Forestry winches: technical characteristics and applications

The winch is an absolutely indispensable piece of equipment for a business operating in the forestry sector, and is offered on the market by many manufacturers. The prices vary depending on the product characteristics, and are within the reach of both forestry companies and the agricultural farms that do sporadic forestry activities

Given the work it carries out, especially if compared to its relatively low purchase and maintenance costs, the forestry winch is to be considered one of the indispensable machines in forestry mechanization, where it is used for logging. This tool is indispensable when there is a need to bring close to the tractor the timber that has been felled on terrain that is too rough or in any case difficult to reach. It is usually used to concentrate several scattered trunks in a single area, ensuring greater care for the ground surface when the tractor comes and goes.

Although it is normally applied to the tractor's rear three-point hitch, there are versions that provide a stirrup on the tractor, and in this case they remain in most cases connected to the tractor in a fixed manner. The advantage of the first solution is an increase in the versatility of the tractor, the advantage of the second solution is the fact that it can be mounted with a lower overhang than the tractor itself, with greater stability of the assembly, which is valuable when carrying out more burdensome pulling.

The types of winches that can be mounted on the agricultural tractor are somewhat varied, not only as regards the pulling force that they can exert, but also as regards the accessories available for the various models and therefore the purchase prices. The cheaper models are priced at around € 1,500 (excluding VAT) while radio-controlled models equipped with two drums have a cost that sometimes exceeds € 10,000 plus VAT.

The various models are capable of exerting tensile forces ranging from 2,500 to 12,000 kg, although the vast majority of the models sold are between 4,000 and 6,000 kg. Their weight ranges on average from about 200 kg (without rope) for the smallest and lightest single-drum models to over 800 kg for the heavier versions, sometimes equipped with two drums.

The power required of the tractor to be connected to them obviously varies accordingly, not so much for the actual power absorption induced by the winch, but above all for stability issues. In agricultural tractors, higher power corresponds on average to greater mass, also given a typical weight/power ratio for agricultural tractors of about 40 kg/Hp. Precisely on the basis of this consideration, if a winch capable of exercising a "pull" of 3,000 kg requires at least a 40 Hp tractor (about 30 kW), a 6,000 kg one needs an 80 Hp tractor (about 60 kW). It goes without saying that for models capable of exerting the highest traction forces (about 12,000 kg), a 150-160 Hp tractor (about 110-120 kW) is required.

 

What does it look like. First of all forestry winches differ from traditional ones in that only the first ones have a logging mouth and a mobile shield. The logging mouth can be equipped with rollers, or with a flag pulley, and is used to keep the load heads raised from the ground and to pull loads that are not aligned with the tractor.

The logging mouth is a pulley device or equipped with a double pair of rollers that allows you to use a tow rope, without it being damaged when it is operated to carry out pulls that are not perpendicular to the drum. The rope guide device, on the other hand, is made up of a pulley placed between the drum and the logging mouth, designed to facilitate winding the rope, increasing its duration, and preventing the rope from getting blocked due to irregular overlapping of the coils.

When lowered, the shield allows the tractor to be anchored to the ground, in order to carry out the indirect tow with greater ease and safety. However, at the same time it also uses the shield to prevent any trunks, if not properly hooked, from get under the tractor's axle, preventing the lifting of the heads. Once the trunks hooked to the rope have reached the shield, this can be lifted off the ground to carry out the half-tow transports.

The winch usually uses a drum on which the rope is wound, although in some cases there may be two drums. These are actuated by a transmission that can be mechanical or hydraulic, and the whole is supported by a sturdy supporting structure. The models equipped with hydraulic transmission are more expensive, but they are simpler to use, and above all they allow to modulate at will the force and speed with which to carry out the traction. There are also hydraulically operated mechanical winches, using a hydraulic device that controls the clutch engagement. This construction method is also indispensable for radio-controlled models.

 

Safety. Regardless of its size, a forestry winch must necessarily have a plaque with the manufacturer's details, the machine model, the year of manufacture, the serial number, the required torque, the pulling force with empty drum and full drum, the nominal rotation speed of the operating device, the diameter of the rope, its minimum breaking load and its maximum permissible length, and finally the maximum permissible pressure for winches equipped with hydraulic or pneumatic controls.

In addition to the plaque, all forestry winches must be equipped with an automatic safety brake, which prevents the load from sliding down when the clutch is disengaged. The most recent versions include the use of a simple but effective belt brake, which also allows to modulate the braking effect. Meanwhile, we see less and less use of the now obsolete system based on a crown gear integral with the drum being engaged by a sturdy mechanical tooth.

The clutch must also be operated by a dead man's switch, to ensure it is engaged only when the operator exercises "active" pressure. When the pressure or the operator are absent, the clutch is automatically released and the winch ceases to perform the "pull".

Further mandatory features are a device designed to protect the transmission from overloads, the presence of control levers marked differently according to their function, the now obvious segregation of the moving mechanical parts, the protection of the logging mouth, and the presence of a sturdy grill in the top part of the shield to protect the driver's seat.

 

With wheels or without. Although the majority of forestry winches do not have wheels, some models are equipped with them. This constructive solution certainly penalizes any indirect pulling, although it becomes quite beneficial when it comes to carrying out the direct pulling. In this case, once the trunks have been brought into contact with the winch shield, it is possible to use the winch wheels to relieve the tractor from bearing the load of the trunks and make the movements more stable and safer.

 

The drums. A very important feature for forestry winches is the drum capacity; obviously, the higher, the better. However, even for smaller models, the drum should be able to accommodate at least 80-100 metres of 10mm rope.

Another important parameter is the winding speed, which generally ranges from 0.5-1.5 m/s. For obvious reasons, the more the speed can be modulated, the better, and from this point of view, although the models with hydraulic transmission are unbeatable, even the mechanical ones sometimes offer two or more different gear ratios. In any case, the modulation of the rotation speed of the tractor engine, and consequently that of the power take-off, offers a further possibility of modulating the cable winding speed.