After completion of these alignments, the rotate bearing rings are secured by
means of their fasteners, tensioned to the prescribed values and sequence. The
mounting fasteners of the outer ring, as shown in Figure 16, also serve to clamp
together the two sections of the ring. (The use of machined pilot shoulders or
seats for obtaining ring circularity is not recommended.) The design of the
support structure must provide the space and clearances required for the
employment of fastener tensioning equipment.
Rotate bearing assemblies include a lip seal between the bearing rings,
which seals out external contamination and retains the grease lubricant. This
feature and the choice of internal gear teeth on a bearing ring place the entire
rotate bearing and its drive inside the clean interior of the crane structure.
The entire internal diameter is open; there is no center steadiment. The opening
is sufficiently large to accommodate an access ladder from the portal base or
barge tub. Access to the rotate bearing is provided by circular platforms on the
support column, one outside and one inside.
Travel Truck Equalizers. The function of the equalizers is to distribute
the corner loads of OET, portal, or container cranes equally among the travel
wheels. These components are box beams with pivot points in the middle and at
each end. On cranes that travel on straight rails, all pivot points mate with
horizontal rocker pins. On cranes that travel on rails with curves, the pivot
point may mate with horizontal or vertical pins of gudgeon assemblies. (Gudgeons
assemblies are intermediate members between different levels of equalizers or
between equalizers and travel trucks to allow them to swivel and follow the
curvature of the rails.)
Pivot points are heavy-walled structural steel tubes, blocks, or castings
welded into the structure of the equalizer. Their bores and faces are machined to
receive pressed-in bushings or for direct contact with pins, bearings, or thrust
washers. Bushings are required for the gudgeons and are recommended for the
Normally there are two levels of equalizers. Depending on the number of
wheels per corner, they may be symmetrical (end pivot points equidistant from the
middle pivot point) or non-symmetrical (one end pivot point twice as distant as
the other pivot point). The equalizer box beams are completely sealed weldments.
Equalizers have built-in jacking points to support the crane when travel trucks
Gudgeon Assemblies. Gudgeon assemblies are installed between the portal
base, equalizers, and travel trucks to allow them to pivot about the horizontal
axes to compensate for rail unevenness and to swivel about the vertical axes to
steer on rail curves. (The vertical stem is the "gudgeon"; the horizontal pin is
the "gudgeon pin".) The gudgeon assembly configuration may be in the form of an
inverted "T" or a saddle with the vertical stem on top.
The gudgeon pin of the inverted "T" type, shown in Figure 17, has a loose
fit with the gudgeon and is locked to the webs of the equalizer. The gudgeon
penetrates the top flange of the equalizer through an opening that allows for
unrestricted rocking motion. The saddle type, shown in Figure 18, does not
penetrate the equalizer flange; instead, its side members extend down the sides of
the equalizer. The ends of the gudgeon pin are locked to the saddle side members.
The rocker motion takes place at the loose fit of the gudgeon pin and equalizer.