4. Rotational testing of six different types and sizes of cable showed 

 that cables of similar construction can exhibit quite different rotational 

 characteristics. A double -armored construction is not necessarily torque- 

 balanced and a multistrand construction can be non-rotational. Data on 

 tension versus elongation and torque versus rotation are not sufficient 

 for an adequate description of the cable rotational properties. 



RECOMMENDATIONS 



1. Equation 18a should be used whenever possible to determine the critical 

 tension needed to prevent the formation of kinks. The critical torque, 

 which is the tension-induced torque, in most cases, can be obtained from 

 laboratory test data or from Program TAWAC. 



2. Equation 18a shows that increasing the bending stiffness will reduce 

 the likelihood of kink formation. Therefore, within the flexibility 

 requirements of sheave bending, deployment cables should be selected which 

 have the largest possible bending stiffness. 



3. When rotational data are not available and Equation 18a can not be used, 

 a deck winch capable of providing a minimum line tension of 100 pounds at 

 the lower end should be used to prevent cable kinking. 



4. The analytical cable models developed in this report are recommended 

 as a tool for optimal cable design and selection. 



REFERENCES 



1. M. Chi. "Analysis of operating characteristics of strands in tension 

 allowing end-rotation," paper presented at Winter Annual Meeting of American 

 Society of Mechanical Engineers, New York, New York, Nov 1972. (ASME paper 

 no. 72-WA/Oct-19) 



2. J. W. Phillips and G. A. Costello. "Contact stresses in twisted wire 

 cables," ASCE Proceedings, Journal of the Engineering Mechanics Division, 

 vol 99, no. EM2, Apr 1973, pp 331-341. 



3. Naval Research Laboratory. Memorandum Report 2459: Method of 

 measuring the mechanical behavior of wire rope, by D. A. Milburn and 

 N. J. Randier. Washington, DC, Jul 1972. 



4. . Memorandum Report 2903: Tensile and torsional characteristics 



of electromechanical cables, by Roy K. Samrus. Washington, DC, Nov 1974. 

 5. Massachusetts Institute of Technology, Charles Stark Draper Laboratory. 

 Report E-2497: Kink formation properties and other mechanical characteristics 

 of oceanographic strands and wire rope, by W. A. Vachon. Cambridge, 

 Massachusetts, Apr 1970. 



6. . Group 38 Report: Kink formation in long cables as an extension 



of the buckling theory of slender bars, by W. A. Vachon. Cambridge, 

 Massachusetts, 1968 (unpublished report). 



7. J. W. S. Hearle. "Structural mechanics of torque-stretch yarns: 



The mechanism of snarl formation," Journal of Textile Institute Transactions, 

 vol 57, no. 10, Oct 1966, pp T441-T460. 



8. Timoshenko, S. Theory of Elastic stability. New York, New York, 

 McGraw Hill Inc., 1936, p 169. 



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