Bushranger DV-9TH - Page 8

Page 7
 Required Pulling Force
Your winch must be powerful enough to overcome the resistance caused by an
obstacle, such as moving water, mud, snow, sand or on a steep hill, as well as pulling
the vehicle’s full weight.
As a general guide, you need a winch with a maximum line pull at least 1.5 times
greater than the gross vehicle weight.
There are three factors listed that have influence on the line pull effect required to
recover the vehicle. The values and calculations in this section are approximate and
are for reference only.
a). Gross vehicle mass (GVM)
b). Type of surface to be traversed
c). Gradient to overcome
In recovery and loading, where the winch is used to pull something, the required
pulling force (RPF) can be calculated according to the formula:
RPF = (Wt X S) + (Wt X G)
Where:
Wt
= the gross vehicle mass (GVM)
S
= the type of surface to be traversed
G
= the gradient to overcome
Surface Type
Surface Drag (S)
Gradient
Angle (θ)
Gradient (G)
Metal
0.15
5%
3°
0.06
Sand
0.18
10%
6°
0.11
Gravel
0.20
20%
11°
0.2
Soft Sand
0.22
30%
17°
0.3
Mud
0.32
50%
26°
0.44
Marsh
0.52
70%
35°
0.58
Clay
0.52
100%
45°
0.71