Tractor hydraulic system

One of the characteristics that must be observed by producers when purchasing a tractor is the hydraulic system, as depending on the activity the machine will perform, this characteristic is as important as the engine power and the type of transmission.

Agricultural tractors, since the creation of the first examples, are selected and/or compared at the time of acquisition mainly or only by motor power. It is clear that this intention, when purchasing, is not completely correct. Furthermore, the power must always be available and accompanied by several other technical characteristics that, when combined, provide more adequate operation, to generate a better cost-benefit for the farmer.

Therefore, the factors that contribute to the success of the activity with the tractor are the selection and correct use, where the appropriate choice results from the adjustment during production planning on the property, thus obtaining maximum operational efficiency and effective work capacity, reducing costs.

When researching and choosing a tractor, the availability of information is essential, as it makes it possible to compare models. Despite this, the technical data available regarding agricultural machinery is insufficient and heterogeneous between manufacturers and even between models from the same company, both in quantitative and qualitative form, due to the non-mandatory nature of official tests in Brazil. In this sense, the presentation of data is at the discretion of the manufacturer, who sometimes only demonstrates the advantageous characteristics of the tractor in their technical catalogs, ignoring others that could provide disadvantages to some groups of farmers. Therefore, the choice of which characteristics to consider should be the responsibility of those who wish to purchase the machine and not those who sell it.

Furthermore, farmers already face difficulties in choosing an appropriate model, depending on their own needs, the specific characteristics of their property and especially when associated with the heterogeneity between catalogs and, in some cases, the lack of clear and objective information. Likewise, the diversity of machines available on the national market makes the selection even more complex and difficult to solve.

For all the reasons mentioned above, rural producers normally choose a tractor based solely on issues related to identification with the brand and engine characteristics. However, other characteristics are of equal or greater importance, such as the dimensions of the machine and its adjustments (gauge, for example), tire size, mass and possible ballasting, type of transmission, onboard technology, turning radius, presence or absence of front-wheel drive. auxiliary (TDA), hydraulic system capacity, among others. The latter, despite the increasing use of machines coupled to the drawbar, which from this point onwards obtains the necessary traction, still has a relevant significance in the agricultural activities carried out, regardless of the size of the property. In medium and small businesses, this feature becomes indispensable, being constantly used depending on the conditions imposed by the daily activities carried out and the presence of small implements, which are generally mounted at the three points, such as centrifugal distributors, mounted sprayers, leveling grids , subsoilers, plows, among others.

The hydraulic system is responsible for controlling the relative position of the mounted implements in relation to the ground, where this action is carried out by a mechanical connection system between the implement and the tractor (two lower arms and the third point), and the force required, To lower or raise it, it is transmitted through the flow of hydraulic oil under pressure. Furthermore, it establishes a coupling plan between the tractor and the equipment. This is equivalent to saying that there are no relative movements between both parts other than those controlled by the joints of the coupling system.

Thus, the objective was to verify the lifting capacity, motor power, flow rate and maximum pressure of the pump to highlight the technical differences between brands and models of tractors available on the national market in order to encourage the farmer to carry out a more careful check. when choosing a model.

The following figures illustrate the differences in the relationships between different characteristics for different brands.

Not to mention the brands, since our intention is not to indicate the best or the worst, these were indicated as A, B, C, D, E, F, G and H. In case of lack of information available in the catalogues, it occurs a discontinuity in the line referring to the missing data, since each point on the line represents a model of the brand. Furthermore, these are arranged in increasing order of power, from right to left.

It was found that brands A and C obtained the most balanced relationships between the characteristics addressed, that is, as they increased motor power, they also increased other characteristics.

In brands B and E, a wide difference was observed between the lifting capacity in relation to the other characteristics, noting that the manufacturers opted for a high lifting capacity of their tractors as an advantageous characteristic. In this case, they are preferable machines for the farmer who mainly needs to attach heavier mounted implements that do not require high motor power, such as winches, for example.

Observing the brands F, G and H which, despite having a more balanced relationship between characteristics, are tractors with low power and reduced lifting capacity. However, they are machines intended mainly for small properties and special operations, such as fruit and horticulture, where the requirements are lighter.

It was also verified that the pump's maximum flow characteristics and lifting capacity are similar between models within the same motor power range. This can be seen better in high power tractors, where this presents a variation greater than 100kW (135,96hp), but the pump's maximum flow characteristics and lifting capacity are the same.

The great heterogeneity of agricultural tractors sold in Brazil is beneficial for farmers, given the great demands and existing needs that it aims to meet. However, a more careful assessment by farmers is necessary at the time of acquisition, as the machine must meet the needs of the most different activities that they will perform without this resulting in an unnecessary immobilization of resources.

It is important to highlight that in this work only the characteristics of the models' hydraulic system were evaluated, a component that, therefore, should not be the only criterion evaluated by the producer at the time of purchase and, in cases where it is unnecessary, discarded.

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To carry out this work, catalogs of eight brands were analyzed, totaling 132 tractors. Data on motor power, lifting capacity, flow and maximum power of the hydraulic pump were acquired. The motor power ranged from 10,8kW (14,70hp) to 492kW (670hp), the lifting capacity ranged from 440kgf to 12.000kgf, the maximum pump flow was from 17L/m to 148L/m and the maximum pump pressure was also obtained a variation of 120kgf/cm³ at 220kgf/cm³. It is important to highlight that the data refer to standard characteristics (standard) of tractors.

André Augusto Veit, Tiago Rodrigo Francetto, Airton dos Santos Alonço, Rafael Sobroza Becker, Mateus Potrich Bellé, Laserg/UFSM

Article published in issue 150 of Cultivar Máquinas.