How does radius affect crane capacity?

How does radius affect crane capacity?

• A. Radius increases the speed of lifting but not capacity.
• B. Radius has no effect on capacity.
• C. Capacity decreases as radius increases; load charts show lower limits at larger radii.
• D. Radius affects only the rate of movement, not capacity.

Answer: (C)

Radius is the distance from the crane’s base to the load, and it directly affects lifting capacity because a longer lever arm increases the moment the crane must resist. As radius grows, the load creates more tipping and structural stress for the same weight, so the crane’s stability and strength limits require reducing the allowable load. That relationship is shown in load charts: for a given boom length and configuration, the maximum safe load decreases as radius increases. This is why capacity is highest at a small radius and falls off with distance. The rate of lifting or movement is governed by the hoist and drive systems, not the capacity, so those options don’t describe how radius changes safe lift limits.

Radius is the distance from the crane’s base to the load, and it directly affects lifting capacity because a longer lever arm increases the moment the crane must resist. As radius grows, the load creates more tipping and structural stress for the same weight, so the crane’s stability and strength limits require reducing the allowable load. That relationship is shown in load charts: for a given boom length and configuration, the maximum safe load decreases as radius increases. This is why capacity is highest at a small radius and falls off with distance. The rate of lifting or movement is governed by the hoist and drive systems, not the capacity, so those options don’t describe how radius changes safe lift limits.