Log splitters for firewood production
This equipment is of particular interest in the agricultural field, especially for the models of medium productivity, which can be operated independently through electric or internal combustion engines, or through the tractor's PTO. The most complete versions are equipped with various devices that can make work less tiring and, most of all, more safe
Among the types of biomass intended to produce heat through combustion, wood undoubtedly plays a role of primary importance, particularly in rural areas. Wood chips and pellets are the most popular packaging methods in this regard, but firewood still retains its underlying validity, whether it is actually used for heating or considered for purely aesthetic and recreational purposes (e.g., in the open fireplace).
The most widely adopted size consists of bigger logs obtained from logs properly sectioned by log splitters. This equipment is available in different types and many models, from hobbyist ones for small productions to professional industrial ones. The farming sector is ideal for this kind of production. The agricultural field is well suited to this production: for this purpose, medium-productivity log splitters are suitable, driven by different sources of power (including tractors), which can be equipped with many accessories to make the work less tiring and above all safer.
Different typologies
The operating principle is quite simple and consists of a progressive sawing of the log of wood through the penetration of a strong wedge of varying inclination along the direction of its fibers. This is due to the thrust usually exerted by a hydraulic cylinder against an antagonistic element, i.e., the supporting plate of the log. Medium-productivity models can be vertical or horizontal and can work with two different logics of movement of the mobile element. The latter can be either the wedge that penetrates (the prevalent solution in vertical models) or the plate that pushes the log towards the splitting device (the preferred method in horizontal models). Also available are properly equipped models that can work both horizontally and vertically.
Power sources
The pump that pressurizes (even up to 350 bar) the oil necessary to operate the hydraulic cylinder can be operated differently. By means of an electric motor (alternating current, either 220 or 380 V, depending on the power required), an endothermic engine (often petrol), or even through the tractor's PTO, directly splined to its terminal tang or connected by a cardan shaft. And combined with the tractor, the supporting structure of the log splitter can be equipped with a triangular frame for coupling to the rear 3-point hitch. If powered by an autonomous engine, the log splitter is equipped with suitable devices to ensure stable support on the ground. Wheeled versions are also available, sometimes even approved for use on public roads. Power demand clearly varies according to the performance characteristics of the log splitter, particularly the amount of thrust, but also in relation to the diameter of the log to be split. For medium-sized models, indicatively, the power ranges from 2-3 Hp for 6-8 t of thrust and logs Ø max 40 cm for coupling with the electric motor, up to about 20 Hp for 30 t of force and sections Ø max 100 cm for operation through the tractor's PTO.
Wood splitter organs
The log is split by progressive insertion of the splitter in the sense of the fibers. It is made of a massive wedge with a substantially triangular cross-section in thick, shaped and welded plates. The basic variant is the wedge's insertion angle, which can vary roughly between 6 and 30°, and the possible addition of strong side wings to make a cross to increase splitting efficiency. Still, in the field of splitters, an alternative to the wedge is the threaded conical screw. It can be used to split the log not only lengthwise (i.e., in the direction of the wood fibers) but also and above all crosswise. The narrow cone shape of the screw opens the log by rotating inside it, resulting in cracking that splits it. In this case, the power source is not used so much in terms of thrust force but rather as a driving torque. To this end, this type of log splitter is well suited for coupling with the tractor through its PTO and a cardan shaft.
Operating modes
The actual splitting operation takes place after placing the log on the support base and positioning the wedge in contact with the piece to be split. Then a powerful thrust is exerted that splits the piece. An interesting device on this subject is the "Stop & go" device developed by Thor from Ricca di Busca (CN). After centering the log on the contrasting base with the foot control, the wedge is approached with an electric power that leaves one hand free to hold the piece in the desired position. The blade exerts pressure corresponding to an initial load of 8 kg to keep the part still. At this point, the splitting phase can begin with the dual control with maintained action, which must obligatorily engage both hands for safety. If, on the other hand, the log is not conveniently inserted, it is possible to make a 30 kg heavier load, again electrically exerting on the wedge. If the logs are huge and therefore weigh several dozen kilograms, the preparatory actions to the splitting phase can be facilitated by some helpful equipment. These are designed to reduce or even eliminate the operator's physical load to the advantage of the operator's safety in handling the piece and, at the same time, ensure a high level of attention even for long periods of work. The phase of picking up and moving the log (e.g., taken from a heap or a pile) can be automated by having a grapple combined with a winch "log puller", also radio-controlled. In combination, they forcefully grasp, drag and lift the piece so that it can then be placed in position.
On the other hand, if the log has already been placed in a lateral position adjacent to the log splitter, the lifting and positioning phase can be carried out through specific structures suitably shaped and moved using a dedicated hydraulic cylinder.
Safety
Although it may seem like a simple and easy-to-use piece of equipment at first glance, working with a log splitter involves several causes of risk. For this reason, and above all, because it is a piece of equipment often used on a hobby level, the machine must be equipped with a series of devices and mechanisms designed for this purpose. The operator must also be equipped with appropriate personal protective equipment.
First, the thrust for splitting logs must be exerted by controls that engage both hands with maintained action, which must be protected from any unintended operation. In addition, they must be positioned not to expose the operator to risks of crushing and entrapment, and it must be impossible to operate both controls simultaneously with one hand, arm or other parts of the body. When splitting, the log must remain in position with independent holding devices without operator intervention. The same protection (or another specific one) must prevent the log's sectioned pieces from hitting the operator when falling. If electrically operated, and even more so with a three-phase 380 V current, it is recommended to install a portable device with a maximum residual current of 30 mA (the so-called "lifesaver"), should the electrical system to which the machine is connected not already be equipped with one. In order to avoid dangerous sudden disconnections, especially on versions coupled to the 3-point hitch of the tractor, all pins must be equipped with the relative safety pins connected to the respective pins with chains or rubber or plastic cables. If the tractor's PTO is connected to the log splitter's pump through a PTO shaft, the PTO shaft guard, combined with counter caps or shields placed on the sides of the tractor and equipment, must be able to segregate the rotating elements, preventing accidental contact altogether. Hydraulic system piping must be protected against accidental bursts, which could project very high-pressure, high-temperature fluid at the operator.
Particularly for vertical models, it is crucial to maintain adequate equipment stability during all phases of work. This is ensured by appropriate support means, such as support feet, stabilizers, and wedges for wheeled models.
Finally, the warning pictograms applied directly on the machine are of great importance, especially to make the operator aware of the so-called "residual risks" and remind him of the necessary use of individual protection devices. In this case, in addition to gloves of suitable thickness and strength, it is required to wear protective goggles (against flying splinters), accident-prevention footwear with a steel toe cap (to protect the feet in the event of falling logs or sectioned pieces) and earmuffs or earplugs to limit perceived noise levels, especially in the case of operation with an independent combustion engine. It is also recommended to wear a helmet and a suit of suitable consistency.
Firewood: few thoughts
The Italian forestry heritage covers 11 million hectares, namely 36% of the national surface. However, the annual wood biomass growth collection rate varies between 18 and 37%, much lower than the 62% European average.
Unlike other fossil fuels (coal, diesel, gas), firewood is neutral in the production of CO2 because the one emitted with the combustion is the same absorbed in growth with photosynthesis. It is a renewable energy source (because it comes from trees and shrubs that exploit solar energy), biological (because it comes from living organisms), and readily available (because wood can be produced virtually anywhere).
However, its combustion must be carried out with particular care; in fact, the contribution of wood burned in the home plays an essential role in the emission of particulate matter. For example, in Lombardy, the most recent data show that 39% of PM10 emissions derive from the domestic heating sector and that good part of these come from the combustion of wood in small systems, i.e., open fireplaces, characterized by low energy yields and traditional stoves which are often obsolete and inefficient.
Modern heating fireplaces and the most advanced heating stoves are much better in this respect. However, even the emissions of the best wood-burning systems are still higher than the average levels of natural gas appliances.
Therefore, it is fundamental always to assure the proper operation and practice one scrupulous, careful maintenance. Wood must also be in particular conditions. Contrary to what may be supposed, its humidity has a heavy impact on emissions of particulate matter: By reducing the moisture content of the material from 30 to 20%, combustion emissions drop from about 1150 to just 69 mg/m3, while the effective heating value increases by 17%.
