Sahapat Chalachai creator Soni, Peeyush Chairperson Manukid Parnichkun Examination Committee Huynh, Trung Luong Examination Committee Rajamangala University of Technology Tawan-ok, Thailand Scholarship Donor text series theses th Pathum Thani, Thailand Asian Institute of Technology 2017 continuing eng 188 p. : ill.+ 1 online resource Presently, Thailand is the fourth largest producer of cassava in the world. Due to industrialization in Thailand, there is a shortage of labor for cassava cultivation. Cassava harvesting is time and labor consuming. At the moment, there is no mechanical cassava harvester available for Thai field conditions. Therefore, the main objective of this research was to design and develop a cassava harvester. Two of the most preferred cassava varieties in Thailand, Rayong-81 and Huay-Bong were selected to study their physic-mechanical properties for use in design. The dimensions of stem were: 10 to 34 mm for diameter, 0 to 260 mm for bend, and 430 to 1,500 mm for height. The moisture content ranged between 60.0 and 62.1% (w.b.). The dimensions of root were: 10 to 34 mm for diameter of rhizome, 2 to 18 roots for number of root in one stem. The lengths across the root varied from 230 to 900 mm and root depths varied from 80 to 310 mm. The stem cutting and chopping unit, digging unit and conveyer unit were fabricated separately. The highest cutting quality was associated with 100 teeth circular saw and with a minimum cutting shaft speed of 400 rpm. The highest quality for chopping unit was found at knife bevel angle at 30 degree and chopping shaft speed more than 1000 rpm. The best type for digging unit was curve shear blade type with gears low-3. For the working width of 0.80 m and the depth of digging of 0.30 m, the fuel consumption was 27.08 L/ha. The capacity was 0.20 ha/h with 95.40% digging efficiency. The cassava losses in the soil were around 6.74%. Plastic conveyer was best suited to use in the machine. A flow rate control valve was used to adjust the speed and a hand valve to control the system. Experimental values were used to decide the size and design the components of the cassava harvester. Based on the experimental results, a prototype single-row cassava harvester was designed and fabricated. The machine consisted of a main frame, a cutting and chopping unit, a digging unit, a conveyer unit and hydraulic system. The cutting and chopping unit was installed in front of tractor and the other units were mounted on three point hitch linkage. A 57.4 kW tractor was used as the power source. The hydraulic pump was driven by the tractor P.T.O. The prototype harvester was further modified to increase performance and harvesting quality. For field performance evaluation, three traveling speeds of 1.7, 2.0 and 2.4 km/h were used. The field capacity and field efficiency varied from 0.11 to 0.16 ha/h and 63.2 to 67.2% respectively. The maximum draft requirement of the machine was 1.55 kN/row. Fuel consumption at the tested speeds was between 19.9 to 24.2 L/ha. The results revealed proper (acceptable) harvesting between 67.7 and 72.5%, improper cutting 0%, improper chopping between 5.3 and 7.4%, loss in digging 2.0 to 2.8 %, and loss in conveying between 11.7 to 12.9%. The re-germination was 7.5 %. Economic analysis was conducted. At present, manual harvesting cost in Thailand is 181 USD/ha. Assuming harvester service life of 6 years, the designed machine with rented tractor had the break-even area of 37.1 ha/year when the harvester operated at 2.4 km/h. For a one year payback period, the harvesting areas required are 177.45, 141.75 and 129.85 ha/year for a harvester speed of 1.7, 2.0 and 2.4 km/h respectively. The performance test and cost analysis indicated that the machine can be used economically, as well as efficiently, suitable for Thai farmers. A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering in Agricultural Systems and Engineering Thesis (Ph.D.) - Asian Institute of Technology, 2017 Cassava Thailand Crops Postharvest technology Thailand Cassava machinery Asian Institute of Technology. http://203.159.5.9/ait-thesis/detail.php?q=B21682 http://203.159.5.9/ait-thesis/detail.php?q=B21682 190813 20260818090554.0