Inner city booms

Wheeled mobile cranes in the so-called city class are characterised by a combination of features from rough terrains and all terrains. Early models had a two-axle carrier with AT-like suspension, but with a single cab used for driving and crane operation. Their multi-section, telescopic booms had minimal front overhang and a low boom angle to improve safety on the road between jobsites. As with so-called taxi cranes, city cranes are designed to travel to site ready to work with onboard counterweight.

These features remain key identifiers of the type, but things have changed. The concept has been extended up the capacity range with three-axle models and up to 70 tonne capacity on four axles to meet the European maximum of 12 tonnes per axle. As the capacity increases the cranes inevitably become larger. Larger models have two-seat tandem cabs and extra counterweight like all terrains. A major difference remains shorter overall length, largely achieved by the absence of a carrier cab and a greater number of boom sections.

The first models came from Japanese manufacturers Kato, Kobelco and Tadano, and Compact Truck in Switzerland. Terex-Demag in Germany has been a leading producer and high profile advocate of the concept since the late 1990s. Other manufacturers with models of this type include Liebherr, Locatelli and Marchetti.

Commitment

Since 1998 Terex-Demag says it has delivered more than 1000 city class cranes worldwide in lifting capacities from 30 to 70 tonnes, making it market leader. TerexDemag has recently demonstrated its continued commitment to the sector with the addition of new and upgraded models that raise maximum lifting capacity to 70 tonnes. The full model range is: AC 30 City, AC 40 City, AC 55 City and AC 70 City.

The three-axle AC 55 City with 55 tonne maximum lifting capacity was launched last year. It has a 40 m boom, a new counterweight system to attach additional counterweight on the job site and a new, more ergonomic, two-seater cab.

Also launched last year, the AC 70 City is a development of the AC 60 City. The increase in lifting capacity is achieved by an additionally mountable counter weight plate, as on the AC 55 City. The boom has also been reworked, and at 52 m long, it holds the record in its class, TerexDemag claims. Features of the AC 60 have been retained to support the operator and ease his workload. Included are the offsettable top section, a two-person cab and the computer-controlled, electro-hydraulic rear-axle steering. The compact size of the four-axle machine is another advantage.

Liebherr's model in the category is the LTC 1055-3.1, where the ‘C’ stands for compact instead of city. Around 50 units have been sold around the world, the company says. City Cranes, Inc., the US rental house whose livery the first model was shown in, has taken delivery of its fourth unit. Advantages Liebherr claims for the LTC 1055-3.1 include shorter length and smaller turning circle than the AC 55 City.

Italian manufacturer Locatelli has been in the sector since early 2001 when it introduced its 20 tonne capacity ATC 20. Sales manager Michele Mortarino describes the ATC 20 as being different from other cranes in the category that he mentions, including cranes such as the Kobelco RK 200, Kato CR 250 and Tadano Crevo TR 200, which don't have Euro emissions regulations-compliant engines. Terex-Demag's AC 30 (formerly AC 25 and before that AC 75) is similar, Mortarino says, but the ATC 20 is 2 m shorter, 400 mm narrower and 200 mm lower.

The ATC 20 is an alternative to the biggest telehandlers, Mortarino says, with a price within 10 % of the largest slewing models. Mortarino positions the ATC 20 somewhere between a telehandler and a crane. The load chart is three times stronger than a telehandler and it has a maximum road travel speed of 71 km/h, he says.

It has a 24 m telescopic main boom and there is an 8 m telescopic extension to give a maximum height of 34.5 m.

Marchetti's Trio is not a direct competitor, Mortarino says, because, it is slower, not roadable, and the ATC 20 has more capacity across the load chart. A low-speed version of the ATC is also available.

In the pipeline to be launched at the 2007 Bauma exhibition in Germany is a larger version of the ATC, probably with 35 or 40 tonne capacity. It could, according to the manufacturer, have a maximum of 40 tonnes in one position, unlike all other Locatellis which are rated at maximum capacity through the full 360 degrees of rotation.

Kato looks likely to return to the European market - Paul Rosevere, director of Kato Cranes UK, explains that Kato stopped exporting city cranes to Europe in 2002 when the Euro Stage II engine emissions regulations came into effect, but is preparing to reintroduce them in time for the next wave of regulations.

“Between their introduction in November 1997 and 2002 we sold around 100 of the 25 tonne Kato CR 250 and between 1999 and 2002 around 30 Kato CR 100, 10 tonne city cranes in the UK,” Rosevere says. In addition to crane rental houses, buyers included construction companies, tunnelling contractors, water companies, cement works, docks, steel erectors and factories. Rosevere says he still receives enquiries about the availability of the cranes.

With the potential return of Kato, Kobelco and Tadano, we could soon see increased competition in the European market.

A return to Europe of the Kato CR series, Kobelco RK series, Tadano Crevo, and perhaps some new models, would be strong competition for the existing players.