Page:Willich, A. F. M. - The Domestic Encyclopædia (Vol. 2, 1802).djvu/112

94] CRA the Society for the Encouragement of Arts, &c. in l/Ol, granted him a premium of 15 guineas. The proportion of the beam in the annexed plate (Fig. 1.), is as 1 to 20, the large weight being 5 pounds, and the smaller | of a pound. The latter, when fixed on the beam-end, will equi-poise the former, if hung on the pulley at the end of the gib-beam, which should be placed in a right line with the crane, at the time the weight is adjusted ; otherwise it will occa- sion a friction that may prevent the moveable beam from playing freely. Description of Mr. A. Andrews s Crane in the annexed Engraving, Fig. 1. The gib of the crane stands on a horizontal beam, moveable on a centre, at A: and the distance of the centre A, from the bearing of the upright, being to the distance £, in the proportion of 1 to 20, the weight placed at B, determines that of the body suspended in the same proportion. — C is a stub, or piece of wood, which projects from the weight hanging at the end of the gib, and serves to prevent the beam from rising to too great a height. One of the latest improvements in this useful machine, is that pro- posed by the Rev. E. C. in the 2d vol. of the Repertory of Arts and Manufactures, It. consists simply in introducing the action of a worm, that communicates the first motion to the crane, upon the axis of the wheel in which the man walks. The axis of this wheel, and that of the worm, are proposed to be in separate parts, - and occasionally united by a cou- pling-box. "When goods are to be CRA raised, the two axes should b m . connected ; when lowered, they may be disunited, and the worm turned by a winch. Thus, the ascent, or descent,, of the weight may be accelerated, or stopped, at pleasure, by the person walking on the axis of the wheel, or turning the winch ; without the remotest possibility of being overpowered by the descending weight. Explanation of the annexed En- graving, Fig. 2. A, The wheel in which the man walks. B, The coupling-box. C, The worm. D, The wheel in which it works. E, A wheel upon the same axis, giving motion to F. F, A wheel upon the axis of the. windlass. G, The winch. This machinery (the ingenious projector adds) may be applied to a crane already erected upon the common principle. He proposes to put a wheel on any convenient axis in the machine, in its present state ; and, on this, a worm that may be thrown in or out of gear, at pleasure ; and to let the lever, by which it is effected, lie within the reach of the man's hand in the wheel. The goods being fastened to the crane, and raided from the floor of the Warehouse, in order to be let down, the man puts the worm into gear, leaves the wheel, and causes them to descend by the winch. These contrivances are alike eminent for their ingenuity ; and, though we do not venture to pre- fer either, yet we seriously recom- mend the adoption of some one of these imorovements, as, we are fully