One of the first ancient siege engines, the catapult, was invented by the ancient Greeks for use in battle. Thousands of years later, Americans in a field in Delaware use those same devices to “chunk” pumpkins in an annual, pulp-filled competition. Many of today’s competitors, like Team ETHOS, have a secret weapon—they use SolidWorks® 3D design software to design and analyze their catapults for optimum performance.
Team ETHOS, a group of hobbyists from Wright Patterson Air Force Base, Ohio, uses SolidWorks 3D design solutions to design and simulate their catapult to compete in the Punkin’ Chunkin’® competitions. They use a siege engine relying on torsion, or twisting, power to propel the projectiles. In 2009, the team’s SolidWorks design led to a first place finish in the Adult Torsion Catapult category of the World Championship with a throw of 2,088 feet.
The World Championship Punkin’ Chunkin’ Association (WCPCA) is a non-profit association started in 1986 that hosts the Punkin’ Chunkin’ World Championships, which raises money for scholarships and charitable organizations. The contest has a simple goal: to throw an 8-pound pumpkin the farthest, remaining intact until it hits the ground. In addition to the World Championship, Team ETHOS also competes in a fundraising pumpkin chunk at the Wright Patterson AFB. This year the team’s Phoenix catapult raised $900 for charity with a shot of 2,972 feet, easily winning the contest.
In 2008-9, Team ETHOS re-designed its catapult, now called Phoenix, using SolidWorks software. They started with several designs in SolidWorks and evaluated each design’s manufacturability in the carbon-fiber composite, steel, and aluminum they use to build the catapult. Once they selected the final design, the team performed a stress and dynamics analysis with SolidWorks Simulation to understand how the catapult would function under real-world operating conditions. Any time something in the build didn’t work quite right, the team was able to easily remodel the parts in SolidWorks.
“SolidWorks is integral to everything we do for Phoenix. We use it to virtually test weights, motion, clearances, stress and dynamic analysis,” said David Mollenhauer, senior materials engineer. “It’s a complete game changer for the way we design things. At the same time, the software is very intuitive — I was able to teach myself how to use it.”
The combination of SolidWorks 3D Design and SolidWorks Simulation software allows Team ETHOS to analyze every aspect of the catapult. The team can evaluate force and stress between contacting parts and apply bearing loads, force, pressure, and torque while optimizing the design based on structure and motion. Team ETHOS also works with a CNC machinist, who also donates time, to execute the high-precision aluminum machining for the catapult. SolidWorks drawings are easily translated into a form the machinist can use, resulting in parts that fit the first time.
“It’s great to see people come together to use physics for fun. While the Punkin’ Chunkin’ event is designed for hobbyists, it’s also a testimonial to the role of physics and design in our everyday lives,” said Stephen Endersby, simulation product manager for Dassault Systèmes SolidWorks Corp. “Team ETHOS has combined form, function, and entertainment with its design for the world championship competition. We can’t wait to see how Team ETHOS performs this year.”
Watch Team ETHOS square off against five other teams in the Adult Torsion Catapult category of the World Championship Punkin’ Chunkin’ beginning on November 4, 2011. Discovery and Science channels will air the competition on November 24, 2011. Check your local TV listings for details. More information about how SolidWorks can help you design a catapult is available at http://www.solidworks.com/Sim_Complex_PumpkinChunkin_DOWNLOAD.
Oct 31, 2011
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