I always appreciate great video. Video (to me) is either aesthetic or technical and trying to bridge both is tough. This video from CMC is clearly technical, but I really appreciate the angles of perspective. So often the “clarifying message” of “the how” can get completely lost if the angles are not right. The CMC Clutch by Harken Industrial is a “dream come true”.
Thanks CMC for making this demonstration of CMC-Harken Clutch very straightforward.
In this first rigging scenario, we have the Clutch rigged to two individual anchors with two operators, each operating the Clutch handle and rope tail. As the load, a rescuer and occupied litter, approach the edge, the load that the Clutch sees is relatively light due to the absence of gravity at this stage of lower, i.e. edge transition.
As soon as the litter is over the edge, the operators move from one slack and one tension line to a shared tension system, where the load is split between the two devices. Any catastrophic event to one of the lines will shift its load to the alternate tension line, thereby reducing the shock and extension on the line compared to an untensioned belay system.
The challenge in this scenario comes from coordinating the lower between the two operators. Regardless of proximity of the two individual lines, both operators may find it challenging to balance the load equally, depending on training and experience.
If additional rescuers are available, the team can reduce the risk profile of the system by adding an additional tailer to the lowering system. In this case, a single rescuer can manage both tails from each Clutch device and serve as backup to the Clutch handle operator. The tail can be redirected to a center location.
Regardless of the operators’ failures to control the speed of the lower, the tailer serves as risk mitigator in the operation. The tailer can stop the lower by holding firm on both rope tails.
If availability of rescuers for an operation is a challenge, and anchoring is appropriate and gears available, then this double clutch TTRS rigging scenario replaces people with gear. In this rigging scenario, clutched units are rigged so they can be controlled by a single operator called double Clutch. A Petzl ASAP Lock and insulated shock absorber is connected via carabiner, to each Clutch back plate, and installed on the tensioned side of the Clutch.
One operator controls both Clutch handles and both rope tails. The ASAP Lock serves as an unattended belay device, i.e. a backup tailer. There could be circumstances in less than a vertical operation when the operator fails to control the speed of the lower, but the ASAP lock has not reached its trigger velocity.
The best option to mitigate this risk is to rig the double Clutch with a single operator managing the handles and tails, and a second rescuer as backup tailer, monitoring this system with both rope tails in hand. As each person is able to see and feel the ropes in service, this rigging scenario also promotes better shared tension at each Clutch.
In all cases, a competent and properly trained operator is the best defense against an uncontrolled lower. A twin tension rope system is the current best practice for building, raising, and lowering rescue systems. This video demonstrates four rigging scenarios using the clutch in TTRS, depending on anchor types and location, available gear, and human resources available. Each scenario comes with a different risk profile, and may be appropriate depending on your particular rescue or training operation.
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