344 ENGINEERING ON THE FARM 



Since 2 inches of silage must be fed per day, the height should 

 be 200X2, or 33^3 feet. The nearest commercial height 

 would be 34 feet. It is customary to make the height 

 approximately double the diameter; when the diameter 

 computed by the above rule gives too low a silo, the height 

 can be increased and the diameter decreased, the capacity 

 in cubic feet being kept the same. 



Bursting strain. Silage is supposed to exert a pressure 

 of 11 pounds per square foot per vertical foot of head. 

 Consequently the pressure per square foot on the silo walls 

 at any point is equivalent to the head of silage above that 

 point multiplied by 11. For determining the size of rein- 

 forcement or hoops, the cross section of steel used for each 

 vertical foot should be equivalent to .000344 multiplied by 

 the head of silage in feet above the given point, multiplied 

 by the inside diameter of the silo in feet. This rule applies to 

 all styles of silos. It is customary to consider that the steel 

 carries the entire bursting stress regardless of other materials. 

 For example, to find the size of hoops required for a 12 -foot 

 wooden silo or the extent of reinforcing for a 12 -foot concrete 

 silo 20 feet below the top: .000344X20X12 = .082. The 

 cross section would therefore be .082 square inch, which 

 would require for each foot six ^-inch square rods or two 

 X-i n ch round rods. 



Freezing. Experimental data tend to show that in 

 severe winters freezing will occur in any type of silo unless 

 great expense, which is not ordinarily justifiable, is incurred 

 for double walls. A considerable percentage of freezing in 

 silos is caused by the useless circulation of air through them 

 as a result of a poor roof or of leaving the doors open. If 

 the weather is very cold, a canvas or straw covering should 

 be spread over the top of the silage and the doors kept closed 

 except at feeding time. 



Home construction. Silos can be purchased in a number 

 of ways. Manufacturers will send an expert superintendent 

 to erect a silo, or the materials may be purchased and erected 



