Machine Crop Parameters’ Model of Spike - Tooth Thresher for Soybean

The goal of regular modification of threshing machine is to increase soybean processing efficiency. This study was carried out to deconstruct the thresher’s parameter - output relationship and to evolve a model for such relationship at the Engineering workshop of the Federal College of Agriculture, Ibadan, Oyo State Nigeria. Unthreshed soybeans, CGX14x1448 were used to evaluate the performance of a modified spike tooth thresher fabricated at the Workshop. The summary statistics of the machine output showed that concave clearance had percentage unthreshed soybean of 16.98%, percentage mechanically damaged seed of 8.625%, blown seed of 23.403kg and high seed loss of 44.241kg. Both the mean cleaning efficiency (94.175) and threshing efficiency (83.022) were very high. The trend of the cylinder speed however contrasts with those of concave clearance and moisture content. The percentage unthreshed (83.212%), percentage mechanical damage (16.792%) were in contrast to each other. Similarly, the threshing (44.108) and cleaning (23.321) efficiency were low. The relationships between cylinder speed and machine output showed an increasing trends for blown seed, percentage damaged seed and seed loss. Concave clearance - threshing efficiency can be predicted using 3 most parsimonious models (xy-inverse, exponential and simple linear model). High adjusted coefficients of determinations (R2) were obtained for the best model of cylinder speed - threshing efficiency model. These were 0.9997 for the xy inverse and 0.9998 for quadratic 0.993 for exponential model with estimation variance of 0.00047 (quadratic), 0.000 for inverse xy and 0.000191 (exponential model). The practical application of the models is in the specificity of the measurement of the relationship between thresher’s parameters and output.