No.7 Ring & Ring Cambium Saver
We can choose from a wide range of friction saving devices, pulleys, tubes and rings, some being retrievable remotely and others not. The ring and ring is one of the more simple designs. It can be spliced easily enough too.
A cambium saver serves two purposes. Ropes running directly over a branch can easily cut through to the cambium, opening the tree to bacterial and fungal attack. This is terrible for the tree obviously but also the rope picks up anything that the tree exudes and becomes filthy and possibly weaker.
The second is a 'friction saver'. Having the rope in a ddrt system run over metal instead of bark is a great energy saver for ascent climbing and work positioning.
By products of using a cambium saver in a ddrt system are: Healthy Trees and Clean Ropes.
These days SRT climbers have been using the ring and ring too. Here you can see it set at the TIP (tie in point). An Alpine Butterfly cinches against the small ring and the climbers weight keeps it set there. We can clip rope or a karabiner to the loop for extra safety.
Without the ring and ring we would choke the rope to itself but this means that the climber has to exit the tree parallel to the non working end in order for retrieval. With the ring and ring a climber can exit any which way. With a ring and ring set at the tip a climber has an option to switch between srt and ddrt on the same system.
If you can isolate a limb then it is simple to set from the ground. If it is difficult to isolate a branch then the ring and ring can also be used as a trunk anchor. The photos describe the trunk wrapped rope and daisy chained lock off. In the event of a trunk rescue a hitch should be added and clipped to the rescuer.
The addition of an extra ring and friction hitch modifies the ring and ring for stem work. The adjustability means that we can choke a ddrt system so that in the event of a fall a ddrt climber is safe. srt climbers can utilise the addition for stem work too.