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The systems manufactured by Tridec of Holland allow further savings in tyre wear. And they increase semi-trailer truck manoeuvrability

Fabio Quinto

THE STEERING AXLE on semi-trailers is a peculiarity that is totally Italian. Over 30% of the semi-trailer trucks now in circulation (BPW data) have gone in this direction. It is imposed by our territory, which makes greater demands on manoeuvrability compared to the low-lying lands of northern Europe: just think about our mountain roads or the narrow spaces in ports, factories and cities. It is also imposed by an economic crisis that calls for maximum versatility and efficiency on the part of road transport firms. But to increase the manoeuvrability of semi-trailer trucks and reduce tyre wear to a minimum, there is another possibility: choose semi-trailers fitted with one or two axles controlled by the fifth wheel. This is the system by Tridec of Holland, which reduces steering angles also when reversing, something that does not happen with self-steering trailers. An example: if a semi-trailer with three fixed axles can manoeuvre on a road that is at least 7.045 metres wide, the same vehicle with the second and third steering axle of the Tridec system can do it in 5.395 metres. In both directions. How is this possible? Let’s take as a first example the “traditional” Tridec TD system that has been in circulation for over twenty years. Depending on the movement of the tractor, the semi-trailer’s fifth wheel pin controls a connecting rod and a rocker arm. A central bar then transmits steering movement to the axles. But, in addition to increased manoeuvrability, the system can also cut costs for road transport firms. According to Massimo Simbula, head of sales at Tridec, “the system will cut operating costs by 30%, thanks above all to less wear on the tyres because scrub during manoeuvring is reduced”. Not to mention the possibility of travelling on mountain roads or very narrow routes without having to transfer goods to vans or smaller trucks. Recently introduced to Italy is the Tridec TF system, where the central bar has been replaced by two tension rods: an innovation that makes the device stronger (suitable also for use in construction sites) and allows for steering angles of up to 45°, when previously they were only 35. In addition to the mechanical steering systems, Tridec also has a hydraulic version, the HF, which is particularly suitable for low-loading semi-trailers and tankers. Of course, there are some drawbacks: the Tridec system weighs an average of 650-700 kg and it costs considerably more than three fixed axles or a third steering axle.
The fitters that mount the most Tridec axles in Italy include Omar of Fano (Pesaro-Urbino), which has applied them in a large variety of segments: from closed box to isothermal trucks to tankers transporting technical gas. The Tridec axles can be particularly advantageous for urban distribution as they allow semi-trailer trucks (and those with a two-axle semi-trailer in particular) to replace separate three-axle trucks.

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