FIG. 3.
FIG. 5.
FIG. 6.
These machines are used for raising heavy bodies in a perpendicular direction. They are of various forms suitable for almost every purpose, and to most of them are adapted two or more wheels with teeth, one small and one large, for the purpose of obtaining power at the expense of time ([fig. 1]); the small wheel is turned by a windlass, and turns the larger one very slowly but with great power. The common warehouse or cellar crane is generally an iron frame with two pulleys, and the arrangement shown at [fig. 1]. which is usually inside the warehouse, while the crane is outside to raise goods from carts, &c., into the floors above ([fig. 2]). Cranes at the sides of canals or rivers for landing goods are sometimes made as [figs. 3] and [4]; in the last there is a heavy stone placed to balance the weight at the end of the crane. What is called the “jib crane” is often “rigged” up on shipboard for shipping and unshipping goods ([fig. 5]). Cranes for very heavy purposes have been made upon the tubular principle and consist of iron plates rivetted together so as to form a hollow curved crane, similar to the hollow girders used in bridges. Where goods have to be brought from one particular spot to another, as in [fig. 6], the swing crane is used. Amongst cranes may be named the hydraulic lift; this is exactly similar to the hydraulic press, only applied in a different manner, and is used to lift very heavy weights but short distances, as for raising heavy goods on to railway trucks, &c.
CRANKS.
