WINCHING IN SAFETY.
For the benefit of those unfamiliar with winches, there are two categories of use. ‘Casual’ for such purposes as occasionally pulling a small boat out of harbour, or self-recovery of a disabled vehicle, and ‘Heavy duty’. This category includes any number of jobs: cable laying, tree-felling and removal, putting up overhead power lines, and so on, for which the winch is likely to be in constant use. This Guide to Winching deals primarily with casual use, and is intended to advise and inform the casual user.
Before buying a winch, discuss your specific requirements with the supplier. The foremost considerations being those of safety in operation, the vehicle’s ability to accept the product selected, the winch being of sufficient capacity to meet your needs and that it will not overload the vehicle and damage the chassis.
WINCHING IN SAFETY
The right winch for the job, correctly installed on the vehicle with all manufacture’s instructions having been scrupulously followed, should present no problems and provide the user with a first-class winching system. However, winches can be damaged or put out of action by careless or reckless use, overloading or poor maintenance. They can be repaired or replaced without too much pain, but not so the user, or bystanders. The operator has a responsibility to keep the winch and its equipment in good order.
When fitting a winch, the included literature gives advice on how to use it correctly. This must be properly studied and kept for reference. The emphasis should be on winching without danger - when in doubt, stop and re-appraise the situation and opt for personal safety.
Many vehicles are capable of pulling 3600kg (8,000lb) and there is now a tendency towards 4500kg (10,0001b) and 5400kg (12,000lb) models, which, for self-recovery at least, are regarded as slightly, over-the-top. If necessary introducing a pulley block can double pulling power, the cable routed through the pulley and back to a suitable anchor point on the vehicle. The effect is to increase pulling capacity of the winch by 2:1. So a winch rated at 3600kg (8,000lb) line-pull can effectively have 7200kg (16,000lb) line-pull. Using a pulley block in this way halves the speed of the winching operation, which can be an advantage. On an electric winch the current drawn from the battery with this configuration is also reduced by about 50 per cent. In tricky situations it is possible to use 2 pulley blocks in the line (provided sufficient anchorage points are available) for short-term’ heavy load pulling only.
A pulley block can be a distinct advantage, and pulling another vehicle that has bottomed-out can be relatively easy to winch. The vehicle, however, will not take unlimited strain; too much load over a long period may well twist the chassis and at best it may damage the winch mountings. Pulley blocks are a useful accessory, but only when used wisely and with great care and caution.
Cable breakages should not occur provided the cable is regularly inspected, but it is possible for the cable to be damaged and to start deteriorating after a check, underlining the need for frequent cable inspections. A cable snapping under strain can have the most frightening and serious consequences. A section has been included on care and maintenance of both wire rope and cordage and following these guidelines should forestall most cable problems.
Before tackling a winching operation, there should be a few minutes deliberation, to assess the right line of approach. The operator should look at the ground between himself and the anchor-point at the other end of the cable and question whether the winching operation is safe, or whether the cable has a clear run so that - should the cable part - the winch operator will be afforded some protection. If there is no natural cover, a coat placed over the cable may reduce the tendency for the cable to whiplash. It may be possible to stay in the cab to operate the winch, or perhaps place another vehicle in such a way as to provide some protection. Assistants and/or spectators must stand well back at a safe distance. A parting cable may well whip-back and can cause disfiguring and even fatal accidents. It cannot be overstated that before setting the winch drum turning it is the responsibility of the operator to ensure that no-one, repeat NO-ONE, is in any danger whatsoever. With a little thought and care, winching may be carried out safely with complete confidence.
GLOVES
Steel winch cable can get into an awful mess, especially when it has been pulled out across a boggy field. It will attract anything that will stick to it, and a good pair of gloves is essential for handing it. In any winching operation gloves are vital, whether the sun is shining and the ground is dry, or the rain is bucketing down on marshland half a metre deep in mud. Gloves not only protect hands from muck and grime inevitably acquired, but more importantly, from that strand of steel cable sticking up, ready to tear through the flesh as the cable is innocently fed through. One tiny strand is enough to cut the palm of a hand. Ideally gloves designed for the job should be worn; these are available from most winching manufactures, but in extremis leather-palmed gardening gloves are better than nothing.
SIGNALLING AND COMMUNICATION
Not all winching activities can be accomplished alone; sometimes an assistant can prove invaluable in the operation so it is important that instructions can be communicated clearly to each other. A series of hand signals has been developed for this purpose and are in general usage.
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It is important that the signaller should stand in a secure position where he can see exactly what is happening during the winching operation and be in no immediate danger should things go wrong. He should be able to clearly see the load and be seen by the winch operator. He should face the winch operator if possible and each signal should be distinct and clear. When winching at night, use a torch to convey your instructions in the same way as for hand signals and use a whistle to stop the winching operation in an emergency.
Illustrated are some of the more common signals that are used when winching. LEARN THESE AND USE THEM. If in doubt stop, re-appraise the situation and always proceed with the utmost caution.
TWENTY-FIVE STEPS TO SAFE WINCHING
Anyone can become proficient at winching. It is not necessarily an art, but it does require a thorough awareness on the part of the user, as to the capabilities of his winch and equipment coupled with sound knowledge of how to get the best from them. The Winching Technique section covers in some detail the right approach to a winching operation. Listed here is a guide of dos and don’ts of winching operations. Some will be obvious, some not so. All, though, will lead to safer winching.
(1) BEFORE winching with an electric winch, inspect the remote control lead for cracks, pinched wiring, fraying or loose connections. A damaged, shorted lead could cause the winch to operate as soon as it is plugged in.
(2) Only plug in the remote control lead when you want to use the winch.
(3) When the remote control lead is plugged in ALWAYS keep it clear of the drum fairlead area, the rope and any rigging.
(4) ALWAYS store the control lead in a clean dry area where it cannot be damaged.
(5) When using the remote control from inside the vehicle, ALWAYS pass the lead through the window to avoid trapping the lead in the door.
(6) ALWAYS stand well clear of wire rope and load during winching operations. Insist that helpers/spectators keep to a safe distance when winching.
(7) ALWAYS use vehicle ground anchors when recovering another vehicle.
(8) ALWAYS be sure that an anchor point intended for use is strong enough to withstand the load applied.
(9) ALWAYS use a choker chain, wire rope made for the purpose or tree trunk protector when connecting the winch wire to an anchor point.
(10) ALWAYS use a tree trunk protector when a tree is used as an anchor point.
(11) ALWAYS check that when ground or vehicle anchors are used the anchor is firm throughout the duration of the pull.
(12) ALWAYS keep a check on the winch wire anchor point; under heavy load it could fall with disastrous consequences.
(13) ALWAYS inspect and carefully re-wind wire rope after use. Crushed, pinched or frayed areas severely reduce original tensile strength. (For safety’s sake, wire rope should be replaced when any form of damage is evident.)
(14) ALWAYS stop winching when the hook is at least 3 metres away from the fairlead of the winch.
(15) ALWAYS wear gloves. Do not let wire rope slide through bear hands.
(16) ALWAYS use proper vehicle anchor points. Never hook up to bumpers, spring hangers or axle casings. When recovering an old vehicle be aware of the condition of the vehicle’s anchor points.
(17) Ensure that the rope is correctly spooled onto the winch drum. The spooling (winding-on) of the wire rope can be accidentally reversed by running the rope all the way out and re-spooling in with remote control switch in the ‘power-out’ mode.
(18) NEVER handle wire rope or rigging during winching operations or touch a wire rope or its hook while they are under tension; even when the winch is not in operation there may still be a considerable load applied to winch and cable.
(19) NEVER put a wire winch rope round an anchor and hook it back on itself, as this will damage the wire rope and reduce its tensile strength.
(20) NEVER operate a winch with less than 5 wraps of wire rope on the drum. A winch drum with fewer than 5 wraps of the rope remaining may break loose under load conditions.
(21) NEVER exceed the capacity of the winch. Use a pulley block to double the line-pull, which will almost halve the load on the winch and the wire rope.
(i) The inherent resistance to movement of the vehicle.
(ii) The weight of the vehicle.
(iii) The nature of the surface to be transited.
(iv) The gradient up which the vehicle is to be moved.
(22) NEVER use the winch to tow another vehicle. The braking system on winches is not designed for this sort of abuse and the sudden jerking will eventually cause the wire rope to snap.
(23) NEVER stand astride or step over the cable when winching.
(24) IMPORTANT: When re-spooling cable, ALWAYS release the control switch when the hook is a minimum of 1 metre from the fairlead and inch in the remaining cable onto the drum. The procedure is vital to personal safety and to avoid rope damage caused by over-tightening.
(25) When starting winching, use the control switch intermittently to inch in any slack in the wire rope prior to taking the strain. This will reduce the chance of damage to the winch or wire rope from shock loadings (which could briefly exceed the winch’s capacity).
THE MECHANICS OF WINCHING
To get the best from a winch and its equipment requires some understanding of the mechanics involved in the winching problem. For winching purposes the resistance to motion of a vehicle is dependent on 4 main factors:
(I) The inherent resistance of the vehicle
The inherent resistance to movement of the vehicle depends on the state of its tyres, friction in its drive-chain (which will cause drag), the weight of the vehicle, and whether the vehicle has sustained any damage to its running gear.
For our winching calculations we will assume that the vehicle is in good working order and has its tyres inflated to the recommended pressures - a flat tyre will cause considerable drag, and it may be advisable to change a wheel that has a puncture before commencing recovery operations.
(ii) The weight of the vehicle
The weight of the vehicle is the total weight including all equipment, luggage, fuel, passengers and stores aboard the vehicle.
(iii) The nature of the surface is transmitted
The nature of the surface to be transmitted is the largest variable in the winching equation. A vehicle in good running order on a metalled surface will only require a force of about 1/25 its total weight to induce movement, whereas a vehicle to be recovered from a bog will require a pull equivalent to about 1/2 the total weight of the vehicle. The table below shows that different surfaces require proportionate efforts to produce vehicle movement.
|
Type of Surface
|
Effort required to move a vehicle as a fraction of total weight |
As a percentage of total weight |
|
Hard metalled road |
1/25 total weight of Vehicle |
(4%) |
|
Grass |
1/7 total weight of Vehicle |
(14%) |
|
Sand (hard wet) |
116 total weight of Vehicle |
(17%) |
|
Gravel |
1/5 total weight of Vehicle |
(20%) |
|
Sand (soft wet) |
1/5 total weight of Vehicle |
(20%) |
|
Sand (soft/dry/loose) |
1/4 total weight of Vehicle |
(25%) |
|
Shallow mud |
1/3 total weight of Vehicle |
(33%) |
|
Bog |
1/2 total weight of Vehicle |
(50%) |
|
Marsh |
1/2 total weight of Vehicle |
(50%) |
|
Clay (clinging) |
1/2 total weight of Vehicle |
(50%) |
A simple calculation will show that approximate rolling resistance of an undamaged vehicle on a flat surface can be predicted e.g. the pull required to move a Land Rover Ninety weighing about 2000kg (44001b) along a flat sandy beach of hard wet sand, co-efficient 1/6.
If we take the weight of the vehicle (in kilogram’s) and multiply it by the co-efficient of the resistance of hard wet sand from the table of efforts required to move a vehicle as a fraction of its total weight, we get this calculation.
Weight of vehicle x co-efficient of wet sand
2000kg x 1/6 = 333kg = effort required to move vehicle in this case
However, as well as all surfaces are not flat, the calculation must therefore include a gradient resistance co-efficient.
(iv) The gradient up which the vehicle is to be moved
The gradient up which the vehicle is to be moved (gradient resistance) may only cover a short distance over the total distance of the pull, e.g. a ditch or rock, or it may cover a long climb up a hill. Even for a relatively short upward pull, gradient resistance must be taken into account. That the slope to be negotiated to all intents and purposes is only 150mm (6") high will make no difference to the calculations and should be borne in mind when winching over ridges.
For practical winching purposes, gradient resistance can be taken as 1/60 of the weight of the vehicle for each degree of the slope, up to 450 incline. For inclines over 45 the gradient resistance will be equal to the total weight of the vehicle.
Again a simple calculation can predict the total effort in kilograms required to move our 2000kgs Land Rover up an incline of 15
I.e. gradient x weight of vehicle
60
Which is 15 x 2000kgs 500kgs
60
If we combine the weight of the vehicle, the type of surface to be transited and the gradient to be overcome we get the calculation.
Weight of Vehicle + (Gradient x Weight of Vehicle)
Surface to be transited 60
Therefore the winching formula is
W + (GxW) = effort required
S 60
When W = Weight of vehicle
S = Surface to be transited
G = Angle of gradient (in degrees)
Using this winching formula it is now possible to predict the total effort required to move a vehicle in most winching situations.
Example: A Land Rover 90 weighing 2000kgs (4400lbs) is to be winched up a sand dune of dry loose sand with an incline of 150.
Using the winching formula W + (GxW) = effort required
S 60
Where W = 2000kg (vehicle weight)
S = 1/4 (co-efficient for dry loose sand)
G = 15 (slope in degrees)
We have 2000 + (15 x 2000) = 500 + 500
4 60
l000kgs of effort required to recover the vehicle in these circumstances.
However, if we substitute clinging clay for the surface (co-efficient of 1/2) and 35 for the gradient (shape) in the above equation we get
2000 + (35 x 2000) = 2 167kg (4 660lb) effort required
2 60
The effort required in this case may well be beyond the capabilities of the winch because the rating of a winch relates only to the first layer of wire on its drum and available pulling power decreases with each additional layer of wire rope in the winch drum. In the above case, a solution may be to run out all the winch cable to enable the winch to be used at or near its rated capacity, or introduce a pulley into the system to create a mechanical advantage.
THE USE OF PULLEY BLOCKS in WINCHING
A very useful winching accessory is the pulley block winch, when used in conjunction with the winch, can be rigged to provide a mechanical advantage. There are many types of pulley block, the most common for use with winches employing wire rope being the snatch block. The snatch block is so designed as to permit the bite of a winch cable to be inserted into it.
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Fig 1: Shows a snatch block attached at an anchor-point and the cable run from the winch, through the snatch block and hooked back on to the vehicle. This configuration (disregarding certain losses such as friction in the pulley) will give a mechanical advantage to the winch of about 2:1 i.e. the effort required by the winch will be halved. The speed of advance for the vehicle will also be halved for any given winch drum speed, but this can be advantageous in situations where a snatch block is needed. The snatch block also provides a dual advantage for the winch as it reduces the effort required for a given winch drum speed, and, because twice as much wire is required with snatch block configurations, allows a winch to operate with fewer layers on its drum, so it will operate nearer its rated pull configuration. A snatch block can be useful in many winching situations and can also be used to help create a straight line-pull.
Care must be exercised when using snatch blocks; although they will not necessarily overload the winch, the total weight to be pulled does not change and will still be exerted at the anchor-point.