length of 46 inches and a weight in water of 15 pounds . It has a 10- 

 inch stroke and develops a pulling force of three tons at its rated 

 hydraulic pressure of 4500 psig . The cylinder is attached to a chain 

 hook on one end and a slip hook on the other end. The slip hook is 

 connected to the object to be moved and the chain hook is attached to 

 a chain which is shackled to a solid object. By repetitively extending 

 the cylinder rod and reattaching the chain hook to the chain, the load 

 can be pulled along a horizontal surface. To move a load up an inclined 

 surface, two cylinder and hook assemblies are required. The two 

 assemblies are connected to the hydraulic pump so that one retracts when 

 the other extends . The cylinder with the extended hook is attached to 

 the chain and picks up the load as the retracted cylinder extends . 



The purpose of testing these cylinders underwater was to determine 

 their mechanical suitability for underwater use and establish the 

 practicality of a diver-powered chain and hook pulling system. 



Because of insufficient space it was not possible to evaluate the 

 pulling system in the diving tank. However, several cycles of connecting 

 and disconnecting the chain hook were performed with the load cell in 

 the tank. The mean time for the disconnect/connect cycle was 0.9 minutes. 



During the tests at Anacapa Island, the entire test stand was pulled 

 across the bottom using one-half inch chain and the double-acting 

 cylinder. The divers were able to move the half-inch chain easily, but 

 they were not able to pull it tight because the other end of the chain 

 was fastened two feet above the ocean bottom. Consequently, the test 

 stand was pulled only two to three inches for each 10-inch stroke. 

 This problem can be reduced by using a chain load binder or by using 

 two cylinders as previously discussed. In these open ocean tests, it 

 took from 0.7 to 1.5 minutes (mean 1.2 minutes) for the divers to com- 

 plete a disconnect/connect cycle with the chain hook and chain. With 

 a pulling load of three tons it took the diver using a pull-stroke 

 hydraulic pump 2.5 minutes per 10-inch retraction. Thus, with a diver 

 powered pump, a complete connect-pull-disconnect-extend cycle requires 

 about 4 minutes . With good rigging loads can be moved 7 to 8 inches 

 for each 10-inch stroke. 



The double-acting hydraulic cylinder used for pulling functioned 

 satisfactorily except for the rigging problems . Other types of pulling 

 equipment which use cable, such as grip hoists, cable hoists or winches, 

 are probably superior for pulling tasks which require moving the load a 

 considerable distance. They may be operated continuously or at least 

 to the full cable length in contrast to hydraulic cylinders which require 

 some type of diver rigging action at the end of each stroke. 



For very heavy pulling loads, hydraulic cylinders have the distinct 

 advantage of being operable with the diver pumps. As previously explained, 

 the pull pump is an efficient tool for diver use because arm, leg and 

 back muscles may be utilized. 



If heavy loads must be moved some distance, it would be possible 

 to use a hydraulic cylinder and a cable hoist in line. The cable hoist 

 could be used by the buddy diver to take up the slack in the cable after 



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