A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering, School of Environment, Resources and Development

Thesis (Ph.D.) - Asian Institute of Technology, 2000

This study was aimed evaluate and improve the locally made rice combine harvester with a view to optimize power requirement, minimize harvesting losses and to increase field capacity. The study was divided into five steps; i) the performance of locally mad rice combine harvester was evaluated; ii) the power requirements of the machine and its main components were measured under no load and field conditions; iii) the design and fabrication of stripper header was undertaken; iv) the laboratory testing and field performance of the combine with stripper header was evaluated; v) the comparison between locally made rice combine harvester with cutter bar-reel mechanism and stripper mechanism was made. The no load power requirement of the combine with cutter bar header at design speed of 1600 rpm was 44.5 kW at the engine shaft. Threshing unit consumed 16.9 kW (38% of total no load power), while header unit and hydraulic system for traction consumed 3.6 kW and 15.5 kW, respectively. The power transmission loss was estimated to be 8.5 kW (19% of total no load power). The average power requirement for the whole machine during field operation at 1,600 rpm was 65 kW. The traction, threshing and header units consumed 22.8, 34 and 5.7 kW, respectively and the power transmission loss was 2.5 kW (4% of total operating power). The average field capacity of the 3.0 m wide cutter bar harvester was 0.49 ha/h in the standing crop condition and corresponding field efficiency was 81%. However, for lodged crop the average field capacity was 0.29 ha/h and corresponding field efficiency was 85%. The average working speeds of the cutter bar harvester in the standing and lodged crop conditions were 3.4 and 2.1 km/h, respectively. The total grain loss of the machine were 3.0% in the lodged crop condition and 2.8% in the standing crop condition. The no load testing of the combine with stripper header showed that the power requirement of the machine at design speed of 1,600 rpm was 42.9 kW at the engine shaft. Due to the improvement of belt drive system, threshing unit consumed only 9.0 kW (21% of total no load power). The stripper header unit and hydraulic system for traction consumed 15.5 kW (36% of total no load power) each. The power transmission loss was 2.9 kW (7% of total no load power). The average power requirement for the whole machine during field operation at 1,600 rpm was 58.1 kW. The threshing, traction and stripper header units consumed 11.4, 22.8 and 16.9 kW, respectively and the power transmission loss was about 70 kW (12% of total operating power). Performance evaluate of the 3.0 m wide stripper header indicated that the overall effective field capacity in standing crop was 0.66 ha/h compared to 0.49 ha/h for the cutter bar header. The overall field efficiency of the stripper header combine was 77% in the standing crop condition and the corresponding figure for the cutter bar header combine was 81%. In a lodged crop condition, the overall effective field capacity of the stripper header combine and the cutter bar header combine was found to be 0.3 and 0.29 ha/h, respectively. The overall field efficiency of the stripper header combine was 75% in the lodged crop condition and the corresponding figure for the cuter bar header combine was 85%. The average working speeds of the stripper header combine during field operation in the standing and lodged crop conditions were 5.5 and 2.5 km/h, respectively. The total grain loss of the combine with stripper header was 4.3% of grain yield in the standing crop condition and 5.6% in the lodged crop condition. The average fuel consumption of the stripper header combine was 16.1 liter/ha in the standing crop condition and 17.7 liter/ha in the lodged crop condition. Based on the average field capacities of the combines with cutter bar and with stripper header as 0.49 and 0.66 ha/h, respectively, the total cost of using the cutter bar header was calculated as Baht 2,151/ha whereas for the stripper header it was Baht 1,639/ha, about Baht 512/ha lower than the cost of cutter bar header. Considering the present rate of manual harvesting as Baht 3,860/ha, the break-even areas for the combine with stripper and cutter bar header were found to be 70 and 84 ha, respectively. The economic analysis further showed that the pay back period of the stripper header was about two years, if the machine could harvest 1,000 ha/year. Due to a substantial reduction in harvesting cost, the stripper header combine seems to be a good alternative for Thai farmers in future