Traction and tradition.

The Austrian rail ballast producer Hengl relies on the Unimog U 423 road-rail vehicle.

Hengl Mineral GmbH is a family-run company based in Limberg, which can look back over a century-long association with Austrian railways: as far back as 1918, the Hengls ran the quarrying and stone-crushing operations for the expansion of the Imperial railway line between Vienna and Prague. The Limberg rail ballast is still being used in rail-bound infrastructure projects throughout Austria today.

The company enjoys another more recent, but nevertheless unwavering, tradition that goes back 20 years now: all shunting operations in the sidings of the Franz Josef Railway are carried out using Unimog road-rail vehicles. The latest special-purpose truck, a Unimog U 423 with road-rail system, was supplied last summer in collaboration with Unimog partner Pappas, and since then it has been precision mounted on the tracks every day to transport thousands of tonnes of aggregate around the railway network.

Extensive range of specialist equipment.

The experience of Mercedes-Benz and the ZAGRO Group which carried out the road-rail conversion is evident in every detail of this Unimog. The modern camera equipment ensures safety as well as precision and a glance at the official equipment list reveals just how much technology has gone into this special-purpose vehicle: the list covers eight pages.


Traction on all routes.

The power pack already shows off its advantages on the journey by road to the rail track: thanks to a 5.1 litre Euro VI diesel engine delivering 231 hp and 900 Nm of torque, and differential locks on front and rear axles, it is guaranteed to arrive safely at the next on-tracking point whatever the weather conditions. The task of switching to the tracks is aided by the excellent visibility afforded by the panoramic windows, and the precise positioning of the Unimog over the rails is monitored via a camera – the driver can watch and adjust the process conveniently using a display in the cab. Coupling the wagons is also an effortless task thanks to another camera.

Technology. Weight. Power.

Once the rubber-tyred tractor unit is mounted on the tracks and converted into a shunting vehicle, the real work can start: the quiet-running screw compressor is actuated by the power take-off and delivers up to 1750 l a minute, supplying five air tanks and an operating volume of 4250 l. Enough to release the brakes on 52 axles.

As far as the traction of the four drive wheels is concerned, the high kerb weight of up to 13.8 t guarantees an excellent degree of friction between the rubber tyres and the tracks. A higher total weight for shunting vehicles has been approved for the Unimog especially for this purpose. The Unimog also has its own track-drying system fitted directly in front of the wheels. This is used while the vehicle is being driven.

Fleet manager Bernhard Hengl relies on the towing power of the Unimog U 423.
Fleet manager Bernhard Hengl relies on the towing power of the Unimog U 423.

Fully laden yet precise.

At a maximum speed of 20 km/h the vehicle combination makes its way along the gentle curves of the quarry floor. A large display shows the driver all the relevant data from the conveyor system. Other cameras allow the individual wagons to be positioned with the utmost precision for accurate and efficient loading. Within 15 minutes, all the wagons are loaded and ready for transportation. The Unimog switches from towing to pushing mode, and follows the rails in the direction of the Franz Josef Railway.

As soon as the loaded wagons have been placed ready for collection, the Unimog dismounts from the tracks again. The Unimog road-railer which had just been towing a mass of up to 1000 t can now head towards its next job at speeds of up to 90 km/h. Equally at home on road or rail, it consolidates the traditional link between the railway operator and the rail ballast specialist.

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