5234 HYDROGRAPHIC MANUAL Page 468 



Carbon rubs off the record to such a degree that objects with which it comes in 

 contact, or one's hands, are soiled. 



Holes a half-inch apart are punched along both edges of the paper. The holes 

 along the top are circular, while those along the bottom edge are elongated. These 

 holes engage the teeth of the sprocket roller whose purpose is to move the paper across 

 the recorder platen. This sprocket roller is driven by a shaft directly geared to the 

 same motor that rotates the stylus arm. It is impossible for this roller to rotate, and 

 thus for the paper to travel, slower than at the correct proportional speed. 



However, the sprocket roller is free to rotate around the shaft at a faster speed 

 than the correct one. The take-up roller is driven from the sprocket-roller shaft by a 

 coil-spring belt so adjusted that it will slip. If this adjustment is so tight that it 

 does not slip as intended, the paper can be drawn across the platen by the take-up 

 roller instead of by the sprocket roller, in which case the paper travel is at too fast a 

 speed. 



The paper must lie fiat on the platen, and must be properly centered so that 

 the teeth of the sprocket roUer engage the holes cleanly, without mutilating the holes. 

 When a new roll of paper is placed on the instrument it may be necessary to adjust 

 the take-up roll, or the feed roll, or both. This adjustment is accomplished by first 

 loosening the locknut on the end of each roller and then turning the adjustment knob 

 until the paper is properly alined, after which the locknut is tightened. When the 

 paper is properly adjusted, arcs drawn by the stylus should correspond with the printed 

 arcs on the paper. If they fail to do so by an appreciable amount, either the printed 

 scale is wrong or the instrument is not of standard construction. 



This paper is distributed by the Submarine Signal Company, and the type in 

 present use is known as 15U. 



5234. Motor Speed: Tachometer 



The motor driving the recording mechanism operates from 12 volts direct curient 

 and is rated at Koo horsepower at a speed of 4,026 r.p.m. This motor speed is normally 

 controlled by means of a governor, but a manual control is also provided, selection 

 being made by means of a switch. The governor is a centrifugal type, attached to 

 one end of the motor frame. A reversing switch automatically changes the direction 

 of the current through the governor contacts and the motor once each revolution of 

 the sprocket roller. This eliminates pitting of the governor contacts and, they need 

 attention only about once each season. 



Slight adjustments may be made to the gov.ernor by means of a knob located on the 

 face of the recorder cabinet. By this the governor may be adjusted to operate at the 

 calibration speed of the instrument. The manual control may be substituted in the 

 event of governor failure. Two knobs control resistors in series with the field of the 

 motor. One knob is for coarse and the other for fine speed adjustment. 



For accurate results the motor must al\yays rotate at calibration speed and it is 

 essential to be able to verify this continuously. A Frahmvibrating-reed type of tachom- 

 eter, located on the face of the cabinet where it is always in view of the operator, 

 provides the means for this verification. The tachometer is composed of seven reeds: 

 the middle reed, vibrating at maximum amplitude, indicates the correct motor speed for 

 the calibration velocity of sound in sea water of 820 fathoms per second. The three 

 reeds to the right and left indicate speeds too high and too low, respectively, by 0.75, 

 1.5, and 5.0 percent. These percentages are also applicable to the tachometer used in 



