A crab capstan consists of a barrel, (in shape, a frustum of a cone,) and of a framework of wood and iron by which the barrel is supported in a vertical position with its largest diameter next the ground. It is furnished with two levers, called capstan bars, which are passed through mortices in the upper part of the barrel, and by means of which the barrel may be turned about on its axis. By means of the crab capstan, a few men, acting at the levers, can move weights which would be far beyond their strength, if applied in the ordinary manner; and it may, therefore, be used with advantage in many situations, in which it may be either difficult to command labour, or desirable to economise it.
One end of a rope is made fast to the weight which is to be moved, and is called the standing end. The other, called the running end, is passed two or three times round the lower part of the barrel, the loose or running end being kept above the turns, and stretched taught by the man who passed it round. As the barrel is turned, the standing end of the rope winds round it, forces the turns up the barrel, and clears itself. As fast as the running end comes off the barrel, it is coiled by a man appointed to that duty.
The capstan, when used, is secured by ropes to pickets, driven on the opposite side of it to that on which the strain acts upon it. Three men at each end of both bars—i. e., twelve men in all—is the greatest number that can be employed at the capstan with advantage; and two men are required for the running end of the fall, as previously described. The levers are twelve feet in length, and the power of twelve men, acting upon them, is about equivalent to that of 132 men acting at the end of a taught rope.
If a crab capstan cannot be procured, the windlass of a gyn may be used as a substitute, the cheeks being laid on the ground and secured with pickets; or a temporary capstan may be rigged, by lashing four handspikes to the spokes and felloe of a limber wheel, which is turned upon the pintail of the dismounted limber.
Article 12.
SLING CART.
The sling cart weighs about 15 cwt., and is employed for moving heavy ordnance. It is capable of carrying 65 cwt.
One non-commissioned officer and six men are required, numbered as usual; but it can be worked by one non-commissioned officer and four men.
Articles required:—