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Kulkoni, Inc. v921 WARNING: NEVER EXCEED WORKING LOAD LIMIT Page 88 3. Determine Sheave Size & Wire Rope Strength Strength Efficiency Flexing wire rope reduces its strength. To account for the effect of bend radius on wire rope strength when se- lecting a sheave, use the following table: Example To determine the strength efficiency of 1/2" diameter wire rope using a 10" diameter sheave: Refer to Ratio A of 20 in the table, then check the column under the heading "Strength Efficiency Compared to Catalog Strength in %" ... 91% strength efficiency compared to the catalog strength of wire rope. Fatigue Life Repeated flexing and straightening of wire rope causes a cyclic change of stress called "fatiguing." Bend radius affects wire rope fatigue life. A comparison of the relative effect of sheave diameter on wire rope fatigue life can be determined as shown below: Example To determine the extension of fatigue life for a 3/4" wire rope using a 22.5" diameter sheave versus a 12" diameter sheave: The relative fatigue bending life for a Ratio B of 16 is 2.1 (see above table) and Ratio B of 30 is 10. Relative Fatigue Bending Life = 10/2.1 = 4.7 Therefore, we expect extension of fatigue life using a 22.5" diameter sheave to be 4.7 times greater than that of a 12" diameter sheave. Ratio A Strength Efficiency Compared to Catalog Strength in % 40 95 30 93 20 91 15 89 10 86 8 83 5 79 4 75 2 65 1 50 Ratio B Relative Fatigue Bending Life 30 10.0 25 6.6 20 3.8 18 2.9 16 2.1 14 1.5 12 1.1 Sheave Diameter Ratio A = Rope Diameter Ratio A = 10" (sheave diameter) = 20 1/2" (wire rope diameter Sheave Diameter Ratio B = Rope Diameter = RFBL (Sheave 1) Relative Fatigue Bending Life (RFBL) RFBL (Sheave 2) Ratio B = 12" (sheave diameter) = 30 3/4" (wire rope diameter) Ratio B = 22.5" (sheave diameter) = 16 3/4" (wire rope diameter) SNATCH BLOCKS - WARNINGS AND INFO.

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