After the anchors are propelled into the seafloor, they are then set 

 by pretensloning the embedment anchor cables with a rewind mechanism 

 located in a central housing unit at the junction of the arms of the 

 tripod framework. The objective is to clamp the pads to the seafloor 

 by obtaining a firm grip in the seafloor soil with the anchors. 



The propellant-actuated (explosive) anchors had demonstrated 

 good prospects for accomplishing the desired anchoring action with a 

 minimum amount of installation equipment. Consequently, this type of 

 anchor was selected to develop the uplift resistance in the PADLOCK 

 design. The particular explosive anchor design chosen was the style 

 that employed two flukes. The commercial anchor of this style was 

 rated as having a nominal 10-kip capacity whereas a 20-kip capacity 

 was desired. Therefore, the manufacturer had to build and deliver 

 a specially enlarged size. Figure 17. The configuration, size, and 

 load-supporting capacities selected were judged sufficient to 

 demonstrate the feasibility of the system. 



The PADLOCK prototype fabricated for testing and evaluating is 

 shown in Figure 16. A key feature of the concept is the cable rewind 

 mechanism used to pull up the embedment anchors to a set position. 

 The rewind mechanism consists of three separate cable drivers powered 

 by a common shaft. Each drum wound the cable from one of the embedment 

 anchors and could wind a sufficient length of cable to develop the 

 pretension load for that anchor. Power to the common shaft was from 

 a 24- volt DC motor through a 1356:1 gear reduction as shown in 

 Figure 18. Other features of the concept included: (1) an activator 

 unit to control the sequence of operations of the PADLOCK by acoustic 

 command once it is on the seafloor; (2) an ambient-pressure battery 

 power source; and (3) a shipboard stern roller to assist in the 

 installation of the PADLOCK. This unit is basically an 18-inch 

 diameter sheave with a 12-inch wide shroud designed to permit the 

 passage of lines with shackles, thimbles, and other connective gear. 

 The sheave is connected to two line load-detecting systems. One of 

 these systems is a hydraulic load cell unit with a dial readout and the 

 other is an electric load-cell that may be connected to any electronic 

 readout system. The roller provides a means of handling lines with 

 fittings and a means of constantly monitoring line loads. 



Tests and Results . Five shallow water tests were conducted with 

 the PADLOCK in and about Port Hueneme Harbor. Water depths ranged 

 from 18 to 60 feet. The seafloor was primarily hard-packed silty sand. 

 All of the shallow water tests followed essentially the same procedure. 

 Typically, the PADLOCK was transported to sea by a vessel carrying a 

 crane. At the site, the embedment anchors were loaded and armed. 

 Immediately thereafter, the unit was lowered to the seafloor and the 

 anchors were fired. Divers then inspected the system, and the rewind 

 mechanism was started. 



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