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Episode 56: Killer Whirlpools, Snowplow Flips Car

  • Whirlpools can suck down boats: busted. No recorded whirlpool is even close to the strength necessary for sucking down a ship.
  • Whirlpools can suck down people: plausible. Adam willingly demonstrated this one.
  • A snowplow can blow over a passing car: busted. One their one test run, they couldn't get the other car close to tipping.

Adam really put himself out their physically for the whirlpool myth, donning the wet suit and letting himself get spun like a top as he hung onto a trapeze. All was well until Jamie cruelly suggested a second go, which resulted in partially digested pizza getting spun down the whirlpool

The snowplow myth was one of those myths where nothing went right, frustrating the hell out of the build team. They spent almost no time on the myth itself, instead focusing on how their free snowplow gave them nothing but trouble, taking many days to even get it running. The remote braking system failed to activate, or rather, Grant "forgot" to activate it, so in the final experiment the snowplow went crashing into the barriers, and was later fork-lifted up and flipped over for glee.

Whirlpool of Death

Myths: Whirlpools can kill

See video 1 from the Encinal High Benefit for a little bit of background info on this myth.

Adam and Jamie rode out with the Coast Guard to find whirlpools around the Golden Gate Bridge and found plenty of whirlpools around the pylons. The vortices they found were still nothing compared to the largest whirlpool in the western hemisphere, which is Old Sow off Deer Island Point in Canada. Old Sow is 200 ft in diameter and spins up to 14 knots, which is 3 times faster than the eddies beneath Golden Gate Bridge.

MythBusters man-made whirlpool

Jamie wanted to do a paddlewheel design (paddles attached to the end of a cordless drill) and Adam wanted to do a water jet design, so they decided to face-off their designs, starting with a small-scale model. Jamie and Adam's designs both did well on the smallest model, but as they did a slightly larger model, and then an even larger model with a 50-gallon tank, they soon discovered a big weakness in Jamie's design: Jamie's paddles had trouble creating a vortex in the larger models, but Adam's design actually required less water proportionally as they scaled upwards. Adam's design won, and they later found out that Adam's re-circulating pump method is considered the most accurate method of reproducing a whirlpool

Big whirlpool design

They wanted to do two tests in the big whirlpool version of the re-circulating water pump design: one with scale models, and one with a human lab rat, i.e. Adam.

Jamie: I wouldn't be at all surprised if you didn't just pass out. And if you pass out and you're in that water, unless you're tethered, you're screwed.

Adam: It s not like you're hopping into a pool full of water. You're hopping into a cone of water that drops down potentially 10-15 ft below you. That doesn't sound really pleasant.

The scale models they used were a 1:550 scale container ship and a 1:50 model trawler. They brought back Jess from the Archimedes Death Ray Revisited competition to help build the ships and help with the later parts of the experiment.

For Adam's safety they bought an emergency air tank. They tested it out in the pool at the dive shop to see how long it would take Adam to get it to his mouth. With a little bit of practice with Jamie yanking down Adam from below, Adam figured it all out.

The actual tank was a 10ft wide, 16ft tall tank that they had specially made. Fully filled with ~10,000 gallons of water, it weighed in at about 45 tons. They hooked up a 200 hp construction pump, which was capable of pumping 4500 gallons/minute.

Scale model tests

With the tank filled up, they turned on the pump only to discover that their whirlpool was too good. It immediately went to about 14 knots and 42 rpm. For their 1:50 scale model ship, they need it to move at 1 rpm in order to replicate a real-world whirlpool. For their 1:550 scale model, they need it to move 0.1 rpm.

Adam decided to do a damage experiment instead: see where the scale models get sucked down and calculate the relative speed.

  • The 1:550 scale model container ship (1000 ft long in real life): with their first test, the ship wasn t sucked down even though they got this ship to go 230 mph relative to its scale, which is 20 times faster than the fastest whirlpool ever. They spun the whirlpool up and it sucked the container ship down -- Mach 3 according to Jamie, a mile and a half in diameter according to Adam.
  • The 1:50 scale model trawler: it its first test, it went 130 knots relative to its scale and the trawler wasn't sucked down. 130 knots is four- five times faster than the fastest vortex ever recorded. They wanted to get the trawler sucked down, so they spun the vortex up to 150 ft in diameter relative to the scale model and moving at 100 knots. The trawler went spinning down like a top.

Adam's turn

Adam held onto a trapeze as they spun the water up to 14 knots -- the same as the world's fastest whirlpool. Adam was spun around and around and down and down, seeming to have plenty of fun. After a minute, Jamie shut it down and Adam giddily slowly spun down. Adam felt that it would have definitely sucked him down. Jamie wanted to see if Adam would let himself get sucked down a bit so they could test how strong it was. As Adam started to get sucked down the second time around, he immediately called for Jamie to stop. Jess grabbed his hand and within several seconds, Adam was vomiting pizza down into the whirlpool

NOTE: in person, Adam later praised the efforts of Jess in holding his hand through all of this.

"I'm done with science for today" - Adam

"That is a deadly thing we made" - Adam

Boats: busted
People: plausible

Snow Plow Flips Car

Myth : A snow plow can blow a car off the road as it passes at a high speed.

How much energy does it take to flip a car?

They found a car with a high center of gravity to flip. They towed it with a truck from one side until it started to tip over and measured the force from the truck at 1000 lbs. Kari measured the surface area on the side of the car and figured out that it would take 0.21psi to flip the car from the side.

In order to match 0.21 psi to the force actually generated by a passing vehicle, they hooked up a tube with water to the side of the M5 Industries truck that measured air pressure. At 65mph, the M5 truck managed to generate between 0.018-0.036 psi, or about a sixth of what was required. Tory felt that this put doubts into the myth already.

Full-scale experiment design

The purpose of the full-scale design was to pull a snowplow and car past one another on cables. Their design was to use two fifteen foot cables, one attached to the snow plow and one attached to the car. Each cable would be run through a pulley and pulled by a tow truck. As the tow trucks moved forward, the snow plow and car are pulled past each other.

Curse of the Snowplow

They found a snowplow long abandoned on the California/Nevada border they could claim. It quickly became a problematic component for them, first starting with the rodents, next with the fact that they had trouble getting it to move. Tory cut the driveshaft in order to get the snowplow moving, but next they found out that one of the wheels wasn t turning. After two days of effort, they managed to get the truck rolling.

"You know, considering the man hours, wouldn't it have been a little bit cheaper to get a truck, you know, for a $1000 bucks that all the wheels roll on?" - Kari

Next up for the snowplow was figuring out if the brakes worked, as they would need to be able to brake the truck after towing it past the other car.

Kari: "I don't exactly what it is about today and right now and what we're doing. But something feels like it's dangerous I m not sure exactly what yet and something feels really dangerous."
Grant: And that would be different from usual how?"

They tested first at 20mph. The brakes failed as did the emergency brake. The snowplow rolled over the tow chain and the snowplow jerked to the side.

After three days of working on the snowplow, they brought in snow plow drivers Pat Manning and Matt Edgeman, who were responsible for finding the cursed snowplow, and they managed to get the brakes working in 45 minutes.

The final touch was for Grant to add a remote braking system so that no one would have to be inside the snowplow. In order to test the remote braking system, they attached the cable to the snowplow and truck. They then ran it through a pulley system that was anchored to 1200 lb road barriers, which were also the last precaution if the tow truck failed to stop with its brakes. Kari pulled the snowplow forward using a truck and managed to get it up to 40mph before Grant had to engage the brakes, or rather, tried to engage the breaks: the snowplow kept on rolling into the sandbags and road barriers. They decided that their best solution was to just add more sandbags to stop the snowplow.

"You mean so you spent three days of a remote trigger and we re going to put a wall of sandbags in front of it? Alright this has been like the most troublesome myth we have ever done." - Kari

Big plow

The plow was so finicky and wasting so much time that they decided that instead of testing various psi measurements from the various-sized plows, they would build the biggest possible plow for their cab -- the biggest plow their expert had ever seen -- and just run the full-scale experiment.

Full-scale experiment

The snowplow with big plow got up to 60mph and went roaring past the car with several feet to spare, but the car didn't even come close to tipping. The car and snowplow then proceeded to crash into the barriers, as Grant forgot to activate the brakes until after the plow went through the barrier.

As sweet revenge on their hated plow -- Tory was already pleased that Grant forgot the brakes -- they fork-lifted it up and flipped it over, ensuring that it would never be used again.

mythbusted (and unlikely to be revisited due to build team sanity reasons)

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Comments

I thought the snowplow myth was one of the lamest segments yet. Clearly implausible and uninteresting myth, overly-complex method to test it, and poor mechanical technique from the build team.

Not even the funny "curse" storyline could save it...

The snowplow shoot reminds me a bit of the Dirty Jobs with the monkeys -- the making of the story overtook the story itself. They probably had a difficult production decision given how much time they must have spent on the myth (3 days just to get the snowplow rolling).

I liked the whirlpool myth, though I wish the numbers were more clear in what they were doing. The n knots kept going up and down, but I couldn't tease out what they were measuring because n would go down when they made the whirlpool bigger, for example.

I enjoyed the whirlpool myth, however scaling the speed of the pool to the ships didn't seem even close. I think volume of water moving at given speed (inertia) would be better. (But what do I know, I'm no scientist) On the snowplow, I think the theory is impossible. However, if the plow hit some nice heavy snow and water, I think the snow and water hitting the side of the SUV at 75-80MPH would have no real trouble flipping it over (if you consider the driver's knee jerk reaction, it might go over twice).

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