3.12.4 Vibrating mechanism. A mechanical vibrating mechanism shall
be provided for activating the live-frame. When material from the
deck or decks of the screen impinges on the activating mechanism, the
mechanism shall be equipped with a replaceable, protective cover. The
mechanism shall be driven by a 15-hp electric motor.
3.12.4.l Shaft bearings. The vibrating screen shall have double-
row, self-aligning, antifriction shaft bearings. All bearings exposed
to dust shall be provided with labyrinth grease and dust seals.
3.12.5 Screen-feed hopper. A hopper shall be mounted over the
vibrator screen to receive material from the feed conveyor and dis-
charge it evenly across the full width of the screen.
3.12.6 Screen-discharge hopper and chutes.
3.12.6.l Discharge hopper. A discharge hopper shall be located under
the bottom deck of the vibrating screen to receive all material from the
bottom deck and pass it into the receiving hopper of a portable con-
veyor by means of a chute. The discharge height of the chute shall be
not less than 36 inches and not more than 38 inches above ground level.
188.8.131.52 Material delivery chutes. Material delivery chutes shall
be provided for the aggregate passing over each of the three screen
decks. The ground clearance under the chutes shall be not less than
36 inches and not more than 38 inches above ground level. The chute
arrangement shall provide for not less than a 4-1/2-foot clearance
between centerlines of the discharge ends of the chutes.
3.13 Trailer components.
3.13.1 Frame. The trailer frame shall be constructed to withstand
without damage or permanent deformation, the static and dynamic loads
imposed by operation and by being transported as specified in 3.16.
3,13.1.1 Upper fifth wheel and kingpin. The front of the semi-
trailer shall be instructed so as to be compatible for coupling with
and towing by both the military M123, 10-ton truck-tractor, and the
M52, 5-ton truck-tractor (see 3.29) The upper fifth wheel shall be of
the full width type that permits coupling at any angle up to 75 degrees
from straight ahead and shall cover a 36-inch-diameter lower fifth
wheel. The upper fifth wheel assembly shall conform to ICC 193.70.
The plate shall be high tensile steel (not less than 50,000 psi yield