DEVELOPMENT AND ERGONOMIC EVALUATION OF A SPADING MACHINE AS AN ATTACHMENT TO POWER TILLER

Abstract

Tillage is the physical manipulation of soil with tools and equipment to achieve good tilth for enhanced seed generation and subsequent crop growth. A spading machine works as an alternative to the plough for primary tillage. There are limitations in manual spading and tractor operated spading in small and marginal fields. Manual spading needs more labour, takes longer time, more energy and high cost per cultivable area. The depth of cut is also low while using a manual spade. Tractor operated spading machines have their own set of limitations in small fields, and their cost was also out of reach for small and marginal farmers. These factors lead to the development of a spading machine as an attachment to power tiller. A power tiller (6.7 kW) was selected as a prime mover for the spading machine. The developed spading machine consists of gear box, power transmission system, frame, crank shaft, connecting rod, spade and depth gauge wheel. A laboratory model of spading machine was fabricated and tested to finalize the optimum machine parameters for the development of new spading machine. The actual field capacity of power tiller operated spading machine was 0.1132 ha h-1 which is higher than the traditional method (0.008 ha h-1 ). Overall, the maximum field efficiency 87 per cent was achieved at the forward speed of 2.1 km h1 , when the depth of cut was 10 cm at 30° spade angle and 200 rpm crankshaft speed. It was observed that the actual field capacity and field efficiency of spading machine increased with increase in forward speed and was higher with trapezoidal shape blade than triangular blade since it covers more area per unit time. The maximum clod mean weight diameter of 15 mm was recorded at a forward speed of 1.5 km h−1 with crankshaft speed 100 rpm. The minimum draft requirement and fuel consumption of spading machine were 820 N and 0.87 l h-1 recorded at a forward speed of 1.5 km h−1 with 10 cm depth of cut. The minimum heart rate of 95 beats min-1 was recorded at 1.5 km h-1 forward speed of power tiller and the maximum heart rate 125 beats min-1 was observed at 2.1 km h-1 forward speed of the power tiller. A significant variation in energy expenditure of spading operation was noticed at 5 per cent level with different forward speeds. 162 Minimum energy expenditure rate of 12.26 kJ min-1 was obtained at 1.5 km h-1 forward speed of the power tiller and the maximum energy expenditure rate 21.82 kJ min-1 was noted at 2.1 km h-1 forward speed respectively. The grade of work was “moderately heavy” for power tiller operated spading machine and ‘heavy” for traditional method. Maximum aerobic capacity of subjects varied from 1.75 to 2.08 l min-1 . The mean values of AWL (VO2 Max) for all subjects varied from 40 to 47 per cent indicated that the spading machine could not be operated continuously for 8 hours without frequent rest pauses. The overall discomfort rating was 4.6, 5.1 and 5.7 at 1.5, 1.8 and 2.1 km h-1 respectively and it was scaled as “moderate discomfort”. Overall safety rating was scaled as “moderately secure and less fear”. Overall ease of operation rating was scaled as “Less difficulty” with a score of 4, 4.3 and 4.6 at forward speeds of 1.5, 1.8 and 2.1 km h-1 respectively. It was observed that the, body part discomfort score was maximum for 2.1 km h-1 with a score of 43 followed by 1.8 km h-1 with a score of 33 while it was minimum at 1.5 km h-1 with a score of 25. The rest time for achieve functional effectiveness during the operation of power tiller operated spading machine was found to the 10 min followed by one hour of work. The noise level was recorded for different engine speeds, varied from 86 dB at the operator ear level to 102 dB at the engine top. The vibration level was recorded for different engine speeds, varied from 11 m s-2 at right handle to 37.6 m s-2 at engine top. The cost of prototype of power tiller operated spading machine was worked out as Rs. 50,000/-. The cost of operation per hour and hectare was determined as Rs.335/- and Rs. 3,316/- respectively. The breakeven point, payback period and benefit cost ratio of the machine is 93 h year-1 , 3.5 years and 2.1:1 respectively. The saving cost of operation of machine was calculated as Rs. 6,884 ha-1 and 67.5 per cent when compared to conventional method of spading operation.