Disaster Rescue - Australian Emergency Manual (Natural Disaster Organization, 183 p.

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CHAPTER NINE - DERRICKS, SHEERS, AND GYNS
Derricks, Sheers, and Gyns
Standing Derrick (Figure 9:1)
Sheer Legs (Figure 9:2)
Gyns or Tripods (Figure 9:3)
Derricks, Sheers, and Gyns
9.0 Derricks, Sheers, and Gyns
When no suitable crane or derrick is available in a disaster for lifting, some form of derrick, sheers or gyn must be
improvised for the purpose.
(a) Derricks - are formed from single upright spars.
(b) Sheers - consist of two upright spars with their head lashed together and their feet splayed out.
(c) Gyns - are tripods formed by three spars with their heads lashed together.
Trained rescuers must pay particular attention to the selection of materials for the improvisation of these rescue
systems to ensure the safety of the operation. Consideration must be given to the strength of the material and the height
of the lift required.
(introduction...)
9.1 A standing or pole derrick is a single spar or pole (or two or more lashed together for strength) with the butt on
the ground or on a solepiece, and the pole held vertical by three, or four guys. A weight can be lifted and moved to the
right or left and to the front with this derrick, but only for a limited distance.
To support the lifting tackle and to prevent it from binding on the derrick pole, a short crosstree (or cross head) about
500mm long is secured to the derrick pole by a square lashing with a 12m lashing rope.
The crosstree should not be shouldered or bolted to the upright, as this weakens both crosstree and derrick pole. Its
normal position is from 450mm to 600mm from the head of the pole, but in all cases it is advisable to have it fixed as
far down the pole as will give sufficient room to lift the weight the required distance.
With any particular pole, the shorter the length of pole bearing the load, the greater the load it can carry, within the
limits imposed by the type and size of pole in use.
16mm Manila rope is the minimum safe standard for all guy ropes.
Anchors - The distance of the guy anchors from the foot of the derrick should be equal to twice the height of the
derrick if possible, but never less than the height of the derrick.
Head Rigging - If a winch is being used to lift the load, then all that is required at the crosstree is a steel wire rope
block, through which is passed the winch cable. Normally the block is secured with a 10mm chain sling. Both block
and chain hook must be moused.
Leading Block - To ensure that the load is supported down through the axis of the derrick, a leading block should be
lashed to the foot of the pole, and the hauling rope directed through the block. (Figure 9:1)
Fig 9:1 Standing or pole derrick
Footing - The ground on which the derrick will stand must be firm or steps must be taken to make it so. It is advisable
to form a shallow hole into which the butt will be placed. If the ground is too soft to withstand the pressure of the butt,
a footing of baulks of timber may be necessary, so constructed as to spread the load over a sufficiently large area of
ground. Care must also be taken to prevent the butt from kicking back particularly when luffing (para 9.4).
Layout and Preparation
9.2 Layout and Preparation
Having chosen the position for the foot of the derrick, (allowing for any necessary luffing), the points at which guy
pickets will be driven in should be selected, After preparing the derrick, the tackle should be overhauled to the
required length and the lower block temporarily lashed to the pole to prevent swinging during erection.
Raising
9.3 Raising
The initial raising is done by hand under the leader's direction. The guy at each picket is controlled by a rescuer and as
the pole is raised the slack on the fore guy is taken in. During erection the guys are controlled with a round turn on the
pickets and finally made fast with a round turn and two half hitches.
Luffing
9.4 Luffing
When raising a stretcher or load over an obstruction, such as a wall, it is usually necessary to luff or lean the pole
slightly. When this is being done each guy line must be controlled under the direction of the leader. Since the team must
work in unison the leader must give precise directions to haul or slacken, and must not leave the rescuers to exercise
their own judgement, otherwise misunderstandings may occur and lead to an accident. The maximum luff at any time
the derrick is in use must not exceed one-third of the height of the derrick, while the initial luff angle is one fifth of
derrick height. This limit of incline fixes the distance at which a weight can be picked up.
(introduction...)
9.5 Sheer legs consist of two poles with their butts on the ground and their heads lashed together and held in the air by
fore and back guys. This is sometimes called an 'A' frame.
Sheer legs can be employed where the use of a derrick would be impracticable. They can be used to move the weight
in a straight line by swinging the load between the legs. For a given load, the two spars may be lighter than the one
required for a standing derrick.
Fig 9:2 Sheerlegs or 'A' frame
Layout and Preparation
9.6 Layout and Preparation
Two poles of equal length should be selected and laid on the ground parallel, with their butts flush together. Spacing
pieces 50mm thick should be inserted between the poles, and the heads of the poles lashed with a round lashing. The
butts of the poles should be spread until their distance apart is about one-third of the length from butt to head lashing.
To prevent the butts from splaying, a ledger should be lashed on near the butts, or as an alternative a rope can be tied
to each leg by a round turn and two half hitches, or pickets can be driven in and fastened to each leg. The ledger
should be secured as close as practical to the base of the poles, allowing for ground surface. A sling should be passed
over the fork so that it will rest across the poles and not on the lashing between them. The lifting tackle is prepared and
hooked into the sling, the lashing being suitably protected with adding. The Hook must be moused.
Guy line anchors should be placed at a distance of not less than twice the height of the sheerlegs from its base.
Guys - The guys are similar to those required for a pole derrick but consist of two only: a fore and back guy of at
least 16mm Manila. They should be made fast above the round lashing by Clove Hitches in such a way that they will
draw the spars together when the load comes on to them, (ie. the fore guy to the rear pole and rear guy to the front
pole). The length of the guys is similar to those used with a pole derrick.
The tackle is prepared to the required length and the lower block is temporarily lashed to one of the poles to prevent
swinging during erection. The hauling rope should be reeved through a leading block secured to the butt of one pole.
(Figure 9:2)
Pole butts should be dug into the ground to prevent them from kicking back and the hook should be moused.
Raising
9.7 Raising
The initial raising is done by hand under the leader's direction. The guy at each picket is controlled by a rescuer and, as
the sheer legs are raised, the slack on the fore guy is taken in. During erection the guys are controlled with a round turn
on the pickets and finally made fast with a round turn and two Half Hitches. The butt must be placed sufficiently far
from any obstruction to permit the top of the sheer legs to be luffed over it.
Luffing
9.8 Luffing
Sheer legs are luffed by carefully paying out on one guy and taking in on the other. The team must work in unison
under the leader's direction to ensure sound operation and prevent accidents. The amount of luff permissible is similar
to that allowed in derricks, ie, initial luff one-fifth, thereafter one-third of vertical height of rig.
(introduction...)
9.9 A gyn or tripod consists of three poles lashed together near the heads and with the butts forming an equilateral
triangle on the ground. No guys are required and the space occupied is small, but only a vertical lift is possible. The
lifting tackle is suspended from a sling passed over the fork formed by the heads of the spars. The poles used should
be of equal length and strength.
Fig 9:3 Gyn or tripod
Layout and Preparation
9.10 Layout and Preparation
The three poles should be laid out side by side, the butts flush on the ground. They should be marked about 1m down
from the head of the shortest pole to show the position of the centre of the lashing. The centre pole should be reversed
and the head placed between the heads of the other two so that all three marks are in line. Spacing pieces 50mm thick
should be inserted between the poles, and the poles lashed together with a figure of eight lashing. The spacer blocks
are then removed and the two outer poles are crossed until their butts are at a distance apart equal to about half the
effective length of the poles, the top of the centre pole to rest in the fork of the other two.
A sling is placed in the fork in such a manner as to bind the poles together when the weight is taken, the lashing being
suitably protected. The hook of the upper block is hooked into the sling and moused. The tackle is prepared and
over-hauled to the required length. The lower block is temporarily lashed to one of the legs to prevent swinging during
erection. The hauling rope is reeved through a leading block secured to the butt of one pole.
Raising
9.11 Raising
The head of the gyn should be lifted as far as possible by hand and the centre pole brought in to form an equilateral
triangle. The butts should be evenly spaced at a distance apart equal to about half the height from the butt to the
lashing, they must all be on the same level or the weight will be distributed unevenly, and the gyn must be placed so
that its head is as near as possible over the centre of gravity of the load.
NOTE: Whether a load is suspended or not, the gyn should not be left standing unless the butts are secured against
slipping by one of the methods used for the sheer legs.