A punkin chunkin is a contest for machines, such as catapults, to see how far they can throw a pumpkin. The machines don't use any electricity, engines or explosives. One class of punkin chunkin machine uses air power.

Recently, near the How Stuff Works office in North Carolina, a local FM radio station, WDCG-FM, promoted a human-powered punkin chunkin competition.

Some of the promoter's official rules for this competition are quite interesting:

  1. Pumpkins must weigh between 8 and 10 pounds.
  2. Pumpkins must leave the machine intact.
  3. No part of the machine shall cross the starting line.
  4. For safety, only five people per machine are allowed during the actual contest.
  5. Absolutely no explosives!
  6. Machines may have either springs, rubber cords, counterweights, compressed air or any other device that uses the stored power of one human being in a maximum of 10 minutes.
  7. Machines must be able to reload and fire within 10 minutes.

Teams compete in classifications such as air, centrifugal, catapult, human power, youth unlimited and youth 11-17.

Many of the pumpkin throwing machines are mechanical in design, while the long-range ones use compressed air.

In the 1998 World Championships, an air-powered machine threw a pumpkin 4,026 feet (1.23 km)! In the North Carolina contest, Team Carbo's Onager catapult threw a pumpkin 1,032 feet (314.5 m). The distance is measured by a laser device, similar to what you may see land surveyor crews use along the highway.

Built of heavy timbers and nylon rope and bicycle-powered to help preload the mechanism, the Onager placed second in the national championship in 1999. Onager uses many mechanical devices to throw a pumpkin, as shown at this Web page, including a torsion spring. Torsion means twisting, and in the Onager, the torsion device is a heavy, thick bundle of nylon rope. When released, the device untwists and catapults the pumpkin. Team Carbo tightens the torsion spring bundle with a long lever, and then a winch cinches it down even more with pedal power.

In the photo below, Team Carbo's bicyclist is actually winding a boat winch with gear reduction pedal power. This winch is just above his right foot. Click on the picture to see a 5-second movie in mpeg format.


Below, Team Carbo preloads the heavy yellow nylon rope torsion spring:


Onager's winch is at the bottom; the yellow nylon rope torsion spring is visible the middle:


Onager's sling is ready to throw the pumpkin, from a hole dug behind the machine. The hole helps keep the pumpkin in place and allows for a longer sling.


Special thanks to program director Chris Edge at WDCG-FM and his staff for their cooperation and assistance.

Here are some interesting links: