The coupling of energy from an oscillating rope to a carabiner gate has been implicated as the culprit for gate opening [1, 2] but this phenomenon has not been investigated in a systematic manner. Carabiner failure is relatively rare, but open gate failures make up the majority of failures [?]. In general, the open gate condition is blamed on poor luck, initial conditions that cause the carabiner gate to catch on the cliff surface, or the sudden impact of the carabiner on the cliff surface [?]. In a recent incident in Holland however, no such explanation is likely, which makes one wonder whether the rope oscillations might be more common than is expected (figure #)[].
Evidence suggests that rope oscillations are common and significant in magnitude. Photos taken of climbers (figure #) show such oscillation, and any belayer whose climber insists on hangdogging for long periods of time can break up the boredom by ?plucking? the rope to make it oscillate like a guitar string. Further evidence may be available from drop test data, where the sine wave form of the tension vs. time exhibits an added sine wave whose frequency is several times that of the deceleration of the falling mass (figure #).
To evaluate the likelihood of rope oscillations causing carabiner gates to vibrate open, this project develops a model for when rope oscillation is prone to opening carabiner gates and tests rope and carabiners to veryify the model.
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Abstract:In order to determine the conditions under which an oscillating rope can transfer energy to carabiner gate oscillation during climber fall arrest, a model has been developed to estimate rope oscillation frequency, carabiner gate oscillation frequency, and carabiner acceleration. This model can used to predict the fall geometries and kinematics that should exhibit a propensity for opening carabiner gates. Results:
Conclusion:
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Abstract:In order to determine the conditions under which an oscillating rope can transfer energy in carabiner gate oscillation, this experiment attempted to measure carabiner acceleration, carabiner gate open angle/distance, and gate open times; these measurements were taken under two circumstances: a test fixture where the magnitude and frequency of the oscillation were controlled and a simple snapping shut of the gate. The results of the controlled test fixture experiments show the acceleration needed to open a carabiner gate at 32 Hz. The gate snapping experiments suggest the frequencies at which resonance is expected. Further work is needed to determine the resonant frequency, gate open time, and Q oscillating carabiners. The results of these experiments can be used to predict whether an oscillating rope can cause a carabiner to be open during fall arrest and, further, to determine what fall configurations exhibit a propensity for open gates. Results:
Conclusion:
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