|
|
|
Written by river95
|
|
Wednesday, 27 July 2005 |
|
Episode: Border SlingShot Original Air Date: July 27, 2005 Myths: Border SlingShot
The Myth: People are illegally crossing the boarder into the United States using a slingshot to send them 200 yards (600 feet) over the fence into the United States and it is accurate enough to land the person on a mattress on the other side safely.
The Mythbusters will replicate a slingshot that can launch a 185-pound person 200 yards. Adam decides that the best course of action is to do a series of tests so that when the full scale version is build they donít get it wrong. The goal is to build an equation based on different lengths of materials and different types of materials using different weights of objects that are launched.
Test 1: Calculate Velocity
Styrofoam blocks are set up as targets and Jamie and Adam take turns pelting the target with steel shot. To calculate the velocity a scale is set up along the target range and a high speed camera is used to measure the velocity. The slingshots used sent steel shot at 85 miles per hour, or about half that as slingshots used at competition level - leaving room for improvement.
Test 2: What Material Makes the Best Slingshot
A scissor lift is converted into a mid-range slingshot, then various materials are used to propel a 1.000Kg weight down a firing range set up at the shop. The angle of trajectory was set at 45 degrees and the maximum tension and draw back was measured to scale up to the full size version.
The results -
1 meter of military bungee cord launched the weight 67 feet.
1 meter of stranded shock cord launched the weight 43 feet.
1 meter of solid shock cord launched the weight 38.5 feet.
1 meter of 1/4 inch surgical tubing launched the weight more than twice that of the military bungee cord.
The surgical tubing is chosen.
Test 3: Maximum Pull Strength
To determine how much tension and draw back the surgical tubing can handle a 10-foot section of 1-inch surgical tubing is stretched and attached to a strain gauge. The tubing broke with with 150-pounds of force at a distance of 60-feet, a 6:1 ratio. They decide to use a 5:1 ratio for safety.
Test 4:A 1/10 Scale Trial
Adam converts a bowling ball into an 8Kg (or 1/10 the weight of Buster) projectile. Then they head out to a football field and use a goal post as a slingshot. Jamie notices that the goal posts are wobbly and decides to use guy wires to steady the posts. Adam then measures out 600 feet from the goal post. At 450 feet he decides that even that distance looks to be a tad far to launch a bowling ball.
First they test a 2Kg ball, which fails to release from the slingshot and comes back at them. Adam says, "That was the scariest thing I've even done on this show". After a quick repair they launch the 2Kg ball 205 feet. Next up the bowling ball, which also failed to be properly released, another quick fix and the 8Kg bowling ball is launched 77 feet. They also bent the goal posts in the process.
Now for the real thing. Adam thinks that 12,000 pounds of force is too much and decides that the human cannonball record of 201 feet set in 2002 by David Smith Sr. is much more reasonable. That will require 40 10-foot lengths of surgical tubing, 20 on each side of the launcher, that will produce a final force of 4,000 pounds.
The first day of the test they erect two 45-foot tall radio towers each supported by 3 guy wires to form the slingshot. Adam again states that he does not think that 200 yards is makeable. The second day the build team arrives and sets up a fence "boarder" and Kari measures out 600 feet. She then says "That's pretty far to be slinging a human being" and that "this myth may be slightly absurd." Tory agreed "that's pretty far."
As a comparison the boom lift catapult launched Buster 90 feet, if you ignore the 60-foot boom. In the Raccoon Rocket 10 pounds of black powder launched Buster 80 feet. The Ming Dynasty Astronaut failed to send Buster anywhere.
The first launch they use a 55-pound kid dummy. They launch him 132 feet. Next they use a 130-pound female dummy, named Suzy, positioned in the fetal position. The first attempt fails to release her properly. They then reconfigure the sling and launch her 128 feet. Determined that they can do better and again reconfigure the sling and then launch Suzy 211 feet, beating their goal of 201 feet.
The conclusion - Myth Busted.
|
|
|
Episode Descriptions 
