OO-C-2764
be such that the maximum stress imposed will not exceed the minimum strength
margins contained in SAE J987. Tests in accordance with SAE J987, shall have
been performed on the model crane being provided, and tests results shall be
made available for Government inspection at the time of first article tests.
3.11 Superstructure. The superstructure shall consist essentially of a cab
enclosing the machinery and operator's position, mounted on a full revolving
platform. All operating machinery shall be mounted on and attached to the
rotating platform. The boom and machinery shall be attached to the principal
members of the platform frame. The principal platform walking surfaces and
ladders shall be of an antiskid type. Ladders and steps, when furnished, and
handholds shall be provided in such number and of such size on the sides of the
superstructure so that entrance thereto may be unhampered and nonhazardous. A
ladder shall be attached to the superstructure cab to facilitate accessibility
te the gantry and A-frame sheave. Counterweights as required for the crane
shall be furnished.
3.11.1 Cab. The cab shall be of sheet metal having sufficient windows and
glazed doors to permit approximately 180 deg vision for the operator. Maximum
unobstructed visibility of the work, including the point sheaves of the basic
boom at operating radii, shall be visible to the operator seated upright and
with an eye height of 33.5 inches from the seat. All glass shall be of the
safety type, and held in place by rubber channels or other suitable means for
easy replacement. Windows shall be arranged for easy opening or removal. A
powered windshield wiper shall be furnished, with the control within the reach
of the operator. All cab doors, whether of the sliding or swinging type, shall
be adequately restrained from accidentally opening or closing while traveling or
operating the crane. The seat shall be mounted on a pedestal and base to
provide adjustment, without the use of tools, comfortable seating for (95
percentile group SAE J833) any operator in the SAE range of sizes. The
adjustments, vertical and horizontal, shall be in increments of riot more than 1
inch. The location of the seat shall provide the operator with maximum vision
of the work area and access to hand controls and foot pedals. The cab shall be
furnished with a commercial heater and a defroster having the adequate heat
output for the applicable voltage system. The defroster shall be capable of
defrosting not less than 75 percent of the front window area. Both the defroster
and heater shall be mounted and positioned to permit routine maintenance and to
allow for quick removal. A large heater, used as a combination heater and
defroster, is acceptable.
3.11.2 Gantry. The crane shall be provided with a gantry capable of
withstanding stresses induced by lifting the entire extended boom from the
ground to operating position. The length of boom to be lifted shall be as
specified (see 6.2). The principal compression and tension members shall be
securely connected to the main structural members of the rotating platform or to
other machinery parts capable of sustaining full gantry loading.
3.11.3 Powered load lowering. For crane operations, the primary load
hoisting drum shall be equipped with a powered reversing drive and suitable
control features to provide precision controlled power lowering of loads by the
main hook. The powered load lowering mechanism shall be controlled by a lever
conveniently located within the revolving superstructure and shall be capable of
lowering all rated loads with the manufacturer's recommended reeving: The
powered load lowering mechanism shall be capable of lowering the loads at a
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