ARTIFICIAL DRYING OF FORAGE CROPS 3 



where hot air or furnace gases are circulated through the layer of forage 

 on the apron by means of one or more fans. Driers of this type may 

 have a single endless conveyor, or several conveyors one above the 

 other. As the drying air becomes saturated with moisture it is drawn 

 or allowed to escape from the machine into the atmosphere. The forage 

 may be fed into the drier whole, crushed, or chopped. Drying the for- 

 age whole is more satisfactory in single-apron machines, especially if 

 the plants are small and light as is usually the case with alfalfa, some 

 clovers, and grasses. The crushing operation is intended to be suffi- 

 cient only for cracking open the heavier stemmy plants including weeds. 

 The crushing-roll pressure should not be sufficient for complete macera- 

 tion. In connection with experimental work the crushing was done by 

 passing undried soybean plants between a pair of rollers, one of which 

 was steel and the other rubber coated. The drying was noticeably 

 more uniform through the "mattress" of hay as compared with the un- 



Discharge 



Figure 3.— Revolving-drum type of forage drier, triple-drum design. 



crushed hay plants. The chopped material offers more resistance to the 

 movement of air than do the whole plants, crushed or uncrushed, and 

 many of the finely chopped particles fail through the screen apron. 



Drum driers of the single-drum type (fig. 2) used for drying granular 

 substances such as salt have the feed end slightly elevated. As the 

 drum revolves the material is picked up by baffles or nights fastened to 

 the inside of the shell and then allowed to fall. Each time some of the 

 material is picked up it falls somewhat closer to the discharge end due 

 to the sloping position of the drum. In drying hay the drum is placed 

 in a horizontal position and a current of heated air or furnace gases re- 

 lied upon both for drying and for moving the forage through the ma- 

 chine. With drum driers it is necessary to chop the forage before it is 

 fed into the machine. In some driers of this type the dry material is 

 drawn into a chamber at the discharge end, from which it is conveyed 

 mechanically to a storage structure. In most cases, however, the dry 

 hay passes through the exhaust fan and is blown to a dust collector 

 from which it may be sacked or conveyed to a haymow. 



In the single-drum drier (fig. 2) the chopped hay passes directly 

 from the wet end (feed end) to the discharge end (dry end). In the 

 triple-drum drier (fig. 3) the material moves through the center shell, 

 back through the second, and out through the third, thus traveling ap- 

 proximately three times the length of the drier before it passes to the 

 exhaust fan. 



The apron-conveyor drier is a relatively low-temperature drier in 

 which the material remains for a considerable period of time. The 

 temperature of the drying air or furnace gases entering the machine 



