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It has been observed that the straw of some varieties of wheat was broken into short lengths, whereas that of another variety was relatively un damaged by the threshing action of the combine cylinder. The breakup of straw, and the gradation from short to long lengths, can affect the performance of the separating components of a combine. Adjustments of wind velocity and direction, and sieve openings are of importance if efficient separation of grain from short straws and chaff is to be effected. Also, long straws must be spread in such a way that subsequent field operations may proceed freely. Tests were made at the Research Station, Swift Current, Saskatchewan to determine the effect of threshing two varieties of wheat at different feed rates using two types of combine cylinders on the degree of straw breakup. Thatcher wheat, a hollow-stemmed variety, and Chinook, a solid-stem med variety, were harvested from the windrow using a self-propelled combine equipped, alternately, with a rasp bar type cylinder and a spike tooth cylinder. The feed rate of grain and straw per minute was varied by operating the combine at five different forward speeds and was estimated by weighing the amount of grain threshed in a recorded period of time. Three samples of straw were collected at random from the rear of the combine during each test. Counts of the numbers of straws in one inch increments from one to 17 inches in length in each sample were made, and the numbers were expressed as a percentage of the total sample count. The percentages were low in magnitude and highly variable, there fore an angular transformation was applied to them for the purpose of analysis. The data for 1964 were selected for discussion in this paper.
the breakup of wheat straw by combine cylinder
Dodds, M.E. and F. W. Bigsby 1968. THE BREAKUP OF WHEAT STRAW BY COMBINE CYLINDER. Canadian Agricultural Engineering 10(1):43-44.
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