik did best holding up to factor 2 falls with impact forces of less than 12kN. (FYI acceptable impact forces: CE 6kN, CSA/OSHA 8kN and UIAA 12kN).