But when it is required that the same number of men shall exert a greater power, the bolts h are withdrawn, and the pinion f lowered into geer, with the toothed wheels. The rotation of the drum-head, then carrying the pinion round, causes it to drive the toothed wheels d d d; and these working into the toothed rim e e, attached to the barrel, cause the barrel to revolve with an increased power.
Thus, under particular circumstances, a smaller number of men at the capstan or windlass (which is to be constructed upon the same principle) will be enabled to haul in the cable and anchor, or warp off the vessel, which is an important object to be effected.
In 1819, Captain Phillips obtained a patent for certain improvements in capstans, a part of which invention is precisely the same as this in principle, though slightly varied in its adaptation.
James Brown, ship-rigger, in his capstan, patented in 1833, instead of applying the moving power by handspikes, having fixed two rims of teeth round the top of the capstan, acts upon them by a rotatory worm, or pinions turned by a winch.
[Fig. 257.] is an elevation of this capstan, and [fig. 258.] is a horizontal top view. a is an upright shaft, fixed firmly to the deck, serving as an axle round which the body of the capstan revolves. A frame c, fixed to the top of a stationary shaft a, above the body of the capstan, carries the driving apparatus.
The upper part of the body of the capstan has a ring of oblique teeth d formed round its edge; and above this, on the top of the capstan, is a ring of bevel teeth e. A horizontal shaft f, mounted in the top frame c, has a worm or endless screw, which takes into the teeth of the ring d; and a short axle g, having its bearings in the central shaft a, and in the frame c, carries a bevel pinion, which takes into the bevel teeth of the ring c.
The bearings of the shaft f, in the top frame, are in long slots, with angular returns, something like the fastening of a bayonet, which is for the purpose of enabling the shaft to be readily lifted in and out of geer with the teeth of the ring d: the outer bearing of the axle g of the bevel pinion is also supported in the frame c, in a similar way, in order to put it in and out of geer with the teeth of the bevel ring e. A mode of shifting these is essential; because the two toothed rings, and their driving worm and pinion, give different speeds, and, of course, cannot be both in operation at the same time.
The worm of the shaft f, being placed in geer with the teeth of the ring d, on applying rotatory power thereto, by means of winches attached to the ends of the shaft, the barrel or body of the capstan will be made to revolve with a slow motion, but with great power; and thus two men at the winches will do the same work as many men with capstan bars in the ordinary way.