Rubber-Tyred Gantry Crane Product

Overview

A rubber-tyred gantry crane (RTG) is the workhorse of container-yard stacking. It is a steel portal on eight pneumatic tyres that straddles a block of containers — typically six rows wide and five or six high, plus a truck lane — and shuttles boxes between the stack and road trucks. Because it runs on tyres rather than rails, an RTG can leave its block, turn its Travel Bogie sets 90 degrees, and drive to another block, which lets a terminal share a fleet of cranes across the whole yard. A typical machine spans about 23.6 m, lifts 40 t under the spreader, and weighs 120–140 t.

The rail-mounted variant (RMG) trades this mobility for higher speeds and full automation; the RTG keeps the flexibility and carries its own power plant.

Structure and travel

The Portal Frame is a welded portal: two Main Beam box girders carry the trolley rails across the stack, supported on four Gantry Leg columns about 21 m tall, joined in pairs at the bottom by Sill Beam members. Each sill beam end sits on a pivoting Bogie Frame carrying two Gantry Tyre units, so all eight tyres stay loaded on uneven pavement. Corner wheel loads reach roughly 40 t, which is why RTG runways are paved with reinforced concrete strips even when the rest of the yard is asphalt.

Each bogie has its own Travel Gearmotor of 30–45 kW, giving gantry speeds up to 135 m/min along the block. For crossover, a Steering Actuator rotates each bogie a quarter turn and the crane crabs sideways out of the block. During normal stacking runs, an Auto-Steering Position System using DGPS or buried transponders auto-steers the crane along the painted runway line to within a few centimetres, removing the wander that manual steering produces over a 300 m block.

Hoist, trolley and spreader

The Trolley runs across the main beams at up to 70 m/min, carrying the Main Hoist machinery and the suspended Operator Cab. The hoist is a drum machine: a 200–300 kW Hoist Motor turns a double-grooved Hoist Rope Drum through a helical Hoist Gearbox, spooling left- and right-hand Hoist Wire Rope pairs so the load stays level. Rated-load hoisting runs at about 23 m/min, rising to 52 m/min with an empty spreader because the inverter exploits the motor's field-weakening range. Two Hoist Brake units provide redundancy: a service brake on the motor shaft and an emergency caliper acting directly on the drum flange, which still holds the load if the gearbox fails.

The Telescopic Spreader is the container interface. Its telescopic Spreader Frame adjusts between 20, 40 and 45 ft corner pitches; four Twistlock cones drop into the ISO corner castings and rotate 90 degrees to lock. Seating and locked status are sensed at each corner, and the hoist is interlocked so it cannot lift unless all four twistlocks report locked, nor unlock under load. Hydraulically raised Guide Flipper arms funnel the spreader onto the box during landing, powered by the onboard Spreader Hydraulic Unit.

Power plant

An RTG carries its own Diesel Generator Set: a 350–500 kW Diesel Engine driving an Alternator that feeds a rectifier and common DC bus in the Electrical House. All motions run from Drive Inverter units on this bus, and the arrangement is regenerative — energy from a lowering 40 t container returns to the bus and offsets engine load. Variable-speed "eco" gensets idle the engine down when the crane is waiting, cutting fuel use by 30 % or more versus fixed 1,500 rpm sets. Many terminals now convert RTGs to cable-reel or busbar electric supply, or hybridise them with battery banks, since the diesel genset dominates a terminal's yard emissions.

Operation and control

The operator sits in the trolley-suspended Operator Cab, looking down through floor glazing at the cell being worked, with master joysticks in the Control Chair armrests. The Crane PLC coordinates motions and enforces the interlock chain, while the Anti-Sway Controller function shapes trolley acceleration ramps against the instantaneous rope length so the container arrives over the cell without pendulum swing — the single biggest factor in cycle time, since an unsuppressed 18 m pendulum has a period of about 8.5 s. A productive RTG sustains 15–20 moves per hour. Increasingly the cab work moves to remote operating stations fed by the Camera Set, with the crane executing auto-hoist and auto-trolley moves and the human handling only the final landing.