Figure 4-18.Nomenclature of a fiber line block.
BLOCK AND TACKLE
LEARNING OBJECTIVE: Upon completing
this section, you should be able to identify the
components and operating characteristics of
block and tackle units.
Figure 4-19.Types of tackle: simple (view A) and compound
A block (figure 4-18) consists of one or more
sheaves fitted in a wood or metal frame supported by
a shackle inserted in the strap of the block. A tackle
(figure 4-19) 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
sheave(s) 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
(view A of figure 4-19). A compound tackle system is
an assembly of blocks in which more than one line is
used (view B of figure 4-19).
To help avoid confusion in working with tackle,
you need a working knowledge of tackle vocabulary.
Figure 4-20 will help you organize the various terms.
A fall is a line, either a fiber line or a wire rope,
reeved through a pair of blocks to form a tackle. The
hauling part is the part of the fall leading from one of
the blocks upon which the power is exerted. The
standing part is the end of the fall, which is attached to
one of the beckets. The movable (or running) block
of a tackle is the block attached to the object to be
moved. The fixed (or standing) block is the block
attached to a fixed objector support. When a tackle is
being used, the movable block moves, and the fixed
Figure 4-20.Parts of a tackle.