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Old April 9 2012, 05:06 AM   #42
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Re: Heads up! MYTHBUSTERS season premiere tonight at 9 Eastern!

All automotive myths this week.

Square Wheels: I'm surprised they went right to full-scale with this instead of doing some small-scale tests. Instead they did the bench tests later, after the initial full-scale test failed. Or did they? Maybe they actually started small-scale, but edited it in a different order to create the desired narrative.

Anyway, the results were interesting. Although the ride did get relatively smoother in the cab as the wheels spun faster, the square wheels made things incredibly rough for the wheels and axles themselves, which is what really matters. The non-uniform shape meant there were constantly shifting forces pushing things off-balance and creating torques on the axles and connections and such, even aside from the constant impacts. And of course the tires came off easily because they had only four points of contact.

I was surprised that Jamie's idea about climbing in soft dirt didn't work. His reasoning certainly seemed sound. I'd like to see it tested, not for hill-climbing, but for avoiding getting stuck in the mud like he was talking about.

I'm a little disappointed that they measured vibration with electronic sensors. They've found more creative ways to do that in the past, like in that driving-on-a-bumpy-road myth where they used glasses filled with water or something. But I guess that would've been too fragile here.

Conjoined cars: Interesting that they know this kind of conjoining can actually happen, although I doubt it would be stable through those kinds of maneuvers if it weren't specially rigged. I liked the framework they came up with to join the cars' frames together; that was clever.

The steering issue was interesting, and obvious in hindsight; the wheels that turn are near the center of mass, so there's not a lot of leverage there. Still, I wondered if the corner turn would've worked better if both cars had turned their wheels in complementary directions. I mean, it sure worked in the spin test when they turned their wheels in opposing directions. So it's odd they didn't test that variation. Sure, maybe it wasn't in the movie, but they diverged from that when they reversed which car was exerting the force.

As for this week's Unchained Reaction ("Flight"), for once I actually agreed emphatically with the judges' decision. The artists' rig had some really beautiful elements, especially the finale with the ribbon dancer and the Chinese lanterns. It seemed to work better mechanically too, which I wouldn't have expected from a team of artists vis-a-vis a team of engineers.

Given that in previous episodes Adam and Jamie have looked askance on using team members themselves as triggers, it's surprising that they actually required the teams to incorporate live performers as "objects" in their rigs. Although Adam did have a point about both teams going for the simplest way of using the dancers -- though in their defense, it's hard to do more when they're sprung on you that late in the game.
Written Worlds -- Christopher L. Bennett's blog and webpage
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