The next step is to form the sling for the hoisting
falls. To do this, take a short length of line, pass it a
sufficient number of times over the cross at the top of
the shears, and tie the ends together. Then, reeve a set
of blocks and place the hook of the upper block
through the sling, and secure the hook by mousing the
open section of the hook with rope yarn to keep it
from slipping off the sling. Fasten a snatch block to
the lower part of one of the legs, as indicated in
The guysone forward guy and one after
guyare secured next to the top of the shears. Secure
the forward guy to the rear leg and the after guy to the
front leg using a clove hitch in both instances. If you
need to move the load horizontally by moving the
head of the shears, you must rig a tackle in the after
guy near its anchorage.
A tripod consists of three legs of equal length that
are lashed together at the top (figure 4-40). The legs
are generally made of timber poles or pipes.
Materials used for lashing include fiber line, wire
rope, and chain. Metal rings joined with short chain
sections are also available for insertion over the top of
the tripod legs.
When compared with other hoisting devices, the
tripod has a distinct disadvantage: it is limited to
hoisting loads only vertically. Its use will be limited
primarily to jobs that involve hoisting over wells,
mine shafts, or other such excavations.
advantage of the tripod is its great stability. In
addition, it requires no guys or anchorages, and its
load capacity is approximately one-third greater than
shears made of the same-size timbers. Table 4-1
gives the load-carrying capacities of shear legs and
tripods for various pole sizes.
The strength of a tripod depends largely on the
strength of the material used for lashing, as well as the
amount of lashing used. The following procedure for
Figure 4-41.Lashings for a tripod.