Tower Crane

Overview

A tower crane is the tall, fixed crane that dominates building sites, lifting steel, formwork, concrete skips, and materials high above a structure as it rises. The hammerhead (saddle-jib) type has a horizontal jib along which a trolley runs to vary load radius, balanced by a counter-jib carrying ballast and the machinery. Mounted on a tall lattice mast, it offers great height and reach from a small ground footprint, and can climb to add height as the building grows.

The crane stands on a Foundation & Base, rises through the Tower Mast, and rotates on the Slewing Unit that carries the Jib (Boom) and Counter-Jib & Counterweights.

How it works

A cast-in Foundation & Base or anchored base resists the crane's huge overturning moment. The Tower Mast is a bolted lattice tower; for freestanding heights beyond the chart, it is tied to the building or extended by a climbing frame that inserts new sections from within the mast.

At the top, the Slewing Unit sits on a slewing bearing and ring gear so the entire upper structure rotates. The Jib (Boom) reaches out over the load zone, balanced by the Counter-Jib & Counterweights, which carries ballast and the Hoisting Mechanism. That hoist drum reels wire rope out along the jib and down to the Hook Block to raise and lower loads.

Load radius is set by the Trolley Mechanism, a powered trolley that runs along the jib chords, drawing the hook in or out; capacity falls as the trolley moves toward the tip. The operator works from a high Operator Cab near the slew centre, with the Electrical System system supplying the hoist, slew, and trolley motors and enforcing load-moment limits. A built-in Access Ladders & Platforms ladder and platforms reach the cab and machinery.