



-| — |-< i range of ship periods • p 



H ^ ^ 1 



- 



I 

 \ 

 J 



\ 





FmI t 



\ 

 _\ 



\y 



- wire 



- 



\ 

 \ 

 \ 



- 





\ 



^^nylon 



\ 



<: 



1 1 i -^=^^^4 1 1 1 



1.6 



oj (rad/sec) 



Period (sec) 



Figure 9. Response ratio for 40,000-pound load and 6,000-foot length at 5% rate, 

 comparing nylon rope versus wire cable. 



cylinder from the external accumulator volume. Pin 

 position (adjustable only when the system is in the 

 hard mode) and the settings of the manual crossover 

 valves govern the specific shape of the dynamic spring 

 characteristic as a function of boom position. Nitro- 

 gen gas is used in this system to avoid the potential 

 problems associated with ignition of oils when 

 exposed to high-pressure air. 



Changes in the static boom-tip load are com- 

 pensated for by adding or removing gas from the 

 spring system until the mean gas pressure just 

 balances the load at the midpoint position of boom 

 travel. The gas is transferred by means of the 

 gas-transfer circuit shown in Figure 17. Activation of 

 valves 19A and C allows the compressor to pump 



nitrogen from the storage bank into the spring and, 

 thus, to increase spring pressure to adjust for an 

 increased boom-tip load. Activation of valves 19 B and 

 D allows gas to be transferred back into the storage 

 bank. Control of this function may be either 

 automatic or manual. 



Valves 19A through D are pilot-activated by the 

 circuit shown in Figure 18. This circuit is basically a 

 mechanical integrator that senses by means of valve 

 65 whether the boom position is above or below its 

 midpoint. 



The two banks of hydraulic accumulators, 63A 

 through C and 63D through F, and the associated 

 bleed-off valves 64A through C are used to provide 

 the desired averaging function in the following 



