Shipbuilding in iron and steel / a practical treatise . . , the sectional formsof these blocks being such as to approximate to the curves towhich the plates have to be bent. When placed in the press, thelower surface of the plate rests upon a cast-iron slab carried bythe piston, the upper part of the slab being curved concavely tothe form to which the plate is to be brought. The packing isthen piled upon the plate and the upper surface of the blocksbeing pressed against the framing at the upper part of the ma-chine, when the piston is forced upwards, the plate is graduallybent down until it fi
Shipbuilding in iron and steel / a practical treatise . . , the sectional formsof these blocks being such as to approximate to the curves towhich the plates have to be bent. When placed in the press, thelower surface of the plate rests upon a cast-iron slab carried bythe piston, the upper part of the slab being curved concavely tothe form to which the plate is to be brought. The packing isthen piled upon the plate and the upper surface of the blocksbeing pressed against the framing at the upper part of the ma-chine, when the piston is forced upwards, the plate is graduallybent down until it fits against the curved edge of the slab beneathit. It may be remarked that the outer surface of the plate isthat which is generally placed lowest in the press, and that thepacking for plates of ordinary curves and twists can be selectedfrom a stock kept at hand, those required in extreme cases beingthe only ones specially prepared. The cradle system of bending is that most generally adoptedboth in the private and Royal yards. A sketch of a cradle with an. Fig. 257. armour plate fixed in it is given in Fig. 257. The sides are formedof vertical bars of which the lower ends are secured to a cast-ironslab, and the upper ends are stiffened by longitudinal plates. Thevertical bars are pierced by numerous holes, and the longitudinalbars marked a can be shifted up and down and secured in the mostconvenient position. The cradle is placed near the heatingfurnaces in most yards, and arrangements are made to facilitate Chap. XXI. Armour Plating. 471 the conveyance of the plates from the furnaces to the cradle, asremarked above. In preparing the cradle for bending a plate it isfirst necessary to determine the position in which the plate is to beplaced. Two bars are then procured, of which the upper edges fitthe curves of the sectional moulds made at the butts of the bars or packings are usually about 6 by 2^ inches, and areof sufficient length to span the breadth of the cradle. A
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Keywords: ., bookcentury1800, bookdecade1860, bookpublisherlondo, bookyear1869
