| Physical changes in crop properties have been reported to affect the operational characteristics of combine harvesters. Performance, measured as mass other than grain (M.O.G.) feed rates at fixed grain loss levels, varies as a result of crop property changes (Stephens and Rabe, 1977). Combine performance may vary substantially during the course of a single day making comparisons of performance between combines in field tests difficult.;Fourteen bulk crop properties were collected for wheat and barley from 1980 through 1984. In addition, the performance of the cleaning component and the straw walker was also measured on a conventional type John Deere 6620 combine. Crop properties were measured on grain, chaff, and straw components of wheat and barley. The performance criteria was chaff feed rate at 0.5 percent cleaner grain loss and total M.O.G. (mass other than grain) feed rate at 1.0 percent walker grain loss.;Grain density, grain angle of repose, chaff density, chaff coefficient of friction, chaff compressibility modulus, grain:M.O.G. ratio, straw density, straw compressibility modulus, and straw coefficient of friction were shown to affect combine performance. In general, cleaner performance appeared to be three time more sensitive to crop changes than straw walker performance.;Cleaner performance and straw walker performance prediction equations were developed with explained 92.0 percent of the variation in cleaning performance and 30.0 percent of the variation of the performance in straw walker performance.;A research project was undertaken to determine the effect of bulk crop properties on combine performance. This thesis describes the collection and measurement of bulk crop properties, the correlation between property changes and combine performance, and the development of a combine simulation model based on bulk crop properties.;A computer simulation model was developed using crop property and combine performance data. The model predicted cleaner, walker, and overall processing performance as functions of ground speed, width of cut, crop yield, and a set of crop properties which vary in a stochastic manner. Implemented as an interactive program, the user specifies initial crop properties and variability. Each property is then simulated over a range of selected moisture conditions. The model can be used by students and test engineers to study the effects of crop properties on combine performance. |
