in the art for instance as shown in fig2 the back plate may have lugs 104 extending inwardly therefrom so that bolts extending through the side plates may be attached thereto each carriage also includes a gripper chain drive system 106 and a roller chain drive system 108 referring to fig4 and 5 the gripper chain drive system includes a pair of spaced pair gripper chain drive sprockets 110 rotatably disposed in the carriage sprockets 110 are mounted on a shaft 112 having a center or longitudinal central axis 113 as better seen in fig1 shaft 112 extends through the upper mounting boss on the forward side of the apparatus and into to a flanged bearing 114 a bearing adapter 116 is also included and is attached to the upper mounting boss the gripper chain drive sprockets are driven by a reversible hydraulic motor 118 attached to each carriage on the back side 64 of the apparatus the motor is of a type known in the art and is driven by a planetary gear and has an integral brake thus the hydraulic motor can inject retract or suspend tubing 18 in a well the gripper chain drive system also includes a pair of spaced gripper chain idler sprockets 120 which are rotatably disposed in the lower end of.