Page 55 - The Complete Rigger’s Apprentice

rope semicircular
Kevlar flat-bottomed wire and rope V-grooved
wire and rope notched

Figure 2-15. Sheave score profiles.

Table 2. Recommended Minimum
Sheave Diameters and Block Sizes

The “standard” tread diameters shown in this table are sizes
that will guarantee the longest wire rope life and highest
strength. But if it is not practicable to put a sheave that size
into your mast, be aware that as you approach the “critical”
diameter the wire’s strength and longevity are severely com-
promised. The accompanying diagram illustrates tread diam-
eter. Block length rather than sheave diameter is the desired
standard when working with fiber rope. (Source of minimum
tread diameter: MacWhyte Wire Rope Co.)
Figure 2-16. Keeper bars can be welded on across a
halyard sheave opening to prevent the wire halyard
from jumping out and jamming between the sheave
and mortise walls.

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