the main parameters assessment of clod and stone separation from potato crop (inclined belt type) in potato harvester

harvesting practices of potato is one of the most difficult, troublesome and sensitive stages. potatoes enter the machine with huge amounts of clod and stones: in the meantime separation of potato some stone and clod, which are the same size as of that the potatoes, shall be confide red a major problem. many methods of study by investigators are based on physical properties of potato, stone and clod. in the present research with regards to the farm conditions and economic situation of the iranian farmers, the beveled conveyor method is recommended. in this method, primarily a schematic design of the separating section of the stones and clod and the crop was produced and important parameters such as the surface angle, conveyor-belt motion speed and type of the conveyor, which play a key role in the separation stage, were studied. the test was carried out on the factorial basis and complete random block, using 3 angles factors in 5 levels (5,10,15.17.5 and 20 degrees) and the speed on 5 levels (100,200,300,400 and 600 rpm) and the belt type with 2 surfaces (soft and rough) repeated 5 times. the  spss software was used to analyze data. the result revealed that the ideal combination of the angle, speed and belt type for acquiring the highest separation rate and the least amount of mix clod, stones of the separated potatoes are the order, and the crop would be the angle 15 degrees, the speed of 300 rpm, with the use of soft belt, and the angle of 17.5 degrees and the speed of 200 rpm is recommended for a rough belt.