314 



CRANE, 



Ccane. winch is applied to the pinion of eight, his efforts will be 

 N ""T*"""'' multiplied G4 times. This simple mechanism is render- 

 ed very complete, by fixing a fly wheel upon the axis of 

 the pinion of eight, to prevent all danger of accidents ; 

 for which purpose it is more effective than a ratchet 

 wheel, and requires no attention. The spindles of all 

 the wheels are made capable of sliding endwise, for 

 the purpose of disengaging the wheels from each other 

 at pleasure, that when the wheels are not employed 

 there may be no unnecessary friction in turning them 

 round. 

 ?>lr White's To remedy the inconveniences and defects of the 

 inclined common walking-wheel crane, Mr James White, of 

 walking Chevening in Kent, proposed the construction shewn 

 v ' in Fig. 4-. which is described in the Transactions to the 



PtATH Society for the Encouragement of Arts. BB is an in- 

 tjCXV. clined axis or spindle, turning on pivots at c and b, 

 »' 4 ' which are supported in the different floors of the ware- 



house where the crane is erected : on this axis the rope 

 of the crane is coiled, and, passing over a pulley at D, 

 is conducted to the gib. The motion is given by people 

 walking on an inclined wheel AA, which is strongly 

 framed upon the axis, and revolves with it : it is incli- 

 ned to the horizon about 20 degrees, and works in an 

 opening in the floor m m. Now, it is plain that a man 

 walking upon this wheel will, by his weight, give it a 

 tendency to revolve, and the power will depend upon 

 his distance from the centre of the wheel ; but to in- 

 crease his effort beyond his mere weight, he applies his 

 hands to a rail F, extended across the wheel about breast 

 high, and pushes the wheel round beneath his feet. By 

 this combined action of his weight and muscular action, 

 the inventor supposes a labourer will work to a great- 

 er effect than in any other manner. To render it quite 

 safe from accidents, a brake is thus applied : the rail 

 F is fixed at one end to an upright axis EG, so that it 

 acts in the manner of a lever ; G is a shorter lever fixed 

 on the same axis, and connected by an iron rod H, 

 with a gripe K, which embraces part of the circumfe- 

 rence of the wheel, to prevent its turning unless the 

 brake is first removed by pushing the rail F ; g is a 

 chord fastened to the extremity of the rail F, and, go- 

 ing over a pulley in the floor, has a weight suspended 

 from it. This always gives the rail a tendency to draw 

 the gripe close, and stop the wheel ; and by the weight 

 coming up to the pulley, it stops the rail from going 

 too far, when pressed by a man walking on the wheel. 

 The stationary end of the gripe is jointed to a stout 

 upright beam, going from the floor to the ceiling ; and 

 to prevent the gripe falling down, and getting from its 

 work, the intermediate part of it is suspended by cords 

 from the ceiling. The safety of this crane is its greatest 

 recommendation; for it is obvious that it cannot move 

 but during the pleasure of the workman, and while 

 he is actually pressing upon the rail F; and if he should 

 slip down, or the crane rope break, the gripe stops the 

 wheel the instant he ceases to press on the rail. Mr 

 White's crane admits of an almost infinite variety of 

 irs powers, different powers within its limits ; and this variation is 

 obtained, without the least alteration of any part of the 

 machine; if, in unloading a vessel, there should be 

 found goods of every weight, from a few hundreds to 

 a ton and upwards, the man who does the work will 

 be able so to adapt his strength to each, as to raise it 

 in a tipace of time proportional to its weight, he walk- 

 ing always with the same velocity, as nature will 

 teach him. It is a great disadvantage in some cranes, 

 that the smallest weight must be as long in raising as 

 the largest, unless the man turns or walks with a 



greater velocity, which tires him in still greater pro- C"ne 

 portion. In some cranes, two or three different powers """"^ 

 may be procured, to obtain which some pinion must 

 be shifted, or a fresh handle applied and resorted to. 

 In this crane, on the contrary, if the labourer finds lus 

 load so heavy, as to permit him to ascend the wheel 

 without its turning, let him move only a step or two 

 towards the circumference, and he will be fully equal 

 to the task. Again, if the load be so light, as scarce- 

 ly to resist the action of his feet, and thus oblige him 

 to run through so much space, as to tire- him be- 

 yond necessity, let him move laterally towards the cen- 

 tre, and he will soon feel the place where his strength 

 will suffer the least fatigue by raising the load Ui 

 question. 



The gibbet of a crane is a very principal member, Crane gilt! 

 as we have before explained; but, in its common con- 

 struction, it has some defects. The rope by which the 

 burden is raised, passes exactly over the upper gud- 

 geon of the vertical beam of the gib, and is confined 

 between two small vertical rollers, in order that it may 

 constantly lead fair with the pulley or sheave at the 

 extremity of the gib. According to this construction, 

 whenever the gib turns round its axis, the rope is bent 

 so as to form an angle more or less' acute, which cau- 

 ses a great increase of friction, and produces a conti- 

 nual effort to bring the arm of the gib into a parallel 

 position to the inner part of the rope. These inconve- 

 niences may appear to be trifling, but, in actual prac- 

 tice, they are of no small importance; for they ne- 

 cessarily require a much greater exertion of power 

 in raising goods, and the application of a constant force 

 to keep the gib in the position that may be requisite ; 

 while the partial stress which is exerted on only a few 

 strands of the rope, whilst bent into an acute angle^ 

 destroys it iri a very short time. 



A simple construction of the gib, invented by Mr M . Bra _. 

 Bramah, obviates all these defects, and at the same mah's gib* 

 time possesses the very desirable property of permit- 

 ting the gib of what is termed a wharf, or landing 

 crane, to revolve wholly round its axis, and to land 

 goods at any point of the circle described by the arm 

 of the gib. 



The simplest form of this contrivance is shewn in p LAT & 

 Fig. 1. in which AA represents the gib of a warehouse ccXY; 

 crane projecting from a wall. It has, as usual, a pulley Fig. 1. 

 at the extremity, from which the goods are suspended. 

 The improvement consists in placing a pulley at S, ta 

 conduct the rope down through the axis of motion cf 

 the gib, the collars or rings, a a, on which it swingf, 

 being perforated for that purpose. The rope after- 

 wards passes under a pulley b, which conducts it into 

 the house to the crane or machine, by which the weight 

 is elevated. The pulley b may be placed between the 

 two collars a a, and then there will be no necessity for 

 a perforation of the lower pivot of the gib. When the 

 gib is required to describe a complete circle, instead of 

 the two brackets at a a, fixed to the wall, a cast-iron 

 pillar is used to support the gib, the collars a a fitting 

 upon it. The pillar is hollow, to admit the rope through 

 it, and is firmly fixed in a vertical position, by a 

 plate cast on the lower end of it, and screwed down 

 upon the timber of the wharf. Beneath these beams 

 there is another pulley, in place of b, to conduct the 

 rope to the crane. 



In many cranes, the whole machinery turns round 

 together upon the pivots of the gib, which method an- 

 swers extremely well, as it simplifies the machine, takes 

 up less room, and admits of its reaching all round in- a. 



