The Rusch RS 4500-H - a blend of the best?

Decked out in Rusch Special Products' company livery of black and purple, the RS 4500-H is the latest in a line of five very special demolition machines that have emerged from this Dutch company's fabrication facilities. D&Ri has been to see the machine during its construction but the full scale and nature of the new 'demolisher' is now evident, as are its major design components.

First, the RS 4500 cannot be called a demolition excavator! True, it may have started life as a Hitachi 870 carrier (hence the -H designation), but the final result has been modified to a point that this is almost meaningless and incorporates design features that you do not see on even the largest demolition excavators. Incidentally, should a future customer order an RS 4500 based around a different OEM's carrier, say for example a Caterpillar machine, the -H designation will change to reflect that fact.

It is the new machine's designation that gives the first clue to the fact that while it may look like the high reach demolition excavators we are used to seeing on site, whether high reach or straight boomed, there is more to the RS 4500-H.

Almost without exception, an excavator designation has some connection to the weight of the machine, or in some demolition excavators' cases, the weight and height they can work at. In the case of the RS 4500-H, the designation reflects something unfamiliar to most in the demolition industry but very familiar to the crane sector - the maximum front tipping load moment, usually taken over the front idler on the track set that in this machine's case is 4,500 kilogramme Newton metres or 450 tonne metres. In its very simplest form, this number is derived from the weight on the boom multiplied by the distance of the load away from the carrier, but of course there is a lot more to it than that. Suffice it to say, it is a complex calculation, especially for a machine like the RS 4500-H.

As seen from the summary box, the machine has numerous operating configurations for its three boom options, and this is where maximum front tipping load moment comes in. The weight of the machine will vary according to the configuration adopted for the task in hand - hence a designation based on weight would not be a sensible one. However, the maximum tipping load moment remains constant irrespective of the configuration, hence the decision to adopt this as the designation.

Easy transport

A major design driver for the machine was the need to make transport as simple as possible and Rusch researched the varying regulations around Europe. Germany proved to have the most restrictive (maximums of 100 tonne weight, 28 m long, 3.5 m wide and 4.2 m tall) and designed accordingly, hence the selection of the ZX870 as a base rather than the Hitachi ZX1200, a popular choice among demolition contractors. Provision of a hydraulically extending undercarriage to provide an additional 1 m (3.3 ft) on each site in working configuration results in a square footprint that allows the machine to operate with full 360° rotation.

So far, only the four stage articulated boom has been produced. Its transport will require at least four special trailers, one for the body excluding counterweight, including the lower cylinders and boom element (although these can be removed and transported separately if required), one for the lower (main) and second (auxiliary) boom, a third for the third (main stick) and fourth (auxiliary stick), a fourth for the two track elements. The counterweight can be transported by a standard truck.

Once these reach the work site, the RS-4500-H body jacks itself up, allowing the trailer to be removed, and then acts as a crane to lift the two track elements into place where they are hydraulically secured. Once this is done, the counterweight is secured to arms that then hydraulically lift it into place on the back of the carrier superstructure. The two section main boom is then connected to the carrier body, followed by the two upper elements, all of which are securely locked into place by hydraulically activated locking pins.

The telescopic boom, when fabricated, is likely to have similar transport requirements, and the dig boom will naturally require less.

High strength

Another feature of the machine inherited from the crane sector is the metal used in their fabrication. Excavators normally make use lower yield strength steel than that found in cranes of most types, and it is the latter's 955 yield strength steel that has been used by Rusch (resulting in a strength almost 300% greater). While stronger, this steel is more brittle, therefore the weight saving that can be made in practice is only of some 30%, and it also requires skilled welders and the latest techniques to form the sections.

Safe operation

With its number of configurations, operating such a machine as the RS 4500-H safely and efficiently is a challenge, and here another element has been brought over the crane industry - an extensive load monitoring and control system that can accommodate the 15 separate configurations that are possible.

Separate working range diagrams have been developed for each. An IQAN system controls all the movements of the machine, with the safety features controlled by a separate system developed specifically for the machine by Rusch working together with system provider PAT. The latter software monitors inputs from a number of different sensors that monitor factors such as wind speed, counterweight position, boom configuration and angles, pressure in luffing cylinders, telescopic boom positions and locking, and hydraulic cylinder end of stroke. Should the system record a 90% approach to the established safe limits, an audible warning will sound, with all further movement cut if the 100% limit is reached. The operator can always retract from the limit position, even in the latter situation.

At time of writing, the machine has yet to prove itself on site, but it has been certified by the relevant TUV authorities in the Netherlands. D&Ri hopes to be there when it does start work in earnest and will report at that time. Irrespective of this, the RS 4500-H certainly looks the part - a logical evolution of the approach adopted by Rusch over the last few years into what is a true demolition 'hybrid', where the best from two technologies have been combined to produce what could reasonably be called a new machine class - the Demolisher.

The RS 4500-H in summary

Telescopic high reach:
3 stage lower, 2 section dipper gives 60 m (197 ft) pin height with 5 tonne tool

3 stage lower, 1 section dipper gives 54 m (177 ft) pin height with 10 tonne tool

Can also be used with telescopic stages progressively retracted to allow heavier tools

Articulated boom:
4 section gives 42 m (138 ft) pin height with 5 tonne attachment or 3 tonne breaker

3 section gives 32 m (105 ft) pin height with 10 tonne attachment or 7 tonne breaker

2 section gives 22 m (72 ft) pin height with 13 tonne attachment or 10 tonne breaker

1 section gives 14 m (46 ft) pin height with 17 tonne attachment

Dig boom:
9 m³ (318 ft³) bucket capacity, with dig force of 65 tonnes to depth of 4.5 m (15 ft)

These varying configurations naturally result in differing operating weights - at its heaviest (telescopic, two section dipper) it comes in at 180 tonnes and in its lightest configuration (articulated, 1 section) it weighs 150 tonnes.