Trebuchet

http://www.instructables.com/id/Floating-Arm-Trebuchet-F2K/

http://www.trebuchet.com/firstfat

http://www.teslaworks.net/portfolio/floating-arm-trebuchet/

http://www.sciencebuddies.org/science-fair-projects/project_ideas/ApMech_p013.shtml

http://trebuchet.howtopool.com/

http://www.instructables.com/id/Floating-Arm-Trebuchet/

http://store.rlt.com/