I found this looking for actual dead pull weights on recovery pulls. This is why I feel strongly that deuce winch is better than no winch AND why it stands a chance of living a long happy live on the nose of a five ton truck. AND, again, if there's anything questionable, throw in a snatch block and you're over 20,000, another should double that in theory. If the winch is available slap it on. Remember this is pulling NOT overhead lifting where the weight IS what it IS. A 5 ton truck doesn't weigh 22,000 lbs until it's got the axles in the goo.
The effort required to free a stuck vehicle depends on:
· Weight of the stuck vehicle,
· Type of material (mire) in which the vehicle is stuck,
· Depth to which the vehicle is mired,
· Slope up which the vehicle must be winched.
The following are approximate “mire” resistance values for different materials when the vehicle is only shallowly stuck and not grounded:
· Hard surface = 4 percent total vehicle weight
· Grass = 15 percent total vehicle weight
· Gravel = 20 percent total vehicle weight
· Dry Sand = 25 percent total vehicle weight
· Clay Mud = 50 percent total vehicle weight
The following depth resistance will be encountered, regardless of type material, by a vehicle buried to:
· Wheel hubs (axles) = 100 percent total vehicle weight
· Top of the tires = 200 percent total vehicle weight
· Hood = 300 percent total vehicle weight
It is the steepness, and not the length of the slope up which the vehicle must be winched, that matters. Keep in mind that if the vehicle’s wheels have to climb out of a hole, or over a rock or log, the slope of these gradients can be very high, even 90 degrees.
· Add 10 percent of the total vehicle weight for every five degrees of inclination for slopes up to 50 degrees. For slopes greater than 50 degrees, just add the total vehicle weight.
In addition, whenever we use snatch blocks in a winching operation, we must take into account the resistance they add (because of friction) to the load.
· Add 10 percent of the load resistance for every block used.
So a vehicle weighing 5,800 pounds stuck in 6 inches of mud on a 20-degree slope would require:
· 50% x 5,800 (mire resistance) + 40% x 5,800 (grade resistance) = 5,220 lb.
Available Effort
An often overlooked fact is that a winch’s greatest pulling force, its rated capacity, is only available when the rope is pulling from the layer directly on the drum. As shown below, the pulling force decreases significantly with each successive layer.
· Drum Layer = 100 percent of rated capacity
· 2nd Layer = 85 percent of rated capacity
· 3rd Layer = 72 percent of rated capacity
· 4th Layer = 62 percent of rated capacity
· 5th Layer = 53 percent of rated capacity
