Special axles – millimetres make all the difference

From special low-loader trailers for transporting wind turbines to comparatively small low-loader trailers for gardening and landscaping, they all need to be as flexible and manoeuvrable as possible, with low loading heights and exceptional robustness. BPW Bergische Achsen KG offers a wide range of running gear systems for this kind of Special vehicles, with axle loads from 5.5 to 14 tonnes and 17.5" or 19.5" tyres: 

• Air-suspended axle units with rigid and steering axles as flexible all-round vehicles,
• Swing axles for maximum stroke
• and stub axles for compact installation spaces.

BPW boasts a comprehensive range of running gears. Our 260-page interactive reference work AxleGuide – running gear for commercial vehicles provides an initial overview of the range. Alternatively, vehicle manufacturers can use the online platform MyBPW to download our standard data to make an initial selection for their projects. 

This initial overview does not usually allow for a precise configuration of the running gear for low-loader trailers, but it does provide a good starting point. New types of low-loader trailer are always in demand on the market. When a large construction equipment manufacturer designs a new wheel loader with the capability to carry a greater volume in the bucket, it typically involves the installation of larger, more load-bearing wheels. The new low-loader trailer, designed to transport the larger wheel loader without requiring a special permit, can be loaded to a maximum height of 4.10 metres. Consequently, the grooves in which the wheel loader sits must be enlarged, presenting a substantial challenge when it comes to integrating the running gear. In such cases, BPW can tailor the details of the running gear to optimise them according to the specific customer needs. 

Vehicle manufacturers often develop new vehicle types based on existing models and initially use axle units they are already familiar with. If the engineers then discover space constraints, such as the brake cylinder being too close to the frame or the steering angle no longer being suitable, we assess whether we can reposition the brake cylinder or adjust the brake placement slightly to ensure the required installation space or ride height. In this case, we're talking about as little as five millimetres that need to be found somewhere.

The earlier we are involved in special projects, the better. This allows us to contribute our expertise during the early design phase and help vehicle developers to avoid unnecessary diversions. 

In doing so, we take account of all relevant technical specifications, including tyre sizes, wheel bases, steering angles, axle loads, spring deflections, ride heights and installation spaces. These parameters are essential for developing customised running gear solutions that satisfy both practical requirements and the highest technical standards. There are three main variants of suspension technology for low-loader trailers – air suspension, which is renowned for its high ride comfort. Hydraulic suspension, which is preferred for its robust performance and superior damping properties under heavy loads. And the swing axle, which really comes into its own in challenging off-road conditions. This is also combined with hydraulic suspension. 

The selection and combination of these technologies depends largely on the specific requirements of the project, such as ride performance, load index and environmental conditions.

In part 2, you can learn how BPW's experts develop customised solutions above and beyond standard products, and how vehicle manufacturers can collaborate with BPW to conduct tests and trials.