Here is a picture without the cover/bumpers. The rotating mass is the blue and white striped drum. It is powered by a cim and then dropped by two cams (out of view) onto the two black semicircles with go-kart tire treads. These two objects mesh and the rotational kinetic energy is transferred to the kicking arm, producing a kick. See more on our award-winning website: www.techhounds.com Match videos here: http://streaming.more.net/robo2010/match_091.asf