THE IOWA SILO 71 



steel pins 16 inches long, N, extending through 1-inch holes 

 in the uprights. Eight of these are required, as one set 

 should not be removed from a lower hole until the other pins 

 are placed to support the scaffold in case any of the hoisting 

 parts should break. As already noted devices and short 

 chains may be used to suspend the scaffold instead of support- 

 ing it from below. 



Each upright consists at first of a 2x6 eight feet long and a 

 2x6 sixteen feet long screwed together with three 2^-inch No. 

 14 or No. 16 flat-headed screws. It is necessary to use flat- 

 headed screws in order that the head will countersink itself 

 into the wood, thus not interfering with the raising of the 

 scaffold platform. One of the bottom members of the up- 

 right is 8 feet long and the other 16 feet long in order that the 

 post may be added to as needed by simply screwing 16-foot 

 2x6's on alternate sides. These upright posts are secured to 

 the wall by means of light wires, P, which are placed about 

 3 feet apart vertically. Every alternate time the scaffold is 

 moved, 2-inch blocks, 0, should be placed snugly between 

 the post and the wall and nailed to the wall. This places the 

 post about three inches from the wall. Then it should be 

 toenailed to the block, and the wires passing through the wall 

 drawn tight. This holds the scaffold support rigid in all 

 directions and enables the builder to keep them plumb. The 

 distance between the holes in the upright will depend upon 

 the kind of hoisting apparatus used, but usually 18 inches is 

 most convenient. The most convenient device for raising 

 the scaffold are ^-inch triple blocks. 



METHOD OF BUILDING 



The Guide Device. It is essentially important, for the 

 sake of appearance, preservation of silage, and strength of 

 wall that the silo be circular and plumb. It is highly desir- 



