CHAPTER VIII. 



THE BLAST 



The blast requires its share of attention, and when 

 it is once thoroughly understood and mastered, it 

 becomes an obedient servant capable of accom- 

 plishing good work. But few changes have been 

 made in the blast fans since they were first used in 

 separators. They have faults as well as virtues; they 

 do not always send the proper amount of blast just 

 where it is intended they should or where it is needed 

 the most. 



There is a great difference in the condition of the 

 material which the shoe has to handle at different 

 times, each section of the country furnishing a partic- 

 ular kind or quality of grain to be threshed. In parts 

 of the country where spring wheat is raised, there is 

 more work for the shoe to do, as there is more chaff ; 

 the straw, as it is stiff and hard to thresh, breaks up 

 more than does that of the winter wheat raised in 

 other sections of the country. Though the kernels 

 of spring wheat are not much heavier than the 

 berries of the winter variety, the chaff and dust from 

 the former is much more dense and weighty than 

 from the latter, requiring more than double the 

 pressure of blast to penetrate and lift it. 



The cylinder and concave should be adjusted to 



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