To determine the weight of the block or overhaul ball that is required to free fall the block, the following information is needed:
- Size of wire rope
- Number of line parts
- Type of sheave bearing
- Length of crane boom
- Drum Friction (nominally, 100 pounds)
Formula to Determine Block Weight:
Required Block Weight = Multiply Boom Length by Rope Weight Factor “A” and add Drum Friction then Multiply by Overhaul Factor “B”.
For Example: Using 5 parts of 7/8" Wire Rope, 50 ft. Boom and Roller Bearing Sheaves, Required Weight = [(50 x 1.42) + 100] x 5.38 = 920 lbs.