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Episode 55: Archimedes Steam Cannon, Cereal Nutrition

  • Archimedes Steam Cannon: mythbusted. Using modern materials and a design from Leonardo da Vinci, they were unable to get the cannon to launch. Using a more modern boiler design, they were able to launch the cannonball a mile down the Alameda runway.
  • The cereal box can be healthier than the cereal: mythbusted. In the cereal they tested, there were less calories and almost no detectable nutrients (fat, starches, protein, sugar).

Archimedes returned again, this time with a steam cannon myth. With only vague designs to support the myth, they decided to go a bit more modern in their construction to show the designs at their fullest. Their first steam cannon build, based on a Leonardo drawing, didn't do so well. After a could of attempts that ended in hisses, the most they could manage was plopping the cannonball out. They didn't want to end the show with a plop, so they built a steam cannon with a proper boiler. They didn't get anywhere near their intended psi because the sun was setting and it was taking too long, but they still managed to launch the cannonball a mile down the runway (unclear how much of that was rolling, but still...). Who knows what fun would have ensued if they actually got to full power.

This episode was originally supposed to show with a segment on teeth whitening, but it was cut due to sponsor conflicts. There was also more footage shot for the cereal box myth that had to be cut due to the unintentionally gruesome result when they tried have mice survive on the box alone.

Archimedes Steam Cannon

Myth: Archimedes created a steam cannon in 214 BC to protect the city of Syracuse from a siege.


Historical evidence

The only design reference for the Archimedes cannon was a one-page drawing from Leonardo da Vinci in which he mentions Archimedes as the originator as well as plans from the Greek inventor Sacchus (spelling?). As for historical mentions of the cannon, they found two quotes. One from Petrach's Remedies for Fortune, Fair, and Foul: "What used to be thrust forth by the clouds of heaven is now being thrust forth by a machine conceived in hell," and another from Valturio s De Re Militari: "The cannon, or bombarda, as its commonly called, Is a contrivance made of metal which through the agency of flame and sulphurous, or perhaps one should say hellish, powder hurls bronze missiles." Neither mentions steam cannons.

They decided to start with the Sacchus design.

Small-scale cannon

Adam and Jamie built a small-scale model of the cannon. Jamie bought some copper piping in order to make the chamber that would be heated and Adam made the wooden cannon barrel on a lathe -- much to the anger of Jamie, as Adam nearly broke the $30k lathe and left a huge mess of wood shavings.

The copper chamber was fed by a copper pipe in which water could be introduced. The Sacchus design works by first heating the copper chamber and then adding the water -- if the chamber is hot enough, it should flash immediately into steam and launch the projectile.

At 250 degrees, they dropped in the water, which generated a nice fizzle, but not much else. For the second firing, they covered the tennis ball in a cloth and grease to improve the seal, added more water, and used twice as many propane burners to heat the chamber. This time, the chamber made it to 400 degrees, but the result was the same: hisssss. For the third firing, they got the chamber up to 500 degrees, but again, just the hiss of steam.

They brought in Roger McCarthy, engineering disaster investor, Chairman Emeritus of Exponent Incorporated, to debug their small-scale design. McCarthy was certain that they could fix the design and came up with four design changes: thicker pipe to add water, a tube with holes to distribute the water across more of the chamber, copper nails inside the chamber to increase the surface area, and even hotter temperature.

For their next set of test firings, they used the modified design along with a blowtorch to get even hotter. The tennis ball plopped the ball out pitifully for several feet of distance. Jamie: "It fired." Jamie noted that the steam had melted and distorted the tennis ball, which allowed more steam to escape.

Jamie: "I think there is a reason that this thing wasn't firing as energetically"
Adam: "No I think what we have is a reason why the Greeks didn't use tennis balls."

Full-scale steam cannon

They switched to Leonardo's drawings for the full-scale cannon. They also decided to forgo using period materials under the reasoning that they wanted to show the best possible result that Leonardo's design could achieve.

Leonardo's design featured barrel heated in a blazier. With their upgraded components, their steam cannon featured:

  • a 20 ft long, schedule 80, pipe. The same size as a WWII howitzer barrel
  • a 24-lb, cast-iron, Civil War Cannon ball
  • a coal-fired blazier built by Adam with a target temperature of 900 degrees.
  • an air actuator that Jamie converted into a water injector that could work in less than 30ms.
  • Civil War-style wheels.

Adam's probabilities:

  • 20% nothing will happen
  • 70% chance of success
  • 10% chance of finding the ball

For the first launch, they managed to get the blazier up to 1000 degrees. The blast was barely enough to cause a sheet at the end of the tube to wave, i.e. nothing happened. For the second launch, they pushed the blazier up to 1500 degrees. Once again, the sheet was flapping and not much else. The video showed the piping leaking, so Adam welded the leaks and they added more coals. This time, the ball finally launched, or rather, the ball rolled out of the cannon barrel.

Steam cannon take 2

In order to get a good cannon launch, they decide to build a proper boiler with a valve so that they can heat the water inside of the chamber and release the steam into the barrel.

They first built a small-scale version of the new boiler design. Adam re-rigged the air actuators to turn the boiler valve and they reused parts of the original small-scale design. Their new small-scale cannon fired the tennis ball into the piping along the ceiling.

For the full-scale design, they reused the piping from the Sharammer to make the boiler. They setup their new cannon at Alameda, pointed it at San Francisco, built a coal fire underneath the boiler, and waited for the psi to reach 200 psi. The pressure gauge wasn't going anywhere, so they wrapped the boiler in insulation, which finally got the gauge to budge.

At 68 psi, with the sun setting over SF, they decided to launch: big boom. They found the ball a mile down the runway -- it was unclear how much of that it rolled, but it went far.

mythbusted: with modern materials and a period design, they were unable to get the cannonball to launch.

Cereal Nutrition

Myth: The cereal box can have more nutritional value than the cereal inside.

Jamie blended up the cardboard box into a mush to make it easier to eat and proceeded to taste some.

Jamie: "Kinda reminds me of high school for some reason"
Adam: "It tastes uncannily of cardboard"

Calorimeter test

In order to measure calories of food, you burn the food underneath a pot full of water. When it is done burning, you measure the temperature to determine the caloric content.

Adam measured the caloric content of 1 gram of cereal at 9 calories and the caloric content of 1 gram of cardboard box at 20% less than the cereal.

Nutrients test

The nixed the idea of a human lab rat test as Adam was worried they'd cheat and Jamie was worried that the cardboard might have some toxins. Instead they decided to test for some common nutrients: fats, starches, sugars, and protein.

"My original plan was that you'd eat cardboard for a week and I'd eat some sugary cereal for a week, it seems kind of ideal for both of us, but I'd think we'd both cheat. I'd know you'd cheat, and I'm pretty sure that I'd end up cheating too." - Adam

The nutrients test showed what you might expect: the cereal had fat, starch, sugar, and protein, while the cereal had much less or none of all four, i.e. no real nutrients.

mythbusted: The box has less calories and almost no nutrients.


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