A thesis submitted for partial fulfillment of the requirement for the degree of Master of Engineering

Thesis (M.Eng.) - Asian Institute of Technology, 1995

Power tiller with disk plow are commonly used in Thailand for cultivation of wet rice fields. All these designs of the disk plow are locally made and not scientifically tested but copied from the foreign designs. Therefore, a performance evaluation of a commonly used power tiller drawn disk plow was conducted in Bangkok clay soil. The field tests were conducted with an original disk spacing of 365 mm and with an enlarged disk spacing of 485 mm. The experiments were conducted in flooded as well as saturated soils. The depth of cut was maintained constant at 9 cm. The working speeds were 1.8 and 3.5 km/h in flooded and saturated soils. The tilt angle was varied from 15 to 20 and 25 degrees. The disk angle was varied from 40 to 45 and 50 degrees. The draft and vertical forces were measured with the help of an octagonal ring transducer. A minimum draft of 1603 N was recorded at 15 degree tilt angle and 45 degree disk angle with an original disk spacing in flooded soil condition. The vertical force during this test was 53 N, specific draft was 3.7 N/cm2 and slip was 29.7 %. With enlarged disk spacing at the flooded soil test condition, the draft was 1707 N, vertical force was 59 N, specific draft was 3.9 N/cm2 with 32.2 % slip. In saturated soil condition, field capacity of the disk plow with an original design was 0.2 ha/h, field efficiency was 71.2 %, soil inversion was 87 % and fuel consumption was 4.41 I/ha. With enlarged disk spacing the field capacity was 0.23 ha/h, field efficiency was 7 6.3 % , soil inversion was 87 % and fuel consumption was 4 .1 I/ha. Both tests were conducted at 15 degrees disk angle. The enlarged disk spacing could result in 8 % more area coverage and reduce fuel consumption. Some modifications for the improvement of the disk plow design are suggested.