/ TENSIONING SYSTEMS
operations often require evacuations up cliffs or steep slopes. Since a
"Load" (defined as the weight of the element that is being raised
i.e. litter with tenders, equipment, etc.) can be as much as 600 lbs. (or
higher), and a haul team could consist of only a few rescue members,
mechanical advantage (T-System calculation) is needed to make a raising system possible. This chapter
covers systems used by the rescue team for raising and tensioning (Tyrolean
Advantage systems employed by SAR include the following:
3:1 "Z" pulley system (Read
as "3 to 1" advantage)
5:1 Pre-Rig Haul System
systems may be augmented by:
2:1 Advantage systems
Piggy Back systems (3:1
hauling on a 3:1 making a 9:1)
The following is an attempt to answer, "Why does mechanical
advantage systems work?" Regardless
of the type of system used to haul a load, the same amount of technical
"WORK" is always done. Work is defined as:
= LOAD FORCE X LOAD DISTANCE
= HAUL FORCE X LOAD DISTANCE
is equal to the weight of the load
DISTANCE is the distance that the load moves (In this case the
FORCE is the amount of force the hauling team applies
DISTANCE is the amount of rope hauled by the hauling team
ignores the effects of friction in the system. (The best systems minimize
friction). Therefore 72,000 FT-LBS of work is required to raise a 600 LB load
a distance of 120 ft. independent of the type of haul system that is employed.
(3:1, 6:1, 5:1 etc.)
no mechanical advantage (1:1) the haul team must haul the least amount of rope
(distance) but with the most amount of force. This is the case presented in
figure -1. Assuming that each rescuer could haul 80 lbs, 7 to 8 haulers
would be required to raise the load. From the definition of work it is
apparent that if the distance that the hauling team moves is increased the
amount of force that must be applied to raise the load will be decreased,
therefore reducing the number of haulers that are required. The device that
allows this capability is the pulley.
-2 is an example of the use of a pulley to generate a 2:1 advantage. In
both systems the load will be raised from point A to point B. In system Y
(Note the pulley used here is a change of direction only.), the hauling
distance is the same as the load distance and therefore the system is a 1:1
system. In system X however, twice as much roped is used in the hauling
distance as is used in the load distance and therefore 1/2 as much hauling
force is needed in system X as is needed in system Y. This can be verified by
using a small piece of string and a little weight.
determine the amount of mechanical advantage in a given system, the number of
moving lines at the load is the mechanical advantage of the system. (This does
not apply directly to piggy back systems that will be discussed later.)
If the 2:1 system was applied to
the application shown in figure - 1 only half the haulers would be required
as is shown in figure - 3.
The drawback of the 2:1 is that it requires that the available rope be
over twice the load distance. (Which for a 300 ft haul would be considerable.)
THE "Z" PULLEY SYSTEM
"Z" Pulley System is quite universal in the SAR community. It is
easily constructed from standard rescue gear typically carried by field teams.
This system provides sufficient mechanical advantage to suffice rescue
requirements if the load is kept to a minimum and at least 4 haulers are
- 4 is a schematic diagram of the 3:1 system. Note that there are now three
moving lines at the load.
the rescue system were connected exactly as shown in the schematic, even more
rope would be required. A "RATCHET" system is employed to solve this
problem. Figure - 5 shows the actual implementation of the "Z"
pulley system. Two Gibbs Ascenders (prussik ascenders may replace the Gibbs if
Gibbs ascenders are not available) are utilized. The ascender closest to the
load is named the "Ratchet" ascender, and the ascender attached
directly to the anchor is the "Lock-off" ascender. The haul team
hauls on the free end on the rope until the ratchet ascender nears the
lock-off ascender. The haul team then releases (slowly) some tension to allow
the lock-off ascender to assume the load. After the complete load has been
taken by the lock-off ascender the ratchet ascender is free to be moved back
down toward the load after which the hauling process resumes. A runner or a
length of 1"webbing, termed the "Reset Line," may be attached
to the ratchet Gibbs to help facilitate the reset operation. This ratchet
cycle continues until the load reaches the top or it becomes necessary to
re-configure the system to a lowering system. The leader will call out
"HAUL," "STOP," RESET."
"HAUL," to coordinate the activity of the haulers. Note that the 3:1
system is typically comprised of the haul rope.
is not necessary to coordinate "RESET-HAUL" commands with tenders or
over the radio. The ratchet effect is well known and expected by the tender.
This minimizes unnecessary traffic and allows the system to flow more
Note: In all applications
of the Gibbs Ascender the proper placement of the device requires that the
"Fat End" of the ascender to be closest to the anchor. This should
always be considered the rule when using Gibbs ascenders in mechanical
advantage systems. As is always the case when using hard ascenders in rescue
work, slack in the operational lines must be eliminated to minimize the
possibility of a hard ascender catching a dynamic load.
A 3:1 HAUL SYSTEM TO A LOWERING SYSTEM (FIGURE 8)
rescuer should be capable of converting haul systems to lowering systems and
vice versa with little difficulty. A problem managing a difficult overhang by
a litter team may justify a direction change.
a change is required the Site manager will command and control the various
system level requirements. To convert a "Z" pulley system, follow
the following steps:
the pulley with a figure 8 (fig -6a)
all slack between the lock-off ascender and the
figure 8 and lock off the figure 8 (See option note below)
tension on the normal haul point. (to release tension on the lock off
tension is released remove the lock-off ascender (6b)
Release tension on the haul (slowly) to allow the load to be taken by
the figure 8. (6c)
Remove the ratchet ascender and clip unused hardware in an accessible
area (never place equipment in the dirt) (6d)
Note: When converting from a raising to lowering or vice versa, it it
critical that the belay line be as tight as possible.
Option to step 2: If the
figure 8 is not locked off, a higher mechanical advantage will be present for
step 3. It is important to control the lowering lines carefully and lock-off
after step 5. Use this option only if personnel is limited and additional
mechanical advantage is needed.
general, whenever a haul system is to be implemented the necessary lowering
station gear should also be readied and clipped into an accessible area. An
extra ascender, several biners, and a length of webbing should also be handy
in the event a problem arises. In the scenario above, the standard figure 8
brake was used. The system can be adapted to any valid brake.
an operation the rescuer assigned to assemble a given station may wear the
systems rack of equipment or may mount the equipment in an area accessible to
all. It is critical not to lose pieces of equipment or entire racks of
equipment due to careless storage. It is even more damaging to drop a piece of
system gear onto resources or subjects at a lower station.
KNOTS WITH THE 3:1 SYSTEM
times it is necessary to pass knots through a haul system. The knot may exist
to eliminate a damaged section of rope or to simply make a longer haul line.
(Combining two 200 ft rope sections to create a 400 ft main haul line.)
Passing a knot in this situation requires an extra ascender and two additional
runners for attachment reasons. Knot passing appears more difficult than it
actually is. It is essential to a potential rescue that the knot pass
operation be as smooth and quick as is possible. The suggested manner for
passing a knot through a 3:1 haul system is as follows:
Be aware that a knot is present in the haul line.
Prepare an extra ascender that will function as a temporary
lock-off ascender and a runner that will allow the temporary ascender
to be placed closer to the load than the normal lock-off ascender. (The extra
ascender is commonly a prussik.)
As the knot approaches the ratchet ascender, continue hauling until the
knot is as close to the lock-off ascender using the normal reset technique.
With the load being completely assumed by the lock-off ascender,
disconnect the ratchet ascender and replace it on the load side of the knot.
If necessary haul the knot up to a distance of 1/2 to 1 ft from the
lock-off ascender. Connect the temporary ascender
on the load side of the knot. figure C13-7c
Haul up slightly to release tension on the lock-off ascender and to
bring the knot as close to the pulley as is possible. Release haul tension
(slowly) and allow the load to be taken by the temporary ascender.
Disconnect the lock-off ascender and clip it into the anchor
or an easily available location. Extend the length of the pulley runner
so that the knot is on the haul side of the pulley. figure -7d
Haul to progress the knot along the haul line to a position indicated
in figure -7e. This places the knot close to the ratchet assembly.
With the load being held by the temporary ascender, disconnect the
ratchet assembly to pass the knot through the pulley. This requires that the
slack ratchet assembly be slid away from the load to have proper rope length.
the pulley to its original location and replace the original lock-off
ascender. (Note: If additional
knot passing on the current haul line is not required, the rescuer may elect
to complete the haul using the temporary ascender and the new pulley location.
This is a judgment call.
5:1 HAUL SYSTEM
another 2:1 advantage to figure -4 creates the system drawn in figure -8.
There are now 5 moving lines at the load. This system may be created by simply
adding two pulleys to the 3:1 system, however the 5:1 system is best
implemented using special pulleys that have 2 independent wheels on a single
axle. The pre-rigged 5:1 haul system, complete with a ratchet ascender (Gibbs)
and 200 ft of haul line is kept ready to be used in a team pack called the
"haul pack." Note this system is also utilized by Ventura Co. Fire.
In this case the "Lock-off device" must be tended by a rescue
lock-off device may be a figure "8" descended, or an ascender
(Gibbs or Prussik) as is shown in figure -9. The 5:1 is a stand alone haul
system and is attached to the haul line using the ratchet Gibbs which is
contained in the 5:1 haul pack. Since the haul pack is a unique piece of
equipment suited for one task, its application to back country operations is
limited to times when the personnel for transportation of gear to the rescue
site is not limited.
It is very important to note that the 5:1 hauling system must be
connected in the manner shown in the diagram. If the system is connected
backwards a mechanical advantage of only 4:1 will be created. (The reader is
encouraged to prove on their own.)
A 5:1 HAUL SYSTEM TO A LOWERING SYSTEM (FIGURE 8)
the 5:1 haul system is independent of the haul line, converting a 5:1 system
is an easier operation than converting a 3:1 system. The principle remains the
same: Insert the lowering device,
transfer tension momentarily to release the lock-off device and transfer the
load to the lowering device. The following two options exist for the 5:1
WHEN THE LOCK-OFF
DEVICE IS A FIGURE 8
represents the simplest conversion. The rescuer merely needs to remove the
ratchet ascender and the system is a lowering systems.
CONVERTING WHEN THE LOCK-OFF
DEVICE IS AN ASCENDER
On the slack side of the ascender insert a figure 8 and after removing
all the slack between the lock-off ascender and the figure 8, lock off the
Apply tension with the haul system until the load is removed from the
Remove the lock-off ascender.
Release tension (slowly) on the 5:1 until the descending device assumes
KNOTS WITH THE 5:1 SYSTEM
knots with an independent haul system is more straightforward than the 3:1
application. The following technique provides a safe method independent of the
type of lock-off device that is being employed. The rescuer should be aware
that there is a knot in the haul line and should be ready for the event by
preparing an ascender and a runner. The following technique should be
As the knot approaches, haul the knot as close to the lock-off device
as is practical for the given station set-up.
Continue hauling until the knot is within 1/2 - 1 ft of the lock-off
device. Connect the temporary ascender to the haul line on the load side of
Continue hauling 1 or 2 ft of main haul line using the temporary
ascender as the lock-off device. Transfer the load (slowly) onto the temporary
ascender. Move the original lock-off device to the opposite side of the knot.
Continue hauling and remove the temporary ascender at the next
OF A 3:1 OR 5:1 AS A TENSIONING SYSTEM
certain applications it is necessary for the lock-off device to be positioned
to sustain the maximum tension of the hauling system. Tyrolean systems require
this type of capability. In this case the lock-off ascender must be closer to
the load than the ratchet ascender. To capture the maximum tension, the haul
team hauls to exert the tension, while the lock-off device is positioned, then
the haul team releases tension (slowly) and transfers the near complete load
to the lock-off device. See figure -10.
This type of operation requires knowledge of the working strengths of
the equipment being used. Advanced training and experience are needed to
operate this type of system. Power winches are never used to tension rope
areas where a rescue truck is available the winch may be used as a raising
system. For small evacuations the winch cable may be extended directly to the
load. In the more typical case the winch cable is attached to the haul line
using an ascender. (This forms the ratchet ascender.)
The winch cable, more specifically, should be attached to a runner or
similar device which is then attached to the ascender. This provides the
capability of cutting the haul system free of the haul line if a problem
arises that requires such drastic action. Also, in the event of a stock system
scenario, the runner should "snap" before the main line does. The
haul line would then be fed directly through a lock-off device similar to the
set- up for the 5:1 haul system. This hauling system is typically employed
with a change of direction for a "vehicle over the side" operation
as is shown in figure -11. Two winches from two different trucks can be
used alternately to provide an almost continuous raising system. One winch is
hauling while the other is being reset. When one winch reaches the end of its
haul the other takes over and the cycle repeats until the raise is complete.
This would be especially helpful on long hauls (>600 ft).
OF THE MARINERS KNOT IN ANY HAULING STATION.
The Mariners knot should be used to attach the lock off ascender to the
anchor. This gives the capability of extending the "runner" length
of the lock-off ascender to release tension on the ascender. This may prove
useful when converting from a raising system to a lowering system when only a
few rescuers are available. This would also prove useful if "by
mistake" the litter becomes jammed or snagged and there is not enough
slack in the haul system to convert to a lowering system by the conventional
technique. Whenever possible, the mariners knot should be immediately re-tied
and readied after extension. Figure -12 depicts the proper usage of a
mariners knot in a 3:1 application.
standard haul systems employed by SAR have been selected for their
simplicity, ease of operation, and for reliability. Certain problems may arise
in the field which require modifications to the existing standards. A solid
working knowledge allows the rescuer to evaluate any situation. Lack of
equipment is often a problem which excites a reversionary mode. Pulleys can be
replaced by biners. Two biners used side by side create less friction due to a
less hard turn radius. Prussiks can be used in place of mechanical ascenders.
Various biner combinations can replace figure 8 descending devices. The
objective of reversionary systems is to generate the same reliability and
safety as the primary systems with the presence of less than optimum
conditions. The reader is encouraged to try various implementations of the
above haul systems under reversionary conditions before they are needed in