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Winching
Guide
Snatch Blocks
Snatch blocks are the second most important accessory for your winch
(the first being shackles). Being able to change the line direction for
pulls around corners and multiple line pulls makes them extremely
versatile. Let’s understand how they work before we show examples
of vehicle recoveries.
The most basic use of a snatch block is to change the direction
of a rope. In the diagram a 4 ton vehicle is attached to a rope
which passes around a snatch block to a winching vehicle.
Notice that the tension in each of the ropes is
equal to the total load weight, and the snatch block
must carry the combined load of the ropes.
This is a simplified example neglecting the angle of
pull of the ropes. As the angle between the ropes
increases, the load on the snatch block will decrease.
Example 1: Direction Change
In a direction change situation, the objective is
to pull from a direction that has a greater impact
on the stuck vehicle. In this example the weight
is the stuck vehicle and the snatch block is
attached to an anchor point. The snatch block
does not provide any increase to the recovery
force but it does change the direction of the pull.
Example 2: Recovery Force Increase
In a situation where the recovery will take more
force than the winch can provide, a double line
pull should be used. This can help reduce the
load on the winch and decrease the electrical
load on the vehicle.
In this example the weight becomes the
vehicle with the winch, and the snatch block
is again connected to an anchor point. The
usefulness of this rigging is to leverage
the doubled force of the two ropes that the
snatch block carries, allowing the recovery
force to be double that of a single line pull.
Additionally the double line rigging will require
more rope off the drum, allowing the winch to
work on lower layers and provide more available
pull force.
8T
Snatch Block
Winching
Vehicle
Recovery
Vehicle
4T
4T
4T
Load
DANGER ZONE
DANGER ZONE
