Design and fabrication of a wheel operated chemical sprayer for legumes and vegetables

Abstract

Spraying is one of the agricultural practices that are needed to ensure optimum crop growth and increase in the yields. A sprayer is a mechanical device used to spray the liquid chemicals like herbicides, pesticides, fungicides and fertilizers to the crops in order to control pests and diseases thereby maximizing the yield levels. Sprayers are of many different kinds which include backpack sprayers, motorized sprayers, tractor drawn sprayers etc. The most commonly used type of sprayers by the Ugandan farmers are the backpack sprayers due to their initial operating costs. The main drawback with these sprayers is that they cannot be used for long working hours because they cause human drudgery,they have low application pressures hence time consuming during spraying. Motorized sprayers have high pressure but with high investment cost and maintenance cost. Due to the above shortcomings of the commonly used sprayers, there is need for another means which provides output in between the backpack sprayers and the motorized sprayers. This calls for the invention of a wheel operated chemical sprayer. These can have between low to high pressure depending on the capacity of the pump and the rotation of the wheel. These sprayers also have low maintenance costs. For this project, the emphasis was put on the design, fabrication and testing for the performance of a wheel operated chemical sprayer. For the design process, the required tank, piston pump, and nozzles was obtained based on the required output of the chemical. The system consists of the piston pump and a 20 litre tank, the driver and driven sprockets, the crank mechanism, four nozzles, and the integrated horse pipes. The machine is mechanically powered by pushing it forward which changes the rotary motion of the sprockets into the reciprocating motion that is transferred to the piston pump.The system was tested under varying conditions of the soils and energy applied while pushing it. It was observed that the rate of discharge is affected by the strength of the human beings during spraying (pushing) and the walking speed. The cost analysis was carried out using the method of net present value over ten year period with interest rate of 7% and implementation of this project will help in saving costs spent on fuel purchase and reduce the spraying time due to moderate pressure and improve on the yield in ground nuts.