Computer aided analysis of Sit and Stand type coconut climbers for mechanical stability

Abstract

Coconuts are harvested by climbing the palm and cutting the nuts down by hand. Manually climbing up and down the palm is hazardous and tedious. Now a days a few models of mechanical coconut palm climbers are available to overcome these drawbacks. Testing the mechanical strength and stability of the coconut palm climbers is necessary to ensure its safe performance under working condition. Among these types, KAU and Farmer’s models were selected and its three dimensional models were generated in Solidworks 13.0 software. The static and fatigue analysis of these selected models were carried out in the ANSYS 15.0 software. The assembly of each component of the top and bottom frames of the models were created and saved in step file format. The file was then imported to the ANSYS 15.0 software for the static and fatigue analysis. Preprocessing steps such as meshing, selection of material and application of boundary conditions were then carried out sequentially to establish static and fatigue problems. In the KAU model top and bottom frames were steel and aluminium materials, wherein the Farmer’s model top and bottom frame were made of structural steel. The boundary conditions imposed are the application of loads and fixing of supports. Various loads of 400, 500, 600, 700, 800, 900 and 1000 N were applied and under each load the analysis was carried out. In the KAU model, the inner face of the bent tube and V tube and in the Farmer’s model, the rope and curve plate were considered as fixed supports. The static analysis interpreted were the equivalent (Von-Mises) stress, equivalent elastic strain and total deformation while fatigue analysis interpreted the fatigue life and factor of safety. The results showed that as the load increased the Von Mises stress was found increased. Also, there were decreasing trends for the factor of safety and fatigue life. The top frame of KAU models have factor of safety more than three, two and one up to 400, 500 and 1000 N load respectively. The infinite fatigue life cycles were observed up to 800 N. The bottom frame of KAU model have factor of safety more than one up to a load of 1000 N and have infinite fatigue life cycles up to 1000 N load. Hence KAU model is safe to operate up to a load of 1000 N. The top andbottom frames of the Farmer’s model also found out the factor of safety more than one and have infinite fatigue life cycles up to load of 1000 N. Hence Farmer’s model is safe to use up to a load of 1000 N. further changes in material, design or dimensions are suggested to get more factor of safety for loads from 700 to 1000 N for both the selected models. As there is no specified test codes available for manually operated mechanical tree climbers, a draft test code with Minimum Performance Standard (MPS) was also prepared under this study.