If the boom angle becomes shallower, what happens to the crane's capacity?

If the boom angle becomes shallower, what happens to the crane's capacity?

• A. Increases
• B. Fluctuates
• C. Stays the Same
• D. Decreases

Answer: (D)

The lifting capacity is determined by the load moment about the crane’s base. As the boom angle becomes shallower (closer to horizontal), the load’s lever arm from the base increases, so the same weight creates a larger tipping moment. To keep within safe limits, the crane must lift a smaller weight. If the boom is steeper (more vertical), the moment is smaller and more weight can be lifted within the rated limits. So, the crane’s capacity decreases when the boom angle is shallower.

The lifting capacity is determined by the load moment about the crane’s base. As the boom angle becomes shallower (closer to horizontal), the load’s lever arm from the base increases, so the same weight creates a larger tipping moment. To keep within safe limits, the crane must lift a smaller weight. If the boom is steeper (more vertical), the moment is smaller and more weight can be lifted within the rated limits. So, the crane’s capacity decreases when the boom angle is shallower.