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Written by Falling Sideways
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Saturday, 19 August 2006 |
Archimedes Steam Cannon
Episode #55
Original Air Date: July 19, 2006
The Myth: Could Archimedes have created a steam cannon in 214 BC to protect the city of Syracuse from a siege?
The Experts: Roger L. McCarthy, engineering disaster investigator.
The Action/Results:
Archimedes makes another appearance on Mythbusters as Adam and Jamie attempt to construct and test a steam cannon using plans created by Leonardo Da Vinci attributed to Archimedes.
Adam and Jamie began by building a proof-of-concept model of a steam cannon out of copper pipes and wood, using plans provided by Leonardo Da Vinci. Jamie began constructing the propulsion section and steam tank using the copper pipes while Adam created a wooden barrel. However, Adam’s project became an endeavor and by the time he had finished, the shop’s lathe was a mess and Jamie was less than happy about it.
After some struggles, the small-scale cannon was ready to be tested and was brought to the Alameda test range to be fired. The fire was lit and the tennis ball projectile was loaded, but when their cannon was fired, it failed to launch anything. For the second test-fire, they make three modifications: 1) Cover the tennis ball in cloth and grease to ensure a tight seal in the barrel, 2) more water is added to the steam chamber to give the projectile more energy, and 3) the amount of propane heaters is doubled, to enable the cannon to reach a higher temperature, faster. Unfortunately, test number two was also met with failure. In the third test, the temperature was raised to over 500 degrees, but the tennis ball still wouldn’t launch.
Discouraged by their results at Alameda, Adam and Jamie call in an expert on engineering disasters, Mr. Roger L. McCarthy, to assist the team in firing their steam cannon. With a new sense of confidence, they set to work making four design changes on their cannon: 1) More water will be added to the steam chamber with a thicker pipe, 2) a new tube with rows of drilled holes will be added to the end of the water tank pipe to disperse the water evenly throughout the steam chamber, 3) copper nails will go into the steam chamber to increase the hot surface area, and 4) the temperature will be increased further. With the new modifications made to the cannon, they set it up inside of M5 to fire. But for the Mythbusters, the fourth time proves to be more humorous than dangerous, as the tennis ball simply pops out of the cannon and rolls for a few feet. However, they proved that a steam cannon could be made and fired, so they began to make the full scale model.
The second cannon has a much bigger, 24 pound, cast iron, Civil War cannonball as a projectile. Another change in the full-scale cannon was the method of injecting the water into the steam chamber. This time, they utilized an air actuator that pushed the water into the chamber in less than thirty milliseconds. As a finishing touch, Adam added a pair of Civil War era wooden cannon wheels, and the new cannon was complete.
Back at Alameda, the team set up the cannon for a test fire. Adam gave it the following odds:
• 20% chance that nothing happens upon launch
• 70% chance that the ball leaves the barrel
• 10% chance that, upon leaving the barrel, they actually find the ball
The first test failed, though, because the barrel was simply too cool. Test number two also failed because the pipes sprung leaked caused by the high temperature. For the third test, they lowered the angle of the cannon, but it too failed.
With Leonardo’s design BUSTED, they turn to a boiler-and-valve design to create a bigger bang. Another small-scale cannon was made and set up inside of M5, and when it was fired, its tennis ball projectile was launched towards the ceiling and lodged itself in between a pipe and a rafter.
They soon made a full-scale boiler cannon, and made another trip to Alameda. With their cannon aimed straight at San Francisco, they began to heat their cannon. But after several attempts to pressurize the cannon, they tried insulation and more heat, but the best they could muster was 68psi, well short of the planned 200psi. With daylight waning they took their shot and fired the cannon with spectacular results. The cast iron cannonball shot out fiercely and flew off into the sunset. After a brief search, Jamie found the cannonball a full mile away.
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Myth B: Which is more nutritious, your morning bowl of cereal, or the box it came in?
Was Adam’s mom correct in saying that “That cereal box is better for you than the cereal inside of it?”
The cereal versus box battle began as Adam set a calorimeter to find the amount of calories, or energy, in both the cereal and the pieces of the cereal box. One gram of cereal yielded 9 calories, while the box has around 20% less energy. That’s strike one against the cereal box.
The next test was to find out whether fat, protein, starch, and sugars appeared in each potential food. While the cereal had some fat in it, the box had none. Similar results appeared in the other categories, as the cardboard box had none of the four materials.
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Final Results:
Archimedes Steam Cannon: BUSTED
Cereal Box Nutrition: BUSTED
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