PRACTICAL SILO CONSTRUCTION . 57 



wise the silo cannot be absolutely air-tight; and 

 unless so the results will not give satisfaction. 



The view of door shown in Fig. 14 illustrates the 

 cross-bar or 2x4" strip, which is cut 3' long and 

 bolted to the center of door. This strip rests against 

 the walls of silo on each side of the door-openin'g. 

 Thus, by tightening the nut on the bolt, the door is 

 drawn closely into the frame or opening for same. 



The dotted lines in Fig. 14 show how the rein- 

 forcement should be placed at the point where each 

 door-opening will come in the silo wall. Two I" 

 rods are used upon each side of the opening, and 

 these are placed so that they are within 1J " of the 

 surface of concrete around the door-frame. The 

 pressure exerted against the silo wall at this point, 

 by drawing the doors into position, makes this pre- 

 caution of ample reinforcing an important one for 

 the builder who desires durability in construction, 

 even in monolithic silos with heavy walls. This re- 

 inforcement is necessary where plastered silos are 

 constructed, as the thickness of wall is not enough 

 to withstand the pressure exerted by drawing the 

 doors into position with the bolt, unless strongly 

 reinforced. 



A continuous door for the silo is shown in the 

 illustration at Fig. 15. The forms are built to mold 

 this opening of the desired width, which is usually 

 the same upon the inside as the width of the silo 

 door. The thickness of these wing walls is best 

 made the same as the walls of silo, which will avoid 



