The newer cranes have identical (or mirror image) powered trucks with one
driven and one idler wheel. All gearing is enclosed (inside gear reducers) with
the output shaft connected directly to the wheel axle. Except for the wheel
pockets at the ends, these travel trucks are sealed box weldments.
Fasteners and Connections. Keeper bars on various components pivot
pins, rocker pins, boom hinge pins, roller path fixed axles not being subjected
to any calculable or significant loads, are secured with two screws torqued to the
mechanical design criteria. Screws and bolts holding caps and
retainers over bearings and bushings in most cases are likewise out of any direct
load path, and are torqued to the mechanical design criteria. Fastener sizes are
selected to nominally match the dimensions of the surrounding structure and the
installation torque is often governed by the strength of the tapped threads in the
base material. (Fasteners which are in direct load path must be individually
analyzed and sized according to the applicable design criteria.) All these
fasteners, are required to be locked against loosening, either by means of lock
washers or lock wiring of their heads to each other or the adjacent structure.
Bolts and studs holding the roller path rail segments are required to
comply with the structural design criteria. When the rail segments are embedded
in an epoxy resin compound, their installation must follow the recommendations of
the resin manufacturer. The bolts or studs securing the rotate bearing to the
crane structure must be selected and installed according to the bearing
Bushings and thrust washers that have grease grooves that require
alignment with grease injection holes must be fastened to their support structures
with threaded fasteners. Flangeless bushings may be locked in their housings with
setscrews installed in tapped pockets at the press fit bore. Flanged bushings and
thrust washers may be secured with counterbored or countersunk screws. These
fasteners should be locked against backing out by staking.
Wire Rope Pendants. Stationary wire rope assemblies, such as pendants,
should use 6x37 or 6x19 classification bright or galvanized wire rope with poured
(zinc or resin) sockets or swaged fittings.
Painting and Corrosion Protection. Structural-mechanical components
should be painted for corrosion protection in the same manner as the structural
components and weldments, described in paragraph 4.1.29 and subparagraphs but
with the following exception:
Working surfaces those subjected to rolling, sliding, or pivoting
motion must be left unpainted. (The relative motion with mating surfaces, and
periodically applied lubrication, prevent corrosion on them. Various pins, roller
treads, rail and roller path running surfaces are in this category.)
Corrosion resistant metals and plating should be left unpainted.
(Stainless steel, copper alloys, aluminum, galvanized wire rope pendants, and
chrome plated steel pins are in this category.)
Lubrication fittings must be left unpainted.