5221 HYDROGRAPHIC MANUAL PaGE 460 



5221. Description 



The Simplex-Bludworth Fathometer consists essentially of three separate units: 

 a recorder cabinet containing the graphic-recording mechanism, signal sender, echo 

 amplifier, and speed indicator; a submersible unit consisting of a streamlined cast- 

 aluminum housing which contains the transmitting and receiving oscillators; and a 

 12-volt storage battery. For proper operation, the units should be located according 

 to the instructions given for the 808 Fathometer (see 5236) . 



a. Recorder cabinet. — -All essential parts except the transmitting and receiving units and the 

 battery are in one metal case which has a canvas cover for protection from the weather. The operat- 

 ing controls, all conveniently located, consist of an on-off power switch, an on-off recorder switch, a 

 phase-changing control, a "foot-fathom" selector switch, a sensitivity control, a fix-marker button, 

 and a control for compensating for draft or tide. There are also a motor-speed meter and a reed 

 tachometer. All of the controls and meters are located on the top of the case or are accessible through 

 it when the case is closed. The top of the case also contains glass ports through which the draft 

 setting can be verified and the fathogram viewed. 



The recording mechanism consists of a revolving drum coupled directly to the motor shaft clutch 

 for recording in feet and reduced through a 1 to 6 gear ratio for recording in fathoms. The 12-volt 

 d-c driving motor has a speed range from 2,280 to 2,580 r. p. m., with 2,460 corresponding to a velocity 

 of sound of 820 fathoms per second. The electric impulse, which makes the depth record, is trans- 

 mitted through a raised wire set into a helical groove in the drum. A printer blade is mounted in a 

 bridge directly above the revolving drum and is adjustable in the bridge so that a uniform pressure 

 can be maintained on the record paper where it contacts the helical wire. 



The record paper is of the dry facsimile type, impregnated with conductive material and surface- 

 coated with an electrosensitive substance. The paper is rove between the revolving drum and the 

 printer blade so that when an electric impulse is received it passes from the printer blade through 

 the paper to the helical wire, leaving a permanent black mark at the point of contact of the blade 

 and wire. The paper has a continuous printed scale which is 6V2 inches wide, the width being divided 

 by lines into 60 equal parts, each part representing 1 foot or 1 fathom depending on which operating 

 speed is used; and perpendicular to these lines are travel-spacing lines 1 inch apart. A depth range 

 to 180 feet (or fathoms) is provided by three phases as follows: to 60, 60 to 120, and 120 to 1^0, a 

 scale for each phase being printed in different color and style numerals alternately along the paper 

 at 2-inch intervals, each scale being repeated every 6 inches. When the instrument is recording in 

 feet, the travel speed of the paper is 2 inches per minute at a motor speed of 2,460 r. p. m. The 

 paper travel is provided by positive rubber friction rollers and the paper is truly alined by means of 

 limiting rollers. 



The signal sender in the recorder cabinet energizes electrically the transmitting oscillator. The 

 sender operates from a 350-volt vibrator-type power supply, and when keyed produces an electric 

 impulse in the pscillator in exact synchronism with the keying commutator. 



The echo amplifier is a three-stage resistance-coupled thermionic type, tuned to respond at 

 maximum sensitivity at a frequency of 14250 cycles per second. The input stage is transformer 

 coupled to the receiving oscillator and the output stage is transformer coupled to the printer blade. 



b. Submersible unit. — -The submersible unit consists of a transmitting and a receiving oscillator 

 mounted in a streamlined cast aluminum housing 37 inches long by 14 inches wide; the oscillator 

 centers are 13 inches apart; the units are very similar to those of the Hughes MS 12 D (see 528 and 

 5273). The magnetostrictive oscillators consist of packs of thin annular nickel stampings mounted 

 on a spindle inside an air-filled reflector and immersed in castor oil. Each pack is toroidally wound 

 with an energizing coil of neoprene insulated wire. 



The operating frequency of the oscillators is 14250 cycles per second and is outside the normal 

 range of interference from ordinary water noises. The transmitting and receiving oscillators are 

 identical in all respects except that the receiving unit is permanently magnetized. 



The submersible unit should be installed so that its bottom is at least 2 feet below the surface 

 and in a horizontal plane, and its axis parallel with the centerline of the vessel. There should be at 

 least a 1-foot clearance between it and the vessel. 



