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Written by sas
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Wednesday, 03 August 2005 |
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Episode: Killer Tissue Box Original Air Date: August 3, 2005 Myths: Killer Tissue Box, Splitting an Arrow
Myth #1: Killer Tissue Box
Myth: A cardboard tissue box can become a lethal projectile in a car accident.
In US, 2001, approximately 13,000 people were injured by unrestrained objects in the back of their vehicles. Additionally, the Mythbuster'í researches found two cases in Australia where drivers were impaled through their seats by golf umbrellas and another case in the US where a woman was killed by the groceries in her back seat.
Memorable Moments/Quotes:
Jaime: "the only bad thing that can happen is all those [aluminum I-beams] rip and I don't see that happening."
Jaime (after cable rips I-beam): "I didn't do the engineering and I didn't do the math because I thought I understood what was going on and I thought I made a good rig. But I was wrong. I should have done it."
Adam: "This is your head. This is your head with an axe in it. Are we clear?"
Jamie: "Well, you know that's a good indication that this is really deadly though. It's the one thing in the car tough enough to survive an impact."
Test #1:
Setup: A repeatable test using different objects. Jamie and Adam build a crash test rig that can be towed and stop with the force needed for the test. The boys create a "crash sled" out of aluminum using I-beams and a 4/8 sheet of aluminum diamond plate. The deadliness of the objects will be gauged by ballistic gel "slabs" created by Adam.
They use three 4,000lb concrete barriers as an anchor for the crash test sled. The sled is attached to the barriers with 1,000 feet of cable. The rig has been outfitted with a meter in order to determine the velocity of the items and calculate the amount of force imparted to the ballistics gel. The first rig could not withstand the force of the hard stop which resulted in a rip in the I-beam. The construction of the rig had to be revisited.
Jamie reinforces the rig by using heavy nylon strapping (with a combined breaking force of 40,000lbs) to distribute the load. They also agreed to lower the towing speed down to 45 mph. The modifications are successful.
Test #1
Run #1: Einstein bobble head: Did not work as the bobble head got logged into the screw cage
Run #2: Subwoofer: Strikes the ballistics gel at 45mph.
Run #3: Hatchet: At 45mph the axe impaled itself through the ballistic gel and the box holding it.
Run #4: Fire Extinguisher: A 1kg fire extinguisher did not cut the gel deeply. But caused a dent in the extinguisher
Run #5: bowling ball: The bowling ball completely destroyed the front of the rig.
Run #6: Tissue box at 70mph: 323g it doesn't have enough mass to do much damage.
Result: BUSTED. However anything that weighs more than a couple pounds should be restrained in the back of the car as injury could result.
Test #2:
Setup: Using a full sized car (the Fury), they will tow the vehicle into a barrier. Grant builds a steering rig that will enable the car to be towed without steering. A box of tissue is placed on the shelf in the back seat. The pickup tows the fury which hits the barrier at more than 60mph.
Result: The box survived intact. The accelerometer in Buster's head measures 118.8 G's. An astronaut pulls only 8 G's during liftoff.
Myth #2: Splitting an Arrow
Myth: An arrow can be split from the tail to tip by another arrow. In the Adventures of Robin Hood starring Errol Flynn, he splits the arrow.
Experts:
Joseph Snell, Pacifica Archery, Daly City, CA (http://www.pacificaarchery.com/)
Memorable Moments/Quotes:
Tory: "Any archer capable of completing this task shall be awarded a kiss from the fair M... (looks at Kari) Sorry, okay... ya... you're not going to get that... my mistake"
Kari: "Let's Make a robot"
Setup: The build team goes to Pacifica Archery, where they see examples of composite arrows that have been hit in the tail, referred to as "Telescoping", but did not split. They use a chronograph to determine the arrow's speed. They determine that their chances of spitting the arrow is higher using a compound bow than a long bow.
Test #1: Using a compound bow (a Christmas present from his father) and modern aluminum, Tory tries to spit an arrow at 20 feet and then at 15feet. He managed a glancing blow but was unable to split an arrow. He then switched to broad tip arrow heads. They also seeded the target with dowels. With this setup Tory was able to split a shaft about six inches down.
Test #2: Kari suggests that they build a rig so that they can repeat the same shot every time. Grant builds "The Arrow Bot". Even with the bot, the trajectory varies. Upon viewing the arrows path on the high speed camera, they notice that the arrow does not fly straight but flexes and twists in the air. In order to improve the odds, they add a bundle of arrow shafts to the target. They achieve several glancing blows, but no split.
They redo the test with cedar arrow shafts as they were using doweling from the hardware store and did not contain the right humidity and grain. The switch to "real" shafts resulted in more glancing blows and partial splits, but none that split the arrow from tail to tip.
Tory hypothesizes that the power of the rig may be causing splintering vs. splitting so they move the rig back. This action causes the wind to become a factor and decreases the precision of the shot. They moved the rig inside and repeated the experiment. Again, they did not get the results they were looking for.
They set up the rig for a point blank shot, moving the arrow right to the end of an arrow lodged in the target. The arrow was partially split. They notice on high speed that the blade of the arrow follows the grain of shaft.
Test #3: Grant creates a guided channel out of copper and carbon fiber so that they get a straight split. The tube encases both arrow and target. In both tests the arrow continues to follow the grain of the shaft.
Test #4: 16 archers from the renaissance fair attempt to split an arrow. Each archer receives three shots at the target. None are able to split the arrow. They then fire in formation. They were unable to split an arrow. Polling the archers, some had partially split arrows, but none had split one from end to end.
Result: BUSTED
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