284 



AGRICULTURAL ENGINEERING 



Striking examples of how use is made of differences in 

 shape are found in the devices arranged to separate wheat 

 from oats. In one device a riddle is provided with cells 

 having a reverse turn. The short wheat grains are able to 

 pass through this riddle, but the long oat kernels cannot. 

 Another device consists of a cloth apron over the grain on 

 the sieve, which maintains the grain in a thin layer and pre- 

 vents the long oat kernels 

 from passing through, 

 because the cloth pre- 

 vents them from being 

 upended. The wheat 

 kernels, being shorter, 

 pass through without 

 difficulty. 



Certain grains like 

 rye, for example, are 

 heavier at one end of 

 the berry than at the 

 other, and if these grains 

 are allowed to fall a certain distance they are quite likely to 

 strike upon their heavy ends. This principle is made use 

 of to a certain extent in some machines. 



Some of the weed seeds which are found in grass seed 

 have a horny or burr-like hull which enables the seeds to 

 adhere readily to any cloth with which they may come in 

 contact. This characteristic of the seeds is made use of, in 

 separating them out, by passing the seed in a thin stream 

 over a felt roll. 



In general, there are two types of fanning machines: 

 First, those in which the air blast is directed upon the grain 

 as it passes over the sieves; and second, those which use the 

 air blast independent of the sieves and riddles. The first of 



Fig. 179. Another view 



machine shown in Fig. 178. 



type 



