Episode 62: Killer Cable Snaps, Pottery Record
- A snapping cable can cut a person in half
- Sound can be recorded onto pottery like a record
The cable snap myth saw the return of pig carcasses as standins for human bodies. Its not a episode for those easily made queasy. The cable snap myth tested a belief that many of us, including Adam, had: that a snapping cable can cut you in half. But their own researchers had not turned up a single confirmed case of this actually happening and their testing confirmed what their researchers did: a snapping cable isn't going to cut through you like butter. It can kill you and cause many other types of damage, but in their multiple tests, though couldn't get a single cut.
Killer Cable Snaps
Myth: A snapping cable can cut a person in half
See also: American Graffiti/Rear Axle for previous experience with snapping cables.
Despite many anecdotal stories, they could not locate a single definitive case of someone being sliced in half by a cable. There have been plenty of fatalities, but no one sliced in half.
They showed a clip from the USS George Washington in 2003: a F-18 snapped its landing cable, sending it flying backwards at the flight crew on the deck. One person managed to hurdle the cable but another person wasn't so lucky and was knocked down.
Small-scale test (benchtest)
Jamie and Adam setup a small-scale test to see how a cable snap would behave. They marked out a 50x30 scale model room and stretched cord across it. When they cut it from one end, it said in a straight line back across the table. Then then stuck a bolt on the table as a stand-in for a person. The cable wrapped around the bolt when snapped.
The setup inside of a large building on an abandoned military base. They got several 150 lb pigs from Golden Gate Meat Company as well as a hydraulic cable cutter and a hydraulic puller (30 tons, 5" of stroke) from Andy Bull of C.H. Bull. The hydraulic puller was used to pull the cable taut, the hydraulic cable cutter was used to snap it, and a drum was setup to bias the direction of the snap towards their pig target. They also had a Gradall forklift for additional tensioning when needed.
Rope Snap Tests
They first tested with rope, which is more elastic than cable. The hydraulic puller couldn't get the rope taut enough, so they used the Gradall forklift. They snapped the rope at 3500 lbs of tension and it looped around the pig. It appeared to leave an small indentation, but there was no cutting.
They moved the pig closer to the end of the whipping point so that the end of the rope would make contact first and make a cut. This time the rope was tensioned up to 3000 lbs and flew at 227 mph when snapped. It left a mark on one side of the pig, but didn't cut the skin.
Cable Snap Test
They tested various cable sizes and configurations to try and cut the pig. The smaller cables potentially had more cutting ability, but the bigger cables had more tension.
- 3/8" cable (guy-wire for a radio tower or perhaps a hoisting situation): the cable sparked off the barrel and smacked the pig hard. It didn't cut into the pig, but it dealt a strong blow.
- 5/8" cable (40,000 lb. breaking strength): they were able to get it up to 30,000 lbs. of pressure. There was still no cut, but it left a strong indentation
- 3/16" cable attached to end of 5/8" cable (combine the cutting with the strength): not really different from previous tests.
- 3/16" cable looped around the pig and attached to 5/8" cable: the smaller cable cinched tight around the pig and crushed it, but there was no cutting
There still hadn't gotten anything close to slicing in half, so Adam went all out the replicate the result. They wrapped a pig around a drum with a cable and then pulled on the cable with the forklift. The cable had no trouble slicing the pig in half.
Pottery Record (Archaeoacoustics)
Myth: Scientists have been able to play back sounds inadvertently recorded onto ancient pottery
Myth Variant: On an episode of CSI, the investigators are able to retrieve a recording from a piece of pottery at the crime scene.
This myth may be based on this blog post: A phonograpic phony. The post discredits a Belgian video clip that claims to have made recordings from 6500-year-old pottery. The post then goes on to detail various occurrences of this myth, including:
- CSI's "Committed" episode
- X-Files "Hollywood AD" episode. A laser-scanning device is able to retrieve a recording in Aramaic from the time of Jesus.
- Richard Woodbridge's letter to the Proceedings of the Institute of Electrical and Electronics Engineers (IEEE) (1969, pp. 1465-6) titled, "Acoustic Recordings from Antiquity", in which Woodbridge claims to have made pottery recordings. (IEEE subscribers can read the pdf).
The MythBusters got some background on sound recording devices from 'Thorny', a sound system expert and collector of historical recording devices. He showed the MythBusters his collection, including the Edison Voicewriter/Ediphone. Thorny believed that the myth should be possible. The Voicewriter records dictations onto a wax drum, which is similar to how the pottery recorder could work.
The MythBusters used two setups to do their recordings onto the pottery. In the first setup, which was meant to test the historical version of this myth, they spun a piece of potter on a pottery wheel with a stylus etching into its side. The stylus sat on top of a drum, which transmitted vibrations. Tory and Kari took turns screaming sayings to be recorded.
For the "forensic show"/CSI variant, they cut some straw from a broom and held it against the side of the spinning pottery. In their first recording with Kari, they were worried that wind from Kari's mouth was moving the straw instead of her voice. They added a wind screen and did some more recordings.
Playing the recordings
Grant dissected some turntables to read their pottery recordings back. The stylus on modern turntables is too sharp for pottery, so Grant made a glass stylus by heating a shard of a wine glass. He heated up the shard and stretched it out into a thread. He then re-heated one end of the thread into a little bulb so it could be glued to the turntable arm.
The build team gathered around their pieces of pottery as Grant held the glass stylus on them for playback. They heard some promising whoops and squeaks, but nothing they could discern as a real recording.
They took tapes of their playback to DeNoise in SF, which specializes in audio processing. Albert Benichou, sound mastering expert, took his best shot at eliminating the noise from the recording to find some evidence of voices. The best they got for his efforts was a squeak.