Since the skip hoist operated outside of the 200 foot tower and passed up through an opening in a platform at the top level, minor changes were required on the skip cab (platform), As it did not have to open a trap door at the top level, the framing above the railing level was removed. Because the skip was loaded at one end at ground level and at one side at the top level, it was necessary to make the railing on one side removable (the removable end portion used for 300 foot towers was not changed). These changes on the skip cab were necessarily made in the field at the time of installing on the 200 foot tower, because the cab had been shipped with the 300 foot towers before the 200 foot towers were conceived. The portable hand-operated winches and cable from the 300 foot tower cab, were used on the 200 foot tower, but because of structural design of the tower house, the supports for the winches, cable, and sheaves had to be of a different design, The winch supports were mounted on the tower house structural members instead of on the Aframe as on the 300 foot tower. Figure 5.11-7 shows the main hoist sheave assembly and cable arrangement for a 200 foot Tower. A 7+ ton single I-beam type traveling crane was provided for each 200 foot tower. The crane was equipped with a 2-speed electric hoist with gear type trolley. Hoisting speeds were 24 fpm and 10 fpm on the total lift of 17 feet for the full height towers and total lift of 36 feet for the 25 foot mock-up section of the tower which was installed at Los Alamos. Proposals were received from three crane mamifacturers and analyzed. The acceptance of the low bid was recommended on May 24, 1950, In a phone conversation on May 31, 1950, J-Division requested H & N to design a detachable main hoist platform (or pallet) for lifting freight from the ground to the tower house, using the main hoist. At this point the pallet would be transferred to the 74 ton traveling crane, to be moved to any desired location in the tower house. H & N prepared a sketch showing a platform camposed of a structural channel rectangular frame and covered with ¢ inch plate with a 6 inch high toe plate on all four sides. The platform was lifted by a wire rope sling attached to each corner and was provided with double sets of roller guides on opposite sides of the platform framing. The roller guides were to operate along the main hoist T- guide rails and were spaced approximately 1 foot apart vertically. Because eccentric loading of the platform was possible, the double- roller guides were changed to single-roller guides. Also, the platform was provided with pull-out legs on each corner, so that the platform could rest on the floor of the tower house while it was being transferred from the main hoist to the bridge crane. To comply with this request, a new drawing (3G-5445) was made, using 6 inch pipe and 7 inch channels for the platform framing, single-roller guide assem blies, and lifting cables at each corner of the platform. The pullout legs were of 5 inch pipe and made to telescope into the 6 inch pipe. The platforms were fabricated according to this drawing. Figure 5.11-8 shows a main hoist pallet platform for a 200 foot Tower, and Figure 5.11-9 shows a complete perspective of a 200 foot Tower. 5-146