AT the World’s Fair to be held in New York during 1939, there will be seen two structures of outstanding interest; they are the Trylon and the Perisphere. The Trylon,
which is a three-sided steel tower 610 ft. in height tapering to a point at the top, has been referred to by the steelworkers as the "Needle." There are approximately 39 lengths of column in each of the three legs. Starting at the base, heavy box sections are employed. The fist section which is attached to the column footing, although only a little over 12 ft. in length, weighs 26 tons. As the legs taper upward they gradually become lighter, a variety of box sections being used with cover plates laced and battened ; the top leg sections are formed of straight beams. Two types of construction are used, and at a height of 480 ft. the framework of the Trylon changes from column legs, braced with diagonals and struts, to plate construction. The complete
130 ft. of plate tower section was assembled as a whole, a task which presented difficulty to both the erectors on the site and to the fabricators in the workshops, on account of the triangular shaped piece being less than 15 ft. across the base and only 2 ft. 7 in. at the top. Also the holes in this part of the tower were all countersunk, making it harder to pin and assemble the material. The work involved an unusual amount of bending and welding, and in the plate sections at each corner a large heavy angle section had to be closed for its full length from the usual right angle as received from the rolling mills, to 60 degrees.