Fad or future

25 April 2008

A pair of Mantis duty cycle telescopic crawlers working at the South Pole

A pair of Mantis duty cycle telescopic crawlers working at the South Pole

Developments over the last 12 months in the telescopic boom crawler crane sector started with the 40 tonne capacity Hitachi Sumitomo SCX400T (IC March 05). Following on were the 65 tonne capacity Marchetti MTK 1004 C (IC June) and the 100 tonne Liebherr LTR 1100 (IC August). They continued with the TCM model RTC 35 and the Terex-Bendini TCC 45, both announced in IC in November. Since then announcements include two more from Terex in the form of the TCC 40 and TCC 60, and the Link-Belt TCC-450 (see this month's News).

Existing product offerings include the three- model ranges from Japanese manufacturer Kobelco (TK350, TK550 and TK750 introduced in 2000 and designed for the foundation market) and Sennebogen from Germany has 16, 40 and 80 tonne capacity models in the 613 HD, 630 HD and 683 HD, respectively. Also with a three model range is Favelle Favco in the US (owned by Muhibbah Engineering in Malaysia) of 30, 40 and 60 US ton capacity units.

For about 30 years SpanDeck, also in the US, has been building telescopic crawler cranes. Early on these were mostly at the lower capacity end but in the 1990s the larger models were developed. Its Mantis range includes five base models from 18 to 70 US tons capacity.

Italian manufacturer TCM has been offering telescopic crawlers for three years and says it sells about ten units a year. Terex-Bendini, also in Italy, has been offering the soon-to-be replaced 60 tonne capacity A600C for several years and Japanese manufacturer IHI offers the 30 tonne capacity CCH 300T and 50 tonne CCH 500T (IHI also builds some smaller models outside the scope of this article).

Looking ahead, Kobelco is considering extending its range and is assessing the potential of the European market with a view to introducing one or more models there. Expect to see new models from at least two US-based manufacturers before the end of the year. Pat Collins, Link-Belt product manager, says “it's conceivable we could expand to three or four different sized units.” This fits with the possibility of a new 65 tonner and perhaps another larger model under consideration by Hitachi Sumitomo, according to Rod Abbott managing director of UK distributor, NRC Plant (Sumitomo owns Link-Belt).

Up the scale

Liebherr, meanwhile, which introduced the 100 tonne capacity, 52 m boom LTR 1100 last year, says it does not have any plans for additional models at the moment. The company says it has sold 25 units of the new model since its launch last August, many of them in Europe, some further afield but, as yet, none in the US. (Liebherr's previous foray into telescopic boom crawler cranes was the 800 tonne capacity LTR 1800, a one-off delivered to Japan in 1990.)

Further back, among others, Coles, (now Grove) built a telescopic crawler on rubber tracks. Against the grain of current trends, Kato in Japan has stopped making telescopic boom crawler cranes. It used to make the 8 tonne capacity CR-80C, which, at the lower end of the capacity scale, is really outside the scope of this article. (See a future issue of IC for more on small telescopic crawler cranes).

Among the growing band of enthusiasts of the breed is Robert Law, managing director at AGD Equipment, which is the IHI distributor in the UK and also operates a rental fleet. “This type of crane is a thing of the future,” Law says, “We are looking at buying another half a dozen of each [the IHI 30 and 50 tonners] for the rental fleet.” In addition to smaller telescopic crawlers, AGD's fleet includes seven 30 tonners and five of the larger model. The 30 to 35 tonne capacity range is the future, at least in the UK, Law says.

Commenting on Link-Belt's entry into the sector in the US with the TCC-450, Pat Collins, product manager, says, “We have long been aware of the special niche market that drives the core demand for this type of machine. However, we felt the full potential for this type of machine was not being realised. Current manufacturers providing this machine are either highly customised, without the latest technologies, creating some quality and support issues and some manufacturers simply use an excavator base unit. These two issues are keeping many potential buyers of telescopic crawlers on the sidelines waiting for the complete package.” Collins estimates the total US market has increased from the traditional 25 to about 45 units a year.

The view at Kobelco is that “the market is still developing although it will not become a major market like the market for lattice boom crawler cranes. However, the telescopic boom crawler crane has good potential in principle.”

One reason Terex is adding to its range is “to meet the rising demand in the niche sector of specialist equipment for deployment on tricky soils.”

Despite the current rush of interest in the sector, Bill Mitchell, Mantis Cranes president and CEO, says, “we don't see a boom coming. Changes in the structure of the crane market happen very slowly. Over the past 30 years we've seen almost every crane maker in the world build a tele crawler - for a year or two. Almost without exception, they have introduced a model or two, ended up selling way less than they'd hoped or suffered major technical problems and given it up.”

Applications for telescopic crawler cranes in general include power transmission line construction, other utility type jobs, and foundation work. Other typical uses include water tank construction, assembly of precast concrete and steel buildings, and handling shuttering and formwork. Sheet piling contractors use them as service cranes for piling rigs.

Taking advantage

As all design is a compromise, just like any other type of crane, there are advantages and disadvantages to telescopic boom crawler cranes. Comparisons are typically made with lattice boom crawlers but also with all terrain and rough terrain wheeled mobiles. Some pros and cons are general and apply to the overall principle of a machine with crawler tracks and a telescopic boom while others are more specific and apply according to differences between machines in the category. Some machines are, for example, designed for heavy duty foundation applications while others are pure lifting machines. Some operate solely “free on tracks” and others have outriggers.

Strong demand for land, with its consequent increase in value, puts the pressure on developers to squeeze as much as possible out of even the smallest plots. As a result, construction sites are becoming more congested and smaller - or both - which increases the potential value of telescopic crawler cranes. Where, for example, telescopic cranes do not need the (possibly unavailable) space on site that lattice boom crawlers and tower cranes might need to lay out the boom flat on the ground for erection (and an assist crane might also be needed).

In addition to the space required for rigging and de-rigging, time saved is another bonus of a telescopic boom over, for example, a lattice crane. Time is money and the cost to rig a lattice crawler with 30 m boom is around £1,000 (US$ 1,800), says Rod Abbott, managing director of UK Hitachi Sumitomo distributor NRC Plant.

Compared with rough terrains rigging time is similar except that on crawler models without outriggers no time is needed for outrigger deployment or mat placement. In addition, Pat Collins says, they are easier to operate than rough terrains and have a lower centre of gravity.

To accommodate picks at different radii the telescopic boom length can be adjusted much more quickly than a lattice boom. Retracting the telescopic boom is quicker, occupies less space than a lattice and no assist crane is needed. This has benefits during transport and for work on congested sites, quickly moving under obstructions such as bridges.

Bill Mitchell at Mantis explains, “the inability to change boom length easily and quickly often means that contractors select a much larger lattice crane than would otherwise be needed as they want it to do all required work without changing boom length. Therefore, often, a smaller and lower cost telescopic can replace a larger and more costly lattice.”

Quick change

Rapid boom length change is a particular benefit on larger telescopic crawlers at, for example, an airport where the crane's boom needs to be lowered at night. It is similar on railway jobs where there can be no encroachment over adjoining tracks. They can also be useful inside buildings where access and operating space is restricted. A common fitment is a short offset jib to maximise hook height under a roof.

Telescopic crawlers designed without outriggers have a pick and carry lifting duty chart for travel with a load on the hook. It is also possible to telescope under load to manoeuvre around obstacles. This is where the differences between the types of telescopic crawler become most apparent. Models with outriggers also have a chart for duties on tracks or might not have a pick and carry duty. Some also have a duty chart for when the undercarriage is retracted, usually done to reduce the width for transport but it also can help access on restricted sites. The 30 tonne capacity IHI CCH 300T, for example, becomes a 20 tonner with the undercarriage retracted.

Crawler tracks make telescopic crawlers ideal for negotiating steep gradients and soft, muddy and uneven ground. Less site preparation is needed and ground pressure is lower than on a wheeled crane. The degree to which they can handle out of level conditions under load, however, varies widely. Some machines are built to handle this and others are not. TCM says its machines are designed to handle out of level conditions up to an angle of 2 degrees.

Transport is another area where telescopic crawlers score points. Small and medium sized machines can be moved on one low loader and require no special permits, no extra trucks, or support cranes, or rigging (boom assembly, mounting of counterweight, etc.). Lower transport and rigging costs than, for example, lattice boom models, helps offset the often higher initial purchase price of a telescopic.

The easy transport and quick set up time of a telescopic crawler helps viability for shorter term rentals, perhaps down to a couple of weeks, Rod Abbott says.

There are advantages over other types of crane, especially lattice crawlers, truck cranes, all terrains and RTs but there are also disadvantages, which tend to increase further up the capacity scale, at least in terms of transport and rigging and de-rigging time and cost. On larger models having to mount and remove counterweight and use extra trucks to carry it between sites can begin to erode the advantage over other types of crane.

Against lattice boom crawlers there can be disadvantages, for example, many telescopics are unable to compete on the degree of duty cycle operation and are likely to have a shorter overall boom and attachment system length. In addition, further up the capacity scale, “the lattice crane will out pick a telescopic crawler and have longer practical working radius capacities,” says Collins.

In comparison

Depending which side of the business you are on, another advantage is a premium on rental rates for a telescopic crawler. Robert Law at AGD says the premium over, for example, lattice crawlers, is about 25%, on a tonne-per-tonne basis. However, a 40 tonne telescopic, for example, is not as good a lifter as a 40 tonne lattice boom model. A 50 tonne telescopic is about as good a lifter as a 40 tonne lattice.

Development costs of a telescopic boom are higher than for a lattice, which can help make the former more expensive to buy, depending on options and other factors, by between 5 and 10%, Collins at Link-Belt estimates.

However, on the so-called 'hybrid' machines - ones built using an existing upper from a wheeled lift crane such as an AT, RT or truck crane - engineering development costs are much lower, which helps with the price, and components are already proven. Long lightweight booms with impressive lifting charts are a characteristic. Some of these cranes are designed just for lifting work while others are for heavy duty jobs.

All of the Mantis telescopic crawlers, for example, are duty cycle machines. Bill Mitchell comments on the hybrid type “They cannot handle the stresses and side loadings imposed by augering or piling and can be unstable when they travel and swing on grades. Most use a lot of counterweight, which can be a major problem when standing, swinging or travelling on a grade, with serious backward stability implications.” Mitchell continues to say that hybrid cranes seem to be “built to operate on firm and level ground only and since crawler cranes do not have outriggers, our world is not flat.”

Either way, whatever the advantages are of one type over another in some applications, or against other types of crane, the current strong interest in the sector suggests that telescopic crawlers are worth a look and they might just have the edge for an increasing number of jobs.      •

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