Zip line sag. Keep tightening or no?
June 2, 2012 4:58 PM Subscribe
Zip line filter: I'm building a zip line on our property. The issue I'm having is cable sag. Help?
posted by charris5005 to home & garden (13 answers total) 2 users marked this as a favorite
The line is anchored at each end by heavy chain around very robust trees, with the cable hooked to the chains. The cable is 3/8" (14400 breaking point) 7-19. The run is 310 feet from start to end with a drop of about 6-8 feet (hard to tell because the ground drops also).
I am able to tighten the cable until it is near taut (NOT piano wire taut); then I test with a "crash test dummy" hanging from the trolley and weighing about 240 pounds (the weight of the heaviest person that will use it). After 1 or 2 runs with the crash test dummy, the cable is noticeably no longer taut. Per the instructions I got from the kit supplier, who said that new cable stretches and must be re-tightened, I have re-tightened it - probably 6-8 times. Each time it's near-taut after tightening, and then noticeably not so taut after a few runs.
The supplier has now told me that the reason the cable keeps stretching is because I'm tightening it too much. I'm unclear as to what this means. He seems to be saying I should stop tightening it. I'd appreciate feedback from zip line users out there about this issue. Is there a point where the stretching stops? Should I stop re-tightening the cable and deal with the 'sag' by raising the cable at both ends? Thanks as always.