OO-D-2855
be not less than 14 degrees (°). Suitable track rollers shall be provided to
assure smooth track operation and maintain even ground pressure. Track rollers
and the track rail shall be arranged so as to prevent damage to bearings or
grease fittings when the rock drill is operated through abrasive material and
loose stone. The track assemblies shall be equipped with track adjusters for
maintaining tension on the track. Track frames shall not be spliced. The
minimum overall track width shall be 96 inches (2438 mm) from outside-to-outside
of tracks and a ground bearing length of not less than 96 inches (2438 mm).
3.10.1 Tracks. Track links and shoes shall be heat treated steel of drop
forged or rolled construction, and all similar parts shall be interchangeable.
The shoes shall be not less than 15 inches (381 mm) wide. Track links shall be
equipped with replaceable pins and bushings. The master pin shall be secured by
a lock or a press fit and shall be identified.
3.10.2 Tramming motors. A tramming motor, using a drive gear train or chain
drive, shall drive each track. Each motor shall have a self centering "deadman"
control valve for forward and reverse movement of the track. The motor and
drive train shall be enclosed. The rated horsepower of the motors shall be not
less than that required to advance the rock drill up a grade of not less than 40
percent and over level ground at a speed of not less than 1.5 miles per hour
(mph) (2.4 kilometers per hour (km/h)).
3.10.3 Brakes. Each track shall be provided with brakes to prevent movement
of the track drill when on a 50 percent longitudinal slope.
3.10.4 Platform. A platform, for use by the rock drill operator while
manipulating the necessary controls during travel (tramming) and prepositioning
the mast, shall be furnished.
3.11 Boom. The boom shall provide not less than 50° total vertical lift
from horizontal. Total horizontal boom movement (swing) shall be not less than
80°. Boom length shall be expendable not less than 5 feet (1.5 m) for a total
length of not less than 15 feet (4.6 m). All boom movements shall be controlled
hydraulically. The rock drill shall be capable of drilling regardless of the
position of the mast or boom. Boom movement shall be so controlled that the
boom can be stopped and fixed without creepage at all points in its range of
vertical or horizontal travel.
3.12 Mast. A mounting plate shall be used to secure the steel mast to the
boom. The mounting plate shall be hydraulically operated and shall be capable
of sliding on the mast a minimum distance of 3 feet (0.91 m). A reversible
hydraulic feed motor secured to the mast shall be used to drive the feed
mechanism. The mast assembly shall include an adjustable feed chain, upper and
lower feed chain idler sprockets, a drifter drill mounting plate, a foot pad,
and a drill steel centralizer. Feed chain and idler sprockets shall be arranged
so that total travel of the rock drill shall allow the operator to change
12-foot (3.7 m) sectional drill steel and couplings by disengagement of the
centralizer only. When operating at rated hydraulic pressure, the hydraulic
feed motor shall deliver not less than 5,000 pound-force (22 241 newton (N)) for
crowding and retracting. The vertical mast dump from horizontal position shall
have a minimum arc of 140°. The mast movement shall be controlled so that the
mast can be stopped and fixed without creepage at all points in its range of
travel. The mast shall be of such strength to support the rock drill and
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