City cranes are small road legal cranes, with short carrier bases and compact dimensions. Typically they are used on a taxi crane basis for jobs in restricted environments, such as inside buildings or on restricted urban job sites.
City cranes have been produced in Europe for more than a decade. Over recent months, two new models have been announced: Manitowoc’s GCK3045 was launched at Intermat in Paris this spring and, more recently, Liebherr has shown the first pictures of its planned new LTC 1045-3.1. Manitowoc’s new crane was built for the US-owned firm by the Japanese manufacturer Kobelco, with Japan the home of the city crane concept.
Kobelco’s Shu Umemura explains, “Throughout the long history of the Japanese wheeled crane market, as had been almost the same for various other countries, truck cranes had dominated the market, from the smallest size to the largest.
“As the economy had rapidly grown and many cities, as well as metropolitan areas, became extremely condensed and crowded, a need emerged for relatively small- to medium-sized truck cranes to evolve into a much more compact but, at the same time, stronger crane.
“And so, the Japanese manufacturers did actually develop something new.
“Compared to America or Europe, the Japanese choice of rough terrain cranes incorporated a degree of mobility, which could cover the major jobs that three- or four-axled truck cranes had been doing, with only a two-axled crane.
“Some people would say that it had to be two axles tomeet the economics of the small- tomedium-sized crane’s owners. And naturally, it needed to eliminate any need for assist cranes or assist trailers to even cut back the expense.
“Single cabin was new to the Japanese at that time but it was already popular in America.
“The difference between typical American type of RT and the new Japanese type of RT was that the Japanese type was intended to travel on the road. Nowadays it is not so surprising to see similar types of wheeled cranes on the road in Europe, either from the Italian manufacturers or the Germans, whether it is with a horizontally set boom or with slanted boom. But, when the Japanese first introduced them, it was unique at that time.
“The slanted boom came in at a rather later stage of the history of the development of these cranes. The slanted boom, of course, makes the crane very compact. Some may say that initially the need for compactness was fulfilled by squeezing the number of truck crane axles into two. But the new demand for more compactness was stipulated when Kobelco first introduced the smallest RT, the RK70, with the first ever slanted boom, which also could travel on-road in Japan. It was no longer a replacement for truck crane. It was really something new.”
These first cranes set the basic standard for city crane design. The chassis was short; they had only a single cab, more like a RT than an AT; the boom was slanted down, rather than being carried level, so it took up less space in front of the crane; and the counterweight was incorporated into the crane.
However, that slanted boom presented its own challenges. Umemura explains, “This trend for a slant boom went on from 4.9t and 7t capacity cranes to 16t and became even more popular, but stayed within that capacity range for a while, until some had tried to come up with 20t–35t range, but this did not quite catch on. Why?
“The slanted boom adds more weight, since it normally requires an increased number of boom sections, and therefore incurs a transportation handicap in terms of road permits and access hours. So, the Japanese crane owners tended to stay with the currently available cranes with a horizontally set boom.”
Umemura explains that part of the pressure on Japanese crane designers to develop these new cranes came from the country’s road regulations. He says, “Adding more weight is always a problem for any wheeled crane manufacturer around the world, especially when it comes to a mobile crane, and Japan is not an exception.
“But the criteria of road regulation in Japan, especially for RTs, seems to be slightly different from the others, enabling a little more weight to travel on the road. Road regulations around the world generally ask first whether it is a vehicle or self-propelled machinery. And when it is classified as a vehicle it is allowed to travel on road, but if it is not, then it is no longer able to go on road.
“With this similar sense, the Japanese RTs may be deemed as ‘self-propelled industrial equipment’. However, and this situation in Japan may be something unique, they are allowed to travel on road, but with less freedom to transport in comparison to larger sized ATs (or truck cranes), in terms of permits. The Japanese RTs were historically offered with a maximum road speed of 49km/h.
“The slanted boom in Japan for the RTs above 20t was not a boost initially. So we questioned ourselves, ‘has the demand for compactness perished?’ Under our evaluation, the answer was no, so we have decided to make challenge.
“The answer for us was our Panther-X 250 (RK250-7), a 25t capacity RT launched last year. While maintaining the lifting ability of our previous models RK250-6, it become even more of a taxi crane with less restraints from permits, by reducing total dimensions and weights.
“This was only possible with the combination of the hydrostatic drive system and slanted boom with less boom over-hang. Removing the engine from lower to upper structure worked as counterweight, and the freedom of design over the chassis made it possible to optimise the total balance of the machine.
“We are expecting more sales of this Panther-X 250, and in meantime, another new series model Panther-X 700, a 70- tonner, is to come. Panther-X 700 is finally a four-axle RT, to tolerate the pressures from our government to develop road easy models, and will replace some of the old two-axle RTs from45t-60t capacities. Of course, this Panther-X700, as well as Panther-X 250, is equipped with all those Japanese‘gizmos’ like hook-in storage systems or sophisticated LMIs, but first ever in this class size, we are to offer with slanted boom.”
While the city crane concept was born in Japan, it has gained popularity in Europe. The first European city cranes were produced by Swiss firm Compact Truck in the early 1990s. The specialist manufacturer, despite its innovation, struggled to sell the concept. At Intermat, in 2000, then Terex president Fil Filipov announced that Terex would be producing 200 cranes a year under licence from Compact Truck.
This wasn’t the first city-type crane to be manufactured by one of the companies that now makes up Terex Cranes, however. A few years earlier, German firm Demag (acquired by Terex in 2002), had launched its own range of city cranes.
Arndt Jahns, Terex Cranes product marketing manager for all terrain cranes, explains, “We launched the city class cranes in 1996 under the Demag brand [with the AC 25]. We’ve developed the market for these cranes over more than ten years. We’ve taken them from a niche product to a regular part of our customers’ fleets: for some customers they’re an alternative to ATs, for most they’re something to be used alongside other all terrains.
“Our customers for these cranes have jobs in various space or otherwise restricted environments. They include both rental companies and companies that own and use their own cranes. Customers use the city cranes in environments where all terrain or truck cranes can’t go: through narrow gates or streets, inside buildings, or in any other confined space.”
Terex Cranes senior manager for product marketing Rüdiger Zollondz adds, “A lot of our customers use these cranes for industrial applications. That normally means working inside buildings, but also from the inside of the building, through a hole in the roof, and onto the top of the building, where a normal crane could not reach.”
The cranes are designed not just to be compact on the job site, but when being transported and set up. Jahns says, “The city cranes have a really compact design. The carrier length is very short, the retracted boom is very short. The AC 70 City has eight telescopic boom sections. That means there is only a short overhang when the crane is traveling.
“It’s also important to have independent steering on each axle. That means that the cranes have a very low turning radius. The counterweight and main boom extensions are integrated into the crane, for a 12t per axle axle load. The crane should be able to work without additional transport. All of the cranes have a limited pick and carry capacity over the rear (all ATs do), but that’s not something we consider an important feature in this class.
“The selling point for us is the compactness, and the shortness of the retracted boom. The AC 70 City, for example, was the first all terrain crane to have eight boom sections. The AC 70 City also has a hydraulically offsetable last boom section: the last section can be offset by 25°. We can also offer different runners, with very short extensions, for working under roofs.”
Zollondz sums up the cranes’ appeal: “The city cranes are designed to be usable by one man, and to be rigged by one man.”
Terex Cranes and its precursors haven’t had the European city, or compact AT, crane business to itself though. As well as imports from Japanese manufacturers such as Kato, some of the first local competition came from German crane builder Liebherr. Liebherr avoids the city crane term, preferring to highlight a range of options for jobs on space restricted urban sites.
Marketing manager Wolfgang Beringer says, “We prefer the name ‘compact cranes’ not ‘city cranes’, as standard all terrain cranes can also drive in cities without restrictions.” Beringer says that users working in restricted environments will see advantages in the city-type LTC cranes, “but smaller LTM cranes as well. Our AT cranes (the LTM range) are also designed to be very compact, with all-wheel steering. mobile construction cranes (the MK range of truck-mounted tower cranes) are suitable for cities as well, as with their vertical mast they can stand very near to buildings. The jib reaches over the buildings and offers excellent load capacities at large radii.”
Beringer outlines some of the advantages of these types of cranes. As well as their extremely compact design, he says they offer a small turning radius, sensitive manoeuvrability, short tailswing and a short basic boom.
Liebherr currently produces one model most similar to other companies’ city crane designs, the LTC 1055-3.1. At a recent open day, it released pictures of a new addition to the range, the LTC 1045- 3.1. The new crane exposes one of the key debates in the design of city type cranes: whether to use traditional transmission systems, or hydrostatic transmission. While the older LTC model, like Manitowoc’s recently launched TK3045, uses hydrostatic transmission, the new LTC 1045-3.1 will use a traditional system.
Beringer explains, “The LTC 1055-3.1 has a hydrostatic drive: this offers an extremely compact design of the carrier frame, as the engine can be installed in the slewing platform. This is the high end compact machine for jobs in extremely restricted environments, but high tech means higher costs and prices.
“The new LTC 1045-3.1 is compact as well, but is also suitable for standard AT jobs. To reduce manufacturing costs and to improve operating costs, the engine is installed in the carrier and an automatic powershift gearbox with a torque converter for sensitive manoeuvring is used in the drive train.”
One of the objections to hydrostatic transmission is that these systems more often require the attention of a service technician. Manitowoc global product manager for all terrain and rough terrain cranes, Neil Hollingshead, isn’t convinced this objection is true any mor. “The hydrostatic transmission is good at manoeuvring in tight spaces, but doesn’t affect highway driving. We’ve performed 20,000km of tests, and we’re very confident it is working well. With hydrostatic transmission, you can use the retardation of the system when braking, so you don’t need an auxiliary braking retarder. That reduces wear on the brakes.”
Liebherr has innovated in other ways. Back when the city crane concept was first taking off, in September 2000, Liebherr-Werk Ehingen technical director Ulrich Hamme told Cranes Today, “The crane is the workplace of the driver. It needs to be comfortable. A crane with one cabin cannot be a good mobile crane. It is not a good driving position. The operator sits on his crane like he is on a horse. Crane drivers tell us they don’t like single cab cranes.”
Nearly a decade later, this problem is still a key concern for Liebherr. On the new crane, the cab is mounted on a telescopic arm. Beringer explains, “For driving on roads the cabin is in the front position, which improves the view for the driver. For crane operation the cabin is in the rear position. So the new LTC 1045-3.1 offers the advantages of a compact crane as well as of a conventional AT crane.”
Liebherr has worked to make the driver’s job easier during set-up and on the road. Beringer says, “With the new Liccon 2 control and the BTT (Bluetooth terminal) set-up of the cranes is faster and safer: detaching the hook from the bumper, supporting the crane and assembling jibs. Our cranes offer an automatic levelling per push button, which saves set-up time. Also ballasting of the cranes is fast and is done from the cab.
“We designed cranes with axle loads not exceeding 12t or even less. Some of our model are “all-in” cranes, which means, that no additional transport vehicles are required. Driving performances on-road as well as off-road has been optimised, such as with our active rear-axle steering.”
With its design for the GCK3045, Manitowoc has also looked to the importance of fast and easy set-up. Hollingshead says, “The set-up options for the crane also offer advantages in restricted environments. The five position outriggers can be extended in staggered configuration, with each outrigger extended according to the space available. The different outrigger positions are covered by the LMI, which offers an optimum load chart and ‘safe zone’ for the boom position.
“The twist jib can be erected within the width of the crane. As it swings under, not out, it can be rigged by the operator within the 2.55mm crane width. The crane is fitted with a self-stowing hook block. The operator just needs to retract the boom, and a bracket holds the hook block in place.”
The GCK3045, like other city cranes, isn’t just designed for city centre environments. Hollingshead says, “The GCK3045 is designed to operate in tight spaces at ground level; but it also offers advantages in low headroom environments in industry. For example, its height and width make it possible for the GCK3045 to pass through doors into buildings that other cranes couldn’t reach.
“The GCK3045 can be used for machine tools, in factories, or as a taxi crane in tight city environments. The heavy duty runner on the optional 1.2m short jib only has one sheave at the tip, giving additional headroom. The GCK3045 has very strong pick and carry capacities, both over the front and the rear; it can lift on wheels over 360°, but can only pick and carry over the back or front. It requires no additional counterweight. It carries its full counterweight integrated in the crane, within 12t axle loads.”
The manufacturers detailed here aren’t the only ones building city type cranes. In Italy, for example, manufacturers like Locatelli are building city cranes, and many rough terrains are designed for limited road travel (see the article on p25 of this issue). As manufacturers continue to innovate, their cranes will offer more options to fleet owners working at lower lifting capacities. With this sector hardest hit by the downturn in residential construction, maybe the options for other types of work, such as industrial lifting, that these cranes offer will provide a ray of much needed hope.
