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This little burg I live in has a fair once a year. Including carnival rides. Not quite like Disneyland, but some of them would get your heart pumping a bit on the adrenaline factor. They've got a tilt and spin, a hammer like ride, among others. But the impressive engineering is they are able to set them up and tear them down in about 4-5 hours. By Carnys.

I don't know if you've ever met any, I have a couple, they tend not to be exactly Mensa candidates, but do have a fondness for a certain white powder. Not necessarily bad guys, just not overachievers. And these are the people who are setting up and tearing down the rides once a week. So in my mind, for them to be able to do that, that quickly, without things flying apart and people dying regularly, there's got to be some incredible engineering going on. When one of these things fails, usually someone dies. But that usually seems to happen at the big parks. And these guys are doing it every week? The mind boggles, mine at least.

The last time I went on a carnival ride was a Ferris wheel at a county fair ~45 years ago.  While on the ride one of the cross members broke loose above our heads.  It flailed around and broke off a fluorescent tube that sailed past our seat and stuck in the ground.  The same thing happened the next night, except that time it stabbed some kid in the chest.

That was enough of carny mechanical ability for me.

Billy "Billy Boogie" Worrell would insist that his near perfect safety record on the Tilt-A-Whirl was due strictly to his prowess as an operator, but you may have a point that he was helped by some good engineering:

https://www.youtube.com/watch?v=9zuP5nbT68g

One of the factors that likely reduces the number of carny ride failures is that they are torn down and put back together again so often; the guys get to know the equipment well, and they're better able to spot & rectify problems before they are able to manifest as major failures during operation. The big park rides don't get that kind of thorough inspection very often. 

One of the highlights when we were in Germany was being able to take part in some of the local festivals. Every fall, Basel, Switzerland, throws a fall festival -- Herbstmesse. The festival features a number of carnival rides, some like you would see in the US at county fairs & whatnot, but some are just massive. Like the Ferris Wheel... It's 60 meters tall. And it is not a permanent structure; it gets hauled in and assembled the week before the two-week festival, then torn down and carted off to the next venue. That is some impressive engineering!