There are many types of climbing systems and equipment that can be used in professional tree work and other rope access industries. Mechanical Descenders act like rope friction hitches to slow, control or stop a climbers descent, and can be used as belay devices.
Made of aluminum or steel, descenders operate by providing friction to a rope running over the smooth surface of the device. The more rope in contact with the descender the more friction, thus more control of the speed of the climber’s descent.
Descenders fit into four categories:
- Figure 8
Figure eights allow fast but controlled descent on a rope. They are easy to set up and are effective in dissipating the heat caused by friction but have a tendency to put a twist in the rope.
- Rescue 8
Rescue 8’s has “ears” for added friction and easy tie-off. Racks consist of a ‘U’ shaped frame, attached to the rappeler’s harness, into which snap multiple bars that pivot from the other side of the frame. The rope is woven through as many of the bars as are required to provide sufficient friction. This arrangement allows for variations in rope diameter and condition, as well as controlled rate of descent.
- Rappel racks,or
Cam devices are considered active belay devices which have a built-in mechanism that locks off the rope without the help of any other pieces of equipment. The GriGri, Rig and I’D by Petzl are examples of active belay devices, often used as descenders. The offset cam locks off the rope automatically to catch a falling climber, much like a seat belt in a car locks off to hold a passenger securely. The cam is released for descent by gradually pulling on the integrated handle.
Rope climbing with mechanical descenders is becoming more widely used, but requires knowledge and experience beyond more common climbing techniques.
For more information about climbing descenders and other mechanical equipment, contact Pinnacle Arborist Supplies at 501-663-8733.