346 



ENGINEERING ON THE FARM 



be as near air-tight as practicable. Where winters are long 

 and severe, a style of door should be selected which will 

 open and close readily so that there will be no temptation 

 to leave the door open for a long period and permit the inlet 

 of a large quantity of cold air. 



Material. Wooden silos (Fig. 275) are used all over the 

 country. From the standpoint of preservation of the silage 

 they are satisfactory. However, wood silos can be destoyed 

 by fire, and when they are empty their walls may shrink 

 and render them subject to damage by windstorms. This 

 can be prevented if the hoops are kept tight. The shrinkage 

 objection in a stave silo may be avoided if the walls are made 

 of panels placed between upright studs. Wood-hoop silos 

 (Fig. 276) are frequently built, and they readily lend them- 

 selves to home construction, as the materials can be secured 

 at local lumber yards. Steel is used for silo construction. 



-I j/ob roots 

 3 /8"o.c. 



\ 



Horizontal reinforcing eouots 

 reinforcing /n fotverporto/H'a// 



t:£:4 concrete 



/:3 5 concrete 

 /n /oof/ngS\ 



v'i 



.* 



t:2.3 concrete 



Bet/trap^ 





Gracfe 





4'cfra//? 

 tite. 



WSj&SPSi 



Fig. 274. 

 For wooden silos: 



H— 2' o" to 6' o" 



T — 6" reinforced 

 T — 12" without reinforcing 

 W — 14" for most soils 

 W — 16" for wet clay or similar poorly 

 bearing soils 



After University of Minnesota 



Recommended practice for silo foundation 



For concrete, cement block, masonry, or 

 clay-block silos : 



T— 8" up to 30' high 



T — 12" for height exceeding 30' 



W — 16" up to 30' in good soil 



W — 2' o" up to 30' high in wet clay, etc. 



W — 20" over 30' high in good soil 



W — 2' to 2' 6" over 30' high in wet clay, etc. 



In cold climates a single wall of steel does not afford protec- 

 tion from frost, but a double steel wall with tight air spaces 

 is entirely practical. Clay tile, concrete blocks, and concrete 



