My Uncle Ben could be counted on to provide amazing amounts of rope and hardware for our amusement. I always liked designing "rolley-coasters" (although the only things that rolled were the sheaves in the blocks).
A rope strung from high in one willow to the base of another was the foundation for such devices. Some sort of seat, harness or other platform was suspended from a pulley. The object was to make the ride down as terrifying as possible without actually killing anyone. Rope-burns and other minor injuries were non-events.
One main danger was that you were heading in the direction of whatever tree had been chosen as the lower anchor at a considerable rate of speed. Elaborate stops, restraints, or snub-lines had to be designed (and tested). I don't recall how the valuable life of the designer was designated "most-expendable," unless it was because I was smallest. Like the recent sport of bungee jumping, the idea was to get as close to the tree as possible without actually hurting yourself.
One year, the RC was strung across the Cut. The end of the ride was to be signaled by releasing the passenger for a drop into the water. The first design was an innertube with a 2" galvanized ring tied to it. A pin through that ring and two others shackled to the pulley was to be jerked out at the last second, saving the rider from smashing face first into the seawall on the other side of the cut.
With my head and arms through the innertube, I was hauled to the top for the first test. Doooowwwwn I went; a monstrous jerk; blinding pain!; and splash. Imagine how much energy was stored in that stretched-out innertube, before the pin released the ring to smash me between the shoulder-blades.
With the quick substitution of a riding platform with less elasticity, and a final test, that summer's rolley-coaster was in business. One of the neighbors, Mrs. Smiley, came over to see if any of her kids were about to be killed. When her husband followed a half-hour later to see why she hadn't brought the kids home to safety, he found her in line for her second ride.
I can't say there was no risk. Another bit of summer fun was the "injun death ride". one person got in the hammock -- the rest tried to get him out by yanking on the ropes. My Uncle Harold thought we couldn't dump him out and said so. That turned out not to be the case. By swinging the hammock high enough that it was facing the ground and then giving the ropes a violent snap downwards, Uncle Harold was ejected (and had three ribs broken.) That was the end of that as a formal activity.