324 NOTES ON DOCKS AND DOCK CONSTRUCTION. 



removed, the vessel, now supported entirely by the main cradle, 

 is run down the ways and launched. 



Hydraulic Hauling-gear. 1 The form of hydraulic hauling- 

 gear introduced by the late Mr. Morton consists of a direct- 

 acting single cylinder, with one ram having about 10 feet length 

 of stroke. On the outer end of the ram is a cross-head, and to 

 this cross-head are attached two wrought-iron bars, one bar 

 passing on each side of the cylinder. These two bars aro 

 connected at their lower extremities to a second cross-head, to 

 which wrought-iron links for hauling up the cradle are secured. 

 Figs. 322 and 323 show the general arrangement of this gear. 

 In hauling up a vessel, after the ram has made one outward 

 stroke, it is necessary to disconnect and remove one of the links, 

 which are made in length to suit the stroke of the ram. This 

 having been accomplished with the assistance of a small hand- 

 crane, the ram is run back by a constantly acting weight, and a 

 new attachment made between the links. The ram then makes 

 another forward stroke, drawing up the cradle another 10 feet, 

 and the process of disconnection and connection is continued 

 until the vessel is hauled up a sufficient distance. With the 

 heaviest vessels, two lines of links are generally used, and two 

 links have therefore to be disconnected and connected at each 

 stroke. The great objection to this system is the delay and 

 labour incurred by the removal of the links after each stroke. 



An improved form of hydraulic gear designed by Messrs. 

 Lightfoot and Thompson, with the view of obviating the delay 

 incurred in removing the links, is shown in Figs. 324 and 32 5. 2 



In place of working the press directly from the pumps, a 

 small accumulator is introduced for the purpose of accumulating 

 the water pumped, during the act of reversing the rams, and, 

 as the water-pressure is constant, a set of treble-power cylinders, 

 or a cylinder with two or more concentric rains, is used for giving 

 the variable power. A cross-head is actuated by the rams, and 

 is connected with a second tail-cross-head by two forged bars. 

 From this tail-cross-head a double set of links extends nearly to 

 the end of the ways, resting upon the wings cast on the centre 

 rails, and being guarded thereby. To the top cross-head is 

 attached a ram working in a cylinder always open to water- 

 pressure. The action is as follows : Water from the accumulator 

 having been admitted to one or more of the main hauling-rams, 

 1 M.P.I.C.R, vol. Ixxii. p. 142. Ibid., p. 143. 



