132 



USRL TEST STATIONS 



CONTROL FOR 

 POSITIONING 

 TRANSDUCER 



TRANSDUCER 



Figure 73. Sketch of offset rotator and synchro con- 

 trolled rotator with attachment for taking directivity 

 patterns of a transducer inside a dome. 



Figure 74. View of corrugated dome on special rigging 

 for directivity measurements. 



The types of carriages, suspension rods, and rotat- 

 ors with synchro control are identical with those at 

 Mountain Lakes. The carriage shown at the far end 

 of tire test basin in Figure 72 is especially designed 

 for use in the rotation of devices around points other 

 than the center of gravity. This carriage and an offset 

 rotator proved so useful that a synchro control was 

 added. A further attachment was designed for taking 

 vertical directivity patterns, such as that of an echo- 

 sounding projector inside a dome. In this case, the 

 dome is turned on its side, the projector mounted in- 

 side at any desired bearing relative to the nose, and 

 the two are then rotated together. These features are 

 shown in Figures 73 and 74. 



The electric equipment lor the pier station is 



housed inside the main building with the panels ar- 

 ranged in an arc facing the lake, as shown in Figure 

 75. The operator is stationed between these panels 

 and a desk for recording test data, and a window 

 above gives a view of the pier. The electric apparatus 

 is similar to that at Mountain Lakes with the excep- 

 tion of the recorder and the high-power amplifier 

 shown in Figure 78. Operation and circuit of the 

 recorder have been described in Section 6.2.1. In 

 this case, the drive by a double-armature motor is 

 replaced by a magnetic clutch which makes contact 

 between the rails of the pen carriage and either side 

 of a continuously revolving disk. Coordination of the 

 oscillator and the paper drive is obtained by driving 

 both by one motor. The bay on the extreme left of 



