Experimental Study Of Maize Seed Damage During Operating Of Harvester With Lengthways-horizontal Rollers

Maize is one of the three principal grains and its planting area has reached2.43 million hectares in China. The maize harvesting is a taxing labor and theexpense for maize harvesting occupied 55% of the total labor expense of the maizeproduction. Compared with the wheat harvesting and rice harvesting, themechanization of maize harvesting has been in very low level. There are only 3%in mechanizing harvesting at present. So, to develop mechanizing harvesting formaize is one of important works of agricultural mechanization at present in China.Seed loss of maize during harvesting is one of the main property indexes ofmaize harvester. The serious seed loss of maize during harvesting has become animportant factor restricting the auto-mechanization of maize harvesting in ourcountry. In order to reduce seed loss rate, it is important to study the lossmechanism, reduce the seed loss during harvesting and the optimize configurationparameters of the snapping unit of maize harvester.The tensile property of cornstalk and the ear-corn handle were examined onWDW-10 electron universal testing machine controlled by computer. The resultsshowed that the fracture force of cornstalk ranged from 1000N to 1500N and thefracture force of the ear-corn handle is 350N, which is less than the fracture forceof cornstalk considerably. Therefore, it can be concluded that the fractures ofear-corn handle takes place more easily than the cornstalk. It was also found thatthe fracture force of cornstalk is high when the cornstalk had no maize cob or highmoisture content.The working principle of roller-snapping unit was analyzed theoretically. Thediameter of columned roller was calculated. It was shown that the factors affectingthe damage and loss of maize seeds were the height of the spiral bulge of the rollersbesides the diameter of root circularity of the rollers. The damage and loss of maizeseeds take place due to that the maize cob contacts the spiral bulge and root of theroller alternately. It was found that the length of the gnawed part of maize cob atthe bigger end is about equal to the height of the spiral bulge of the rollers;thealternating contact of the spiral bulge and root of the roller to cornstalk increasedsnatching force of roller to cornstalk.In order to verify the effect of spiral bulge roller on the damage of maize seeds,the integrated design scheme of a testing apparatus for harvester withlengthways-horizontal rollers were determined. Through theoretical calculation, theconfiguration and the parameters of the working parts were established, and atesting equipment was manufactured and assembled according to the designdrawings.The field tests showed that the performance of rollers is influenced mainly bythe type of rollers when the working speed had a little changes. The damage loss ofmaize seeds is relative to the parameters of spiral bulge and pressing-pullingsegment of cornstalk, and therefore the pilling performance of maize cobs can beimproved by increasing the height and width of the spiral bulge. The workingspeed of the roller had a little effect on the damage loss of maize seeds comparedwith the roller type and a increase of working speed resulted in a little increase ofthe damage loss of maize loss. It was also found that the damage loss of maizeseeds was affected, to some extent, by the transportation of maize cobs.The laboratory tests showed that the working speed of the snapping rollers ismainly factor affecting the damage loss of maize seeds. The damage loss was littlewhen the working speed is lower than 700r/min. The damage loss was increasedconsiderably when the working speed of the rollers was higher than 700r/min. Thedamage loss was least when the working speed was 500 r/min. The form of thesnapping rollers, inclining angle of the rollers, and the vertical interval betweenaxes of the two rollers had less obvious effects on the damage loss of maize seedsCompared with the working speed. It was demonstrated that the rollers designed inthis work had less damage action against maize cob.It was found that the damage loss of maize cob was mainly due to impactingof maize cob against the snapping rollers. To reduce the contacting time of maizecob with the rollers and decrease the chances of the collision, and as a result, thedamage loss of maize seeds can be decreased. To increase the height of the spiralbulge, to increase snatching force to stem, to avoid the slipping of picked maizecob and cornstalk, and to change the transportation route of picked maize cob canreduce the contacting time and fatherly reduce the collision of maize cob againstrollers.The moisture content of maize seed and the peeling ratio of the bract of themaize cob also affect the damage of maize seed. The magnitude of damage lossdecreases with the moisture content of the maize seed when it is in between24.1%wt and 28.2%wt. The bract has protective function to maize seed and, so, thedamage loss of maize seed decreases with the peeling ratio of the bract of the maizecob.It was demonstrated through the comparative analysis of Jilin spring maizewith Tianjin summer maize that the linear relationship between ear-corn diameterand ear-corn handle diameter with the diameter of cornstalk near the ear-corn. Therelative equations were obtained.