A mobile crane is a crane mounted on its own carrier, with wheels or tracks, so it can travel to a site, set up quickly and lift. Unlike a tower crane, which stays on one site for months, a mobile crane may do several jobs in a day: placing air-conditioning units on a roof in the morning, lifting a bridge beam in the afternoon. At the top of the range, giant mobile and crawler cranes install wind turbines, refinery columns and bridge sections weighing hundreds or thousands of tonnes.
Brief History of Mobile Cranes
Early mobile cranes were steam-powered machines on rails or crawler tracks, used in ports, railways and heavy construction in the late 19th and early 20th century. Truck-mounted cranes with lattice booms followed as road vehicles became more powerful.
The key breakthrough was the hydraulic telescopic boom, which spread from the 1950s and 1960s. It allowed a crane to extend its boom in minutes, without assembling lattice sections, and turned the mobile crane into a fast, flexible tool for crane hire companies. Rough-terrain cranes, with a single cab and large tyres, developed in North America for construction sites. In Europe, the need for cranes that could drive fast on public roads and still work off-road led to the all-terrain crane, introduced by German and other European manufacturers in the late 1970s and early 1980s.
Since then, capacities have grown dramatically. Liebherr’s 400-tonne LTM 1400, launched in 1988, became a best seller, and today the largest all-terrain cranes exceed 1,000 tonnes of nominal capacity, while the largest crawler cranes reach several thousand tonnes.
How a Mobile Crane Works
- Carrier: the truck or crawler chassis that moves the crane. On wheeled cranes it includes the engine, transmission, axles and outriggers.
- Outriggers: hydraulic legs that extend and lift the crane off its wheels, spreading the load onto pads or mats. Most of a wheeled crane’s capacity depends on correctly set outriggers.
- Superstructure: the rotating upper part, with the operator’s cab (on many cranes), hoist winches and counterweight.
- Boom: telescopic (several sections sliding inside each other) or lattice (assembled from steel sections). Jibs and extensions increase reach.
- Counterweight: modular ballast plates, often carried separately by trucks on large cranes.
- Load moment indicator (LMI): an electronic system that continuously calculates the load, radius and configuration and stops the crane before it is overloaded.
Types of Mobile Cranes
All-Terrain Cranes
Multi-axle carriers with all-wheel steering and drive, able to travel at road speed and work on rough ground. They are the backbone of European crane hire fleets, from compact two-axle “taxi cranes” to nine-axle cranes with lattice jibs for wind turbines.
Rough-Terrain Cranes
Two-axle cranes with large off-road tyres and a single cab. They are slow on the road and usually transported on a trailer, but very capable on construction sites, refineries and industrial plants. They are especially popular in North America and the Middle East.
Truck-Mounted Cranes
A crane superstructure on a commercial truck chassis. Lighter and cheaper to run than all-terrain cranes, they are widely used for general lifting and in markets where road speed matters most. Boom trucks and loader cranes (knuckle-boom cranes) are close relatives.
City and Compact Cranes
Short, highly manoeuvrable cranes designed for tight urban sites and indoor work. Industrial pick-and-carry cranes and spider cranes on compact tracks belong to this family.
Crawler Cranes
Cranes on tracks, usually with lattice booms, although telescopic crawler cranes also exist. They can travel with the load, do not need outriggers and offer very high capacities, which makes them the choice for heavy lifts, wind farms, bridges and long-term foundation and pile work. They are transported in pieces and assembled on site.
Telescopic or Lattice Boom?
| Telescopic boom | Lattice boom | |
|---|---|---|
| Set-up time | Fast | Longer, requires assembly |
| Weight for a given capacity | Heavier | Lighter, very efficient |
| Maximum capacity and height | High | Highest |
| Typical cranes | All-terrain, rough-terrain, truck cranes | Crawler cranes, large lattice mobile cranes |
Size Classes
| Class | Typical nominal capacity | Typical use |
|---|---|---|
| Compact and city cranes | up to about 60 t | Urban lifts, indoor work |
| Taxi cranes | about 40 to 100 t | Daily hire work, HVAC, precast |
| Medium all-terrain and rough-terrain | about 100 to 300 t | Industrial and infrastructure lifts |
| Large all-terrain | about 300 to 1,200 t | Wind turbines, bridges, heavy industry |
| Large crawler cranes | several hundred to several thousand t | Energy, petrochemical, heavy lifts |
Nominal capacity is measured at a very short radius; real working capacity depends on radius, boom length and configuration. Figures are indicative.
Main Manufacturers
- Liebherr, the market leader in all-terrain cranes and a major crawler crane manufacturer.
- Tadano, including the former Demag all-terrain business.
- Grove (Manitowoc), with all-terrain, rough-terrain and truck cranes, and Manitowoc crawler cranes.
- XCMG, Zoomlion and Sany, now among the largest crane manufacturers in the world.
- Kobelco and Link-Belt for crawler and rough-terrain cranes.
- Terex, Marchetti, Valla and Maeda in specialist and compact segments.
Main Uses
- Crane hire and contract lifting.
- Construction: steel erection, precast, roofing, HVAC installation.
- Infrastructure: bridge beams, rail and road projects.
- Energy: wind turbine installation and maintenance, power plants.
- Industry: machinery installation, refinery and petrochemical work.
- Ports and logistics.
Crane Hire and Ownership
Most mobile cranes work for crane hire companies rather than for the contractors who need them. Hire companies offer two main services: wet hire or crane hire with operator, where the hire company supplies the crane and its operator and the customer remains responsible for planning the lift; and contract lifting, where the hire company takes responsibility for planning and carrying out the whole operation.
For owners, the economics of a mobile crane depend on utilisation, transport and flexibility. Taxi cranes that carry most of their counterweight on board can do several jobs a day without support trucks, which is why many European fleets are built around 40 to 100 tonne all-terrain cranes. Large cranes earn more per day but need escort vehicles, permits and ballast trucks, and must be kept busy on long-term projects such as wind farms and industrial shutdowns.
Safety
Most crane accidents come from poor planning, ground failure and overloading.
- Lift planning: every lift needs a plan covering the load weight, radius, crane configuration, ground conditions and rigging. Complex lifts need an engineered lift plan.
- Ground bearing pressure: outrigger loads can be very high. Mats and pads must be sized for the ground.
- Wind: large boom and load areas are sensitive to wind, especially with wind-turbine components.
- LMI and anti-two-block systems must be working and never bypassed.
- Power lines: minimum clearances must be respected at all times.
- Competence: operators, riggers and signallers must be trained and certified.
Trends and Technology
- Variable outrigger positions with capacity calculated for the actual set-up, allowing work in tight spaces.
- Lighter booms and carriers to carry more counterweight within road axle-load limits.
- Electric and hybrid cranes, with electric superstructure drives running on grid power and battery-powered city cranes.
- 3D lift planning software and digital load charts.
- Remote diagnostics and telematics for fleet management.
Key Terms
- Outriggers: extendable legs that level the crane and spread its load to the ground.
- Counterweight: removable weight at the rear that balances the load.
- Radius: the horizontal distance from the centre of rotation to the hook, on which capacity depends.
- Luffing: raising or lowering the boom angle.
- Jib: an extension fitted to the end of the main boom to gain height or reach.
- Load moment indicator: a safety system that monitors the load against the crane’s limits.
Frequently Asked Questions
What does “100-tonne crane” mean? It is the nominal maximum capacity at the shortest radius with full counterweight. At working radius the crane lifts much less, according to its load chart.
All-terrain or rough-terrain crane? All-terrain cranes drive on public roads at highway speed and work off-road; rough-terrain cranes are designed mainly for work on site and must usually be transported.
Why do large cranes need so many trucks? Counterweight, boom sections and jibs are transported separately to respect road weight limits, and assembled on site.
Why does a crane with a 100-tonne rating lift much less at long reach? The headline rating applies only at short radius with full counterweight and outriggers. As the radius increases, the tipping moment grows and the allowable load falls, as the load chart shows.
What are crane mats for? Crane mats, or outrigger pads, spread the load from each outrigger over a larger area of ground. They help prevent the ground from giving way under the very high forces generated during a lift.
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