the shim bearing surface 174 the mounting base 170 also includes a bushing 168 to support and stabilize the pinion 30 and a guide post 171 to facilitate horizontal translation of the racks 40 and 41 if desired stop members 80 and 82 can be inserted in bores 84 and 86 or 88 and 90 fig5 to limit the motion of the racks referring to the embodiment disclosed in fig5 and 6 the racks 40 and 41 travel a distance to produce a 90 u00b0 rotation which distance is much less than that of the racks shown in fig3 and 4 therefore travel stop extensions 180 and 182 are required additionally electronic sensors 92 and 94 fig2 may be provided to indicate full open and full closed positions of the valve the sensors 92 and 94 may be connected to indicator lights 96 and 98 through appropriate circuitry which is well within the skill of one skilled in the art to construct in operation referring to fig3 and 4 the output shaft of the actuator not shown is connected to the pinion 30 by slot 34 when the actuator rotates the actuator shaft the motion is imparted to the pinion 30 which causes the pinion 30 to rotate in turn the rotation of the pinion 30 which has teeth 32 in engagement with the teeth 42 of rack 40 and teeth 43 of rack 41 causes the pair of.