Considerable works on this area were initiated by Graham Jost, Max Morris, Alan Esplen and others and plenty of excellent design examples are available in You Tube.The present effort is to construct a very simple one with only two Ping Pong balls. I thank Bob T for embedding the video clip from You Tube. I also thank my colleague Charu, for helping me to collect Ping Pong balls.All green parts and all brass parts are by Ashok. By observing the video clip, Edmundo Veiga of Brazil has created a drawing using Virtual Meccano, which he kindly permitted to upload in this album.