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FAQ's from the ACCT Installation Standards Committee

FAQ's from the ACCT Installation Standards Committee

What class of pole is required for use in supporting high elements and towers?
Installation Standard A3.3 states no specific class of pole is required for towers or high elements. Class 2 is recommended for most structures based on the traditional designs that have been commonly used. Designs for towers or high elements can vary considerably with different structural needs. Issues such as bracing, guying and the overall size of the structure will affect the class of pole necessary and may allow for smaller poles. As designs become more complex, consultation with structural engineers is highly recommended.
Are thimbles required by ACCT when connecting cables to eyebolts?
The ACCT Standards do not require the use of thimbles when connecting cables to eyebolts. A thimble should be used when wear is expected between the eye and the cable in any connection.
What is responsible for the greatest amount of fatigue on a course installed in trees?
Weather has the greatest impact on the wear and tear of a challenge course installed in trees. The constant exposure to wind and environmental conditions is always impacting the course components, causing wear on parts as the trees move.
What is the primary reason for proper spacing when installing cable clamps or ferrules?
In order to get the full strength from each of the cable clamps or ferrules gripping the wire rope, the clamps and ferrules must be loaded equally. The farther the clamps or ferrules are apart, the greater chance that the two cables between them will not be parallel. This will cause one clamp to be loaded before the other and slippage will occur at a lower load. The manufacturers' specifications must be followed, if available, when using any materials for challenge course construction.
Under what conditions can I use an element connected to a dead tree?
ACCT does not support or condone the use of dead trees as support structures for challenge course installation. However, initially healthy trees used for elements will occasionally die or suffer from injury or disease that can make it difficult for them to rejuvenate and maintain their health. Some trees will remain structurally sound and capable of supporting the loads necessary for an element for a period after the canopy has died back. A qualified arborist should be relied upon to make these assessments. Under no circumstance should an unhealthy or dead tree be used as a support for a new challenge course element.
Is 1" tubular nylon webbing with a breaking strength of 4,200 pounds acceptable as a lifeline?
According to Installation Standard C1.1: "Rope used for belay purposes must have a manufacturer's rated breaking strength of at least 5,000 lb. (22.2 kN) when new." All cordage, whether rope or webbing, used as a lifeline on a challenge course must meet this standard. This, however, does not negate the use of 1" tubular webbing for other appropriate applications, such as Swiss seats.
What is the required installation depth for a 40' pole in average soil conditions listed in the ACCT Standards?
Due to the variables that are often found in the field, such as unusual media (sandy or rocky soil composition) and high moisture content of the soil or high ground water, there is no "average soil." Additionally, there is no "required" depth for poles set for challenge courses, although there is a recommended depth for the setting of poles. According to the ACCT Installation Standard A3.4, "Utility company standards are generally used as a guideline for the installation of challenge course poles. Normally, poles will be installed to a minimum depth of 4' feet (122 cm) or 10% of their length plus 2 feet (61 cm), whichever is greater." Therefore, in the case of a 40-foot pole, the typical recommended depth of installation would be 6 feet.
Is it possible to safely support more than one ground (dynamic) belay system on a 3/8" cable, and if so, under what conditions?
It is possible to have two participants on a typical horizontal traversing element, such as a Two-Line Bridge, without exceeding the safe working load of a single belay system. The belay cable may require a greater sag/span ratio than 10% due to the additional weight. Basically the system would still need to be designed within the safe working loads of the 3/8” cable. In reality, this is more difficult to do on the longer cable spans because of how the cable sag affects the operation of the element. (See Appendix D in the ACCT Standards book.)
Why can you use a 5% sag/span ratio a zip wire (using standard 3/8-inch cable system described in the standards) and still stay within the safe working load of the cable?
On a zip wire (static belay) the vertical force is created by the participant only, thus it is 1/2 of the expected vertical force generated by a dynamic belay. With a dynamic belay the vertical force of the belayer doubles the vertical force of the participant on the horizontal belay cable. This makes it possible to tighten the zip wire twice as tight as regular horizontal belay cables. (See Appendix D.)
Can I use a thimble eyelet on a bolt for a cable attachment point?
Though not preferred, thimble eyelets are okay to use for cable attachments. The thimble eyelet should be used on the head end of the bolt only, and the pull on the assembly should be approximately in line with the bolt. A flat washer should be placed between the thimble eyelet and the pole or tree.
I moved my cable clamps and the exposed cable is now deformed. Do I need to retire the cable?
Usually deformation caused by cable clamps will not cause enough damage (protruding core or broken wires) to require cable retirement. If the deformation is in an area of the cable that will have hardware rubbing on it (i.e., pulley or rapid link), it may be advisable to retire the cable. (See Inspection Standards C2.)
Why can't I use 1x17 strand cable on a challenge course?
Cables with less flexibility, such as 1x17 or 1x19 construction, are acceptable to use when properly installed using connectors suitable for the type of cable used. When these stiffer cables are bent around a bolt or anchor, internal stresses are set up which can cause cable failure over time. Because there are very limited options for terminating these cables, especially if the termination has to be backed up, their use is discouraged.
How long might I expect my wire rope to last before I need to retire it?
Under normal conditions, one might expect wire rope to last 10-15 years. However, there are a wide variety of factors that affect the life of wire rope. Harsh environments, such as salt water, industrial pollution, and high use, can significantly reduce the life of wire rope. For retirement criteria, refer to Standard C2 in the ACCT Inspection Standards.
Do checks in poles affect the safety (structure) of the pole?
No. Checking is a normal occurrence in wood, particularly poles. Checking occurs as the pole dries out. This does not affect the structure or strength of the pole. However, if checks are deep enough, some untreated wood may be exposed and becomes more susceptible to rot and insects, so treatment is necessary. If the location of the check impacts the integrity of any hardware placement, it will need to be monitored and possibly relocated.
Can I use Penta-treated poles on my course?
All treatments used for poles are toxic in one way or another. Penta is the most common treatment used for Southern pine utility poles. The name is short for a treatment called Pentachlorophenol, a chemical treatment that uses a petroleum medium to make it adhere. It is mainly the petroleum that is a skin irritant. After a number of years, the surface of Penta poles becomes less oily and therefore better for skin contact. On challenge courses, Penta poles are best reserved for use where there is low potential for this direct skin contact (some tower designs, Zip Wire end poles, support poles for some low element cables, etc.). When in doubt, verify that state environment and health regulations allow the use of Penta poles for a challenge course.
Should I back off the nuts on through-bolt connectiions to allow the tree to grow under the washer?
Section C1 of the Safety Inspection Standards states that: The practice of loosening nuts to allow for tree growth is discouraged because the movement of the bolt in the tree after loosening may harm the tree. Backing off through-bolts (not lag screws) on wood braces may help extend the life of the platform by reducing the crushing of the lumber as long as no movement results in the connection.
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