GttANE. 



weight is very great, D must be made 

 to work upon the largest wheel e, which 

 being four times its diameter, will cause 

 D to turn four times while c turns but 

 once. The figure is not exactly in the 

 above proportions ; but the explanation 

 will suffice to render that minutia of less 

 importance. D is turned by a crank-han- 

 dle, or winch, and is made to fit into three 

 different sockets, where its axis is keyed 

 down, opposite to whichever wheel is to 

 be acted upon. It should have a small 

 ratchet, or pall, to prevent its retroces- 

 sion, incase the weight should overpow- 

 er the operator. 



Some cranes are made to weigh goods 

 as they are raised ; but this can seldom be 

 done with accuracy, though the general 

 estimate may be correct enough for ordi- 

 nary occasions. It is done by allowing 

 the jib, or projection m, (fig. 2.) to play 

 on a joint at n, and by having a movea- 

 ble weight at the other end of the beam 

 s, of which the jib forms a part, with an 

 index on the principle of the steel-yard. 

 But this cannot answer where very hea- 

 vy articles, such as cannon, &c. are to be 

 raised, as the joints would soon give way. 

 Whatever may be the construction of 

 cranes, power and safety ought to be the 

 principal objects. 



We shall proceed to describe some 

 other cranes that are much in use in the 

 present day. Fig. 1. Plate Cranes, is an 

 elevation of a crane sideways, and fig. 2. 

 is a plan ; A B is a stout beam, turning in 

 a cast iron collar at B, affixed to beams in 

 the floor of the wharf; it goes down 

 about twelve feet below this, and has a 

 steel pivot in the lower end, which works 

 in a brass collar, so that the beam A B 

 can turn round freely without shake ; C 

 D are the two beams of the jib, with a 

 pully at E, over which the chain for hoist- 

 ing the goods works ; the other end 

 of this chain is wound round a roll, e,l foot 

 diameter ; a cog wheel, marked 100, of 

 100 teeth, turned by a pinion of 7 leaves, 

 on the same axle with another wheel 31, 

 of 31 teeth : this is turned by a pinion, 

 14, of 14 teeth. If great power is requir- 

 ed, thewinch handle isappliedto a square 

 on the end of the spindle of the last pi- 

 nion, and for less weight the winch is put 

 on the axle of 31 : when this is the case, 

 the pinion 14 must be disengaged from 

 its wheel, by sliding its axle lengthways. 

 G is a clip, to keep the pinion in or out of 

 gear, as it has been placed by the atten- 

 dant. A plan of it is also shewn in fig. 

 2 : the two semicircular bands in it fit 

 into grooves turned in the spindles, and 



the weight a at the end keeps them 1 n 

 this prevents them moving endways; 

 when the weight a is raised, it releases 

 them both ; and when they are moved, 

 the clip fits into another groove turned 

 in them, so as to prevent their return. 

 The frame containing the wheels is form- 

 ed by two cast iron crosses, bolted to the 

 main beam A B by the ends of their ver- 

 tical arms, the two other arms forming 

 the bearing for the wheels. 



Cranes of this kind are now coming in- 

 to very general use in London, as they 

 require no expensive framing over them, 

 and they can be turned all round. A fur- 

 ther advantage they possess, in common 

 with several other kinds, is, the chain not 

 being bent suddenly round the small 

 pullies over the jib when they are swing- 

 ing overland, as in the common kind, 

 and fig. 4. 



A crane of this kind, which we saw at 

 Woolwich Warren, had an apparatus 

 (shewn in fig 3.) attached to it for lower- 

 ing with safety great weights without any 

 exertion of the workmen. It consists of 

 a cylinder, b d e, of cast iron, smoothly 

 bored through ; fg is a passage connect- 

 ing the top and bottom of the cylinder, 

 and h a cock by which this passage can 

 be closed ; i is a piston fitting the cylin- 

 der, and k the rod affixed to it, moving 

 through a stuffing box in the lid of the cy- 

 linder; the axis of the wheel 31 (fig 1 and 

 2.) or one in the place of it, has a crank on 

 it working the piston rod of the cylinder 

 (fig. 3.) which is bolted fast to the back 

 of the beam A B, with the usage sliding 

 motion to render its motion parallel. The 

 cylinder is filled full of oil, and as the han- 

 dle of the crane is turned, the piston is 

 moved up and down in the cylinder : now 

 if the cock h is open, the oil flows freely 

 from one part of the cylinder to the 

 other, without obstructing the motion 

 of the crane ; but if it is closed, the oil, 

 finding no other passage, and being an, 

 incompressible fluid, stops the piston, and 

 the descent of the goods suspended by 

 the crane. By opening the cock partial- 

 ly, the friction (or, as it is technically 

 termed, the wire*drawing) of the oil im- 

 pedes the motion of the wheels, so as to 

 lower the greatest weights with any ve- 

 locity required. A portion of the circle 

 m is fastened to the cock, with fine teetk 

 cut in it ; a click takes into these teeth, 

 to hold the cock at any opening it may be 

 set to. This contrivance is described in 

 Gregory's Mechanics, published in 1806, 

 applied to a different kind of crane, but 

 the invention is ascribed to Mr. David 



