What is the main purpose of the overhaul ball (headache ball) on a single-part whipline?
- Its weight adds to the crane's rated capacity when on the whipline
- It stops the hook from being drawn into the boom tip
- Its weight keeps the line taut and pulls it down when unloaded
- It measures the load on the line for the operator
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C. Its weight keeps the line taut and pulls it down when unloaded
With no load on the hook, the ball's weight overcomes friction and the weight of rope on the drum side so the line pays out and stays seated in the sheaves. Its weight is a deduction from capacity, never an addition.
Reference: Mobile crane components
What are boom stops on a lattice boom crane for?
- To keep the boom from going over backward
- To limit how far the boom can be lowered
- To hold the boom when the pendants are removed
- To stop the upperworks from swinging freely
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A. To keep the boom from going over backward
Boom stops resist the boom being pulled or blown back past its highest working angle, for example if a load is suddenly released. They are a safety device that must be working before operations begin.
Reference: 29 CFR 1926.1415(a)(2)
What is the difference between gross capacity and net capacity?
- Net capacity is gross capacity plus the weight of the block
- Net capacity is gross capacity minus the chart's deductions
- Gross capacity applies on rubber; net applies on outriggers
- Gross capacity is the tipping load; net is the structural limit
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B. Net capacity is gross capacity minus the chart's deductions
The chart lists gross (rated) capacities. Subtracting the weight of everything the manufacturer counts as load, such as the block, ball, rigging and stowed or erected attachments, leaves the net capacity: the heaviest object that can be lifted.
Reference: Mobile crane load chart principles: gross and net capacity