Figure 13-43.A. Simple tackle; B. Compound tackle.

Mechanical Advantage

Block to Line Ratio

Equipment Operator Basic - Beginning construction equipment operators manual
Page Navigation
358

Figure 13-43.—A. Simple tackle; B. Compound tackle. inserted in the strap of the block. A tackle (fig. 13-43) is an assembly of blocks and lines used to gain a mechanical advantage in lifting and pulling. In a tackle assembly, the line is reeved over the sheaves of blocks. The two types of tackle systems are simple and compound. A simple tackle system is an assembly of blocks in which a single line is used (fig. 13-43, view A). A compound tackle system is an assembly of blocks in which more than one line is used (fig. 13-43, view B). Various terms used with a tackle, as shown in figure 13-44, are as follows: . The fall is either a wire rope or a fiber line reeved through a pair of blocks to form a tackle. l The hauling part of the fall leads from the block upon which the power is exerted. The standing part is the end which is attached to a becket. . The movable (or running) block of a tackle is the block attached to a fixed objector support. When a tackle is being used, the movable block moves and the fixed block remains stationary. l “Two blocked” means that both blocks of a tackle are as close together as they will go. You may also hear this term called block and block. . To “overhaul” means to lengthen a tackle by pulling the two blocks apart. Figure 13-44.—Parts of a tackle. To “round in” means to bring the blocks of a tackle toward each other, usually without a load on the tackle (opposite of overhaul). The block(s) in a tackle assembly change(s) the direction of pull, provide(s) mechanical advantage, or both. The name and location of the key parts of a fiber line block, as shown in figure 13-42, are as follows: l The frame (or shell), made of wood or metal, houses the sheaves. . The sheave is around, grooved wheel over which the line runs. Usually the blocks will have one, two, three, or four sheaves. Some blocks will have up to eleven sheaves. . The cheeks are the solid sides of the frame or s h e l l . . The pin is a metal axle that the sheave turns on. It runs from cheek to cheek through the middle of the sheave. . The becket is a metal loop, formed at one or both ends of a block; the standing part of the line is fastened to the becket. l The straps hold the block together and support the pin on which the sheaves rotate. . The shallow is the opening in the block through which the line passes. . The breech is the part of the block opposite the swallow. 13-24

Privacy Statement
Press Release
Contact