National Commission for the Certification of Crane Operators (NCCCO) Mobile Crane Practice Exam

Which boom position causes the greatest ground pressure when lifting with crawler cranes?

1. Over the right side

2. Over the end

3. Over the corner

4. Over the left side

The correct answer is: Over the corner

When lifting with crawler cranes, the boom position that causes the greatest ground pressure is when it is positioned over the corner. This is due to the distribution of weight and forces exerted on the crane's tracks. When a load is lifted over the corner, the load is exerted in a manner that maximizes the lever arm effect, thereby amplifying the ground pressure beneath the tracks. In this position, both the weight of the load and the crane's structural weight are concentrated where the tracks support the crane, leading to increased ground pressure. This is crucial for crane operators and site managers to consider, as excessive ground pressure can lead to ground instability or support failure, necessitating proper ground assessment and, if required, reinforcement measures. The other boom positions, while they may still exert significant ground pressure, do not concentrate the load and the structural weight in the same way as when positioned over the corner.