The ability to lower large branches or pieces of a tree under control is often quite desirable in tree care operations. This need for control may be generated by obstacles as simple as manicured turfgrass the client does not want damaged by free-falling wood to ones as complex and hazardous as energized electrical conductors beneath the branch or tree to be removed. In either of these scenarios, the ability of ground personnel to control the descent of the piece or branch safely and efficiently, while minimizing the forces generated within the rigging system by shock loads, is extremely important.
Traditionally, tree care crews have generated the necessary friction to lower pieces safely by taking “wraps” around the trunk of the tree itself or an adjacent tree. This method, though quite simple, has a number of disadvantages. The friction generated will vary widely between species of trees, with rough bark requiring few wraps and smooth bark many more. This knowledge can only be gained through on-the-job experience, and may require a certain amount of trial and error when confronted with species the ground personnel are unfamiliar with.
Unfortunately, in this case, the trial may result in an error that might include a piece descending at a high rate of speed out of control; ground personnel “lawn skiing” toward the trunk of the tree rapidly; or a piece coming to a dead stop, putting an unacceptable shock load on the rigging point itself. In addition, having to walk around the tree with a rigging line again and again to install or remove wraps before and after every lowered branch or piece will not only test the patience of the most highly motivated ground person, but also does not lend itself to an efficient and smooth work process.
The toll taken on rigging lines by this friction against the trunk may not only reduce their effective strength, but also do serious damage to the cambium layer of trees not being removed. A safer and more efficient option may be the purchase and use of a lowering device. Lowering devices provide tree care professionals with tools that are not only fairly easily installed on any tree, but also provide the same amount of friction regardless of species.
This consistent friction allows operators to use the appropriate number of wraps for the size of the piece being removed, with no concern for the roughness or smoothness of the bark, and to do so without having to carry the rigging line around and around the tree. The increased safety, ease of use and attendant efficiency of lowering devices make them an obvious choice in rigging and removal operations for tree care professionals.
The Port-a-wrap is one of the simplest of lowering devices available, yet also quite safe and efficient. It is available in a number of sizes and materials with a safe working load (SWL), dependent on model, of 1,000 to 2,000 pounds.
The required friction for lowering is generated by simply taking turns around the barrel of the device, more turns meaning more friction, while the device itself is attached to the tree with an eye or whoopie sling. Girth hitching the sling to the Port-a-wrap will prevent the need for a connecting link that may become dangerously cross or side loaded during dynamic rigging operations.
Though primarily designed and intended as a lowering device, it also works well in lifting or pulling systems with the addition of fiddle blocks or some other form of mechanical advantage to generate the desired lift or pull.
Good Rigging Control System
The GRCS, though much heavier and more complex than a Port-a-wrap, has a number of excellent features. It is equipped with an aluminum rope brake for straightforward lowering operations and a Harken 44: 1 two-speed winch for those operations requiring lifting, pulling and lowering.
These units are easily switched by sliding them in or out of the mounting bracket that is attached to the tree with a heavy-duty ratcheting strap. The GRCS will accommodate ropes from .5 to .75 inch and features a self-tailing device and fair leads that allow easy operation by one person.
H2 Hobbs Lowering Device
The H2, an upgraded and redesigned version of the Hobbs Lowering Device, also features lifting, pulling and lower-ing capabilities in one unit. Straightforward lowering operations are performed on the same bollard or drum that advances the line in lifting or pulling operations, and lifting power is generated by a simple ratcheting device and the operator using a breaker bar to turn the drum and advance the line. Fair leads help feed the line onto the drum correctly, and the H2 is attached to the tree with a heavy-duty ratcheting strap.
These three lowering devices obviously have many more features, abilities and even complexities than are discussed here. Hopefully, this introduction to lowering devices will help to encourage tree care professionals to research and explore some of the appropriate options available, and then use that knowledge to integrate lowering devices into their rigging and removal operations. The end result can only be increased safety, productivity and efficiency.