applied to the track-loading air cylinders. Slippage at 

 this load occurred when the air pressure was reduced to 



90 psig. From these data, and the geometry of the machine, 



* 

 a value for /i of 0.29 was canputed. 



STERN SHEJ^.VE 



Three methods of passing the cable ^ with in-line 

 modules, over the stern have been considered: 



1. Single, large-diameter sheave . 



Use of a single, conventional sheave would necessi- 

 tate a sheave about twenty feet in diameter to pre- 

 clude excessive local stress in the individual 

 cable-armour wires near the fitting which secures 

 the cable to the module. 



2. Tandem-sheave arrangement 



Excessive sheave diameter could be avoided by trans- 

 ferring the cable between two tandem-mounted sheaves, 

 avoiding contact between modules and sheaves as 

 shown in Figure 9a. The diameters of such sheaves 

 need not exceed the minimum requirement for rea- 

 sonable cable life (3 feet for f-inch-diameter cable) 



The lack of agreement with the value of M given in Table 1 

 for equivalent conditions may be attributed to inexactitude 

 in the pressure measuratnent, the use of double armoured 

 cable rather than wire rope, and friction in the mechanical 

 elements of the track loading system. The use of double 

 . annoured cable should yield a real increase in the value 

 of y>c due to the lay of the outer wires; whereas the in- 

 crease due to friction in the mechanical linkages is 

 present only because the measurement was taken with de- 

 creasing pressures. 



25 



