Figure 13. Motion-compensating lift system. Motion-compensating/traction unit (left); 

 cable-storage reel (right). 



pounds; normal setting for wire rope is about 500 

 pounds. The level-wind mechanism is adjustable for 

 all line diameters between 1/2 and 3 inches. Provision 

 was made for the addition of electrical slip rings to 

 allow the future use of electromechanical cables. 



Control System 



Operation of the MCLS is controlled from a 

 single point by one operator. The controls and instru- 

 ments, shown in Figure 19, are grouped in functional 

 clusters for ease of operation. The control console 

 itself is constructed in an L-shape with the top 

 sloping down toward the operator. 



A typical operation begins with the system in 

 the hard mode and the engine running. After com- 

 pletion of a preoperation checklist the operator raises 

 the payload off the deck high enough to clear the 

 ship's rail. Then he activates the turntable control to 

 rotate the payload out over the stern into launch 

 position. When the launch position is reached he 

 begins to payout cable and, as soon as the payload is 

 in the water, he shifts into soft mode and activates 

 the automatic boom-centering circuit (spring pressure 

 was set previously to just balance the load). Rate of 

 descent is then controlled by the winch control lever 

 and, with the system operating as designed, this is the 

 only control the operator needs to touch during the 

 remainder of the lowering or lifting operation. 

 Recovery is accomplished by reversing the launch 

 procedure. 



TEST PROGRAM 

 Shop Tests 



Formal testing of the MCLS began at the con- 

 tractor's facility with a static load test soon after 

 fabrication of the hardware. Strain gages were placed 

 at all critical areas, and a series of loads was applied to 

 the boom tip. Analysis of the strain-gage information 

 showed one location near the turntable bearing 

 mount where stress levels would be marginal at the 

 designed maximum boom-tip load. The addition of 

 stiffening gussets eliminated the high stress levels. 



Dynamic shop tests were made to determine the 

 system's natural resonant period. In these tests the 

 boom in the compensated mode was displaced from 

 its mean position and released. Recording of boom 

 displacement as a function of time allowed deter- 

 mination of the natural period for various boom-tip 

 loads. Several tests were made for each of four loads 

 with the following results: 



om-Tip 



.oad 



A 



I'erage 



Resonant Period 



(lb) 









(sec) 



10,180 









13.8 



19,240 









13.3 



44,000 









11.6 



62,350 









9.8 



It was also determined — from the shape of the 

 response curves - that the internal system damping 

 was between 30 and 100% of the critical point, the 

 percentage decreasing with increasing payload weight. 



12 



