WINCH AND AXLE is a machine constituting a small windlass, and consisting of a cylinder of wood which is capable of turning on its axis between two upright posts of the same material, or between the ends of a cast-iron frame : a lever at one or at each extremity of the cylinder, is attached to an iron axle passing through the latter at right angles to its direction, and is furnished with a handle, which is parallel to that axle. The name winch is given to a lever or handle of this kind, and the word is supposed to be derived from the verb guincher, signifying, in old French, to turn or bend in a curvilinear manner. The machine is used to raise a weight vertically, or to draw an object towards It ; for which purposes the object is connected with it by a rope or chain which continually passes over the curve surface of the cylinder as the latter is made to turn on its axis by a man acting at the handle. Since the cylinder revolves once while the handle, or the extremity of the lever to which it is attached, is made to describe the circumference of a circle, it is evident that the mechanical power of the machine is precisely that of the wheel and axle. [Writes AND AXLE.] NVIsen of a Simple form it is employed to raise water from a well, and earth or sonic other material from tho shaft of a small mine : and one of a complex nature is used, by means of a crane, to raise casks or heavy packages from the ground to the upper part of a building.
When great weights are to be raised, the machine is usually fixed in a frame of cast-iron, which is rectangular on the plan, but its extre mities or faces have the form of a triangle, or of the letter A. The axle of the cylinder is supported on a horizontal bar at the middle of each end of the frame, and to the cylinder is attached a toothed-wheel which turns with it on the common axis : above this wheel and parallel to the cylinder is an iron axle which carries a pinion with teeth working in those of the wheel, and causing the latter to revolve, the pinion itself being turned by means of the lever and handle at one or at each extremity of the frame. A machine of
this kind is called a crab ; and when a weight is to be drawn horizon tally, or raised above the cylinder, the machine must of course be bolted to the floor or firmly fixed in the ground, in order to prevent it from being moved from its place. In such machines there is generally, at one extremity of the cylinder a wheel, having on its circumference teeth like those of a saw ; and a click or catch, which turns freely on a pin, is attached by that pin to the side of the frame in such a manner that it may fall between the teeth. By this contrivance, if the handle should break, or the moving power be taken oft while the weight is suspended in the air, the latter is prevented from descending.
Machines of this kind are occasionally constructed which have the power of holding the weight in any part of its ascent or descent with out a ratchet-wheel and catch. Such a machine consists of a barrel formed in two cylindrical portions, A and s, of different diameters, but having a common axle : the rope passes under a pulley in the block c, to which the weight is attached, and over the two cylinders, in such a manner that when the handle is turned it uncoils from the smaller and coils upon the larger portion. Thus every revolution of the barrel causes the larger cylinder to take up a quantity of rope equal in length to its circumference, while there is uncoiled from the smaller a quantity equal to the circumference of the latter : consequently, after each revolution, the quantity of rope between the axis of the cylinder and the pulley is diminished by the difference between the two circumferences, and the weight is raised up through a height equal to half that difference. Hence by mechanics, if 2na- represent the circumference of the circle described by the handle of the winch in one revolution, (1)—r), half the difference between the circumferences of the two cylinders, w the weight to be raised, and r the power applied to the handle, we shall have, in the state of equilibrium, r.