Special axles – from complex customer requirements to customised running gear solutions

When designing a new series, low-loader trailer manufacturers are often in close contact with us at an early stage of the process. Let's take a typical low-loader trailer for transporting construction machinery as an example. As a first step, we work with our customer to agree on the technical specifications of the running gear, such as the axle loads and tyre sizes. We suggest suitable dimensions for the axle modules, depending on the planned vehicle width, overall height and frame construction. To comply with legal requirements, the use of steering axles may be necessary, especially for low-loader trailers with large wheel bases or excess length. 

As a rule, rigid axles and steering axles are combined for this purpose. We make a distinction between self-steering axles and force-steered axles. The steering angle is dimensioned differently for each axle; the further back it is located on the vehicle, the greater the steering angle requirement. This in turn defines the space for the pivoting wheels – the greater the steering angle, the narrower the space in the running gear. This is where vehicle manufacturers have to fight for every cubic centimetre.

The ride height also depends on how much upward travel and downward travel is required. The more axles the vehicle has, the more spring deflection is required. The combination of spring and steering movements ultimately determines the all-important installation spaces. Critical situations can quickly arise if the vehicle is steering while being lowered, such as when passing under a bridge. In these cases, the distance between the fixed component and the rotating wheel is often only a few millimetres. 

When it comes to those last few millimetres, we at BPW can modify existing trailer axles and, for example, change the position of the brake cylinder. The brake cylinders in particular dominate the installation space. Another option is to do something with the tyres. We stay up to date with the latest developments in the tyre industry, which continuously introduces smaller tyres with higher load capacities. Additionally, we offer the option to choose between single and twin wheels. In certain cases, even cranked axles can be provided.

We not only offer assistance with engineering, but also with trials and tests. The vehicle manufacturer can test their products together with our running gear components, for example their new axle suspensions. We test the test vehicles in accordance with automotive industry standards and equip them with the appropriate measurement technology for this purpose. We then assess the loads on specified routes and are able to replicate them in the test centre. This allows use to create a customised running gear tailored specifically to our customer's needs. 

Consultation on our latest innovations is also a key aspect of our customer meetings. A recent example is the BPW tyre pressure control system AirSave, which is now available for all force-steered and self-steering BPW low-loader trailer axles. Another innovation is the optional electro-hydraulic auxiliary steering BPW Active Reverse Control (ARC) for BPW self-steering axles up to 12 tons. With ARC, the last axle can be steered automatically at speeds of up to 10 km/h, both when driving backwards and now also when driving forwards. This enhances manoeuvrability, particularly for low-loader trailers.