Page:Popular Science Monthly Volume 89.djvu/814

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��Popular Science Monthly

��The Construction of a Small Concrete Com- Crib

THE roof of this corn-crib is made of lumber and the side walls and floor are of concrete. The walls consist of concrete fence posts — the ordinary kind with 3-in. tops and 6-in. bases. The foundation and floor of the building are of concrete mixed in the proportions of I part cement, 3 parts of sand and 5 parts gravel or stone broken in pieces not larger than 2 in. in any dimension. It is a permanent crib, reasonable in price.

���CONCRCTE. FLOOR & FOOTING^^

Corn-crib made with concrete posts for the side walls and with solid concrete floor

The posts are anchored at the bottom to the concrete and at the top are securely clamped together with a box- plate made of three 2 by 6-in. pieces bolted together every 4 ft. over the top of the posts. Along the front side of the crib there is a short studding about 2 ft. long which supports the roof and makes a convenient place where the grain may be thrown in the crib. The rafters are spiked to the plates and are set on 2-ft. centers. Across the top of the posts from plate to plate a cross-tie is run from each rafter. This makes the crib solid and will prevent the sides from spreading.

I n the ccn t cr of 1 he crib criss-crossbraccs of wire should be put in, twisted taut and fastened to bolts at the foundation line.

��Cover the roof with shiplap for sheathing, making a tight and smooth foundation for the three-ply asphalt-and-felt pre- pared roofing material which is laid lengthwise of the building.

The posts should be of a l-to-3 mixture of cement and sand made into a sloppy consistency before pouring it into the forms. One sack of cement will make about 8 posts, weighing 90 lbs. each. There should be three )^-in. round steel rods placed in the center of each post to reinforce it. For an 8oo-l)Ushel crib of a size 9 ft. by 32 ft. the following amounts of materials will be required:

13 barrels cement for floor and founda- tions 6 cubic yards of clear sand 10 cubic yards of coarse gravel 80 concrete posts 2 dozen bolts 5^ by 8 in. 300 ft. of 2 by 6 in. material for box- plates 16 ft. long 100 ft. of 2 by 4 in. material for cross- ties 9 ft. long 150 ft. of 2 by 4 in. material for rafters

12 ft. long 40 ft. of 2 by 6 in. material for studding 2 ft. long 450 ft. of shiplap sheathing lumber 4 squares of three-ply roofing felt.

��Experiments with Antennas of Varying Lengths

AT some wireless stations very interesting results have been secured by providing a number of single-wire aerials of various lengths and extending them in different directions from the operating room. By the use of single-pole, double- throw switches these may be connected to the receiving tuner or directly to the ground, or left open-circuited. Various combinations are found to give good results in receiving from particular stations, depending upon the direction and wavelength of transmission.

It has sometimes been found valuable to ground one wire through tuning inductance while receiving on an entirely separate aerial.

��Those of us interested in science, engineering, invention form a kind of guild. We should help one another. The editor of The Popular Science Monthly is willing to answer questions.

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