Investigation of vane-type rethresher of combine harvester

Abstract

The volume and composition of the material in the tailings returns is directly responsive to the major combine settings, and dependent on the throughput (feedrate) and crop conditions. The research has shown that tailings returns frequently contain loose grain that does not need to be rethreshed. Loose grain in the tailings is more susceptible to damage when it is returned to an aggressive threshing cylinder or auxiliary rethresher. Published data by other authors showed some evidence that grain damage could be reduced with the use of an auxiliary rethresher instead of returning the tailings to the main threshing cylinder. The amount and composition of the tailings are considered sound indicators of how well a combine is performing. This paper deals with the investigation of structural and technological parameters of the vane-type rethresher in the combine harvester with the throughput of 8 kg·s-1. The field trials show that when the combine harvester is operating at low speed more of the threshed grain is passed to the rethresher which results in higher levels of damaged grain. Increasing the forward speed of the combine harvester from 2 km·h-1 to 5 km·h-1, causes the amount of tailings being fed into the rethresher to be reduced by half. Low throughput and its consequential grain damage can cause dramatic increases in combine losses. Grain damage is also dependent on the rotational speed of the rethresher rotor. High levels of damaged grain in the tailings indicate excessive speed of rethreshing or inadequate throughput. A laboratory experiment was conducted to substantiate the estimated rational value for the rethresher under investigation, namely 1300 min-1. As the results and findings of the research show, this particular parameter of the rethresher located within the combine harvester should be adjusted depending on the operational conditions, as well as the type and characteristics of the crops being thre.