The easiest approach was to purchase a kit that has everything I need to build a zipline. I found this kit on Amazon and ordered it.
The kit included a trolley, cable, harness, and helmet. It was less expensive to buy these items as part of a kit than it would have been to purchase each separately.
When the kit arrived at my doorstep two days later (it was ordered via Amazon Prime) I was anxious to see how it worked. I spent maybe an hour stringing the cable between the two trees and getting the trolley installed on the wire.
I noticed a couple of things right away that I wanted to eventually change. The cable was made of quarter-inch steel, but I wanted something bigger and stronger. My research showed that a three-eights inch cable had a tensile strength of 14,400 lbs (quarter-inch cable is 5,480 lbs), so I would want to use this stronger cable on my final configuration. Also, the trolley seemed to be well designed and made and included bearings in the wheels. But once the trolley was installed on the cable it could not be removed without disassembly. The cable threads through the trolley housing; removing the trolley from the cable required a disassembly of the housing. Other trolleys are designed so that they can easily be installed and removed from the cable without having to disassemble the housing. The significance of this is that I’ll have to either leave the trolley on the cable in all weather, or go through a hassle to remove it for storage. I’ll use it for now, but may want to upgrade later.
The quarter-inch cable included some hardware for fastening the cable. While the tensile strength is 5480 lbs, the strength of some of the hardware components is much less. Since the cable is only as strong as its weakest component, that was a concern. I’ll have to consider the strength of any cable components when I eventually replace the cable with the larger diameter one.