CRANE. 



317 



Cract?. 



With an 

 air ves^el. 

 Plate 

 CCXV. 



Kg. 9. 



pump is %vorked by a mill, and will burst any vessels 

 without the appearance of strain on the moving parts 

 of the pump. 



The construction of a pump and air vessel of this 

 kind is explained in Fig. 2. A represents the piston 

 of the pump moving in a tight collar of leather at a, 

 and is worked from the beam of a steam-engine, or 

 other convenient power ; b the suction valve of the 

 pump, and e the forcing valve ; d a small copper pipe 

 communicating from the pump to the air vessel BB, 

 and conducting the water into it; / i is one of the pipes 

 proceeding from the air vessel to one of the cranes, 

 and may be of any length, according to the distance 

 of the crane. Near the cylinder of the crane, which 

 may be either like Fig. 1 . or Fig. 2. the pipe is pro- 

 vided with a stop valve e, formed on the end of the 

 screw g, by tinning which the valve can be opened or 

 shut to admit the confined water from the air vessel 

 into the cylinder, and thus raise the weight required : 

 A is a similar valve, for lowering the weight, by per- 

 mitting the discharge of the water at the opening t ; 

 for it is plain, that by shutting the valve e, and open- 

 ing the discharge valva h, the water will return from 

 the large cylinder of the crane along the pipe i, and 

 rush out at the aperture t, and by that means permit 

 the descent of the weight. On the other hand by 

 keeping the discharge valve h shut, and opening the 

 other at e, the water will have free passage from the 

 air vessel to the great cylinder, which has been before 

 described. The air vessel in this crane being charged 

 with a great pressure by the pump, becomes a common 

 reservoir for the supply of any number of cranes; and 

 by opening the valve e, the water enters the great cy- 

 linder, and takes the weight up at once without loss of 

 time. A safety valve, such as that shewn in Fig. 3. must 

 be placed in some convenient part of the pipe d, to pre- 

 vent the air vessel from being burst by overstraining it. 

 The common method of lowering goods, in wheel- 

 cranes, by a brake and wheel, even with the advantage 

 of a counterweight, is liable to injurious accidents to 

 the men, as well as the goods, when they consist of 

 damageable articles, such as wine, spirits, glass, &c. 

 and sometimes from the rapid motion of the crane, 

 parts of it fly off with violence, killing or woundino- 

 the persons near it; af other times the brake-rope be- 

 comes entangled by turning off the pullies or otherwise, 

 or the rope may slide out of the hand of the man who 

 conducts it; in either of which cases, the goods descend 

 with all the accelerated velocity of a falling body, recei- 

 ving damage, and killing or hurting the men, horses, &c. 

 which happen to be beneath them; but these evils are 

 completely removed by a lowering cylinder invented by 

 Mr Hardie, and explained in Figs. 10. and 11. A A is 

 a cast iron cylinder, bored true within, and screwed 

 down to the iron bottom BB; by the side of this cy- 

 hnder a pipe C is cast, communicating with it at the 

 top and bottom at c d; the pipe C has a cock D in the 

 middle, shutting off, at pleasure, the communication 

 between the top and bottom of the cylinder A A ; the 

 spindle of this cock passes through a stuffing-box at a, 

 and has a rack or sector b, fitted on it, to confine the 

 cock m any position by the claw e, which drops into 

 the teeth of the sector, at the same time showing the 

 extent of the apertures which is opened. The large 

 cylinder A A, has a tight piston E, sliding up and down 

 m it, and its rod F slides through a stuffing box G, 

 packed with leather to prevent leakage ; the connect- 

 ing rod H is jointed to the piston rod, at bottom, and 



1 



Operation.- 



Plate 

 CCXV. 

 Figs. 10, 11 



Cast iron 

 cranes.. 



to the crank I at the upper end. This crank is formed Crane. 

 on the axis of the chain barrel, or any other convenient ~~ "Y""" 

 spindle of the crane, so that the burden cannot descend 

 without turning the crank, and giving the piston a re- 

 ciprocating motion up and down in the cylinder. 



To explain the operation of this cylinder, suppose 

 the piston pushed down to the bottom* and the cock D 

 opened, it must be filled with oil, water, or any other 

 liquid not likely to freeze or change by the weather, 

 and the lid of the cylinder screwed fast down. Now, if 

 the cock is quite shut, the oil or other liquid confined 

 between the bottom and top of the cylinder, and the 

 piston, will prevent it from moving, consequently the 

 crank I, and chain barrel, or other part of the crane 

 connected with the crank, stand at rest, suspending 

 the weight of the goods hanging from the crane ; but 

 if the cock is opened a very little, the oil passes 

 slowly through its aperture, and allows the piston E 

 to move up and down slowly, and compelling the 

 crane to move so too, regulates the descent of the 

 goods. Thus the cock, by being more or less opened, 

 regulates the precise velocity of the crane, or descent 

 of [the goods to be lowered, whatever their weight 

 may be. (j. f.) 



Cranes have been generally constructed of timber, 

 but cast and wrought iron have been lately introduced, 

 and, we think, with advantage, as they are generally 

 exposed to the variations of the weather, which must 

 soon injure the mortises and joinings of a wooden 

 crane ; besides, cast iron offers all the advantages of a 

 judicious combination of its parts in having the strength 

 duly proportioned, and in adapting its formation to any 

 situation or circumstances. 



Plate CCX VI. Fig. 1. is a small cast iron crane: the 

 post is made to turn in a collar fixed level with the 

 ground's surface, and the bottom part is fixed on a wall 

 or an iron cylinder. The gib and stay are in one 

 casting, and joined to the post by screw bolts. This 

 crane will carry one ton weight with safety. Fig. 2. is 

 a similar crane, of greater strength and power. The 

 collar is here drawn to revolve on a number of balls to 

 lessen friction, but we think this unnecessary. It has 

 a double gib and stay, which screw on each side of the 

 post, and admit the pulley between them. The thick- 

 ness of the plates of the gib may be 1 ^ inch each, and 

 will carry three tons with safety at the extremity of 

 the gib. Fig. 3. and 4. are side and front elevations of a 

 crane ; the post is immoveable, and is fixed on an iron 

 frame with arms extending in the form of a cross; the 

 extremities of which are bolted down by strong screws 

 to large blocks of stone sufficiently heavy to more than 

 counterpoise the weight to be raised by the crane. In 

 the top of the post is fixed a wrought iron pivot, by 

 which the weight is supported, and a strong cast iron 

 cap bears on the pivot, and has attached to it two iron 

 frames, one on each side, that receive the pressure from 

 the stay, as well as support the pull of the gib, which 

 is formed of two bars of wrought iron. The lateral 

 pressure is borne by the bottom of the post, round which 

 two friction rollers turn to facilitate its motion. The Fi- 

 gures will sufficiently shew the construction of its parts. 

 Tin's crane will carry five tons with safety. Fig. 5. is Fig. 5. 

 another crane nearly similar to the last in construction, 

 but the gib and stay are of cast iron in one piece or frame, 

 two of which are used, (one on each side of the post,) 

 and are supported by the cross cap at top and friction 

 rollers at bottom. Here the wheel work is supported 

 between the frames, which extend sufficiently wide ta- 



Plate 

 CCXVI* 



Fig. 1. 



Fig. 2, 



Figs. S, *, 



