It is composed of two principal parts: a frame to contain the moving machinery; and a capstan or windlass, which is erected on a sill or plank, that is sunk a few inches into the ground: the frame is by this means, and by six braces or props, rendered steady. The cross rail, or transom, is strengthened by braces and a king-post to make it lighter and cheaper. The capstan consists of an upright shaft, upon which are fixed two drums; about which a rope may be wound up, and two levers or arms by which it may be turned round. There is also a screw of iron coiled round the lower part of the shaft, to show the properties of the screw as a mechanic power. The rope which goes round the drum passes over one of the pulleys near to the top of the frame, and under another pulley near the bottom of the frame. As two drums of different sizes are employed, it is necessary to have an upright roller to conduct the rope in a proper direction to the pulleys, when either of the drums is used. Near the frame, and in the direction in which the rope runs, is laid a platform or road of deal boards, one board in breadth, and twenty or thirty feet long, upon which a small sledge loaded with different weights may be drawn. Plate 2. Fig. 1.
F. F. The frame.
b. b. Braces to keep the frame steady.
a. a. a. Angular braces to strengthen the transom; and also a king-post.
S. A round, taper shaft, strengthened above and below the mortises with iron hoops.
L L. Two arms, or levers, by which the shaft, &c. are to be moved round.
D D. The drum, which has two rims of different circumferences.
R. The roller to conduct the rope.
P. The pulley, round which the rope passes to the larger drum.