one of the rachets, moving it inboard ^/le of 

 an inch. This movement removes the support 

 for a weight and the weight falls free of the 

 housing. The next time hydraulic pressure is 

 applied, the piston and carriage move in the 

 opposite direction. A rachet finger engages 

 the other rachet bar and a weight is dropped 

 as the bar moves inboard. 



DEEP JEEP incorporated the same princi- 

 ple with thirty 4-pound steel plates sur- 

 rounding its battery pod; in this case, each 

 plate was held in place by an electromagnet 

 which, when power ceased, dropped the 

 weight. In the event of a total power failure 

 all weights were automatically jettisoned. 



Iron Shot: 



Adopted from the FNRS-2, the dropping of 

 iron shot to attain positive buoyancy has 

 been incorporated into several contemporary 

 submersibles and was used on all the bathy- 

 scaphs (Table 6.5). The type of shot used 

 resembles "BB's" and the only hard require- 

 ment is that the shot have magnetic proper- 

 ties. The younger Piccard, in Seven Miles 

 Down, related the difficulty in attaining shot 

 with sufficient residual magnetism in the 

 U.S., thus necessitating ordering shot from 

 Italy to accomplish TRIESTE'S early mission 

 leading to the deep dive. 



In concert with the host of dissimilar pro- 

 cedures to accomplish similar functions from 

 submersible-to-submersible, no two shot sys- 

 tems are identical in location of shot tanks or 

 method of shot control, though all use "fail- 

 safe" electromagnets to hold in the shot. 

 BEN FRANKLIN is one example of this 

 method of attaining positive buoyancy. 



The shot ballast system of BEN FRANK- 

 LIN has two functions — to adjust the buoy- 

 ancy of the boat by metering out shot 

 through a specially designed electromagnetic 

 valve, and to provide 6 tons of buoyancy 

 (6,372 pounds per tank) in an emergency by 

 rapidly dropping all of the shot (release of 

 hydraulic pressure on a piston opens a large 

 door at the bottom of the shot ballast tank). 



Separating the two main ballast tanks port 

 and starboard, the shot ballast tanks are 

 filled with iron shot (Globe Steel S-780(J) up 

 to a point about 4 inches below the waterline. 

 The tanks are free-flooding and are always 

 open to the sea in order to pressure compen- 



sate the tanks and to prevent rusting of the 

 shot into an unmanageable agglomeration. 

 When completely immersed in seawater, the 

 corrosive action on the shot is minimized and 

 the granules remain free. 



Each shot ballast tank is fixed to the sides 

 of the hull by attachments similar to those 

 on the main ballast tanks but with elongated 

 bolt holes designed to allow for any play 

 which occurs during expansion or compres- 

 sion of the pressure hull. The tanks are 

 constructed of sheet steel supported inter- 

 nally by steel truss frames. 



The shot dropping systems consist of two 

 electromagnetic valves — one for each shot 

 tank. Each valve has two sets of coils — 110 

 VDC and 28 VDC. The 110-volt holding coils 

 are made up of soft iron cores which can be 

 permanently magnetized by coils when sup- 

 plied by 110 volts. These "magnetic valves" 

 are used to hold the soft iron shot in the 

 ballast tanks when permanently magnetized 

 and the power is removed. This is accom- 

 plished when the shot ballast becomes mag- 

 netized in the "throat" of the valve. The 

 valve can be demagnetized to release its hold 

 on the shot by cycling the 110-VDC voltage 

 through progressing voltage dropping resis- 

 tors. Dropping the voltage and cycling both 

 the plus and minus values through the coils, 

 the cores become totally demagnetized since 

 any residual magnetic effects are erased in 

 this manner. 



The 28-volt metering coils are essentially 

 electromagnets which are used to control the 

 flow of the soft iron shot through the valves. 

 This is accomplished when the 110-volt coils 

 are demagnetized and the 28-volt coils are 

 de-energized. Flow of shot is stopped when 

 the full 28 volts are used to energize the 

 electromagnet and the soft iron shot in the 

 valve's throat is magnetized. This condition 

 can be maintained when the voltage is re- 

 duced to 14 volts. 



The electric metering system, used to 

 measure the amount of shot in each of the 

 two tanks, consists of a transformer verti- 

 cally oriented in each tank. The primary coils 

 are excited by 20 VAC which has been 

 stepped down via a transformer from the 

 110- VAC bus. The secondaries of the meter- 

 ing transformer are returned into the boat 

 and terminated into voltmeters. The voltage 



299 



