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Next up: actually swinging all the way over the top of the swingset
February 23, 2014 9:47 AM   Subscribe

Damien Walters runs the loop-the-loop.
posted by jacquilynne (33 comments total) 3 users marked this as a favorite

 
(Fair warning: this is sponsored by Pepsi, and the actual run happens at 2:25.)

That is neat.
So, those last few steps (from the 3/4 mark down to the ground) seem to be the key to not falling off - makes me wonder how much actual pressure he's getting in those steps vs just kind of "touching" the track.
posted by LobsterMitten at 9:58 AM on February 23


I always just spin-dash if I'm having trouble with a loop.
posted by Mr.Encyclopedia at 9:59 AM on February 23 [9 favorites]


Pepsi Bloop?
posted by 256 at 10:00 AM on February 23 [7 favorites]


Sort of good they show the preparation with mats and such, I've expected an outbreak of massive spine injuries for a while now, maybe it's just being suppressed by red bull?

I may have save one free runner once, leaping over steps and barricades looked like they were having fun, waved him off his next obstruction, 40+ foot drop.
posted by sammyo at 10:05 AM on February 23


Pepsi Max is one of the ones with benzene in it, right?
posted by Sys Rq at 10:20 AM on February 23 [2 favorites]


As any Physics 101 student knows, if you go the minimum possible speed, then, at the top, there would be almost no force of your feet pressing against the ramp. No normal force, no friction, and you'd lose speed due to aerodynamic drag, and not be able to complete the loop. So he'd have to go faster than 8.6 mph to really pull it out.
posted by BrashTech at 10:23 AM on February 23


The little quote from the woman in the video suggests he has to keep accelerating and that's the key? So does he start at 8.6 mph and then speed up with each step? (maybe I'm reading too much into what is clearly a bit of fluff explanation)
posted by LobsterMitten at 10:28 AM on February 23


The problem is the way we run is completely unlike the way a little RC car rolls. We push hard against the ground with every stride. When you're counting on centripetal force to oppose gravity, pushing against the surface when you're upside down is going to throw you at the ground. So to do this requires a runner to have either a lot more velocity than 8.7mph (or whatever she said) or to train himself to use a different style of stride as he goes around the curve. I suspect what happened here is a little of both. He ran hard and adapted his stride a bit with practice.
posted by George_Spiggott at 10:48 AM on February 23


More previously
posted by pipeski at 10:51 AM on February 23


Couldn't he just do a barrel roll?
posted by Brocktoon at 11:23 AM on February 23 [1 favorite]


A barrel roll would be a longitudinal rotation, this is more like a back flip while running.
posted by borkencode at 11:49 AM on February 23 [1 favorite]


LobsterMitten, acceleration is not just change of speed but also direction. In order to run in a circle, he needs to accelerate, i.e. not move in a straight line. For uniform circular motion, the acceleration is related to the speed and radius of curvature (a=v^2/r). Gravity is also acting on him, giving him an acceleration, and if the acceleration of his circular run (a=v^2/r) is just equal to gravity's acceleration g he's weightless at the top. If he moves too slowly, v<sqrt(g r), then gravity will give him more acceleration than needed to stay on the circular path and he'll fall.
posted by Schmucko at 11:52 AM on February 23 [1 favorite]


I'm pretty sure that's Dankey Kang.
posted by Sing Or Swim at 12:07 PM on February 23 [1 favorite]


Gotta go fast
posted by 2bucksplus at 12:12 PM on February 23 [1 favorite]


The title got me curious, found these idiots, and these idiots (who may have learned something from the first idiots, but suck at video editing).
posted by stinkfoot at 12:24 PM on February 23 [2 favorites]


Wow! And this idiot!
posted by stinkfoot at 12:27 PM on February 23


Uh, last link is the same as your second link in the line above...

The actual stunt is cool, but I have a distinct memory of a black and white film stunt where someone runs a loop. I don't recall the details, but the stuntman was being chased by a large man wearing a turban and wielding a scimitar, and the loop carried the stuntman behind the guy who was chasing him. I think it dated back to the silent era.

Of course, they could have shot it through camera tricks, but at the end of the day, there didn't seem to be anything in the stunt shown that couldn't have been done centuries before.
posted by YAMWAK at 12:34 PM on February 23


For a moment I thought this was going to be science fiction critic Damien G. Walter.
posted by MartinWisse at 12:55 PM on February 23


Obviously this couldn't be done without Pepsi Max. It's like loop fuel.
posted by chavenet at 1:03 PM on February 23


This is pretty impressive, ad or no. More impressive, even, than the .gif that's been making the rounds, because it answers the question, "Could I do this?", handily.

I could not do this.
posted by sandettie light vessel automatic at 1:08 PM on February 23 [1 favorite]


Thanks YAMWAK, meant to link to this idiot.
posted by stinkfoot at 1:31 PM on February 23


I really appreciate that they showed all the preparation and a lot of attempts and dusting off and starting again. I often see stunts and things that show the one perfect time and not the hours of practice and I think that distorts my own view of the amount of effort that really goes into accomplishing amazing things.

And, this is pretty amazing.
posted by gauche at 3:03 PM on February 23 [1 favorite]


Yeah, I agree that it's great they showed all of his practice runs. It helps you appreciate how much time and effort goes into this sort of thing.
posted by Gymnopedist at 3:13 PM on February 23


Now do it on a tiny bicycle that you catch in your mouth and swallow at the end, then ring the bell!
posted by Parasite Unseen at 3:18 PM on February 23 [5 favorites]


I wondered about a similar stunt some time back.
posted by Tube at 3:29 PM on February 23


Make 'em laugh! Make 'em LAUGH! Make 'em LAAAAAAAAAAAUGH!!!
posted by Ian A.T. at 3:37 PM on February 23 [5 favorites]


Really neat that they included the practice runs. I might have missed something, but is the size of the loop determined by his height?
posted by variella at 3:44 PM on February 23


At first I thought he might have done better with a larger loop. He'd need to run faster to maintain his centrifugal acceleration (i.e, what is apparently pushing him against the track) but more of his mass would be further out. As it is, his head is actually above the central point, so it's giving him a slight inwards acceleration.

The apparent force on an object doing a loop-the-loop is mv2/r where m is the object's mass, v is its velocity, and r is the radius of the circle. If we assume that the runner's body lies along a radius of the loop then each part of it is moving at a different velocity: the runner's head is close to the loop's center, so it's moving in a slow circle, while the runner's feet are further away and they're moving faster. So if the runner takes t seconds to go around the loop, and the runner's feet are moving at a speed of 2πr/t (from the formula for a circle) then if the runner's height is h the runner's head is moving at a speed of 2π(r-h)/t.

Substituting this result back into the first formula gives us an apparent centrifugal force of
  m * (2π(r-h)/t)2 /(r-h) 
= m * ((2π/t) * (r - h))2 / (r-h)
= m * 4π2/t2 * ((2π/t) * (r - h))2 / (r-h)
= 4mπ2/t2 * (r-h)2/(r-h)
= 4mπ2(r-h)/t2 
In other words, the apparent centrifugal force experienced by any part of the runner's body is proportionate to its distance from the center of the loop, and inversely proportionate to the square of the time taken to traverse the loop. In a case like this where the runner's height (h) is very close to the loop's radius (r), increasing the size of the loop a little will greatly increase the centrifugal force apparently felt by the runner's head but hardly affect the force apparently felt by the runner's feet. On the other hand, by increasing the amount of time taken to traverse the loop, it will greatly reduce the general feeling of centrifugal force.

So you really want a loop the runner can traverse in the minimum amount of time. All other things being equal, this will be a small loop, but that's complicated by two things: it's physically harder to run when you need to move your legs up and out of the way; and when you run you bob up and down, which means that your center of gravity is moving towards the center of the loop and away from the feeling of centrifugal force. So it should be small, but not too small or else you won't be able to traverse it efficiently. Like many things in life, it's a combination of practice, natural ability, and the heaviest boots you can find.
posted by Joe in Australia at 3:58 PM on February 23 [5 favorites]


This guy could be anybody. He's just some schmo, not out of the circus.

That pepsi stuff must be high test indeed.
posted by Colonel Panic at 5:55 PM on February 23


Was anybody besides me disappointed that the guy wasn't on one of those big metal swing sets with the splintery wooden seats and the chains that pinched your fingers? The ones that were set in asphalt on the playground?

We spent hours trying to flip over the top bar. I'd bet enough energy was expended at recess to power New York City for 2 weeks.
posted by BlueHorse at 6:30 PM on February 23 [4 favorites]


Was anybody besides me disappointed that the guy wasn't on one of those big metal swing sets with the splintery wooden seats and the chains that pinched your fingers? The ones that were set in asphalt on the playground?

We spent hours trying to flip over the top bar. I'd bet enough energy was expended at recess to power New York City for 2 weeks.


Good thing you were so unsuccessful. I imagine that the result of almost succeeding would be to fall head-first onto the top bar and then the asphalt, from the top of the arc at 15 feet or so.
posted by lostburner at 5:16 AM on February 24 [3 favorites]


We spent hours trying to flip over the top bar. I'd bet enough energy was expended at recess to power New York City for 2 weeks.

Good thing you were so unsuccessful. I imagine that the result of almost succeeding would be to fall head-first onto the top bar and then the asphalt, from the top of the arc at 15 feet or so.


Actually what happens is you get turned inside out.

anyone?
posted by ultraviolet catastrophe at 11:41 AM on February 24 [3 favorites]


niiiice UV Cat- I had forgotten about him!

(link for mortals)
posted by stinkfoot at 6:04 PM on February 25


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