Episode 34: Bulletproof Water, 360 Swing
- Water stops bullets: confirmed
- You can do a full 360 on a swingset: mythbusted
The surprising thing about the bulletproof water was how poorly the high-powered rifles did. The full metal jacket bullets for the high-powered rifles came apart upon hitting the water. Even the dreaded .50 caliber rifle was only able to penetrate about 3 ft of water.
I didn't think the 360 swing set myth was that interesting, but if you were patient through the whole episode you got to see them strap rockets on to a dummy in a swing set -- rockets are always good fun on the show. According to host Adam Savage, "Well hopefully that's our job, to strap rockets onto everything"
Myth: Water will protect you from being shot by bullets
They know that water will eventually stop a bullet, so they want to test to see how deep you have to dive to avoid being shot.
The various guns they tested during the myth were:
- 9mm pistol
- M1 Garand/.30-06
- Replica Civil War black powder rifle
- .50 cal rifle
Regarding the .50 cal ammunition:
Adam: "That's what this thing fires?"
Jamie: "It's smaller than my head, it's alright"
Water tank tests
They built a 'ballistic tank' out of 1" thick acrylic and iron girders. They stuck a block of ballistics gel into the tank that could be raised up and down to different depths.
- 9mm @ 6ft: the bullet went straight through the ballistic gel -- fatal
- 9mm @ 7ft: the bullet went straight through again -- fatal
- 9mm @ 8ft: the bullet only went 1/2" into the gel -- non-fatal
- 3" deer slug + Shotgun @ 6ft: As one might have expected, firing a shotgun into a narrow tank of water shattered the tank and sent everyone running to turn off all the lights to prevent short circuits. The slug shot went through the ballistics gel -- fatal
The shotgun test was the end of that particular test setup.
A vertical rig was a worst-case scenario. In order to make it easier to test and also to make it correspond better with a real-world scenario, they decided to make their new rig be at a 30 degree angle. At a 30 degree angle with an 8 ft penetrating bullet, you would only have to be 4ft underwater.
Someone strangely agreed to allowing Adam and Jamie to shoot off guns in their pool. Adam made a new 20 ft railway for the ballistics gel target and they mounted it at a 23 degree angle.
For the first test they used a replica Civil War black powder rifle shooting Jamie's homemade bullets at 1000 ft/s.
- Replica Civil War rifle @ 15 ft: The bullet veered way off target.
- Replica Civil War rifle@ 5 ft: they couldn't find the bullet and the ballistics gel was still intact -- nonfatal
- Replica Civil War rifle @ 3 ft: The bullet went through the gel -- fatal. At this distance, though, the gel was only 2 ft underwater because of the angle.
They switched to a .223 rifle, which shoots at 2500 ft/s
- .223 rifle @ 10 ft: the full metal jacket bullet shattered into tiny bits upon hitting the water -- nonfatal
- 223 rifle@ 3 ft: once again the bullet broke up. The tip of the bullet was resting on the ballistics gel -- nonfatal (myth confirmed)
The next gun up was the M1, which shoots at 2800 ft/s. In their Bulletproof Glass mythbusting, the M1 was capable of penetrating 2.5" of bulletproof glass.
- M1@ 10 ft: tiny bullet fragments once again
- M1@ 2 ft: the bullet only pierced the gel 4", which would be enough to just pierce the skin.
They finally broke out the big gun, the .50 cal with armor-piercing rounds, which are shot at 3000 ft/s.
Adam: "Hopefully we'll be gone before the pool fully drains"
- .50 cal @ 10 ft: even though the water exploded, the ballistics gel was intact. Water made it all the way up to the ceiling. As it was with the previous guns, the bullet round came apart on impact. It lost all of it's energy within the first 3 ft. You would be safe 14" underwater at a 23 angle from a .50 cal.
confirmed: you can protect yourself from a bullet by diving underwater. If the shooter were directly overhead, you would probably be safe from most guns at 8 ft. At a 30 degree angle, you would only have to be 3 ft underwater to be safe.
360 Swing Set
Myth: If you go fast enough, you can swing all the way around a swing set in a 360 arc
Jamie: "Yet another common everyday item turned deadly"
They placed a scale behind a swing set so they could measure the speed of the swing using a high-speed camera.
Kari under her own strength: Kari was able to make it 11ft high (just over horizontal) with a top speed of 23.5 ft/s
Tory under his own strength: Tory cracked his butt as the swing broke under his weight. Earlier they showed Tory reading the warning label on the swing that said it was for kid's use only. Tory didn't make it as high as Kari and only went 22.4 ft/s
Grant in the red safety suit, pushed by Tory and Kari: Tory and Kari were able to get Grant up to 22.9 ft/s and 11.5 ft high
Simulaid Susie (65 lbs) with half-length chain: They shortened to chain to make it easier to flip her over. Grant and Tory tried to flip her over using ropes to pull Susie but were unsuccessful. Tory called in some biker friends and all four of them pulling were able to get Susie over. Even though they got Susie over the bar, it wasn't a full 360 -- closer to 300 before she came crashing down.
The Circus Tests
They did a scale model test with swing set and found that you needed to go 36 ft/s to make it over in a 360. However, if you used a rigid-arm swing instead, you only needed to go 10 ft/s.
Grant, Kari, and Tory went to Trapeze arts in Oakland, where they have a full-size rigid arm swing. Eric Braun, circus acrobat, helped each of them try out the rigid arm swing. One by one they got on the swing and Eric jumped on behind to get it going higher:
- Eric + Grant: Eric and Grant got up to 230 degrees before Grant asked for him to stop, lest he hurl.
- Eric + Kari: Eric and Kari up to 240 degrees before she asked for him to stop.
- Eric + Tory: Eric and Tory made it to 280 degrees but they just didn't have enough energy to make it over.
- Eric alone: Eric made it easily around
Rocket Susie Tests
They still wanted to get a 360 degree swing on a non-rigid-arm swing, so they decided that they were going to strap rockets onto the back of Simulaid Susie to get her over the swing. They first did some scale model tests to figure out the best way to mount the rocket onto Susie:
- horizontal (max velocity): Scale-model Susie was sent tumbling and lost her hand.
- vertical: Pretty useless in getting Scale-model Susie over the bar
- 40 degrees: Scale-model was sent over the bar four times
With their scale model tests done, they got the full-size Simulaid Susie setup for a real attempt at doing a 360 on a swing set. Despite the results of their scale model tests, they decide to attach four rockets to Simulaid Susie for the actual test for 400lbs of thrust.
First firing: Only one side of the rockets ignited, sending Susie into a spin
They decided to take two of the rockets off so that less could go wrong
Second firing: One side fired off before the other, sending Susie bouncing around and twisting.
They dropped down to a single rocket so that they wouldn't have to worry about simultaneous ignition. They also set the angle at 60 degrees because they were worried about Susie's weight.
Third firing: Susie barely swung back and forth as the angle of the rocket was too steep
They set the angle back to 40 degrees, which meant that they were finally back at the original parameters their scale model said they should have used.
Fourth firing: Simulaid Susie made it over in a full 360