This is the Chalk painting mechanism of the "Artist Robot". The mechanism has 3 functions: the one is to release the chalk gradually as the robot writes because the chalk will be destroyed due to the ground friction, and the second is that the mechanism must constantly push smoothly the chalk holder in to the ground, in order to keep the touch with it, and simultaneously must absolve the shocks and vibrations like a suspension. Here are some videos:chalk pen lifter 3 function http://youtu.be/NF8Z1Sq7ibw Artist chalk figure8 http://youtu.be/zt9quhxz2RU chalk robot drawing http://youtu.be/gN_oHED36yk Chalk mechanism assembly http://youtu.be/n7MNV67Fz3whttp://youtu.be/NF8Z1Sq7ibw http://youtu.be/n7MNV67Fz3w