FOCT TOWERS The 75 foot towers were used as phototowers, The prime User was Edgerton, Germeshausen, and Grier. Standard radar towers using standard design were considered, but in addition to not being designed with the special requirements of photography as a basis, they would be subjected to excessive horizontal forces, These facts were presented to Los Alamos by letter on April 22, 1949. On July 28, 1949, a letter from LASL set up the preliminary design specifications for six towers and requested H & N to proceed with preliminary drawings, The preliminary tower design was submitted to AEC on September 13, 1949, and design comments by Los Alamos and Edgerton, Germeshausen, and Grier were returned to H & N on October 5, 1949. Authorization for purchase of six towers was received by H & N on December 6, 1949, with the provision that the low bid not exceed the estimated cost of $88,800.00. Bids were requested and on Jamary 16, 1950, six firms submitted bids, the low bid being $76,470.00 by International Derrick and Equipment Co. The purchase order for the six towers was released to the low bidder on March 31, 1950. On May 15, 1950, the tower shafts were completed and ready for shipment,. The tower cabs were entirely aluminum and by the time the alumimium had been procured, the subcontractor was hampered by a labor strike, The work was moved to the Union Steel Company's yard and com- pleted by Union Steel Company on October 6, 1950. As one of the towers was located at a site on the coral reef at the Proving Ground, it was necessary to change the one tower so as to include a battery roan at the 25 foot level. This design was made in Los Angeles and the materials required sent to the field, where all the necessary changes were made. A small change in the original scope occurred on September 22, 1950, when E G & G requested that H & N purchase the rolling metal doors that comprised the siding for two sides of each tower, Until that time E G & G was to furnish them. H & N let bids and had the doors in the field in sufficient time so that the User was not delayed in his installation work. The mechanical design required for the 75 foot towers consisted of an open type dumb waiter capable of handling a net working load of 1500 pounds at a hoisting speed of approximately 40 fpm, powered by an electric hoist mounted on the ground, outside of the tower base. The dumb waiter platform was guided by bronze guide shoes, riding on standard 15 pound elevator guide rails, mounted on the outside of the tower. The guide shoes were mounted on the substructure of the platform. The platform was provided with instantaneous safety rail grips to prevent the platform fram dropping in the event of hoisting cable failure or a slack cable condition. This safety device was designed after considerable study and investigation of devices used in standard 54.50