Heads up! MYTHBUSTERS season premiere tonight at 9 Eastern!

Discussion in 'TV & Media' started by Christopher, Mar 25, 2012.

  1. Forbin

    Forbin Admiral Admiral

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    I said out, dammit!
    Well, that's a darn rational explanation, then. :lol:

    Always makes me feel like I'm being treated like an idiot with no - SQUIRREL! - attention span, though.
     
  2. Christopher

    Christopher Writer Admiral

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    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.
     
  3. davejames

    davejames Vice Admiral Admiral

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    The square wheel thing was definitely fun to watch. I certainly expected the ride would smooth out once they got going fast enough, but I wasn't sure the tires would actually hold up LONG enough for that (and they very nearly didn't).

    Of couse the catch appeared to be that the faster you go, the less traction you have, because the tires are skipping along and only contacting the ground at those 4 points.

    I do wish they had tried the slower approach on the hill though. The tires might have functioned more like a tractor tread than the way they did it, where the spinning tires just dug giant holes in the dirt.
     
  4. Christopher

    Christopher Writer Admiral

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    ^Uh, they did try a slower approach on the hill as their second try, and it didn't get them quite as far as the faster approach.

    I wonder if part of the reason the ride was so rough was because they didn't have inflated tires, just the rubber strips against the metal rim. If they could've designed some kind of square inner tube thing to go around the wheel rims, would that have given a smoother ride? Or would the constant shock of the points hitting the ground over and over just rupture the inner tubes?
     
  5. Trekker4747

    Trekker4747 Boldly going... Premium Member

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    I'm actually sort of disappointed Jamie and Adam didn't expend more effort to make a "proper" "square tire." But it seemed all they did was cut the tread off a regular tire and affixed to a square rim. I'd like to see them re-do this only make an ACTUAL, air-filled, tire.
     
  6. davejames

    davejames Vice Admiral Admiral

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    No I mean slower than that, like how they were slowly clomping forward at the begining of their first test.

    That's one instance when having all the tires at the same orientation would have helped as well.
     
  7. archeryguy1701

    archeryguy1701 Rear Admiral Rear Admiral

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    If I remember the bumpy road myth correctly, they were able to get up to speed before going over the bumps, which allowed their measurements to be fairly accurate... in this case, they would have lost all of their water before they got anywhere near fast enough to notice an improvement.

    I enjoyed this episode. Part of me found watching the truck shake itself to pieces to be thoroughly entertaining. The conjoined cars myth was ok, not overly interesting.
     
  8. Christopher

    Christopher Writer Admiral

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    Well, I wasn't saying they had to use the exact same "vibration sensor" they used in the bumpy-road myth. I just meant that I was hoping for one of those cool MacGyverish types of measuring devices they often improvise for myths like this.
     
  9. Christopher

    Christopher Writer Admiral

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    Now the April 15 episode:

    "Pirate Swing": The idea behind this seemed pretty plausible in the movie -- certainly more so than a lot of stuff in the Pirates of the Caribbean movies -- but I guess what works on a swingset doesn't necessarily scale up. Still, I'm not entirely sure of their results, because that steel cage seemed like it would be heavier than the bone cage of the movie. On the other hand, now that I think about it, the bone cage would've been a lot less rigid, and thus its deformation would've absorbed a lot more of the force and made it even harder to get it swinging.

    I was expecting the weight issue to be a problem with the climbing part, but that turned out to be surprisingly doable, so never mind. I agree with Adam -- it's always cool when things turn out differently than you expected. The part I would've figured was easiest was actually impossible, and the part I thought was hardest was entirely feasible.

    Anyway, I love that machine that bends straight pipes into circular arcs. That is so cool.


    Rocket cart: A pretty straightforward one, moderately interesting from a physics and engineering standpoint as they explored the adjustments they had to make to get thrust from the pulse jet design (which struck me as basically the same principle as an internal combustion engine's cylinders). And it was kind of sad watching how thoroughly the reality failed to live up to the myth, these poor pitiful "rocket" carts just puttering along. Even at their best, they only got up to 5 MPH, and the gentlest impact the Mythbusters have ever inflicted upon the fences at the Alameda Naval Yard.

    It feels kinda like cheating that they had to go with a professional designer to come up with a vehicle that could actually do something, but I guess it illustrated how much more complicated the reality is than the myth. And it was intriguing how much the professionally made pulse jet sounded like a propeller-driven plane, though I bet it was much louder.


    One touch I liked here was that the sound-effects editors incorporated some vintage sound effects that were commonly used in the cartoons I grew up watching in the '70s -- first in the bit where the "pirate" acrobats were "teleporting" into the frame, then to accompany the "glowing red eyes" on Kari's hood ornament, and then over one of their title bumpers right around the end of the episode.


    As for Unchained Reaction this week, I didn't have a preference, since both teams were fairly equally matched; on the one hand, they both had very clever narratives, and on the other hand, they both failed to exploit the "tools" theme very well. But I don't mind the designers getting the win, since the woman on that team was kinda cute.

    And as soon as Jamie proposed a "sticky" wild card, I knew it was gonna be duct tape. What else?
     
  10. Trekker4747

    Trekker4747 Boldly going... Premium Member

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    I can't help but wonder if Jamie and Adam might have missed an element of the swinging cage "myth." I don't recall the scene from the movie but it seems to me to get the cage to really move you have to apply more force in the direction you want to go than in the direction opposite you want to go. I'm thinking about this in a F=mass * acceleration sort of way.

    Follow with me. The gang runs from one end of the sphere to the other as "best" as they can at a certain rate and all of their collective mass hits the far end which would give a touch of forward momentum. They then move back to the other end of the sphere and begin a gain. I'm thinking by moving back to the other end of the sphere the same way they ran in the direction of desired travel they cancel out the energy they just built up.

    I think of when you use a playground swing, if you want to move-forward you kick your legs forward, shifting your weight and then let gravity pull them back to a resting position. (This, of course, is after you've started swinging to begin with by backing up while sitting in the swing.)

    So I sort of wonder if there wasn't a way they could've gotten more of swing by being more aggressive in the run-up and let gravity do it's job or just return to the other end in a more gentle way?

    But, no matter what, I suspect it wouldn't be possible to get as much swing as they needed without any outside help. The "myth" proved to be a bit more interesting that I was thinking it'd be (and this was a rare case of Jamie/Adam getting the "movie myth, while the Jr. Mythbusters do the more complicated one.)

    The pulse-jet drum thing was interesting to see them test and I sort of wonder if more design testing and such could've produced better results? Like their initial "full-scale" design had a very long exhaust port which I suspect soaked up a lot of the energy they were making with the interior explosion. I think a shorter nozzle before going with shorter and narrower.

    I agree it seems like "cheating" that they went with a professional to re-tool their design rather than just doing it themselves in the most insane way they could think of but the cart the professional had made was pretty cool.
     
  11. Christopher

    Christopher Writer Admiral

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    ^I don't think you can treat the motion of a pendulum that asymmetrically. However high you manage to get on one end, you're going to get nearly as high on the other end, minus whatever momentum you lose to friction, deformation, and other inefficiencies. So it doesn't matter which direction you exert more force in.

    When it comes to pendular motion, what matters is how high you get above the resting point, not how far to the side. Because what actually imparts the acceleration is gravity. Remember equal and opposite reactions. As you saw, when Adam and Jamie tried to move the cage on their own, all they did was rotate it around their mutual center of mass. You can't actually push yourself sideways on a swing without touching the ground, any more than you can pull a car forward by dangling a magnet in front of it. But if you can raise the center of mass and move it off to one side, then gravity will pull it back down and the pendulum's string will impart a centripetal acceleration that will convert some of that downward pull into lateral motion; and then you'll overshoot the starting point and the centripetal pull of the string will curve you upward, so that gravity will pull you down again, and so on.

    So when you're on a swing and you stick your legs out on the upswing, that's not about thrusting laterally, it's about raising your center of mass higher. The higher your CoM is at the top of your swing, then the more acceleration you get from gravity on the way down. If you bend your knees back under you on the backswing, that has the same effect of raising your center of mass. The same if you pull back on the chain on the forward swing or push forward on it on the backswing, so that you tilt your body even higher.
     
  12. Trekker4747

    Trekker4747 Boldly going... Premium Member

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    Makes sense.
     
  13. Christopher

    Christopher Writer Admiral

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    There's a swingset in the park a block from my apartment, so I get lots of practice. ;)
     
  14. Trekker4747

    Trekker4747 Boldly going... Premium Member

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    I haven't been on a swing for years.

    :)
     
  15. Professor Zoom

    Professor Zoom Vice Admiral Admiral

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    I'm bored of them "busting" things that happen in Hollywood movies. Seriously, what are they saying: things in movies aren't real? Shocker.
     
  16. Marc

    Marc Fleet Admiral Admiral

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    well if people didn't believe the stuff they see on tv and in movies was real.......
     
  17. Professor Zoom

    Professor Zoom Vice Admiral Admiral

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    Sure. It's still boring.
     
  18. Roger Wilco

    Roger Wilco Admiral Admiral

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    I'm not sure it's possible to make such a tire, I don't think it could hold the air pressure. And even if they could, I think the forceon the edges of the square rims would be so high when the wheel turns, that it wouldn't make much difference.

    I was a little surprised about the Pirate myth this week, I thought the swinging would be possible, but that the cage would be far to heavy to climb the wall. Turns out it was the other way round.
     
  19. Christopher

    Christopher Writer Admiral

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    I'm with Marc. Lots of people believe the nonsense in movies and TV. Sure, they know the characters are fictional and the invading aliens or zombies or superheroes are imaginary, but if enough movies show them that bullets spark when they hit metal or that cars explode when they crash or that a lit cigarette can ignite a pool of gasoline, they're generally not going to question that. (Indeed, the pervasive belief that crashed cars explode is genuinely dangerous, because it motivates well-intentioned bystanders to try to rush accident victims out of their vehicles and risk exacerbating their injuries.)

    Besides, the swing myth this week was genuinely interesting. Movies aside, the underlying idea was something fairly basic and close to everyday experience -- we've all had experience with swings or pendulums -- and the test revealed some flaws in our expectations about something so familiar.
     
  20. Trekker4747

    Trekker4747 Boldly going... Premium Member

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    Yeah, the swinging cage myth was less "movie myth" and more a demonstration of physics at work.