Certified Questions and Verified Answers – Graded
A 100% Correct – Detailed Rationales – Pass
Guaranteed – A+ Graded
Tower Crane Components & Configurations
Q1: You're looking at a tower crane with a horizontal jib that stays level during operation,
using a trolley to change the load radius rather than raising or lowering the jib tip. This
configuration is characteristic of a:
A. Luffing jib tower crane
B. Hammerhead or saddle jib tower crane [CORRECT]
C. Self-erecting potain crane without jib
D. Bottom-slewing mobile tower crane
Correct Answer: B
Rationale: Hammerhead cranes (also called saddle jib) maintain a level jib and use a
trolley to move loads in and out, maximizing hook height in tight spaces. Luffing jibs (A)
raise and lower the entire jib to change radius, while self-erecting (C) and
bottom-slewing (D) describe different operational characteristics, not the jib geometry.
Q2: On a self-erecting tower crane, which feature distinguishes it from traditional
top-slewing tower cranes that require auxiliary cranes for assembly?
A. It uses a fixed concrete base only
B. It can assemble and extend its tower using built-in hydraulic systems without an
assist crane [CORRECT]
C. It has no counterweights on the counter-jib
D. It operates exclusively on rail systems
Correct Answer: B
,Rationale: Self-erecting cranes feature integrated hydraulic systems that allow them to
fold and unfold their jib and tower sections, and often climb using their own power,
reducing setup costs. They still use counterweights (C) and can have various bases (A),
but the self-assembly capability is the defining trait.
Q3: You're comparing two tower cranes on a job site. Crane A has the slewing
mechanism (slewing ring) located at the top of the tower, while Crane B has it at the
base with the tower anchored to a fixed foundation. Crane A is best described as:
A. Bottom-slewing with fixed tower
B. Top-slewing with climbing capability [CORRECT]
C. Traveling on rails with rotating base
D. Self-propelled mobile crane
Correct Answer: B
Rationale: Top-slewing cranes have the slewing ring above the tower, allowing the upper
works (jib, cab, counter-jib) to rotate while the tower remains fixed. Bottom-slewing
cranes (A) rotate the tower itself from the base. Traveling cranes (C) move on rails but
can be either top or bottom slewing.
Q4: A contractor needs to move heavy materials along a linear storage yard and requires
the crane to travel while carrying loads. The appropriate configuration would be:
A. Fixed base hammerhead crane with extended reach
B. Traveling tower crane on rail system with bogie trucks [CORRECT]
C. Self-erecting crane with outriggers
D. Luffing jib crane anchored to building only
Correct Answer: B
Rationale: Traveling tower cranes run on dedicated rail tracks (or sometimes wheels on
concrete) allowing longitudinal movement along the site. Fixed base (A) and
building-anchored (D) cranes cannot travel, and outriggers (C) describe mobile hydraulic
cranes, not tower cranes.
Q5: The vertical structural element of a tower crane that provides the height and
supports the slewing upper works is properly called the:
A. Jib or working arm
B. Tower mast or tower section [CORRECT]
C. Counter-jib assembly
, D. Trolley track beam
Correct Answer: B
Rationale: The tower mast (or tower sections when stacked) provides the vertical
support. The jib (A) is the horizontal working arm, counter-jib (C) holds the ballast, and
trolley track (D) is part of the jib structure.
Q6: The horizontal structure on the opposite side of the tower from the main jib, which
holds the counterweights and typically houses the hoisting machinery, is known as the:
A. Boom tip assembly
B. Counter-jib or rear arm [CORRECT]
C. Tower head assembly
D. Luffing drum platform
Correct Answer: B
Rationale: The counter-jib (also called rear jib or machinery deck) provides the moment
arm to balance the load on the main jib, carrying concrete ballast and often the winch
drums. The tower head (C) is where the jibs connect to the tower top.
Q7: The mechanical component that allows the upper works of the crane to rotate 360
degrees (or limited degrees) around the tower axis is the:
A. Trolley drive motor
B. Slewing unit with slewing ring bearing [CORRECT]
C. Hoist drum assembly
D. Climbing frame mechanism
Correct Answer: B
Rationale: The slewing unit consists of a large ball or roller bearing ring (slewing ring)
with pinion gears driven by electric motors, allowing rotation. The trolley (A) moves
along the jib, and the hoist (C) raises/lowers loads vertically.
Q8: On a hammerhead tower crane, the wheeled carriage that travels along the jib to
change the load radius is called the:
A. Counterweight trolley
B. Load trolley or traveling block [CORRECT]
C. Slewing bogie
D. Jib pivot carriage
Correct Answer: B