NCCCO Principles of Crane Stability and Structural Integrity 2

Question 1

What is the 'tipping axis' of a mobile crane on outriggers?

Accepted Answer

The line connecting the outrigger pad closest to the load and the adjacent outrigger pad

Answer

The center of the crane

Answer

The rear axle of the crane

Answer

The boom pivot point

Question 2

What factor has the greatest effect on crane stability?

Accepted Answer

The operating radius — the horizontal distance from the center of rotation to the load

Answer

The color of the crane

Answer

The height of the boom

Answer

The number of boom sections extended

Question 3

What happens to crane stability when the crane is not level?

Accepted Answer

The crane becomes less stable because the effective tipping axis shifts, and the load effectively moves to a greater radius

Answer

Nothing — outriggers compensate for unlevel conditions

Answer

Stability increases on a slope

Answer

Only the operator's comfort is affected

Question 4

What is 'structural failure' in a crane and how does it differ from a stability failure?

Accepted Answer

Structural failure is when a component (boom, pin, wire rope) breaks; stability failure is when the crane tips over

Answer

They are the same thing

Answer

Structural failure only happens to old cranes

Answer

Stability failure only happens in high winds

Question 5

How does the weight of the boom itself affect crane stability?

Accepted Answer

The boom's weight creates a tipping moment that increases with boom length and angle, reducing available capacity for the load

Answer

Boom weight has no effect on stability

Answer

Boom weight improves stability by acting as counterweight

Answer

Boom weight only matters during travel

Question 6

Why are outriggers critical for crane stability?

Accepted Answer

They provide a wider support base and transfer loads directly to the ground, dramatically increasing the crane's stability and rated capacity

Answer

They prevent the tires from getting flat

Answer

They are only used for appearance

Answer

They protect the crane from theft