316 



CRANE. 



Crane. 



Eramsh'* 

 .hydrosta- 

 tic crane. 



ccxv. 



i-'g- 1. 



weight to a small height. A metallic cylinder suffi- 

 ciently strong, and bored truly cylindrical within, has 

 a solid piston fitted into it, which is made perfectly 

 water tight, by leather packing round its edge, or other 

 means used in hydraulic engines. The bottom of the 

 cylinder must be made sufficiently strong with the other 

 parts of the surface, to resist the greatest strain which can 

 ever be applied to it. In the bottom of the cylinder is in- 

 serted the end of a small tube, the aperture of which com- 

 municates with the inside of the cylinder, and introdu- 

 ces water or other fluids into it. The other end of the pipe 

 communicates with a small forcing pump, by which the 

 water can be injected into the cylinder beneath its pis- 

 ton. The pump has of course, valves to prevent the re- 

 turn of the water. Now suppose the diameter of the cy- 

 linder to be six inches, and the diameter of the piston of 

 the small pump, or injector, only one quarter of an inch ; 

 the proportions between the two surfaces, or ends of the 

 said pistons, will be as the squares of their diameters, 

 which are as 1 to 24. Therefore the areas will be as 1 

 to 576 ; and supposing the intermediate space between 

 them to be filled with water, or any other dense and 

 incompressible fluid, any force applied to the small pis- 

 ton will operate on the other in the above proportion 

 of 1 to 576. Suppose the small piston, or injector, to 

 be forced down when in the act of forcing, or injecting 

 with a weight of 20 cwt. which can easily be done by 

 means of a long lever, the piston of the great cylinder 

 would then be moved up with a force equal to 1 ton 

 multiplied by 576. Thus is constructed a hydro-me- 

 chanical engine, whereby a weight amounting to 576 

 tons can be raised by a simple lever, in much less time 

 through equal space than could be done by any apparatus 

 constructed on other known principles of mechanics, be- 

 cause it has so little loss from friction ; and it may be pro- 

 per to observe, that the effect of all other mechanical com- 

 binations is counteracted by an accumulated complication 

 of parts, which renders them incapable of being usefully 

 extended bey ond a certain degree ; but in machines, acted 

 upon or constructed on this principle, every difficulty of 

 the kind is obviated, and their power is subject to no 

 finite restraint. To prove this, it will be only necessary to 

 remark, that the force of any machine acting upon this 

 principle, can be increased ad infinitum, either by ex- 

 tending the proportion between the diameter of the in- 

 jector and the great cylinder, or by applying greater 

 power to the lever actuating the small pump. 



Fig. 1. Plate CCXV. represents a crane constructed on 

 the hydrostatic principle, that is, by the injection of wa- 

 ter from a small pump into a large cylinder, which is 

 fitted Avith a piston, having a rack attached to it for the 

 purpose of turning a pinion upon the axis of a large 

 chum wheel or barrel, round which the rope is coiled, 

 and from thence passes to the gib. In the Figure, AA 

 represents the gib made of iron, and supported upon two 

 brackets a, a, projecting from the wall of the warehouse 

 in which the crane is supposed to be erected. The rope 

 passes over the pulley S, and down through holes in the 

 brackets a, a, then turns under the pulley b, and comes 

 to the lower side of the great drum wheel B. The pi- 

 nion C is fixed on the same axis with this, and its gud- 

 geons turn in small iron frames d, bolted down to the 

 floor of the warehouse. The pinion c is actuated by the 

 teeth of the rack D, and a small roller, whose pivot is 

 shewn at e, presses against the back of the rack, to keep 

 its teeth up to the pinion. The rack is attached to the 

 piston D erf' the cylinder L, in which the power for 

 working the crane is obtained. This piston passes 

 through a tight collar of leather in the top of the cylin- 



der at E, which does not admit of any leakage by the Crane, 

 side of it, and therefore if any water is forced into the s — *v^™ / 

 cylinder, it must protrude the piston from it. The cy- 

 linder is supported in a wooden frame FF, and has a 

 small copper pipe g g proceeding from the lower end of 

 it, communicating with a small forcing pump at h. This 

 stands in an iron cistern H, which contains the water, 

 and sustains the standard ii for the centre of the handle 

 G, with winch the pump is worked by one or two men. 

 The upper extremity of the standard ii, guides the pis- 

 ton rod k of the pump, to confine it to a vertical mo- 

 tion. / is a weight for counterbalancing the handle G 

 of the pump. From what we have said before, the ope- 

 ration of this machine is evident. The power of the 

 cylinder D is, in proportion to its size, compared with 

 the size of the ;urap ; but as it acts only through short 

 limits, the pinion and drum B are necessary to lift the 

 weight a sufficient height. The operation of lowering- 

 goods by this crane is extremely simple, as it is only ne- 

 cessary to open a cock at m, which suffers the water to 

 escape from the cylinder into the cistern H, and the 

 weight descends, but under the most perfect command 

 of the person who regulates the opening of the cock; for, 

 by diminishing the aperture, he can increase the resist- 

 ance at pleasure, or stop it altogether. 



Fig. 2. is the section of a cylinder for'a crane, which Another 

 is only adapted to raise weights to a small height, but kind, 

 possesses a great power ; O is the chain, which is con- p 

 ducted over pulleys to the gib ; CC is the cylinder, ccxv. 

 having a lid screwed on the end, with a stuffing box m Fig. 2» 

 in the centre, which makes a close fitting round the rod 

 / 1 ; this, at the other end, has a piston k fixed on it, 

 which accurately fills the cylinder, and has leather all 

 round to make it water tight. The other extremity of 

 the cylinder has an eye cast on it for the reception of 

 a hook, by which the cylinder is made fast. The pipe 

 from the injecting pump is marked i. This cylinder 

 may be placed horizontally beneath the floor, or sus- 

 pended vertically by the side of the wall, and forms a 

 most excellent and convenient crane for lifts of not 

 more than 6 or 8 feet, though it may occasionally be 

 used for a much greater height. Thus the rod I ter- 

 minates in a large eye, through which the chain O is 

 conducted ; and a peg or pin being put through one of 

 the links, gives a hold on the chain to draw up the 

 weight, which being raised till the piston k reaches the 

 bottom of the cylinder, the chain is to be made fast 

 by a pin put through the links, and stopped against 

 any fixture ; the piston rod drawn out, and a new part 

 of the chain taken through the eye at the end of it, 

 to take a second lift ; and so on of a third if required. 



The greatest advantage of the hydrostatic principle, Applica- 

 is, that its power can so easily be transmitted to any tio " of tue 

 distance, and in any direction, by means of pipes, con- n y drostauc 

 ducted along in situations where all other means of 

 conveying the motion would be complicated and ex- 

 pensive in the extreme ; thus, in an extensive range of 

 warehouses for a dock or depot, an injecting pump may 

 be kept in constant action by horses, a water-mill, or 

 steam-engine, and may inject water into an air vessel, 

 from which pipes are conducted to cranes in all parts of 

 the works ; and by simply opening a cock at any crane, 

 the required load will be instantly raised by the elas- 

 ticity of the confined air operating on the enlarged sur- 

 face of the piston of the crane. The air vessel has of 

 course a safety valve, to allow the escape of the water 

 when the pressure becomes so great as to endanger the 

 rupture of the vessels ; for it is to be observed, that 

 the power of this principle is irresistible when ^h« 



