EV3 is a robotics sets from LEGO Mindstorms. With EV3 you could build an infinite number of robots like Vehicles, Animals and Tanks. The set comes in two parts - base set (45544) and a resource set (45560). EV3 robots are very popular at LEGO Mindstorms Robotics Competitions
Robot attachment that shows you how a circular motion could be transferred to linear by using a gear and a rack. The final motion is for pushing and pulling things.
The attachment could be built from LEGO Mindstorms EV3 and NXT parts.
This construction demonstrates one way of using а rack with a gear wheel. It allows to turn circular motion in to a liniar one.