Studying the strength of a small-sized loader working equipment

Abstract

Problem. The growth in the volume of construction work carried out in the improvement of adjacent territories, playgrounds, and pedestrian paths requires the use of a wide range of small-sized machines for earthwork and road construction, including loaders. The main requirements for small-sized loaders are small dimensions, which makes it possible to perform work in cramped conditions, good maneuverability, light weight, which allows for low pressure on the surfaces on which the equipment moves, ensuring the safety of loading operations, efficiency and economy. These conditions are fully met by a variety of construction equipment that is combined with self-propelled chassis, which have been manufactured for many years at Ukrainian enterprises and used by organizations for the improvement and beautification of urban space. The indisputable advantage of self-propelled chassis over a large number of short wheelbase loaders, which are also widely used in the public utilities sector, is greater stability due to the large wheelbase and the possibility of using additional outriggers installed on the machine, as well as the availability of a self-unloading platform for transporting goods. The operation of small-sized forklifts based on self-propelled chassis in cramped conditions, along with builders performing installation work, requires increased attention to ensuring the strength of the machine's metal structure, so the issue of studying the load of working equipment is an urgent task. Goal. The aim of the study is to develop scientifically based recommendations for reducing the load of small-sized forklift equipment based on the created design scheme, determining the acting forces and stresses, and rational modes of operation of the forklift. Methodology. The design position in which the handle of the working equipment is located horizontally and the maximum load acts on it is considered. The design load is the maximum weight of the cargo, taking into account the dynamic coefficient. The calculated position for the boom is the position of the greatest bending moment, i.e. the position at maximum reach. The center of gravity of the boom and handle, as well as the weight of the metal structure, were determined using a computer model. The loads acting in the boom joints are determined using a simplified, calculated, boom scheme, for which We will discard the handle, replacing its action with the corresponding reaction and consider the handle separately to determine this load. Given that the force of action from the boom on the handle will be equal in modulo to the force of action from the handle on the boom, and the reactions in the hydraulic cylinder joints will also be equal, we will depict the diagram of the forces acting on the boom. Results. Based on the developed design schemes of the boom and arm, we studied the loading of working equipment, which was carried out using the created program at variable values of the load weight from 4000N to 4500N, the coefficient of dynamism equal to 1, 1.1...1.5, and the height of the arm section from 0.14 to 0.16 m. The analysis of the research results showed that an increase in the coefficient of dynamism to a value of 1.5 at a load weight of 4500N leads to an increase in the acting force to 6840N, but the stresses are within the permissible limits. Increasing the load with which the forklift operates to 5000N requires an increase in the height of the handle section to 0.15m to ensure that the stresses are within the permissible limits. The analysis of the dependence of the acting stresses on the weight of the load and the coefficient of dynamism made it possible to propose recommendations for rational modes of operation of the forklift, which consist of limiting the load to 4500N and the coefficient of dynamism within 1.3-1.4 with a handle cross-sectional height of 0.14m and a wall thickness of 0.05m. It is also proposed to work without jerks, smoothly at low lifting speeds, within the range of the coefficient of dynamism up to 1.3-1.4. Practical meaning. The developed research methodology is proposed for use in the operation of a small-sized forklift in various modes, as well as in the design of working equipment for forklifts of a similar class and design.