^■\ 



load becCTnes 15^000 pounds. The normal force required to 

 develop this line pull would be about 37^500 pounds since the 

 frictional forces act on both sides of the cable. If we 

 assume the maximum permissible loading over the total length 

 of track i, L„ to be p pounds per inch of contact between 

 track and cable, the length of track is given by 



T -( 37,500 lbs ) 



p 



If a value of 500 pounds per inch is taken for p^ 

 in accordance with one manufacturer's recommendation Sj the 

 length of track beccanes 75 inches, which is about that of 

 the Western Gear unit tested at sea. It would not be de- 

 sirable, in any event, to reduce the track length used in 

 that unit^ since it very nicely envelops the modules while 

 maintaining pressure on the remaining cable, as shown in 

 Figure II-2. 



The total tractive capacity can be increased by increas- 

 ing the allowable value of p. Discussions with cable manufac- 

 turers indicate that it should be possible to load the cable 

 transversely by several thousands of pounds per inch. Hence, 

 if the track and fairing materials permit, or if other suitable 

 materials can be found, it appears reasonable to retain about 

 a six-foot effective track length and increase the tractive 

 capacity by increasing the normal loading. If p could be 

 increased to 1500 pounds per inch, for example, the winch 

 could sustain the maximum pull imposed by the cable. 



39 



