Pumpkins are useful in many ways -- as a filling for pie, a jack-o'-lantern, and, as it turns out, as a projectile. Since 1986, the great pumpkin has been at the center of the World Championship Punkin Chunkin, where "backyard engineers" test the limits of pumpkin physics during a three-day festival in Bridgeville, Delaware [Science Channel].
So far the limits of punkin chunkin stand at 4,438 feet, the world record for hurling these orange gourds through the air without the aid of electricity or explosives. [Science Channel]. Pumpkins rocket into the sky from three different types of launchers, or "chunkers": catapults, trebuchets and air cannons, a spectacle that attracts upwards of 30,000 onlookers.
The event has its beginnings in a blacksmith shop owned by John Ellsworth. In 1986 Ellsworth, Trey Melson, Bill Thompson and Donald "Doc" Pepper began experimenting with punkin chunking after reading an article about a physics class that that threw pumpkins as an exercise in energy and mass. (Previous to this, the group held an anvil tossing competition.)The longest shot, or "chunk" the group recorded that year was 126 feet [World Championship Punkin Chunkin Association]. Compare that to the world-record holders, air cannon team Young Glory III's 4,438-chunk, and it's evident that the event is becoming more and more competitive, with teams putting their engineer skills to the test (not to mention specially grown "aerodynamic pumpkins) [Science Channel].
Here are a few simple rules:
- Pumpkins must weigh between 8 and 10 pounds.
- All pumpkins fired must remain intact until they impact the ground to obtain an official measurement.
- No part of the machine shall cross the firing line.
- No wadding can be used in the machines (including bean chaff, straw, foam, metal, or any other object).
- No explosives are allowed.
- Machines can have either springs, rubber cords, counterweights, compressed air or any other device that use the stored power of one human being.
Teams compete in divisions such as air cannon, centrifugal, catapult, human power, trebuchet, theatrical and torsion. The competition is divided into three classes: Adult (18 and older), Youth (11 to17) and Youth (under age 10).
Many of the pumpkin-throwing machines are mechanical in design. The current record holders use compressed air. Depending on the team's ingenuity and budget, a punkin chunker can cost anywhere from 0 to $50,000. (Some teams use scrap metal, which can greatly reduce the cost.)
Think you might be up to the punkin chunkin challenge? Up next, choose your weapon.
Types of Punkin Chunkin Machines
Punkin Chunkers have a few options when it comes to streaking the skies with squash. All are based on the concept of force, power and torque:
Any machine using compressed air to launch a pumpkin is called an air cannon. Air is compressed into a tank. When the constraint holding that air is removed, air expands back to its normal volume. The result is released air acts like a spring and forces the pumpkin through the tube at great volume, expelling the pumpkin out.
A machine using stretched springs or rubber bands, which store energy. When the springs or bands are pulled and then released, the stored up energy is transferred to the arm of the device, which hurls the pumpkin.
A Torsion machine is any device that uses twisted rope as its primary source of power. It relies on a rope that works by torsion or twisting. The rope stores mechanical energy when it is twisted. The amount of force it releases is proportional to the amount it is twisted.
Any machine with an arm that spins at least 360 degrees to launch a pumpkin. The basic idea in a centrifugal is to accelerate a pumpkin by spinning it in a circle many times, with each rotation gaining more and more momentum until it can build up enough energy to propel the pumpkin forward.
The basic idea of a trebuchet is to transform the potential energy stored in the lifted heavy mass into the kinetic energy that is the motion of the smaller mass (the pumpkin). It uses a short arm, which is weighted down with a heavy object to counterbalance against the long arm, where the projectile (the pumpkin) is placed. When the heavy mass of the short arm falls down, it provides energy to fling the long arm.
[Information on types of machines courtesy of the Science Channel]
For more information on the world of force, power and torque, check out the next page.
More Great Links
- World Championship Punkin Chunkin Association. [Accessed Nov. 9, 2009]http://www.punkinchunkin.com
- "Air Cannons, Catapults and Trebuchets." The Science Channel. [Accessed Nov. 9, 2009].http://science.discovery.com/tv/punkin-chunkin/how-it-works/how-it-works.html
- "What's Punkin Chunkin?" The Science Channel. [Accessed Nov. 9, 2009]http://science.discovery.com