The net effect of both swinging and spinning, especially with a balanced load, lead to an unpredictable ride. The period of the swing and the rotation of the bench rarely matched, so most of the journey was spent off to the side, tilted at a slight angle as you rocketed up to the highest point or swung down and into the claustrophobic nadir, only to miss the peaks just slightly. It was deliciously unpredictable.
One of my favourite things to do on the thing was to first spin the thing, building up as much momentum as I could, before pushing the ring toward the pole as far as I could and letting it swing back. The thing's mass meant that it didn't lose momentum easily, and if I timed my entry right, I could wrap both my arms around the wooden bench and be hefted not only high up off my feet into the air, but also be whipped around in a circle at high speed.
It wasn't that I was ignorant of how dangerous it was at the time. The prospect of the momentous steel and wooden contraption breaking my arm by catching me on the upswing, crushing me between the inner rail and the unbumpered post, breaking both my legs as a vigorous push nudged the cap off the top of the post and the wooden bench fell with all its weight on my tiny, fragile calves wasn't completely out of the realm of possibility. Most kids who injure themselves on playground equipment do so because they took a calculated risk but miscalculated, high on adrenaline or too bored to avoid upping the ante. It's always been my philosophy, even as a youngster, that these kinds of mediated dangers are great for kids, and that though accidents are never deserved, or predictable, they sure as hell teach a lesson.
A woman in Geraldton in Australia tried to save this delightful relic, which resembles the one from my childhood quite a bit (except for the bench, which on the island had a rounded, protruding bench which was painted red, and for the fact that this one has a safety bumper and a thicker, sturdier post) but she was ultimately unsuccessful. More's the shame. AFAIK, I don't think they were ever mass-produced, and so every iteration has a unique design. Sadly, nobody seems to have archived any information on dangerous playground equipment of yore.