Stuck vehicle
A steady-pull estimate. Real recoveries are dynamic and load gear well above this.
1The vehicle and the slope
Weighed, not tare. Gear and water add up.
Rise over run. 10% is about 5.7°.
2What it is stuck in
Where these numbers come from. Rolling resistance is the vehicle’s weight divided by a ground condition factor, gradient resistance is its weight multiplied by the slope in degrees and divided by 60, the two are added, and a 25% margin is applied to the sum. Bogging to the axles reduces the ground condition factor by one. This is the I4WDTA recovery resistance method, unchanged.
Do not select recovery gear from this result. This is the steady force needed to move the vehicle, not the force gear will see. A snatch recovery is a shock load and can be several times higher. Inspect rated recovery points, equipment WLL/MBS, angles, anchors and bystander exclusion zones. Use trained assistance when uncertain.
Why the winch figure is bigger than the pull
rolling = weight ÷ ground factor
gradient = weight × degrees ÷ 60
estimate = (rolling + gradient) × 1.25
winch = 1.5 to 2 × vehicle mass
gradient = weight × degrees ÷ 60
estimate = (rolling + gradient) × 1.25
winch = 1.5 to 2 × vehicle mass
The estimate is what it takes to move the vehicle once. A winch is sized on vehicle mass instead, because it has to cope with a line that is not straight, a drum on its outer wraps, a vehicle that shifts, and a load that spikes the moment something breaks free.