The work is presented in three parts. The first one presents the use of the mechanization in Germany. In this case the form is presented in which is carried out the soil preparation; planting and it ...harvests using a great variety equipment (tractors and agricultural machine). In the second part the use of the mechanization is exposed in the Cuban case; emphasizing in the importance of introducing in Cuba some of these technologies of wide use in the developed world. The third part it carries out a discussion of the advantages and limitations that could be kept in mind to achieve a perroductive mechanization and a high quality, which could report an increase in the production and quality of the obtained products.. Keywords: Mechanization, Germany, Cuba. El trabajo se presenta en tres partes. La primera presenta la utilizacion de la mecanizacion en Alemania. En este caso se presenta la forma en la cual se realiza la preparacion de suelo; siembra y cosecha utilizando una gran variedad de equipamiento (tractores y maquinas agricolas). En la segunda parte se expone la utilizacion de la mecanizacion en el caso cubano; enfatizando en la importancia de introducir en Cuba alguna de estas tecnologias de amplia utilizacion en el mundo desarrollado. La tercera parte se realiza una discusion de las ventajas y limitaciones que pudieran tenerse en cuenta para lograr una mecanizacion productiva y de alta calidad, la cual pudiera reportar un aumento en la produccion y calidad de los productos obtenidos. Palabras clave: Mecanizacion, Alemania, Cuba.
The work is presented in three parts. The first one presents the use of the mechanization in Germany. In this case the form is presented in which is carried out the soil preparation; planting and it ...harvests using a great variety equipment (tractors and agricultural machine). In the second part the use of the mechanization is exposed in the Cuban case; emphasizing in the importance of introducing in Cuba some of these technologies of wide use in the developed world. The third part it carries out a discussion of the advantages and limitations that could be kept in mind to achieve a perroductive mechanization and a high quality, which could report an increase in the production and quality of the obtained products..
A comprehensive indirect method is proposed in this study to estimate the dynamic characteristics of the fundamental mode and evaluate the element stiffness of a girder bridge using a passing tractor ...with two identical trailers. The novelty of this study is the use of the dynamic interaction between the two identical trailers and the bridge rather than that between the truck and the bridge. One of the advantages of this is that the dynamic characteristics of trailers are easier to model and analyse. Under the proposed method, the residual acceleration of the two trailers is first used to eliminate the adverse effects of road surface roughness. The fundamental natural frequency of the bridge is obtained from the Fourier transform of the resulting signal. Next, the component corresponding to this fundamental frequency was extracted using bandpass filtering. The corresponding damping ratio and mode shape can be reconstructed through a short-time Fourier transform (STFT) under the assumption that the fundamental mode shape amplitude peak is located at the midspan. Finally, the element stiffness of the bridge was evaluated using the reconstructed fundamental mode shape. In this study, the proposed method is investigated via numerical examples and performs well in different scenarios, for example, in the presence of high-level measurement noise and low-level road surface roughness. Furthermore, the method was validated through field testing on the Li-Zi-Wan bridge in Chongqing. The extracted fundamental mode shape agrees well with that obtained using the stochastic subspace identification (SSI) method. The evaluated element stiffness matches very well with both the original design and the static deflection test results.
In this work, the objective is to design an implement to collect the plastic used in strawberry mulch, cutting it at the ground level on each side of the agricultural bed on which the strawberry is ...planted, and winding it on a shaft that rotates so proportional to the advance of the tractor, driven by a chain power transmission system that relates the movement of the implement tires and the winding of plastic film. As a result, the design of an implement is obtained that works at a proposed speed of 7 km h.sup.-1 and that collects the plastic, cutting the soil of the agricultural bed 10 cm on each side, in order to ensure that it cuts the plastic of the mulch. It has a width of 1.3 m and a load capacity of 646 kg of plastic that can be kept in the collection shaft before having to deposit it in a warehouse.
In this work, the objective is to design an implement to collect the plastic used in strawberry mulch, cutting it at the ground level on each side of the agricultural bed on which the strawberry is ...planted, and winding it on a shaft that rotates so proportional to the advance of the tractor, driven by a chain power transmission system that relates the movement of the implement tires and the winding of plastic film. As a result, the design of an implement is obtained that works at a proposed speed of 7 km h.sup.-1 and that collects the plastic, cutting the soil of the agricultural bed 10 cm on each side, in order to ensure that it cuts the plastic of the mulch. It has a width of 1.3 m and a load capacity of 646 kg of plastic that can be kept in the collection shaft before having to deposit it in a warehouse. Keywords: Mulching, Agricultural Bed, Chain Drive, Shafts. En este trabajo el objetivo consiste en diseñar un implemento para recolectar el plástico utilizado en acolchados de fresa, cortándolo a ras de suelo por cada lado de la cama agrícola sobre la cual se siembra la fresa, y lo enrolla en un eje que gira de manera proporcional al avance del tractor, accionado por un sistema de transmisión de potencia de cadena que relaciona el movimiento de los neumáticos del implemento y el enrollado de película plástica. Como resultado se obtiene el diseño de un implemento que trabaja a una velocidad propuesta de 7 kmh.sup.-1 y que recolecta el plástico, cortando el suelo de la cama agrícola 10 cm por cada costado, para poder asegurar que corta el plástico del acolchado, tiene un ancho de 1.3 m y una capacidad de carga de 646 kg de plástico que pueden ser mantenidos en el eje de recolección antes de tener que depositarlo en un almacén. Palabras clave: películas plásticas, camas agrícolas, transmisión por cadena, ejes.
Winches are machines that are widely used in a wide variety of industrial and agricultural tasks, such as cement, metallurgical and mineral works, as well as in vehicles and tractors, specifically ...those with high capacity of passing or of traffic. Within their structure there are elements of force transmission and power (axles and sprocket wheels) that could fail due to superficial fatigue and pitting caused by the work. For these reasons, the objective of the present work was to determine the parameters to redesign the structural elements of a winch for load traction, since the chain transmission was affected by the wear phenomenon in the sprocket, keyway and setscrew. That caused strong vibrations that affected the fixings of the reducer in its chassis, as well as in the bearings. The replacement of the chain transmission by a speed reducer directly coupled to the motor is proposed, in addition to increasing the diameter of the drums that tighten the cable. For this, calculations were made for the new gear ratio. Among the results, the transmission ratio to the exit of the reducer stands out, as well as its efficiency 0.87.
Winches are machines that are widely used in a wide variety of industrial and agricultural tasks, such as cement, metallurgical and mineral works, as well as in vehicles and tractors, specifically ...those with high capacity of passing or of traffic. Within their structure there are elements of force transmission and power (axles and sprocket wheels) that could fail due to superficial fatigue and pitting caused by the work. For these reasons, the objective of the present work was to determine the parameters to redesign the structural elements of a winch for load traction, since the chain transmission was affected by the wear phenomenon in the sprocket, keyway and setscrew. That caused strong vibrations that affected the fixings of the reducer in its chassis, as well as in the bearings. The replacement of the chain transmission by a speed reducer directly coupled to the motor is proposed, in addition to increasing the diameter of the drums that tighten the cable. For this, calculations were made for the new gear ratio. Among the results, the transmission ratio to the exit of the reducer stands out, as well as its efficiency 0.87. Keywords: torque, gear reducer, reverse engineering, static analysis. Los malacates son máquinas que presentan una utilización muy extendida a una gran variedad de labores industriales y agrícolas, tales como la cementera, metalúrgicas y mineralúrgica, así como en vehículos y tractores, específicamente en los de gran capacidad de paso o traficabilidad. Dentro de sus elementos estructurales se encuentra elementos de transmisión de fuerza y potencia (árboles y ruedas dentadas). En los cuales producto del trabajo puede aparecer la fatiga superficial y picadura, como causa de falla en los elementos de trasmisión de fuerza y potencia de estas máquinas herramientas. Por estas razones se realizó el presente trabajo que tuvo como objetivo la determinación de los parámetros para el rediseño de los elementos estructurales de un malacate para la tracción de carga, debido a que la transmisión por cadena que presenta se vio afectada por el fenómeno del desgaste en la catarina, chavetero y prisionero. Provocando fuertes vibraciones que afectaron las fijaciones del reductor en su chasis, así como en las chumaceras. Se plantea la sustitución de la transmisión por cadena por un reductor de velocidad acoplado directamente al motor, además de aumentar el diámetro de las tamboras que tensan el cable. Para ello se realizaron los cálculos para la nueva relación de transmisión por engranajes. Dentro de los resultados destacan, la relación de transmisión a la salida del reductor, así como la eficiencia del mismo 0,87. Palabras clave: momento torsor, reductor de engranajes, ingeniería inversa, análisis estático.
Abstract
We address the problem of the stable reverse driving of a vehicle with multiple trailers. By itself, the reverse driving of a multiple trailer vehicle is highly unstable, so a proper ...steering control is needed. First, the straight reverse driving is analysed and a stable solution to the problem is explicitly calculated. The solution depends on the specific geometry of the vehicle, namely on the lengths of the tractor and the trailers, and on the set of parameters that determine the rate of convergence of the reverse driving towards the straight reverse driving. We describe two different approaches towards the derivation of the solution of the stable reverse driving. We show that the solution to the problem is uniquely determined and finally we show that the proposed solution can be easily applied to the reverse driving of the tractor along an arbitrary, gently curved, path.
As it is known, the modern agricultural tractor is no longer just a machine capable to pull agricultural trailers and to operate implements but has evolved into a multi-purpose and mobile energy ...source with standardized interfaces (mechanical, hydraulic and electronic) to connect to a several typologies of agricultural operating machines. It follows that the selection of the most appropriate tractors for the specific production realities is a crucial aspect for farmers, advisors, contractors and farm machinery experts. The tractors choice thus must consider different parameters, concerning not only the cost of the machines but also their dimensions, power, weight, technological level, etc. The availability of simplified models for estimating the purchase investment and sizing the machine in relation to its mechanical characteristics could be a useful tool in the choice of the tractor more suitable for the specific agricultural context. The aim of this study was to collect and to analyse the technical parameters of tractors present on the Italian market (more than 1300 models), divided into: i) four wheel-drive (4WD) standard tractors, ii) two wheel-drive (2WD) standard tractors, iii) narrow track 4WD tractors, iv) Isodiametric specialized 4WD tractors, v) crawler tractors and vi) rubber-tracked tractors), in order to define the most relevant parameter-to-parameter and parameter-to-price relations for updating reference models to calculate the machine price and the weight to engine power ratio. Other relations, including the three-point hitch efficiency with respect to tractor’s weight and the relationship between the rated engine power and its displacement, are proposed in order to provide synthetic tools to characterise and to compare - from the mechanical point of view - the different categories of agricultural tractors.
