Material Selection

All materials used for outdoor installations must be corrosion resistant and the treatment type must be matched with the environmental conditions and type of lumber treatment used. The minimum diameter for cable shall be 3/8” and all bolts used for belay systems will have a minimum diameter of 5/8” or in some circumstances use multiple 3/8” or ½” bolts in unison to achieve desired strength ratings (such as in platform construction).

 

Bolt Strength

All Through-bolts (eyebolts, thimble eyebolts, angle thimble eyebolts, machine bolts timber bolts and other bolts) that are used for the support of belay cables, foot cables and guy wire cables must have a minimum breaking strength of at least 11,500 lbs (51.2 kN). Staples, shoulder lag eye screws may not be used to replace the bolts in these applications and should never be used as a primary fall protection anchor.

Chart of Tensile Strength of Common Cable Connection Hardware (lbs)

Type of Bolts

5/8” 

¾”

Oval Eyebolt

13,500

20,050

Nut Eyebolt

17,500

26,000

Thimble Eyebolt

13,550

20,050

Angle Thimble Eyebolt

13,550

20,050

Machine Bolt

13,550

20,050

Washers

A round, square or curved square steel washer at least equivalent in area to a 1-3/4” (4.5 cm) diameter must be used on both sides of all bolts  (except timber bolts and shoulder patter eyebolts which will require only one washer as each have washer heads on one end.).

 

Double locking ring washers should be used for all application in wood and concrete. Single coil may be used in steel installations.

 

Washer Images

Curved Square Washer

Square Flat Washer

Round Flat Washer

Double Coil Lock Washer

Single Coil Lock Washer

 


Belay Cable, Bolt and Guy Wire Alignment

Typically bolts should be installed in line with the expected load, except for use with bolts (angle thimble eyebolts for example) or with specially designed fittings intended to support angled loads.

 

Location and Installation of Bolts

No bolt shall be installed less than 12” from the top of any pole (14” minnimum preffered). A single variance of an inch or two on an occasional pole is not itself an issue. If however you’re inspecting a course that has all eyebolts installed 8” from the top of the pole the course should be repaired to reflect the industry standard.

 

WIRE ROPE TERMINATIONS

 

Swaged Eyes

For new installations only Zinc Plated Copper (for outdoor use) and/or Copper Ferrules should be used. However in the inspection of older courses aluminum ferrules are acceptable when installed on foot cables and non critical element suspension systems. Aluminum ferrules must not be used on belay cables or critical element cables and there presence shall result in the failing of the element. A wire rope thimble should always be used when wear is expected on the eye, if significant wear is expected then a Heavy Duty Thimble should be used.

Proper Swaged Termination for Belay Cables

Proper Swaged Termination for Foot and/or Element Cables

 

StrandVices

While ESI does not use StrandVices in any of our installations they are a commonly used piece of hardware frequently installed  by other builders and more commonly found on dynamic belayed designs. StrandVices used on challenge courses must be model 5202 and in all applications must be backed up.  See current ACCT standards for illustration of appropriate ways to backup StrandVices.

 

Things to inspect for include:

  • Proper type and size – 5202 – some older course may have other models if it’s not 5202 it fails.
  • Damage to the Bail (bent, twisted or fatigued). If it’s bent it fails.
  • Broken strands of cable where it enters the narrow end of the cone.
  • Backed up appropriately for its application (See ACCT Standards). If it’s not backed up it fails.

 

Strandvises® in any application must be backed-up to prevent connection failure due to wire rope slippage and bail failure. In critical cable systems, this back up must be done according to ACCT Installation Standard Section B4. In other applications, the strength of the back up must be five times the expected load on the cable.

 

 

Cable Clamps and Fist Grips

All cable clamps and or Fist Grips must be manufactured from drop forged, galvanized steel or equivalent corrosion-resistant material such as stainless steel.

 

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 allways be followed.

 

Wrap Style Belay Cable

                                                  

Proper Cable Clamp Assembly

 

Wrap Style Foot and/or Element Cable

                                                               

Fist Grip (or double saddle clamp) and Proper installation

                                                                                                                                                                                           

 

Non Typical Terminations

If other termination methods are required or used, it must be rated by the manufacturer to be at least 80% of the strength of the cable and corrosion resistant if used outdoors. Non typical termination may be required by an engineer.

 

 

BELAY CABLES

 

Wire Rope

Belay cables, Zip Wires, Soaring Eagles, Giant Swings and or other fall protection systems or support systems for critical applications must be made from 3/8”  7 x 19  Galvanized Aircraft Cable or “flexible” wire rope. Stainless steel wire rope may be necessary in marine rich environments with a high salt air content.

 

Belay Cable Strength

The entire belay cable system, including connections,  terminations and or any required back up systems must have a breaking strength of at least 11,500 lbs (51.2 kN), and must be designed and built so that the maximum intended load does not exceed one fifth of this breaking strength. At minimum the safe working load of any belay cable or belay cable system must support at minimum 2,300 lbs (10.2 kN).

 

Through Bolt Termination Redundancy

Through-bolted belay cable terminations must be backed up with a cable system rated at least 80% of the primary belay system strength, and configured to protect against bolt and termination failure, not just wire rope failure. In backing up belay cables and critical applications, three properly installed wire rope clips or two copper ferrules must be used on the cable termination.

 

Redundancy in Cable Wrap Systems

When a cable wraps around a tree or pole and  is used as the primary belay termination (no through-bolt is installed), three properly installed wire rope clips , fist grips or two copper ferrules must be used and installed the correct distance from the tree or pole. The third clip, grip or second ferrule acts as the redundant termination point.

 

Belay Cable Placement

Belay cables, whether supported by a through-bolt or cable loop must be installed at least 14” from the top of a wood pole. However, during inspection a belay cable can be within 12” of the top of a pole.

 

FOOT CABLES

 

Wire Rope

Foot cables  must be made from at minimum 3/8”  7 x 19  Galvanized Aircraft Cable or “flexible” wire rope. Stainless steel wire rope may be necessary in marine rich environments with a high salt air content.

 

 

Foot Cable Strength

The foot cable system, including connections and/or  terminations must have a breaking strength of at least 11,500 lbs (51.2 kN), and must be designed and built so that the maximum intended load does not exceed one fifth of this breaking strength. At minimum the safe working load of any cable must support at minimum 2,300 lbs (10.2 kN).

.

 

GUY SYSTEMS

 

Guy System Design

Guys wire systems are designed to transfer the bending loads from horizontal cables into a compressive load within the pole or tree. The intention is to restrict the bending load, for which the pole or tree has a limited tolerance. Guys should be located so that they directly oppose the load generated by the cable(s) that the guy(s) are supporting.  All poles that have horizontal support cables must be guyed unless they are attached to a separate structure that provides the rigidity and/or flexibility required.

 

Wire Rope

Guy wire cables  must be made from 3/8”  7 x 19  Galvanized Aircraft Cable or “flexible” wire rope. Stainless steel wire rope may be necessary in marine rich environments with a high salt air content.  Depending on the challeneg coruse design including the number of guy wires and there location other types of cable may pass and inspection.

 

Strength

Each guy wire system, including all connections, terminations and anchors, must be installed so that the maximum intended load does not exceed one fifth of the breaking strength of any component in the system.

 

Guy Wire Placement

The guy wire termination may be above or below the cable termination and will c=vary depending on the element and course design. When installed above the belay cable, the guy termination must be at least 12” (30.5 cm) from the top of the  pole.

Ground Anchors

Ground anchors (plate anchors, no-dig ground screws, etc.) should be inspected for the following:

  1. Proper type and size for the application
  2. Properly installed angle for load(s) being applied to the anchor.
  3. Properly spaced and installed clamps or alternative cable attachment (StrandVices must be backed up)
  4. Ground around anchor should be inspected for signs of upheaval or erosion.
  5. Ground anchors should be inspected for bending, twisting or other fatiguing or stresses that weaken the intended application of the anchor.

 

Types of Anchors

 

Screw-In Anchors

Screw-in anchors are recommended for softer soil types, Classes 5-7 in Table 1. They do not work well in rocky soils. The screw-in anchor is a 66" (1.67m) hot-dip galvanized steel bar with an eye on one end for attaching the guy wires and a 6" or 8" (152.4mm or 203.2mm) diameter screw at the bottom (see Figure 2). These are standard anchors used in the utility industry. The screw-in anchors must be installed at approximately a 45° angle so that the load on the anchor is in line with the guy wire axis. Screw-in anchors can also be used in applications where an anchor will be embedded in concrete.

 

Drive-In Anchors

Drive-in anchors are recommended for denser, rocky soils, Classes 2-5 in Table 1. The anchor is a 6" (152.4mm) wide malleable iron triangle with a 48" (1.22m) long cable attached to it. A drive-rod is used to drive the anchor into the ground. Drive rods can be driven manually with a sledge or with power equipment if available. The drive-in anchor must be “set” by pulling the anchor until it rotates 90°, as shown in Figure 3. These anchors are useful in denser soils because they can be forced into the soil more easily, and the triangle design tends to thread around rocks in the soil.

 

Cross Plate Anchors

The Cross-Plate anchor is made for installation in holes drilled by augers. Because the size of the hole does not affect holding capacity, the hole can be dug by the same auger that is used to dig the pole holes. Cross-Plate anchors are installed in a diagonal bored hole

which is undercut so the anchor is at right angles to the guy. A rod trench is either cut with a trenching tool or drilled with a small power auger. Both anchor and rod trench should be refilled and tamped.

 

Expanding Rock Anchors

This anchor expands and wedges against solid walls of rock. And, once it is expanded, the harder the pull on the rod—the  tighter it wedges. Wedges are made of malleable or ductile iron with a rust-resistant coating. Rod should be in line with the guy.

 

Guy Wires that Are Critical

A guy cable is considered critical if its malfunction results in either a major drop in the height of the element cable (endangering the participant) or a failure in a support member (pole or tree). Critical guys must be installed just like a belay cable. Appropriately installed ground anchors that meet ACCT strength standards, do not require backups.

 

Examples of critical guy wires include: Guy wires supporting a single element (not part of hub and spoke design), Zip Line guys, Giant Swing Guys, Flying Squirrel Guys, Power Pole guys, and guys helping to support significant weight. This list is not all inclusive of the elements that require critical guys.