Page:Popular Science Monthly Volume 88.djvu/977

 Radio Tower at Tufts College

��THE radio tower recently erected at Tufts College, Medford, Massachu- setts, is attracting unusual attention. In September, when the tower was completed to a height of over 275 ft., one of the temporary guy ropes parted during a high wind and allowed the tower to topple over. Instead of snap- ping at some point above the ground the structure pulled away from the sub-base and fell as a complete unit.

It has been shown that the collapse was not due to faulty design, and the tower has been re-erected without im- portant changes.

The tower itself is built entirely of angle irons and assembled in the manner shown in the illustration. It is 288 ft. above the concrete base, and 3 ft. 4 in. square in section from base to top. The corner, or upright, angle-irons are

3 ins. by y^ in., while the diagonal and cross angle-irons are 2 ins. by 3/16 in. The corner angles are each nearly 12 ft. long and, as shown by the diagram, are divided into three sections. The sections are placed directly on top of each other and held together by means of angle- irons fitting inside of the corner angles and extending several inches either side of the joint. These angles are secured by bolts >^ in. in diameter and I in. long. This bolt construction is employed throughout the tower, there being no rivets. Washers are not used with the bolts.

The structure is mounted on two concrete bases. The upper base is 5 ft.

4 ins. square and 12 ins. thick. It is to this base that the iron work of the tower is secured. This sur-base rests on four porcelain insulators set so as to leave 5 ins. between the two bases. The lower base is the same size in section as the upper base, but extends 6 ft. into the ground. When the first tower collapsed these two bases pulled apart.

As the tower is not self supporting, the system of guying is of great import- ance. Three sets of four guys each have been adopted, thus giving 120- degrec guying with four guys fastened to each of the three deadmen. These

��guys consist of stranded steel cable with rope core, the two upper of which are yi in. in diameter and the two lower ^in.

After the complete erection of the tower the fourth guy was added to each of the three sets at a point about 75 ft. from the ground. These guys are extra and were not included in the original design, but as it now stands the tower has 12 guys.

The guys are broken up by porcelain strain insulators 5 ins. in length and 3 ins. in diameter. The ends of the wire are secured by a series of Crosby clamps. Twelve- inch turn-buckles are inserted in each set of guys.

The three dead- men are made of concrete and weigh about 25 tons each. On the surface they are 5 ft. 3 ins. square. They are placed 150 ft. from the base of the tower so as to give an angle of 45 degrees to the lower guy, which is placed mid-way up the tower.

The tower was erected aloft, each separate piece being placed in position before another was secured. Temporary guy ropes were used in large numbers during the erection of the second tower, as it was due to insufficient temporary guying that the first structure collapsed.

Harold J. Power, for whom the tower was erected, is a graduate of Tufts College. While there he was president of the Wireless Society, to which organi- zation he has granted the use of the new tower and experimental station.

Many methods of mast construction have been tried, and while a serviceable tower of wood can be built, wood is generally considered inferior to steel.

���Construction details of the tower

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