Pl. XIV.
Fig. 1. is an Elevation of the Crane. In cranes of the common construction, the beam is a fixture, and is placed at right angles to the upright-shaft; but in the machine represented in this Plate, its attachment is at the lower extremity of the crane, where it is moveable up and down upon a journal or bolt. This crane is therefore termed a Moveable-beam-crane. The moveable property of the beam, in so far as the writer knows, is new, and possesses the advantage of laying any stone within its range perpendicularly on its site. This, from the dove-tailed form of the stones at the Bell Rock, rendered it essentially useful to this work, to which a crane of the ordinary construction could hardly be said to be applicable. At the Edystone Light-house this operation was performed by means of Triangular-sheers; but, from the greater extent of the Bell Rock works, and their greater depth in the water, such means must have rendered the process of building extremely tedious.
In reference to this Figure, a a a is the upright shaft of the crane; b b the cast-iron foot into which the lower journal of the shaft was stepped; c the cap into which the upper journal works, and into which two of the hooks d d of the four guy-ropes x x x x were entered, for commanding the top of the upright-shaft. From the immersed state of these cranes, while the building was low in the water, a guard-plate was introduced, and bolted to the cap, which laid hold of a collar raised round the journal, to prevent the cap from being unshipped by the waves; e e is the moveable beam, formed and built of two strong pieces of oak timber, connected in the centre by a serpentine row of bolts. This beam was mounted at the upper and lower extremities with strong cast-iron plates; f marks the cast-iron sheers or cheeks, fixed to the bottom of the upright shaft, into which the moveable beam works upon the journal or bolt g.
In order to direct the strain of the main purchase-chain h h h h h h passing over the cheek pulley i fixed upon the shaft, and to prevent its effect from bringing home the moveable beam e e to the upright shaft, a martingale or tail-block l is introduced and made fast to the shaft at m. When the purchase-chain is not in action, the block l is suspended from the small chain at n, which prevents it from falling too low, and thereby deranging the position of the purchase-chain. That the beam may be made applicable to laying the stone marked k, at the foot of the crane, or at the utmost reach of the beam, a chain or purchase marked o o o, is introduced, which also passes over a cheek-pulley i on the opposite side of the shaft. By this additional apparatus the beam is capable of being elevated or depressed at pleasure. The handle marked p p, with its pinion and connecting wheel q q, and larger wheel r r, together with its intermediate pinion, form the main purchase, and exert a force calculated at the rate of about 98 to 1. When a smaller weight was to be lifted, and greater speed wanted, the handle was transferred to the axle s, whose pinion being always in gear with the wheel r r, produced an accelerated motion, with a power in the ratio of 20 to 1; at the same time, the handle t t, with its pinion in action with the wheel u u, worked the beam e e, so as to lay a stone perpendicularly with the greatest facility within any part of its range.
Fig. 2. is the cast-iron tripod, used as a prop to the moveable beam, when applied as a lever, for lifting the crane; a a a mark the foot, b the cross head, having a stud which works into a circular hole perforated in the top of the tripod. By this simple apparatus, the crane could be moved and shifted either perpendicularly or horizontally, with a facility which added greatly to the conveniency of the operations. When the tripod was applied to use, it was placed under the heel-plate of the moveable beam marked v, and when rested upon it, the beam became a lever of great power.
Fig. 3. is an Elevation of the Working-gear of the Moveable Beam-Crane. a a a is the upright-shaft, as in Fig. 2.; b b the cast-iron foot; c the cap with its guard-plate; d d guy-hooks for commanding the top of the shaft; f f the edges of the sheers or cheeks, for the heel of the moveable beam; g the bolt or journal on which the beam is moveable; h h the purchase-chain; i i the cheek pulleys; o o the moveable beam-chain; p p the two main purchase-handles; q q the smaller wheel of the main purchase; r the greater wheel, with the intermediate pinion w, connected with the axle s of the wheel q q. The handles and pinion t t are connected with the wheel u u, for working the moveable beam-purchase; x is the drum or barrel for the main purchase-chain; y the barrel of the purchase-chain of the moveable beam.
Fig. 4. is a Section, shewing the connection of the purchases for working the beam, and lifting the weight: the axle s, of the lesser wheel q, with its intermediate pinion x of the main-purchase, work through the eye or centre of the wheel u u, and barrel y of the beam-purchase. x and r refer to the corresponding letters in Fig. 3.
Fig. 5. is an Elevation of the Winch-machine. The machines, used for the various purposes of landing the materials and raising them to the top of the building, were framed or made of cast and malleable iron. a a a a are the cheek plates or frames in which the axles of the machinery work. Those employed upon the Rock were fixed down by means of spear-bolts, to four bats, as shewn at b b; but in other situations they were fixed by straps of iron to beams of timber. The cheeks a a a a were connected by means of three strong bolts passing through hollow tubes, which butted against the inner sides of the cheeks and kept them in their places. The large wheel marked c c measures 3 feet 3 inches in diameter, and the smaller wheel d d is 2 feet 6 inches: these, with their respective pinions, of 6 inches in diameter, exerted powers respectively of 20 to 1, and 98 to 1, being of a size similar to the cranes; as one set of wheel and pinion patterns were made to answer the several machines employed at the work. Letter e is one of the handles connected with its axle and pinions, which, at pleasure, is made to work with a double or single purchase, by simply slipping the axle out and into gear with the larger and smaller wheels.
Fig. 6. is a Plan of the Winch-machine. a a a a is the sole of the frame, shewing the bat-holes for fixing it down; c is the large, and d the small wheel, with its axle; e e the handles, with their axle and pinions f f f; letter g is the barrel attached to the axle of the large wheel, with part of the purchase-chain; h h is the axle of the small wheel and intermediate pinion; and i i one of the hollow pipes through which the bolts pass for connecting the two cheeks or frame of the machine together.
Fig. 7. refers to a machine fixed to the walls of the Provision-store, for raising the stores from the railways to the entrance-door, as pointed out in [Plate XVI.] a a a a a section of part of the walls of the Provision-store, in which a hole x x is perforated, and lined with a copper tube, for the passage of the purchase-chain; b is the pulley, with its case, over which it works; c c c is the frame of the machine; and d the handle, with its bevelled pinion. The distinctive feature of this apparatus is the vertical motion of the barrel, by which it receives and discharges the chain always at the same point; the direction also of the chain may thus be altered almost close to the barrel, which in this case was the chief desideratum. To effect this purpose, the barrel is made to move vertically upon the axle f, by means of a screw y, upon its lower end, which works into a corresponding screw-rack g; in its operation, the wheel h h is worked by the cylindrical upright-pinion of brass, marked i. The two pairs of bevelled wheels, supported upon the small intermediate frame l, are introduced, for applying a double or single purchase, according to the load to be raised.