To ensure your safety, the protection of your equipment, and the success of your recovery operation, use the following as a guide:
- Check the capacity of your winch. The capacity shown on the manufacturer’s plate is the maximum with one layer of cable on the drum. Each successive layer increases the diameter of the drum and reduces the winch capacity to as little as 50 percent of the rated capacity when the last layer is being wound on the drum.
- Check the cable for rust, kirks, or frays.
- Estimate the total resistance. Consider grade or slope, weight of the vehicle, and type of terrain. Then add a reasonable factor for safety.
- Check your equipment. Be sure you rig safely to overcome the resistance with the equipment available.
- Select or provide a suitable anchor. Remember, the purpose of this operation is to recover a vehicle, not to pull stumps.
- Rig and check rigging. Do not put power on your winch until you check every element in your rigging and are satisfied that you made no mistakes.
- Clear personnel from the danger area. All persons observing the operation should stand outside the angle formed by the cable under stress at a distance at least equal to the distance between the two most distant points in the rigging. Clear personnel away before tightening the cable.
Single-Vehicle Winch Operation
If you have been individually dispatched and get into a spot where your traction is not enough to get you through, use your winch and suitable rigging to pull you through or get you back to solid footing. Working alone or with your crew, recovery may take time, but do not skimp on planning. Your training should keep you out of the really bad spots, and if you remain calm, you should get through by applying a little extra effort.
Vehicle With Winch. Select or construct a strong anchor. Attach a snatch block to the anchor with your tow chain. Run the winch cable through the block and back to the truck (Figure 22-3). Take up the slack gradually and pull the truck forward with its winch. Power may be applied to the wheels at the same time. Your vehicle technical manual/order technical order gives details on the operation.
Vehicle Without Winch (Dual Wheels). Dual wheels and ropes may be used to winch out vehicles not equipped with winches (Figure 22-4). Fasten one end of each rope to a rear wheel hub and the other to an anchor. Place the rope between the duals and through one of the holes in the wheel disk. Tie the rope around the hub where it will be clear of the valve stem. Move the vehicle in reverse gear to wind the rope.
Vehicle Without Winch (Single Wheels). Place a bar through the hole in the end of the axle flange of each rear wheel. On each wheel, fasten one end of the rope to the bar and the other to an anchor. Move the vehicle in reverse gear to wind the rope in behind the bar (File 22-5). This procedure cannot be used on vehicles equipped with a Center Tire Inflation System (CTIS).
Two-Vehicle Winch Operation
Mechanical advantage is gained by using a mechanism to transmit force. A small force, when moved through a long distance by one or more mechanisms (pulleys), will move a large weight (vehicle) for a short distance. Use one of the following procedures when rigging for greater mechanical advantage.
Two-Part Line. This simple hookup gives a 2:1 mechanical advantage (Figure 22-6). Attach a snatch block to the load. Next, run your winch cable through the block and secure the cable to the winch vehicle. Place a log in front of the towing vehicle to help hold its ground.
Three-Part Line. To get a mechanical advantage of 31, use two snatch blocks – one at the load and one on the winch vehicle (Figure 22-7). Thread the winch cable first through the block on the load, back through the block on the winch, and then again to the load where it is secured.
Four-Part Line. To get a 4:1 mechanical advantage, use two snatch blocks – a double-sheave block for the load and a single-sheave block for the winch vehicle (Figure 22-8). Thread the winch cable through one sheave of the double block attached to the load back through the single sheave on the winch vehicle, and again to the load through the second sheave of the double block. Finally secure it to the winch vehicle.
Cable. Recovery operations take time. Do not hurry. A broken winch line reacts like a whip. When hooking to a vehicle, use both shackles whenever possible so effort is applied equally and damage to the vehicle is minimized.
Never bend the wire cable at a sharp angle. Straighten out all kinks and twists as you take up the slack. Do not let tractors or vehicles with metal tracks run over the cable. Such abuse flattens the cable, exposes the Manila hemp core, and lets water enter, causing internal rust and weakening the cable.
WARNING: Stand clear of a winch cable before it is tightened. A cable being tightened may break and whip back with enough force to seriously maim or kill.
After using the winch, have one person or preferably two pull back on the cable while it is wound slowly and evenly on the drum in accordance with the appropriate vehicle operator -10 TM. Keep the cable lubricated according to the vehicle lubrication order.
Shear Pin. When the winch is overloaded, the shear pin breaks to protect the cable. Never use makeshift shearing of unknown strength to replace a broken pin. Too strong a pin may snap the cable and damage the winch. Use only authorized replacement pins. Do not depend on the shear pin for protection. Even with the proper pin installed, a kinked, damaged, or weakened cable may snap. Vehicles with electric winches have circuit breakers to protect the winch from overloading. Check the appropriate vehicle operator -10 TM for correct winch.