Hand 3 (pl. 109) shows a light hand truck crane fitted with spur-gear and drum, and adapted for two speeds. Pig nrc 4 exhibits a jib-crane, which has a rotary motion and a travelling trol ley on the jib; the spur-gear mechanism admits of four rates of speed.
the frame of a crane is constructed so as to turn on a vertical axis and a fixed pulley is placed on the outer end of the jib, the sphere of action is in the line of the convex surface of a cylinder or a seg ment of it, of which the steam-crane ( p/. 14 is an example. In this Figure the crane-post or stalk is cast in one piece with a cast-iron plate, which is secured to the foundation. Pivoted to the crane-post is the jib with its stay and its drum or barrel, which can be rotated by the small engine. The latter is supplied with steam from a boiler located some distance away by means of the H-shaped pipe which passes up the axis of the crane-post.
7 (AL 1°9) is an example of what is called a "derrick "- or " free-standing" crane (jib-crane), because the crane-post and jib with its appurtenances are not supported by fixed points, such as a building, etc., but by a separate frame, consisting in this case of obliquely-set wooden stays. This crane is provided with two winding arrangements, one for raising the load and the other for moving the jib.
Cralfe.—A crane whose sphere of action is the hollow space of a parallelopiped—that is, in which the load can be transferred to any place in a long workshop, etc.—is illustrated in the form of construction exhibited in Figure 9. This is called a "travelling" crane, and consists of two supports or beams whose ends rest on wheels and upon which a windlass can be moved to and fro, or, as in the present example, where a carriage is drawn backward and forward by an endless chain operated by a stationary steam-windlass, which stands on one end of the crane-frame. The wheels supporting the beams may run upon rails resting on the walls of the building, or, as shown in the Figure, on a specially-constructed frame. In recent forms the movement of the crane, as also that of the windlass, is effected by rope transmission from a motor separated from the crane.
Trenrrsing Crane or of constructing fixed frames for the support of the rails, vertical supports connected by horizontal stays and provided on their lower ends with trucks with the rails placed on the grou,ic: an be used. The crane is thus moved upon a railway, by which its sphere of action is considerably increased. In this form it is called a " traversing" crane or "gantry" (Jig. 8). The construction shown in the Figure consists of iron supports and lattice-like cross-stays. Its movement on the rails is effected by windlasses upon the trucks. For lifting the load it is provided on each side with a winding-gear, and on the cross-beam, at the top, with two carriages, whose backward-and-forward movement is controlled by a windlass on each of the upper ends of the ver tical supports, and which can be turned from below by a chain passing down and over a driving-wheel or a crank-wheel.
Raihcay Portable combining an ordinary stationary crane with a carriage or truck there results a form of construction, called a "portable" crane, which has the same sphere of action as the preceding. I3y fixing the crane shown in Figure 14 (5/. toS) on a carriage and placing upon the crane-frame the steam-boiler, which in the Fignre is separate from the crane, there is obtained the portable steam-crane in the form exhibited in Figure i (bl. Ito). The boiler is so placed as to act as a counter-weight to the loaded jib. If no steam-engine and boiler are employed, the crane being simply operated by hand-power, a separate counter-weight or a clutching arrangement must be provided, to hold the crane upon the rails.
Railzoay 5 (fl. to9) illustrates a steam rail way crane, which consists of a steam-engine and its boiler mounted on a suitable car, and which is employed in railroad wrecks and for construc tion purposes. Cranes of this type combine the lifting and rotary capacity of the jib-crane with the functions of the travelling crane, but without limitation to the amount of their travel except as to the length of the track available.