Tree Services Magazine - January, 2013
Tools & Techniques: Lowering Devices
Or, getting big wood down without breaking anything
A close-up view of the GRCS with rigging line in place and through the fairlead.
Photo by Odis Sisk.
The most basic and perhaps simplistic, depending on the person, of lowering devices is that stout branch manager on the crew who readily grabs hold of the rigging line and says, "Don't worry, I got 'er!" In this scenario, the tree care professional's first reaction should be to worry a great deal and perhaps explore lowering device options that are less organic and possibly even more cognitively aware, though it may not be readily apparent.
Traditionally, "wraps" around the trunk of the tree were the next option, especially after a crew member has gone "lawn skiing" and perhaps even ascended rapidly into the lower canopy while grasping the rigging line. Tree wraps, in which the rigging line is wrapped around the trunk to provide friction, can still be effective with an experienced branch manager and the right rigging system, but consistency of friction and efficiency are not the wrap system's strong points, especially not when you look at all the lowering device options available.
When used properly, a lowering device not only provides consistent friction and efficient operation, it will also increase the safety of the rigging operation by reducing the forces experienced by the rigging anchor point. To gain these advantages, the key is "used properly," otherwise relying on the best intentions of the stout branch manager may be just as effective.
The point of a lowering device, whether you use tree wraps or a more sophisticated system, is to get the pieces and parts on the ground safely and smoothly without breaking anything. While this may seem simple and straightforward, anyone who's been involved in more than a few rigging jobs can attest to the challenges they present. A well-trained, experienced rope runner will bring the load to a smooth stop with a minimum of forces being experienced at the anchor point in the canopy regardless of what device they are using, but the use of dedicated devices help make this smooth, minimal force operation much more likely and with a shorter learning curve.
A Port-a-Wrap attached to the base of the tree with an eye sling girth hitched to it.
Photo by Michael (House) Tain.
An experienced ground person can look at a load, incorporate the friction provided by that particular species' bark, and pretty quickly and accurately come up with the right number of wraps around the trunk to control the load. The problem comes when they are not experienced, off in their estimation of wraps, either too few or too many, and/or when they're spending a lot of time wrapping and unwrapping a rigging line around the trunk.
All of these factors not only cut into the efficiency of a tree removal, but in the case of too many or too few wraps cause some serious safety issues both aloft and on the ground.
Manufactured lowering devices are fairly cost effective in relationship to use, usually easily installed, portable, and imminently consistent in the amount of friction they provide. In addition, the majority of modern lowering devices are also capable of lifting loads in addition to lowering them, oftentimes on their own or with the addition of a simple mechanical advantage system.
The original Port-a-Wrap was designed and developed by two old-school riggers and climbers: Norm Hall and Scott Prophett. This version remains essentially unchanged, though some basic design changes have happened over the years that make the device even more user friendly. It is quite safe and efficient, one of the simplest ones to operate, and has the added advantage of being the most economical of the devices discussed here.
This device is available in a number of sizes and materials, with the friction generated by taking turns around the barrel of it, more turns producing more friction. It is typically attached to the trunk of the tree with an eye or whoopie sling, and allows the operator to be "back and away," out of the danger zone during lowering operations.
Connecting links should not be used to attach the Port-a-Wrap to the sling due to the danger of side or cross loading. A better, and safer, option is to girth hitch the eye of the sling around the larger of the two U-shaped attachment points.
While it is intended primarily as a lowering device, the Port-a-Wrap can also be used in lifting/lowering operations through the addition of fiddle blocks or some other mechanical advantage system, but users should examine their intended system closely prior to use to ensure that measures are in place to allow simple switches from lifting to lowering or vice versa.
Stein single and dual bollard
Although I lack personal experience with these devices, they would appear to follow the general advantages of lowering devices in providing smooth, consistent friction in rigging operations. Both also offer the option of removing "slack" or elongation from the rigging line, thus reducing free fall distance of the piece being lowered.
The dual bollard also presents the advantage of being able to operate two working rigging lines at once should the particular rigging system require it. The Stein single bollard lowering device is attached to the tree with an eye sling, while the heavier dual bollard requires the use of a ratcheting strap system, as do the GRCS and Hobbs.
Good Rigging Control System (GRCS)
Greg Good, the designer and developer of the GRCS, is also a working arborist, as are the majority of lowering device originators.
While the device is more complicated, heavier and more expensive than some others discussed here, it also has a number of options that make it an "all-in-one" choice for regular tree care rigging operations.
It is secured with a heavy-duty ratcheting nylon strap and can also be used with a visor plate inserted into a chain saw kerf for extreme rigging operations. An aluminum drum is used for standard lowering, but can be easily switched out with a Harken two-speed winch for lifting or pulling. Switching the units out can be complicated by a lack of clearance beneath the mount due to root swelling or bark irregularities, so users should pay attention prior to having to carry out the actual switch.
The GRCS can be used for lowering, lifting, pulling in felling operations, and it has even played a role in stump removal operations. The integrated fairleads make it easy for use by one operator, and the availability of various mounts for trucks increases its versatility, along with an available chuck for gas-powered drills for those jobs requiring multiple lifts.
An older version of the Hobbs, not the H2, in place in a rigging operation. Note the use of chaps for additional preservation padding.
Photo by Michael (House) Tain.
The Hobbs Lowering Device, now upgraded and redesigned to the H2, was in many ways the originator of heavy-duty rigging devices. It has the capability to lift, lower and pull with no switching of drums or winches, and it uses a ratcheting strap for mounting. The modes for attachment are based on the needs of the particular job and include a "cut-in" mode that actually cuts a slot for the device into the tree for extreme loads or lifts.
The alloy drum, or bollard, which is used for both lifting and lowering, dissipates heat well. Lifting/pulling force is generated through the use of a breaker bar to turn the drum, while a ratchet device prevents loss of what has been gained. The H2 also has integrated fairleads to assure smooth rope movement, and general instructions are printed on the body of the device to help ensure correct use.
This is obviously just a basic introduction to the world of lowering devices. Each of those mentioned here has more capabilities than are mentioned, and all will require a certain amount of familiarization and training to be used effectively, safely and to their full capacity.
Any tree company that does rigging removals on a regular basis should explore the lowering device options that are available and consider moving beyond a stout ground person and tree wraps, as to not do so is risking injury and inefficiency.
Michael (House) Tain is a contract climber, splicer, educator and writer associated with North American Training Solutions/Arbor Canada Training and Education, currently located in Lancaster, Ky.