Fig. 3- Assembled instrument section before potting. 



inserts, crimp type pins and other methods of 

 joining two leads were investigated and rejected 

 for various reasons of size, reliability or com- 

 plexity. After many tests, it was decided that 

 the connections would be made by soldering two 

 leads together side by side without twisting and 

 covering the joint with heat snrinkable plastic 

 tubing. The tubing, in addition to adding 

 mechanical strength, provided a watertight bond 

 with the insulation of the cable leads . Numerous 

 tensile tests proved that the above method 

 resulted in a junction stronger than the copper 

 lead itself. 



During array manufacture the terminal assem- 

 blies of two adjacent array sections are mounted 

 about h inches apart. All the necessary elec- 

 trical connections are made, tubing shrunk on 

 and then three wire rope assemblies are installed 

 joining the two sections mechanically (Fig. 3)- 

 Each end of the rope assembly is terminated in a 

 threaded steel fitting swaged to the wire. Self- 

 locking nuts hold the assemblies in position 

 after they are inserted through holes in the 

 terminal assemblies. The volume between the 

 terminal assemblies and around the cable leads 

 and wire rope is filled with polyurethane which 

 bonds to the neoprene jacket on the cable pro- 

 viding a watertight joint that will stand the 

 pressures expected for this application. 



A number of different cable designs were manu- 

 factured and tested with varying success. Part 

 of the slippage problem was traced to the insula- 

 tion on each lead. Because so many leads had to 

 be soldered in such a small volume Teflon insula- 

 tion was originally used. Teflon, however, is 

 very slippery and cannot be bonded easily, so it 

 was replaced by polyethylene. Test evidence also 

 indicated that the relationships of the lays of 

 each twisted pair and the cabling lay of each 

 bundle contributed to the amount the leads 

 appeared to walk in the cable. No cable tested 

 eliminated the problem but the effect was mini- 

 mized by proper design of cable insulation, 

 direction and amount of lay and jacketing thick- 

 ness and hardness. 



To provide protection against lead failure due 

 to non-uniform cable stretch, a service loop was 

 included at each electrical connection. The loop 

 provides approximately 2 inches of slack to 

 allow for non-uniform cable and lead stretch. 

 To prevent the encapsulating compound from filling 

 the interstices of the connector and capturing 

 the leads thus negating the action of the service 

 loop, the connector area before encapsulation is 

 wrapped with tape. The polyurethane moulds around 

 the wrapped area leaving a small void internally 

 in which the lead joints may slide freely past 

 one another as the elements in the cable are 

 worked over the sheave. 



SYSTEM TEST AND OPERATION 



A serious problem was discovered, however, 

 when the array junction was cycled repeatedly 

 under simulated load conditions over a large 

 diameter sheave . The individual leads in the 

 cable did not stretch as a unit with the outer 

 armour and watertight jacket. During repeated 

 flexing under tension, the leads appeared to 

 walk up the cable and eventually the leads that 

 walked the fastest failed in tension. This type 

 of failure did not show up during straight ten- 

 sion test. Repeated flexing under simulated 

 load conditions was necessary to allow the cable 

 parts to work sufficiently until differences in 

 length of the various cable parts caused a break 

 in a lead . 



As pressure increases on the cable in deep 

 water, the connector area is compressed and the 

 internal void volume is decreased tending to 

 freeze the leads in place. This is not serious 

 because slippage occurs primarily during the time 

 the cable curves around the sheave when pressures 

 are negligible . 



It is necessary to bring leads out of the cable 

 at every location of a hydrophone or instrument 

 package . To eliminate breakouts through the cable 

 armour all elements are located next to a ter- 

 minal assembly and the required leads are broken 

 out at the electrical joint section between the 

 terminal assemblies. When the electrical con- 

 nections are being made between two array sec- 

 tions the cable leads associated with the hydro- 

 phone located adjacent to the terminal assembly 

 are selected and brought to the surface of the 



77 



