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Walter HUETTNER, Wolf Systems Mechanical Engineer responsible for the development, production and service of forestry machines, AUSTRIA

Introduction to Wolf Systems

In 1966 Johann Wolf transformed his parent's farm located at Scharnstein (Province of Upper Austria) into a place of business which soon grew into an international group of companies. More than 2 000 employees now work in about 40 subsidiaries in more than 40 countries worldwide, and Wolf Systems ranks among the most enterprising contractors in the prefabricated construction business in Central Europe.

The first activity of Wolf Systems focused on agricultural construction (silos, reservoirs, stables and other farm buildings), as well as on farm equipment. Gradually the product range was enlarged with structures for industry and commerce, and housing construction including cellars. The range now also includes a wide choice of machinery (forestry and wood processing equipment, nail plates).

The history of the company may be outlined as follows:

In 1968 a construction business was founded in Munich, and the first step towards a growing international group was taken. In 1980 a manufacturing plant at Osterhofen (Lower Bavaria, Germany) was purchased. This company is now the centre of the German activities of the Wolf group; 1989 was the beginning of activities in Eastern Europe and Russia. Nowadays we have manufacturing plants near Moscow, Torschok, Irkutsk and many other places. In the same year our English subsidiary, Wolf Systems Ltd., started business. In 1992 our activities in Poland started with a production plant for prefabricated houses in Katowice and a machine factory in Bielsko Biala. In the second half of the 1990s some offices in overseas countries were also opened, among others in China and Japan.

Some examples of our wide product range are:

Wolf house “finally at home”: Wolf Systems manufactures a large variety of wooden-based prefabricated houses, bungalows, country houses, etc., from unfinished to all-inclusive.

Wolf industrial buildings: From a simple roof structure to the complete insulated manufacturing plant, from the design up to turnkey plants, made out of timber, steel and concrete, according to the customer's wishes and needs.

Wolf concrete tanks: Year by year Wolf Systems builds about 5 000 concrete tanks for different uses. In this division we are market leaders in Europe. The tanks have diameters from 2.5 to 50 m, and their height depends on requirements.

Wolf glass coated steel tanks: The glass coating of our bolted steel tanks and silos provides special properties to our structures. Glass coating provides excellent rust protection, shock and abrasion resistance, temperature stability, hygienic surface and resistance to aggressive media. The application of the tanks and silos are in the agricultural and industrial field.

Wolf Systems - Mechanical Engineering

The mechanical engineering department at Wolf Systems deals with forestry machines and machines for special purposes. Apart from this, we design and manufacture different machinery for our production. In addition to this we are making our own tools for nail plate production. As far as forestry machines are concerned, our main goal is to be a serious and reliable partner for our customers. Our plant is located in the province of Upper Austria, in the northern part of the Alps. We are surrounded by mountains with very steep, wooded terrain. This was the reason for our interest in forestry machines. Specifically, harvesting in the mountains with extreme terrain conditions is a challenge for us.

Machines for special purposes are used in the truss building industry. For nail plate construction we design and manufacture hydraulic truss presses with press forces from 20 to 170 tonnes. The most important countries of exportation for this kind of machines are Germany, France, Great Britain and Ireland.

Forestry equipment

Now I would like to describe the forestry machines at Wolf Systems in detail. We started with this type machinery six years ago. Our first products were processor heads equipped with circular saws. These products are known as the former Steyr processor heads KP40, 50 and 60. In autumn 1998, Mr. Wolf and Mr. Ramsauer, from the Austrian Federal Forest Enterprise, signed a cooperation contract. Together with the engineers from the Austrian Federal Forest Enterprise we developed the processor head, Wolf 50B. Further cooperation included a new and bigger processor head, two sizes of cable yarder systems and two carriages.

Our current product structure comprises:

Processor head: There are two sizes available, the Wolf 50B and Wolf 65B.

Harvester head: Based on the Wolf 50B processor head, we developed the new harvester head Wolf 60H.

Cable yarder: We have two sizes, the Wolf PKM 12 for final cutting and the Wolf PKM 6 for thinning.

Carriage: There are also two sizes, both radio-controlled, designed for a 2 to load and a 5 to load, respectively.

Developing a new machine is nowadays a rather complex venture. The machine is the result of the relationship between the design, the calculations, the customer needs and all the regulations and specifications. All these requirements influence each other. If anything is changed, for example in the customer needs, there will be impacts all over the control loop.

As seen from the design point of view, customer needs may, among others, be specified as follows:

In detail the requirements are as follows:

Design embodiment:

In this design phase the basic layout of the machine is created.

Detailed design:

Based on the basic layout, the engineers in charge of the design particulars will create all detailed and assembly drawings for the workshop and for further documentation.

Design relationship

In recent years, the development of Computer Aided Design has brought us a significant step forward. Based on the never-ending process of technical progress in hardware technology, it is now possible to run 3D-software on normal personal computers. It is a great advantage for all engineers to see the machine growing on the screen. Many problems can be solved in the initial stage of product design.

Calculation relationship

Machine development is supported by several calculations. These are among others:


As a result of the technical requirements, the construction engineer has to calculate the energy demand of the machine. This demand can be expressed in kilowatts for motors, possibly together with the number of revolutions per minute and the torque. Another indicator can be the oil flow and the pressure for a hydraulic power supply.

Structural calculation

Based on the statutory basis, we have to perform structural calculations for cable systems. Only authorized calculation engineers who have specialized in static calculations are allowed to carry out this task. They must sign their proven static calculation.

Hydraulic needs

Most of the current machines in forestry are hydraulically driven. Therefore, many calculations must be done for the hydraulic system. For instance, it is of primary importance to maintain the temperature of the hydraulic oil within a defined range.

Relationship regulations and specifications

The development process of machines would be incomplete without mentioning all the regulations and specifications. There are:

With International standards, we think of ROPS and FOPS standards. Depending on the type of machinery and its application in the forest, one or more of the following standards must be considered:

ISO 8082: Self-propelled machinery for forestry; roll-over protective structures. Machines such as skidders, forwarders and harvesters are covered by this international standard. ISO 8084: Machinery for forestry; protective structures against falling objects. The operator cabin of the cable yarder system must be designed according to the instructions of this standard.

With national standards, generally the ONORM L5219 “Mobile yarder for logging” is meant. This standard was created in 1994 by the members of the Austrian standardization organization. It contains the specifications for the construction of cable yarder systems. For the design of cable systems this is the main standard.

Machine safety regulations

The design and production of machinery in the European Community is integrated within a network of international and harmonized national standards. All of them are called “Safety of machinery”. This means that the design and production departments have to consider that the machines are safe. There are various procedures to detect risks originating from the machine.

In the standard EN1050 “Principles for risk assessment” some of these procedures are mentioned. These are:

Determination and directives

To be exhaustive with specifications, the determination of the Austrian accident insurance institution and the directives of the truck manufacturers must be mentioned as well.

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