This thesis explores the mechanics of single molecule machines on a surface, aiming to understand the principles underlying synthetic single molecular machines. The study utilizes scanning tunneling microscopy (STM) at ultra-low temperatures and high vacuum conditions to investigate individual small molecules adsorbed on a substrate. In the first part, the transmission of rotation between single molecule-gears is examined, employing a star-shaped pentaphenylcyclopentadiene molecule manipulated by STM. The second part focuses on a zwitterionic and chiral molecule's dual functionality as a molecule-rotor or a molecule-vehicle (nanocar), with motion driven by tunneling electrons. The third part explores the origin of unidirectional rotation in a single molecule-rotor, analyzing the effects of thermal and electronic excitations on rotation dynamics. Overall, this work contributes to the fundamental understanding of nanoscale mechanical molecular devices and their potential applications
