How does changing counterweight affect crane stability and load capacity?

• A. Increasing counterweights improves stability and increases safe lifting capacity; reducing counterweight decreases stability and capacity
• B. Counterweight has no effect on stability
• C. Increasing counterweight reduces stability
• D. Decreasing counterweight increases capacity

Answer: (A)

Counterweights balance the crane to keep the overall center of gravity within the base, resisting tipping moments created by the load and the boom. When you increase the counterweight, you boost the restoring moment behind the crane, allowing heavier loads to be lifted at the same reach without tipping. This makes stability better and raises the safe lifting capacity for that configuration. If you decrease the counterweight, the resisting moment is smaller, tipping becomes more likely, and the safe lifting capacity drops. The other statements ignore this balance, so they don’t fit: stability is affected by counterweight, adding weight behind the crane does not reduce stability, and reducing counterweight does not increase capacity.