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

Over which quadrant are truck crane capacities usually greater?

1. Over the front

2. Over the rear

3. Over the front right outrigger

4. Over the side

The correct answer is: Over the rear

Truck crane capacities are typically greater over the rear for several reasons related to the design and engineering of the crane. The structural integrity and weight distribution play a vital role in a truck crane's lifting capabilities. When the boom is extended over the rear, it utilizes the counterweight effectively, which is often located at the rear of the crane. This positioning provides a balance that enhances stability, allowing for higher lifting capacities. The weight of the counterbalance helps to offset the load, creating a safer operational environment. As a result, truck cranes are generally rated for more lifting capacity when working in the rear quadrant due to this better leverage and stability. By contrast, when the boom is extended over the front or to the sides, the effective counterweight that helps to lift the load is diminished, leading to a decrease in the crane's lifting capacity. The structural design inherently supports greater loads towards the rear compared to other directions, which is why operational guidelines specify the differences in capacity based on the quadrant.