be 2.0 to 4.0 degrees wider than the angle of the rail head sides, and the fillet
radius with the tread 0.030 to 0.060 inch less than the corner radii at the top of
the rail head.
18.104.22.168 Other Wheel/Rail Combinations. The above formula applies to various non-
standard wheel materials and running surfaces, such as bronze wheels or case rail
segments of roller paths, among others. The value of K may be raised by up to 200
for cranes in light service and should be lowered by up to 200 for severe service.
Wire Rope Drums. Wire rope (hoist) drums are always of steel
construction either cast (on older cranes) or welded (on newer cranes). On
welded drums, the longitudinal welds of drum barrels must be full depth
penetration welds. The end plate connections to the drum barrel and stub shafts
or hubs (for through shafts) must be reinforced radial stiffeners or internal
diaphragms. The end plates must also provide a rigid mounting for the drum gear,
when required. On newer cranes the drum gear is bolted to the end plate; on older
cranes it may be integral or press fitted and keyed to the drum barrel. The
ratchet wheel, on all cranes, is normally integral with the drum flange. The
grooving is helical with two opposite-hand grooves for double reeved systems, or
a single groove for single reeved systems. (Container crane drums, having to
spool four independent wire ropes, require four sets of grooves on the drum
barrel. Alternatively, they may use two mechanically connected conventional
drums.) The grooving is required to have a pitch of not less than 1.125 times and
a depth of not less than 0.375 times the nominal wire rope diameter, respectively;
and a groove radius of 0.52 to 0.55 times the nominal wire rope diameter. Drum
pitch diameter for 6x37 class of wire rope construction must be at least 30 times,
and for non-rotating and spin-resistant wire ropes of various constructions at
least 40 times, the wire rope diameter. The diameter of the end flanges should be
larger than the drum barrel outside diameter by at least two wire rope diameters.
The drum barrel must be sized to spool all the active wire rope in a single layer,
with at least two dead (inactive) wraps ahead of the anchor points. Drum designs
with multi-layer spooling must be approved by the NCC.
The dominant stress on the drum barrel is due to the compression from the
wire rope spooled at maximum wire rope pull (drum line pull). The pull is assumed
to be imposed on a strip of drum barrel of the same width as the pitch and of the
full cross sectional area, including the cusp between the grooves. The bending
stress from the wire ropes of double reeved hoists is assumed to be near the
center of the drum barrel (the position that corresponds to the highest hook
elevation) and maximum wire rope pull. The torsional shear stress is that imposed
by the drum line pull at pitch radius. Stub shafts are analyzed for infinite
fatigue life under loads due to the drum line pull.
The drum line pull, calculated by the formulas shown in paragraph
22.214.171.124, is the governing design load for the drum and all other components of
the reeving system. For the luffing hoist, where the drum line pull varies
greatly with the boom angle, a representative value of 75 percent of the maximum
drum line pull is used for fatigue analyses and bearing life determination.
126.96.36.199 Anchor Points. The dead ends of the wire ropes are anchored on the drum
barrel by clamping or by inserting their swaged or poured end fittings into
reinforced pockets. The clamp is grooved for two parallel wraps separated by one