Transcript for Hoover Dam Construction, segment 14 of 17


The job of transporting the pipe section from the plant to the dam site was in itself a tremendous undertaking, and to accomplish this work, a special road trailer capable of carrying two hundred tons was designed and built. Caterpillar tractors furnished the motive power as the trailer itself was not equipped with a means of locomotion. During handling, the confirmation of the pipe section was maintained by rigid internal bracing. The movement of the heavy trucks was controlled by airbrakes and power steering apparatus with which the trailer itself was equipped.

Upon arrival at the canyon rim, directly over the dam site the unit was maneuvered into position for lowering into the canyon. To perform this task and to handle other heavy equipment, a permanent two hundred ton capacity cableway had been swung over the gorge, its six three and a half inch track cables securely anchored into the rock of the canyon wall.

The cableway was manipulated from a control tower overhanging the canyon from which the operator commanded a full view of all its movements. The heavy hoisting machinery controlled by synchronized motors was the largest and most powerful of its kind ever built, as were also the track cables themselves which spanned the canyon, a distance of twelve hundred and fifty-six feet at an elevation of seven hundred feet above the river from the head tower located on the Nevada side. Over the track cables traveled the carriage to which the hoisting and traveling cables were played. A specially designed heavy-duty rig which became known through the workmen as the moonbeam because of its peculiar shape and from which the pipe sections were suspended was used in lowering the huge tubes into the low levels of the canyon while cradled in a sling of heavy steel cable. After all lashings were secure, the pipe section was lifted from the trailer to begin its slow and carefully controlled movement over the cableway riding from the rim out into space, suspended seven hundred feet above its ultimate position.

When the cable carriage, with its tremendous weight of steel had been maneuvered into location over the intended landing far below, the hoisting cables were slowly played out and the pipe lowered under absolute control into the canyon. Here, a second specially designed car waited at the portal of the access tunnel to relieve the cableway of its burden and carry the pipe section underground to become a part of the extensive conduit system penetrating the cliffs on both sides of the canyon.

With the workmen laboring in the tunnels far underground, the gargantuan task of placing the penstock pipes in position to form continuous conduits between the intake towers and the powerhouse and outlet works was accomplished. The separate units were hoisted into location with the aid of cables and, once placed in position, were joined with pressure pins to form a continuous pipe.