CRANE. 



313 



dears. 



lit Pad- 

 more's ad 

 dition. 



sols, for which purpose it is well adapted, its power be- 

 ing very great. It has a frame, consisting of a strong 

 beam, supported horizontally at 10 or 12 feet from the 

 ground, on the top of several vertical posts, very firm- 

 ly fixed in the ground, and securely braced with stays 

 in every direction. At the extremity of the horizontal 

 beam, the upper pivot of the gib is supported, the lower 

 pivot resting on a post in the ground. This gib, or gib- 

 bet as it is called, from a resemblance to that machine, 

 is a triangular frame of wood, one side being perpen- 

 dicular, and supported on pivots at the top and bottom, 

 so that the whole moves round on those as a vertical 

 axis of motion. Near the upper end of the perpendi- 

 cular post, a beam proceeds, forming the upper side of 

 the triangle ; while the third side is a brace, extended 

 from the foot of the perpendicular to support the upper 

 piece. From the extremity of the latter, the burden is 

 suspended by a rope passing over a pulley ; the other 

 end of the rope is coiled round a vertical roller or cap- 

 stan, turning on pivots, one supported by the horizon- 

 tal beam first mentioned, and the other on a post in the 

 ground. The capstan is turned round by means of long 

 horizontal levers fixed to it, at which a great number of 

 men may be employed to push them round ; or in some 

 cases they are drawn by horses. As the levers admit 

 of a very great length, in proportion to the diameter of 

 the windlass on which the rope coils, the power of this 

 simple crane is very considerable, and may be doubled 

 by a pair of blocks or pullies at the gib. When the 

 burden is raised to a sufficient height, by turning the 

 capstan, the gib, being swung round on its pivots, will 

 convey the load into a cart or waggon placed on shore 

 by the side of the crane. 



Another kind of crane, which is equally common with 

 the above, but used for lighter burdens, has the same 

 gib, as indeed most cranes have ; but the windlass, or 

 barrel for the rope, is placed horizontal, and has a large 

 vertical wheel fixed upon it. This is made of two 

 wheels fixed on the axis at a distance apart, and united 

 by boards, so as to form a large hollow cylinder or 

 drum. Several men get into this wheel, and by con- 

 stantly walking upwards on the inside, give it a ten- 

 dency to revolve, and wind up the rope on the barrel. 

 See Carriage, vol. v. p. 546, and Plate CXXXI. It is 

 surprising, that so imperfect a machine as this should 

 have been so universally adopted as it was, till within 

 these few years. Even when the wheel is sixteen 

 feet diameter, the labourers within cannot walk so 

 far up it, from the perpendicular, as to have any ef- 

 fective leverage to turn it round. Though they are 

 always exposed to extreme danger, and frequently meet 

 with most shocking and fatal accidents, from slipping 

 down in the wheel, or from being overpowered by the 

 load ; in this case, the wheel runs back with an accele- 

 rating velocity, and the people are thrown about within 

 it in a most dreadful manner. From these defects of 

 the common construction, skilful mechanicians have de- 

 vised cranes that are not only more safe, but more 

 powerful in their operation than the common walking 

 crane. Some of the best of these will be described in 

 the present article. 



Mr Padmore, many years ago, contrived to prevent 

 the dangers attending the use of the construction last 

 described, by putting a ring of cogs all round the out- 

 side of the great wheel, and applying a trundle provid- 

 ed with winches to turn it. By this addition, the power 

 was increased in the proportion of the number of cogs 

 in the wheel to the number of staves in the trundle ; 

 and in order to prevent the wheel from running back 



VOL.. VH, PART I. 



by the force of the weight, should the man within it Crane. 

 slip, or leave off walking, he added a ratchet wheel to > *-^,^ a *' 

 the axis of the trundle. Two winches being fixed to 

 the ends of the axle of the trundle, gave the people at- 

 tending the crane the means of assisting the men in the 

 wheel, when the load rendered it necessary. On the 

 axle of the trundle, he likewise fixed a wooden wheel> 

 provided with a brake or gripe, which could be forcibly 

 pressed on the circumference of the wheel by a lever, 

 to cause such a friction as would prevent the weight 

 from descending too rapidly. By this means heavy 

 goods may be either raised or let down at pleasure, 

 without any danger of injuring the men who work the 

 crane. This contrivance is ingenious, but the rapid 

 motion of the circumference of the large walking wheels, 

 in most cases, renders it inapplicable, unless a smaller 

 cog wheel was fixed upon the same axis with the walk- 

 ing wheel. 



A crane, to be turned by winches, was contrived by Mr Fergu- 

 the late Mr Ferguson, which has three trundles with son's crane- 

 different numbers of staves. Any one of these may be 

 applied to the cogs of a horizontal wheel, mounted on 

 an upright axle, round which is coiled the rope for 

 drawing up the weight. This wheel has 96 cogs ; the 

 largest trundle 24 staves, the next 12, and the smallest 

 6 ; so that the largest revolves four times for one revo- 

 lution of the wheel, the next eight, and the smallest 1 6. 

 The winch is occasionally fixed on the axis of either of 

 these trundles for turning it, and is applied to one or 

 the other, according as the weight to be raised is smal- 

 ler or larger. There is also a fourth trundle acting in the 

 teeth of the great wheel; and on its axis is a brake and 

 ratchet wheel. While the load is drawing up, the teeth 

 of the ratchet wheel slip round below a catch which 

 falls into them, and prevents the crane from turning 

 backwards ; thus detaining the weight in any part of 

 its ascent, if the man who works at the winch should 

 accidentally quit his hold, or wish to rest himself before 

 the weight is completely raised. Making a due allow- 

 ance for friction, a man may raise, by such a crane, 

 from three to twelve times as much in weight as would 

 balance his effort at the winch, viz. from 90 to 360 lbs. 

 taking the average labour. See Ferguson's Lectures, 

 vol. ii. 



Many other constructions of wheel- work are in com- Crane wit U 

 mon use for cranes. When they are turned by a winch, cog wheels- 

 it is proper to apply a fly wheel to the axis of it, both 

 to equalize the efforts of the labourer who turns it, and 

 in case he accidentally lets go the handle, to prevent 

 the load from running down so quickly as to en- 

 danger any thing. It is convenient to have several dif- 

 ferent powers to a crane of this kind, to adapt it for the 

 different burdens to be raised. This is best done by 

 employing a train of several wheels, each turned by a 

 pinion smaller than itself. Thus, suppose the barrel on 

 which the rope or chain winds be 12 inches diameter, 

 and has a cog wheel of 96 teeth fixed upon the end of 

 it, this is tinned by a pinion of 12 leaves ; on the same 

 axis with this is a wheel of 32 teeth, moved by a pinion 

 of eight, situated on a third axis, which should cany the 

 fly wheel. A winch of one foot radius can be applied oi - thr ^ e 

 to any of these three axes in the crane, and will give p 0W er*. 

 three different powers. Thus, if it is applied to the 

 gudgeon of the ban-el, it will double the power of the 

 labourei', because the winch describes a circle which is 

 twice as large as the barrel on which the chain winds. 

 If the winch is fixed on the end of the axis which car- 

 ries the pinion of 12, and wheel of 32, it will give the 

 labourer a purchase of 16 times. And lastly, whea the 



