How to Build A Zip Line
Posted on 05 July 2016
When testing the cable with a weight it should sag below the end anchor, and approximately 2% of the zip line’s total length. (don't worry it doesn't have to be perfect.)
The zip line cable should also have a 7 foot ground clearance as well.
Example: For a 100 foot zip line, the end of the cable would anchor 2 foot higher than the lowest point of the cable when a test weight is on the line. The minimum height on the ending anchor would be 9 foot to accommodate 7 foot ground clearance.
All tree anchors must be at least 12” thick in diameter. Only healthy, sturdy trees are suitable as anchors. Never attach cable to trees with excessive decay, cracks, exposed roots, diseases, excessive lean, lightning damage or poor tree architecture. Free-standing poles (without guy-wires) must be 12” diameter, minimum. Poles must be sunk into ground at least 4’ or 2’ plus 10% of the pole’s height, whichever is greater.
Eyebolts that are used to terminate a zip line to a pole or tree must penetrate the anchor entirely in order to be secured with a washer and nut.
Bolted Trolleys (uncommon)
If the trolley does not mount freely on the cable, be sure to thread the cable through the trolley before terminating the zip line to the anchor.
Otherwise, the trolley wheels can be un-bolted to allow the trolley to assemble onto the cable.
When dealing with cable lengths up to 100’, you can create a loop at the end with a cable clamp. Wrap around the anchor and loosely clamp the intersecting cable. Pull loop to tension line, then secure cable with three clamps.
If the cable is too difficult to tension a cable by hand, hitch the loop to a vehicle or winch. A winch and cable grab combination is most practical, requiring no cable loop.
Turnbuckles are used to adjust cable tension. While major adjustments require a winch and cable grab, the turnbuckles are useful for fine tuning.Turn the buckle to screw the shafts in or out. This often requires a bar or wrench, slid into the buckle, to leverage the rotation.
It is recommended in the zip line industry to back up every turnbuckle with a cable and clamps.
Note: Turnbuckles extend the start of the zip line ride even further from the tree, so if your platform is too small, you may not have the space to safely mount on the cable.
Do not under any circumstances use chain link carabiners, only link attachments directly to trolley. Multiple carabiners can link to trolley. Do not put more than one attachment in a carabiner.
For any life support connections, (where the link is bearing the rider's weight) use a locking carabiner.