Mobile Crane Operator Fundamentals Flashcards

What happens to a crane's rated capacity as the working radius increases?

Answer: Rated capacity decreases as working radius increases

As the working radius (horizontal distance from the crane's center of rotation to the load) increases, the rated capacity decreases because the load moment (load × radius) increases.

What is the maximum allowable side loading on a mobile crane boom?

Answer: Side loading is not permitted — booms are designed for vertical loads only

Crane booms are engineered to handle vertical (compressive) loads only. Side loading places lateral bending stress on the boom that can cause structural failure at loads well below the rated vertical capacity.

In the context of crane operations, what does 'working radius' refer to?

Answer: The horizontal distance from the crane's center of rotation to the load

Working radius is the horizontal distance from the crane's center of rotation (centerline of the mast/turntable) to the center of the suspended load.

What is the purpose of outrigger pads (cribbing) when setting up a mobile crane?

Answer: To distribute the concentrated outrigger load over a larger ground area

Outrigger pads distribute the concentrated point load from the outrigger float over a larger ground area, reducing ground bearing pressure to levels the soil can safely support.

Which of the following crane configurations typically provides the highest rated lifting capacity?

Answer: Outriggers fully extended on firm, level ground

Outriggers fully extended on firm, level ground provide maximum crane stability and therefore the highest rated lifting capacities as shown in the load chart.

What does the term 'load moment' mean in crane operation?

Answer: The product of the load weight multiplied by the working radius

Load moment is the product of the load weight and the working radius, representing the overturning force (torque) applied to the crane's structure.