1. AN ELECTRICAL COLLECTOR ASSEMBLY HAVING A COLLECTOR HEAD FOR CONTACTING A CONDUCTOR BAR OF AN ELECTRIFICATION SYSTEM COMPRISING A MOUNTING BASE, A COLLECTOR HEAD, A PAIR OF APPROXIMATELY PARALLEL SPACED APART SUPPORTING ARMS EXTENDING BETWEEN THE MOUNTING BASE AND COLLECTOR HEAD, MEANS PIVOTALLY CONNECTING OPPOSITE ENDS OF THE ARMS TO THE MOUNTING BASE AND COLLECTOR HEAD ON SPACED PARALLEL PIVOT AXES, AND A COIL SPRING SEVERAL TIMES LONGER THAN THE SPACING BETWEEN SAID ARMS CONTAINED ON THE ARMS AT A POSITION BETWEEN THE MOUNTING BASE AND COLLECTOR HEAD FOR URGING THE ARMS ABOUT THEIR PIVOT AXES SO THAT THE FORCE THE COLLECTOR HEAD EXERTS AGAINST ITS CONDUCTOR BAR WILL REMAIN SUBSTANTIALLY CONSTANT AND RELATIVELY INDEPENDENT OF THE SEPARATION BETWEEN THE CONDUCTOR BAR AND THE MOUNTING BASE OF THE COLLECTOR ASSEMBLY, THE ARMS HAVING ACCOMMODATING SLOTS FORMED THEREIN, THE COIL SPRING EXTENDING FROM WITHIN THE CONFINES OF THE SLOTS AND DIAGONALLY BETWEEN THE ARMS, AND OPPOSITE ENDS OF THE COIL SPRING BEING COUPLED TO OPPOSITE ARMS.