No.3 Compatible Rigging System
I began to think about 'compatible rigging systems' these days. We learn about equipment in England but 'compatible' includes tree, climber, equipment and method of rigging. What an interesting subject, I will write about those four elements.
1. Tree 2. Climber 3. Equipment 4. Method
Each element affects the other and management should not neccessarily follow the elements in a 1,2,3,4 direction.。
A Job plan will always take the TREE as a starting point. We should look at the health of the tree and make decisions about the Work Plan for the job specification based on this. Tree structure, health, strength and timber qualities as well as any obstacles within the drop zone will dictate the pruning or rigging method.
We must then choose a suitable CLIMBER with a skill level compatible with the proposed work plan.
The EQUIPMENT choice and Method are dictated by several considerations. The initial tree survey should be checked when deciding upon a suitable rigging method. Will we be Dynamically or Statically rigging or both? Will we be running ropes Fast or Slow. Having a wide selection of ropes, slings and lowering devices will aid in the safety and efficiency of the Work Plan and we can choose EQUIPMENT accordingly.
We must follow rules when combining EQUIPMENT into a rigging system. Here are some of them.
The Rope should be the weakest component. If a manoeuvre goes wrong and an element in the rigging system breaks it is better to suffer a broken arm from a snapping rope than be decapitated by a piece of steel.
There must be a suitable Bend Ratio at the pulley and lowering device and by suitable I mean CHECK MANUFACTURERS RECOMMENDATIONS and put these figures into your proposed rigging method. A 14mm rope may be suitable on a mid size portawrap for running pieces at mid speeds but when you have to let pieces run very quickly you will find the rope glazing. The large aluminium bollard on the GRCS or the Treeworker Friction Tube would be a better choice in this instance.
Most people rig with a 10:1 safety factor on their ropes and it keeps us far away from the possibility of snapping a rope. If a rope is designed to break at 4000kg then we would assign a 400kg Safe Working Load when working. Dynamic loading is very common in rigging scenarios and we should all be aware of the potential load forces involved and what it does to equipment. Learning about the management and care of equipment is an important aspect of rigging practice and it is encouraging to see the growth of rigging courses in Japan. Through study and practice climbers can become the most important part of a rigging system. Safe, efficient, flexible and commercial components with deep and inspiring craft skills.