Determination of the Effects of Some Operating Parameters on the Performance of an Acha Harvesting Machine

Abstract

Acha (Digitaria exilis) harvesting is still being done by manual traditional methods because harvesters for the crop are non-existent. This method is expensive and time consuming, yet the demand for the crop is on the increase. It is difficult to adapt regular combines to acha harvesting due to its unique grain characteristics as well as the current small sizes of acha field. The objective of this study was to evaluate the performance of a locally developed acha harvester. The machine consists of a header, transport mechanism and collection tank. A 33 factorial experimental design was used to collect data for evaluation of the performance the machine. Factors varied were operating speed (V) (1, 3, and 5 km/h); knife cutting speed (S) (300, 400, and 500 rpm) and reel index (I) (1.0, 1.25, and 1.5). Quantity measured was the amount of grain retrieved from each plot of the field. This was used to determine the material capacity (Cmat) of the harvester. Analysis of variance (ANOVA) was used to determine the effect of each of the parameters as well as their interactions. Results obtained showed that increasing machine forward speed, knife cutting speed and reel index had a reducing effect on the material capacity of the machine. Operating speed and reel index had a significant effect at p≤0.01, while knife speed effect was only significant at p≤0.05. The interaction of reel index and operating speed, as well as the interaction of all three factors were very low, significant only at p ≤ 0.05. The study concluded that the three parameters, operating speed, knife cutting speed and reel index were critical to the performance of the acha harvesting machine and recommended that further studies be done to determine their optimum values.