One Way to Build a Zip Line in Your Backyard
Before we proceed, a word of caution is in order (don't worry, this is not about child security; it is about deltoids). What makes this zip line work is the fact that the parent (or other trusted adult) offers the change in raising needed to propel the rider forward: The adult stands on a ladder right behind the rider's launching platform (any veranda chair will do) and lifts up on the line itself, then holds the line in both hands above their head while the rider sails toward the opposite end of the line. This does take some strength— depends on your child's weight. It is also worth noting that this is great exercise for both parent and child: You work your shoulders and triceps, and your youngster gets a cardio work out running back with the trolley after every run (they will also get a great start on constructing those Popeye forearms children are really so crazy about these days).
And now for a word about child security: You, not I, are entirely responsible for anything that happens to your kid as an outcome of zip liner. All I can say is, my zip line has been safe for my 40-lb. daughter for two summers, so far. Now, in the event you'll excuse me, I must go find some wood to knock.
I used the following components to create my backyard zip line:
3/8-inch-dia. x 100-ft. nylon rope (I can not recall the load evaluation, but it was many times more than my daughter's weight)
Ratchet straps (2)
Stainless steel pulley
Big galvanized eye slowdowns (2)
Wood broom handle
This is the process I followed: