Rotary to linear translation mechanism

lasercut hands attached to motors translate the rotary movement into linear

download cad file here

some ideas for the mechanism

Rotation to translation mechanism 1, http://www.youtube.com/watch?v=wtn_T-WMDR4

Rotation to translation mechanism 2, http://www.youtube.com/watch?v=kOyRtiDRZ_o&feature=relmfu

mechanisms&automata (1st one) http://www.youtube.com/watch?feature=endscreen&NR=1&v=0gjyVqwrf3E