and tipping the rocker 90 as shown in dashed lines in fig1 this action actuates the working parts of the tracking device 30 to its previously described operation the elevation tracking mechanism 17 fed with air under pressure by a hose 100 connected to the hose 21 operates similarly to the device 30 moving the crank arm 16 and its associated linkage one way or the other to rotate the pipe 11 the pressure regulator 101 illustrated in fig1 utilizes the reflective plastic film 27 or 37 or 50 forming the collector unit rear wall as a pressure sensing membrane and controls the pressure within the collector unit by regulating the inlet air the regulator 101 consists of a regulator body 102 a spool valve 103 a motion transfer arm 104 pivoted at pivot point 105 and an adjustable spring 106 with its associated spring seat 107 and adjusting screw 108 the air is introduced through hose 21 from the blower modulated by spool valve 103 and passed out of the regulator through hose 107 to the nozzle 75 as shown in fig1 when there is no air introduced as when the system is shut down the reflective plastic film 27 or 37 or 50 is relaxed and moves the motion transfer arm 104 toward the center of the collector unit this action causes the spool valve 103 to compress the spring 106 and fully open the passage between the inlet and the outlet of the regulator as air is introduced upon energizing the system the collector begins to inflate and the plastic film is stretched into its desired shape for reflecting the sun 39 s rays upon.