Mar, 2, 1920.] Agricultural Gazette of X.S.W. 175- 



the blocks a few at a time on otherwise slack days. Working quietly on these 

 lines, it is possible for a farmer to collect, at a minimum of expense, the 

 necessary material for a structure that will be a valuable asset on his farm, 

 and a cheap insurance against periods of scarcity. 



The machine for making the blocks at present costs £60 at least, but with a 

 man and a boy, a hundred blocks can be turned out in a day. The best 

 type of machine is that which turns out the block face downwards; this- 

 allows for a better class of material being used on the face for weathering 

 purposes. With a home-made mould not more than twenty blocks per day 

 can be finished. 



The shape of the block referred to is shown on page 174 (plan of block) 

 and the mould may be simply a four-sided box, with the necessary cores to 

 form the two holes. These holes in the blocks not only economise in 

 concrete material, but forni a cavity in the walls, which acts as an 



insulation. 



Specification. 



Concrete Block Silo. Height 25 feet, diameter 16 feet. 



Materiid.- — The mixture used may be sand and cement for the face (3 of sand to 1 of 

 cement) tamped into a mouhl about f inch thick ; ior the remainder, 5 of gravel and 

 sand to 1 of cement. About sixty to sixty-seven blocks are made from a cubic yard, 

 and 1,676 blocks, including eighteen halves, are required to build a sUo. 



This allows for footings, which may be of blocks laid as shown in section ; or the lower 

 course may be of concrete, laid in the trench 24 inches by 8 inches deep, in which case 

 I ,.553 blocks will be sufficient. 



Excavation. — The lower 4 fc( t 3 inches of the silo is set into the ground; this reduces 

 the labour of elevating when tilling and strengthens the silo. If the ground is firm, such 

 as hard clay, no other floor requires to be provided, but if it is soft, a concrete floor 

 about 6 inches thick should be put in. No drainage from the floor is necessary. 



Walls. — On the footings, set tlie blocks in cement mortar, gauged 3 to 1, and with 

 I inch thick joists. 



At 3 feet from the floor and to each course upwards, bed at 1 inch from the outer face, 

 either a f inch round iron rod or two strands of No. 8 fencing wire twisted together. 



A groove should be made in the top bed of the blocks to receive this, but if wire is- 

 used and it is carefully set, it may be laid in the bed-joint mortar. The outer face joints 

 are sti-uck jointed, and the inner face pointed up, and the whole of the inner face of the 

 silo is bagged over with cement wash. 



Doors.- — The first door frame is set on at 9 inches over the ground hue, and spaced as 

 shown. Frames are made of sawn hardwood, the sUls 8 inches by 3 inches weathered, and 

 the remainder 6 inches by 3 inches, square, and each fitted with two -| inch iron dowels top 

 and bottom. The dowels are set about 4 inches into the cement blocks, which are made- 

 solid for the purpose of receiving them. Over the inner face of the frames, and on one 

 side of the openings, is fixed a vertical hardwood batten to form a groove to take the ends 

 of the door planks. This serves to hold the latter in position when the silo is empty. 

 The door planks are of dressed 12 inches by 2 inches oregon, jointed at the edges, and 

 when set into the frames they are covered over at the inner face with 2-ply roofing 

 material, extending about 6 inches beyond the frame to better exclude the air. 



Roof — The top plates are formed into an octagon and secured at the top course of 

 blocks by means of Jf inch bolts, bedded into the blocks, and a rooi is buUt as indicated 

 on the plan, boarded and covered with either plain galvanized iron, or flexible roofing 

 material with U iiich rolls in the angles. Guttering is unnecessary on the eaves, unless 

 the water is required. A dormer opening is formed, as shown, for entrance of the head 

 of the elevator or blower. No door is required on this. 



A cheaper roof of open gable ends may be substituted for that on the plan; it serves 

 ec[uaUy well, but does not look so well. 



