Co-blogger Lee might not have time to blog much these days — hey, she's swamped doing double teaching duty, with uber-long commutes — but she did find time in between grading stacks upon stacks of student papers to send me an awesome video link called "Millimeters Matter," showing various insects being smacked with itsy-bitsy tarts launched by a mini-trebuchet. Her comment: "Someone is a major geek with too much time on their hands… and an Easy Bake oven."
She has a point. Check out the video below. Whoever made it (ad agency?) had to (1) build a tiny trebuchet, (2) calibrate said device appropriately to fling a plethora of tiny tarts, (3) make those tiny pastries (which may indeed involve the equivalent of an Easy Bake oven), and (4) corral a host of insects to suffer the ignomy of being hit with various pie fillings. Apparently it's an ad for Samsung electronics, and this isn't its first foray around the blogosphere: Cynical C posted it back in 2007. Jen-Luc Piquant has no idea if actual insects were harmed while making this video, but her attitude is, hey, they're insects. Nature will probably make more. (Except for bees — colony collapse disorder is actually a serious problem, and apparently there's a viral cause. Who knew?)
But here's a burning question, raised by one of the commenters in YouTube, who claims the device in the video isn't "really" a trebuchet as technically defined: i.e, it has no counterweight. Honestly, it's difficult to tell for sure, since the actual catapult is only featured briefly at the start of the video. I guess it depends on what one expects said counterweight to look like.
For those who don't know much about catapults, that term applies broadly to many different devices: trebuchets, ballistas (which look remarkably like giant crossbows), and mangonels, among them. They all are designed to fling heavy objects over long distances, and historically were used as weapons of war — pretty darned effective ones, too, when the machines were well-designed. They are distinguished by the projectile mechanism. Ballistas and mangonels are so-called torsion devices: a cord is twisted tightly and then released, causing the projectile of choice to fly off into the wild blue yonder. (With any luck, it hits its target.) In contrast, the trebuchet gets its power from, well, gravity, in the form of a counterweight that is released, causing the lever to whip around like a sling to launch a projectile.
It's simple physics: a lever and fulcrum principle, combined with what amounts to an amped-up slingshot. Think about a typical seesaw (lever) in a playground, carefully balanced on a point (fulcrum) about which it rotates — or rather, moves up and down. Now think about what happens when a much heavier child sits on one end while a small child sits on the other. If the weight difference is significant enough, and the heavier child sits down abruptly, it's entirely possible that the unfortunate smaller child could be thrown from the seesaw, thereby becoming a projectile.
That's pretty much what's happening with a trebuchet, except the fulcrum is positioned a bit closer to the much-heavier counterweight for the most efficient energy transfer. At the other end of the lever is the sling holding a projectile. Dropping the counterweight sets the lever in motion, the sling is pulled along with it, and when it reaches a given angle, the projectile is released. (Finding the optimum angle is one factor among many when it comes to building a successful trebuchet.) In fact, according to the folks at Real World Physics, it's akin to the physics of a golf swing, performed upside down.
There are countless hobby enthusiasts today that love trebuchets and other catapults, even designing and building their own. The popular Punkin Chunkin competition, featured every year on The Science Channel, draws many such people into this arcane world. You can find online classroom activities based on comparing a trebuchet and catapult, courtesy of NASA, and plenty of instructions and design tools, in case you want to take a stab at building your own.
In fact, USC string theorist Nick Warner is such an enthusiast: he once told me of building a trebuchet in the backyard with his daughter — and with that kind of brain power brought to bear on the challenge, I'm sure the resulting machine was quite effective. And that pretty much makes him one of the Coolest Dads Ever in my book.
When it comes to assessing performance, it's really all about range, which in turn depends on things like mass, shape and size; wind speed; the elevation of whatever's doing the hurling; and lots of other factors. Competitors who enter Punkin Chunkin can launch their pumpkins using any mechanical means, usually slingshots, catapults, trebuchets, or pneumatic air cannons. (The pumpkin has to be very firm, because the launch doesn't count if the pumpkin splatters in mid-air, dubbed "pumpkin pie in the sky.") An air cannon holds the current world record: apparently it chunked a pumpkin 4,623.43 feet in 2009, although Wikipedia tells me there's an even longer result pending verification: the same machine achieved a range of 5,545.43 feet just last month.
Small wonder that for several centuries, the trebuchet was the weapon of choice for laying siege to medieval castles. (The projectiles tended to be much larger than your average pumpkin, but the ranges achieved were still impressive.) The earliest version, called a traction trebuchet, was known in Ancient Greece and China around the 4th Century BC. It required many men to pull the lever instead of a counterweight, in order to launch a projectile. The counterweight version appeared in the 12th century, and was far more effective, flinging objects weighing as much as 350 pounds against medieval fortresses. Use two such machines in tandem, and it was possible to launch a projectile every 15 seconds. That kind of damage adds up over time. The trebuchet was a devastating weapon, and only fell out of favor with the advent of gunpowder-based weapons (like cannon).
For instance, in the summer of 1191, Richard the Lionheart used one his favorite trebuchets against the city of Acre during the Crusades. He called it "Bad Neighbor" (Malvoisine), and the accumulated impact of all those projectiles breached the city wall and supposedly shattered the "Cursed Tower." His other favorite trebuchet was nicknamed "God's Stone-Thrower" — consider them the Fat Man and Little Boy of the Crusades. Another English king, Edward Longshanks, had a trebuchet built called "Warwolf" that he used in the siege of Sirling Castle in 1304. Innovation has always been a hallmark of such machines: around 1187, an Islamic scholar named Mardi bin Ali al-Tarsusi described an unusual hybrid trebuchet: as it fired, it also cocked a separate crossbow, most likely as a means of protecting the men operating the machine during battle.
Stones were by far the most common projectiles, although attackers on occasion would launch diseased corpses and manure over castle walls in hopes of infecting the people huddled behind them — an early form of biological warfare. And if you're the henchmen of the French aristocrat, Louis de Lombard, in Monty Python's Holy Grail, you pitchez la vache — hurl cows and other farm animals over the walls at one's enemies. Because the trebuchet isn't just for laying siege to a castle — it's also an awesome defense against an invading army, or just a random group of knights in search of the holy grail.