A luffing-jib tower crane, often simply called a luffer, is a tower crane whose jib moves up and down to change the working radius. Instead of a horizontal jib with a trolley running along it, the luffer raises its jib to bring the hook closer to the tower and lowers it to reach further out. Because the jib can be raised almost vertically, the crane needs much less free space around it than a conventional tower crane, and its short counterweight radius keeps the rear of the crane compact.
These features make luffing-jib cranes the standard choice on congested city sites, where neighbouring buildings, other cranes and airspace rights limit the space a crane may sweep. They are used for high-rise towers, dense residential developments, hospitals, stations and industrial projects, and in heavy versions for power plants and bridges.
Brief History of Luffing-Jib Tower Cranes
Luffing jibs are in fact the older tower crane design. After the Second World War, rail-mounted, bottom-slewing tower cranes with luffing jibs were common on European building sites, with German manufacturers such as Liebherr and Peiner among the leading names. From the 1960s, top-slewing cranes with horizontal saddle jibs and trolleys, promoted especially by French manufacturers, took over much of the general construction market because they were simpler and faster to use.
The luffer, however, found a lasting role in city centres and on very tall buildings. Liebherr developed hydraulically luffed cranes from the late 1950s, and the Australian company Favco introduced rope-luffing climbing cranes in the 1960s; Favco cranes were used on major high-rise projects of that era, including the original World Trade Center in New York. From the 1980s and 1990s, rising land values, tighter urban sites and rules on oversailing neighbouring properties, notably in London, expanded the market for luffers. Today almost every major tower crane manufacturer offers a luffing range, from compact models to heavy cranes lifting several tens of tonnes.
How a Luffing-Jib Tower Crane Works
The luffer shares many components with other top-slewing tower cranes, but the jib works differently.
- Tower. Lattice mast sections are stacked to the required height. The tower stands on a foundation, on a base with ballast, inside the building on climbing frames, or on rails in some cases.
- Slewing unit. The upper part of the crane, including the jib, counterjib, winches and cab, rotates on a slewing ring at the top of the tower.
- Jib. A lattice jib is hinged at its base. The luffing mechanism raises and lowers it, typically between a shallow angle for maximum radius and a steep angle of around 70 to 85 degrees for minimum radius.
- Luffing mechanism. On rope-luffing cranes, a winch and wire rope system pulls the jib up through an A-frame or mast. On hydraulic luffers, one or more hydraulic cylinders push the jib up.
- Hoist. A separate hoist winch lifts the load. Many luffers have a high-capacity hoist with fast line speeds for tall buildings.
- Counterweight. The counterjib is short, so the crane’s tail radius is small. This allows several cranes to work close together or next to buildings.
- Controls. The operator sits in a cab at the top of the tower. Electronic systems control the luffing and hoisting movements, manage the load chart and, on many cranes, set working-range limits.
Types of Luffing-Jib Tower Cranes
Rope-Luffing Cranes
The most common type, where a winch and rope system raises and lowers the jib. These cranes cover a wide range of capacities and are used on most high-rise projects.
Hydraulic Luffing Cranes
Cranes whose jib is raised by hydraulic cylinders. They often have a very short tail and a compact slewing unit, which suits very tight sites, and are often chosen as smaller city cranes.
Heavy-Duty Luffers
Large luffers with capacities of about 50 tonnes and more, used for steel structures, precast, power plants, bridges and industrial projects.
Climbing Luffers
Luffing cranes installed inside the building core or attached to its side, which climb with the building. They are standard on skyscrapers, where they can reach heights far above what a freestanding tower allows.
Articulated-Jib Cranes
A related design with a jib that folds in the middle, combining some advantages of the luffer and the trolley crane. It is used by a few manufacturers for specific applications.
Size Classes
| Class | Typical maximum capacity | Typical use |
|---|---|---|
| Compact | about 6 to 12 t | Tight city sites, residential blocks |
| Medium | about 12 to 32 t | High-rise buildings, commercial projects |
| Heavy | about 32 to 64 t | Steel, precast, large towers |
| Very heavy | about 64 t and more | Industrial plants, bridges, power stations |
Figures are indicative. Capacity drops as the jib is lowered and the radius increases.
Erection and Climbing
A luffing-jib crane is usually erected with a mobile crane, which lifts the tower sections, slewing unit, counterjib, counterweights and jib in sequence. On tall buildings, the crane grows with the structure. An external climbing crane is tied to the building at intervals and extended by inserting new tower sections with a climbing frame. An internal climbing crane sits in a lift shaft or core opening and raises itself floor by floor on climbing collars. At the end of the project, dismantling the top crane on a skyscraper can itself require smaller cranes or derricks placed on the roof.
Main Manufacturers
- Liebherr, with its HC-L luffing jib range.
- Potain (Manitowoc), with the MR range.
- Wolffkran, whose WOLFF B series luffers are common in European city centres.
- Comansa, a Spanish manufacturer that also builds luffing cranes.
- Favelle Favco, a historic name in heavy luffing and climbing cranes.
- Raimondi, Jaso and Zoomlion, with luffing ranges in several classes.
Main Uses of Luffing-Jib Tower Cranes
- High-rise residential and office buildings in dense urban areas.
- Sites next to existing buildings, railways or airspace restrictions.
- Projects where several cranes must work close together.
- Skyscrapers, with internal or external climbing cranes.
- Heavy lifts in industrial plants, power stations and bridge construction.
- Refurbishment and redevelopment projects in city centres.
Luffing Jib or Trolley Jib?
The choice between a luffer and a conventional trolley (saddle or flat-top) crane depends on the site.
- Space. A luffer’s jib can be raised to stay within the site boundary, while a trolley jib sweeps its full length and may oversail neighbouring properties.
- Tail radius. Luffers have a shorter counterjib, useful next to buildings and other cranes.
- Speed and simplicity. Trolley cranes are generally faster for horizontal movements and simpler to set up and operate.
- Cost. Luffers are usually more expensive to buy and to rent, and their assembly is more complex.
- Heavy lifts at height. Luffers often offer high capacity and fast hoisting at great heights, which suits tall buildings.
Safety
The main hazards with luffing-jib cranes are the same as with other tower cranes: structural failure, overloading, collisions with other cranes and structures, dropped loads and accidents during erection, climbing and dismantling. Because luffers often work in groups on crowded sites, anti-collision and zoning systems are essential. Out of service, luffers must be left in the jib position and configuration specified by the manufacturer, which normally includes freedom to weathervane with the wind. Wind monitoring, correct foundation and tie design, experienced erection crews and competent lift supervision are standard on professional sites.
Trends and Technology
Luffing cranes are evolving towards higher capacities, faster hoisting and more compact designs. Modular components shared with other models speed up logistics and assembly. Electronic controls with load and radius displays, working-range limitation and anti-collision systems are now common. Some manufacturers offer cranes that can switch between different hoist gear or jib configurations to suit changing project phases. Energy-efficient drives, remote diagnostics and telematics are spreading, and climbing systems are being refined for faster installation on tall buildings.
Key Terms
- Luffing: raising and lowering the jib to change the working radius.
- Luffer: common trade term for a luffing-jib tower crane.
- Tail radius: the radius swept by the counterjib and counterweight.
- Oversailing: the crane jib passing over neighbouring property.
- Climbing crane: a tower crane that rises with the building, inside or outside the structure.
- Weathervaning: allowing the crane to rotate freely in the wind when out of service.
Frequently Asked Questions
Why are luffing-jib cranes used in cities? Because they can raise the jib to avoid neighbouring buildings and other cranes, and their short tail keeps the crane within tight boundaries.
Are luffing-jib cranes slower than trolley cranes? Horizontal load movements can be slower, as changing radius means luffing the jib. For vertical hoisting on tall buildings, luffers are often very fast.
Can a luffing crane lift more than a trolley crane? Luffers are often designed for heavy lifts, but capacity depends on the model and radius. Both types are available in a wide range of sizes.
What is the difference between hydraulic and rope luffing? Hydraulic luffers raise the jib with cylinders, while rope luffers use a winch and wire rope system. Hydraulic designs are often chosen for compact cranes, while rope luffing covers the widest range of capacities.
How is a luffing crane taken down from a tall building? Usually in stages: the crane climbs down or is dismantled with a smaller crane or derrick on the roof, which is in turn lowered in pieces.
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