Boom Angle and Radius Calculations Flashcards
6 cards from real NCCCO practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Boom Angle and Radius Calculations flashcards as text
What effect does adding a jib (fly section) to a crane boom have on the working radius compared to using the main boom alone at the same boom angle?
Answer: The jib increases the working radius
Adding a jib extends the reach of the crane beyond the main boom tip, increasing the working radius. This increased radius means lower rated capacity than the main boom alone at the same angle.
A crane operator notices the boom angle indicator shows 70 degrees, but when measuring the actual radius on the ground, the distance to the load is greater than the chart suggests for 70 degrees. What is the most likely explanation?
Answer: The boom angle indicator may be out of calibration
If the measured radius is greater than expected for the displayed angle, the boom angle indicator may be out of calibration, showing a higher angle than actual. This causes the operator to reference an incorrect load chart value.
When boom length increases while boom angle remains constant, what happens to the working radius?
Answer: Working radius increases proportionally
Working radius = Boom Length x cos(Boom Angle). If the boom angle is constant and boom length increases, the working radius increases proportionally. A longer boom at the same angle reaches farther horizontally.
According to ASME B30.5, what is the purpose of the boom angle indicator on a mobile crane?
Answer: To allow the operator to determine the working radius and reference the correct load chart capacity
The boom angle indicator's primary purpose is to let the operator determine the current working radius so the correct rated capacity from the load chart can be referenced. Knowing the angle and boom length gives the working radius.
If a crane is set up with outriggers fully extended and the load chart shows 10 tons at a 50-foot radius, which scenario requires the operator to reduce the load?
Answer: The load weighs 9 tons but the operator measures the radius at 52 feet
At 52 feet radius, the rated capacity will be lower than at 50 feet (capacity decreases with increasing radius). A 9-ton load at 52 feet may exceed the rated capacity for that radius.
What is the relationship between the radius used in load charts and the physical measurement taken on the ground?
Answer: The load chart radius is the horizontal distance from the crane's centerline of rotation to the center of the load
The working radius is always the horizontal distance from the center of rotation (the slewing axis) to the center of the suspended load, measured perpendicular to vertical.