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
. 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
. 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