A machine employed in large vessels, principally for "heaving up or weighing " the anchor. It consists of a drum or barrel, revolving upon an upright spindle, and having holes cut in the upper part or drum head, to receive the ends of a series of horizontal levers, named capstan bars. The cable, or, in very large vessels, a smaller rope, called the messenger, attached to the cable, is wound two or three times round the barrel, and as the capstan is turned round by a portion of the crew distributed at the capstan bars, another portion of them take in the slack of the cable or messenger, as it is unwound off the barrel of the capstan. The capstan is superior to the windlass in point of expedition, owing to the circumstance of the latter requiring the levers to be shifted into fresh holes four times in each revolution; and more men can also be employed at the capstan bars than at the hand-spikes of a windlass; but the men exert their strength more effectually at the windlass than at the capstan, since in the latter case they are employed to draw horizontally, when they exert a force of about 35 lbs. only, but at the windlass they may apply their whole weight at the extremity of the lever, and the average weight of a man is about 150, or more than four times his power of traction.
In Hawkes' Patent Capstan, which we are about to describe, is combined the advantageous action of the windlass, with the continuous movement of the capstan; and the power or velocity may be varied according to circumstances. The engraving on the next page represents the patent capstan complete for one deck, a is the drum head of cast iron, with holes for the insertion of the capstan bars in the ordinary way, if from any cause that mode of turning the capstan should be preferred; b is the paul head, round the periphery of which are ranged ten pauls, five of which are in operation at a time, as that shown at d; the other five are kept turned up in readiness for use when the motion of the capstan is reversed. Each paul has two clips, which take into two teeth at the same time at every half inch of the revolution. The inner circle of teeth is for one set of pauls, and the outer circle for the other set, the notches being in contrary directions; both circles are inclosed within the paul-rim f.
The barrel is composed of a number of projecting ribs named whelps, having a projection c in the middle, which divides the barrel into two parts; the upper portion is of a smaller diameter than the lower, so that by shifting the cable from the lower to the upper part of the barrel, an increase of power is obtained. In the figure the capstan is represented divided into six sections; but the number of these sections may be varied according to the size and weight of the capstan; the divisions are made vertically through the whole length of the capstan, dividing also the whelps, the plates of which being strongly bolted together, unite it into one firm and compact body, and admit of its being easily disunited and removed. h is the central shaft of wrought iron, made square, except at the bearings, which are properly turned. l l l are three iron standards for supporting the gearing, which gives motion to the capstan, and may be worked either by means of a winch or crank, as shown by the dotted lines at m, or by means of capstan bars, supported horizontally in holes at the circumference of two vertical wheels n n fixed on the same axle as the crank; the circumference of these wheels being scored in a proper manner for allowing the bars to be dropped in and secured by pins, and to be quickly removed at pleasure.
The bars when secured in the rims of the wheels tin, form a kind of drum or reel, the men on one side of which lay hold of the bars and pull upwards, and those on the other side pull downwards either with their hands, or by stepping on the bars one after another as they revolve, and thus weigh down. The shaft which carries the wheels n n bears also two pinions, one of which is shown in gear with the smallest circle of a double cogged wheel; and on the same shaft as the latter is placed a pinion, which takes into the circle of cogs fixed on the upper surface of the paul-head, and causes it to revolve: if the small pinion is brought into gear with the large wheel, a great addition of power is gained; and according as the one or the other set of the wheels, and as the larger or smaller of the barreis of the capstan, are employed, the power admits of several variations to suit different circumstances