Backyard Zip-Line for Kids

(Click on images to enlarge)

This is not really a Do-It-Yourself site, but I recently underwent the ordeal of building a zip-line by trial and error and thought that sharing my experience might help others trying to do this for their kids. I originally was going to just buy a kit, but they were a little more than I wanted to pay and I got talked into trying to custom build one by a dude at Lowe’s.

He suggested I buy a certain gauge of rope and a metal pulley with a swivel on it. I tried this, and the rope basically acted like a rubber band, sending even my lightest son (I have three, ages 10, 8, and 5) to the ground within about 10 feet of the take-off platform. By the end of the day I had concluded that steel cable would be the only way to fly for the 60 feet was trying to span and the angle of the descent. Back at Lowe’s, I purchased about 70 feet of 3/16 ” steel cable, which was no more expensive than the rope — about $40. When I tried to string it up I found it was hard to get enough tension on it. It too was sagging to the ground. So tension would be the next holy grail.

I weighed several options and wound up buying a “come-along” or “fence puller.” It goes by several names but is basically a ratchet with an 18-inch handle on it and two steel hooks that you can ratchet in to take out six feet of slack or ease back out if need be. This product (from Lowe’s, of course) is called the Pow’r-Pull from Maasdam (about $40). You might think you’re man enough to pull 60 feet of steel cable tight enough for zipping but you’ll be sorely disappointed. This will be the best $40 you’ll spend during this project. The come-along will allow you to make subtle changes in tension from day to day as the trees change or as you might get heavier friends trying out the zip-line. (On that point, my 10-year -old is about 65 pounds, and he probably has a little more than a year left on this.)

The come-along. $40 well spent.

With the steel line up and the come-along in place, I now found that the metal pulley I bought along with the rope wasn’t performing. The trough that the cable rode in was too wide and the pulley wheel was turning this way and that on the way down creating lots of drag and a slow ride.

On a return visit to Lowe’s, I bought a couple of cheap plastic pulleys of different sizes that are intended for clotheslines. I was worried that the steel cable would chew up the plastic pulley wheel, but such has not been the case, and the thinner wheel trough was indeed the key to a faster (and quieter) ride.

Oh wait — I knew I was leaving out a bunch. From the beginning I had intended to fasten the upper end of the line to the boys’ fort, the roof of which was their launch pad. This fort is built for the ages, constructed out of solid walls of landscaping timbers nailed together with six-inch stakes. It doesn’t budge. But when I started putting tension on the steel cable, I started pulling off the superstructure that the cable was attached to. When after another round of purchases I bolted the superstructure on and started cranking the come-along again, the whole fort started to come down. Long story short, GO TREE TO TREE. Find two trees first, THEN measure your distance and buy your cable. After looping the cable around your branches you can connect it to itself with steel clips. Use locking nuts and crank them on as tight as humanly possible. If your line fails (as it did during our first day) it will be here.

The zip-line runs tree-to-tree over the roof of the fort which acts as the launch pad. Trying to attach it to the fort was a time- and money-wasting near-disaster.

The pulley-handle assembly consists of the aforementioned plastic clothesline pulley joined by a steel loop to an eye-bolt that is fed through a dowel of about 1-inch in diameter and capped by a washer and locking nut. We stole a blue seat strap off an old booster seat that lets the boys pull the handle back to the launch platform.

UPDATE: Well, the zipline has been up about a year now, and, of course, the plastic pulley pictured above didn’t fare well in the elements. (It broke on an especially fast run into the bottom turnbuckle. So I poked around the Lowe’s a little more and made a SUBSTANTIAL improvement in both durability and performance. I used a couple of L brackets with a hole pre-drilled in the corner of them, and a couple of garage door pulleys so that the whole assembly (with the exception of the dowel) is now steel. Using TWO pulleys instead of one also substantially increased the speed because it holds the operator straight and doesn’t waste energy on the twisting from side to side that the above assembly did.

Garage door pulleys connected with two L brackets and held to the handle with a steel loop has improved the performance and the safety. The only drawback is that if the cable is allowed to jump outside the pulley it can occasionally jam and have to be forced out of the pinch spot and back into its slot.

Lastly, steel cable with this kind of tension will slice through most branches like hot butter. After some unsuccessful experimentation with lumber scraps to protect the branches, I went (to Lowe’s) and bought a PVC coupling about 5″ in diameter and cut it lengthwise in half, each half being used to protect a different limb.

I had to split the difference in height between these two branches in order for the line to be high enough over the fort but not too high. If you can get away with using one branch, that’s certainly the way to go.

So to sum up:

1. Unless you are working with a hill that increases your slope, use steel cable, not rope.
2. Go to tree to tree, unless you’re coming off a steel or concrete structure. Just to get a steel cable straight takes more tension than you’d think.
3. To create loops at the ends of your cable, use steel rope clips with locking nuts (sold separately) tightened to the max.
4. Use two steel garage door pulleys connected with L brackets for the handle assembly.
5. Buy a come-along or fence puller to give you control over tension. The come-along shown will take up to 6 feet of slack out of your line, so pull it as much as you can manually before you form your loops and attach your clips, hence fixing the cable’s lenth.
6. Protect your trees with a large-diameter PVC coupling cut in half lengthwise.
7. Lastly, I spread a few bags of hardwood mulch under the first few feet of the line in case there’s a fall at the highest point. The low end, fastened at about five feet, basically just sets them down gently on their feet.
8. For a 60′ line like ours, you should be able to get out for just under $100. ($40 for cable, $40 for come-along, $20 for clips, dowel, pulley, eye-bolt, etc.)

Lots of false starts and mid-stream adjustments but it was worth it. And if I had this info, I could have done it at about half the cost and 1/3 the time.

Have fun! Even backwards and upside-down …