Intelligent tracking adjustment

All changes in processes can lead to further adaptations. When modern painting processes came onto the market in the early 1990s, BPW Bergische Achsen was one of the first axle manufacturers to use cathodic dip painting (KTL) – because it allowed for even better quality and higher corrosion resistance. Thanks to the KTL coating, for the first time it was no longer necessary to give the axle unit a top coat, which meant significant savings potential for trailer manufacturers. In parallel, KTL processes were also used for the first time in trailer production. The resultant process changes also posed a challenge for the BPW engineers: they had to find new solutions for tracking adjustment. “With dip-painting processes, it was no longer practical to weld the fully assembled axle unit onto the vehicle frame and then paint it together with the vehicle frame in a single operation,” explains Hans Werner Kopplow, at the time a development engineer and now head of the Electromobility Business Unit at BPW. “Previously, completely assembled air suspension axles were placed on the frame upside down and then welded on. Since the switch to dip-painting processes, supports are first welded to the vehicle frame and then the suspension is mounted after separate painting processes”.

Fine adjustment of the tracking was then necessary to compensate for possible manufacturing tolerances. “In close partnership with leading trailer manufacturers, we have been searching for a solution for efficient and reliable tracking adjustment,” says Kopplow. In the beginning, developers looked at various options but soon decided on spring bolt adjustment with movable adjusting plates. “Before the innovation was fully developed up to series production readiness it went through several optimisation cycles and a series of prototype test runs,” explains Kopplow. The tracking of units is now rapidly set up and adjusted without releasing the spring U-bolts. Easy adjustments of plus/minus five millimetres per wheel side can be made.

The advantages speak for themselves: previously, it was necessary to loosen the entire axle connection with eight bolts and move the heavy axle unit with millimetre precision to adjust the tracking, but now adjustment can be carried out much more rapidly. “The time saved in tracking adjustment is up to 10 minutes per axle or up to 30 minutes per axle unit. This is why spring bolt adjustment has quickly gained widespread acceptance, and its basic principle continues to be used today,” explains Kopplow.

The European patent specification for the adjusting device was published on 20th July 1994. The original version still had a casting welded to the adjustable support, but BPW engineers have been working continuously on further improvements. The current version of the support for the swivelling bearing of the axle guide, which was patented in April 2018, has a contour stamped directly into the adjusting plate to allow adjustment. This saves a welding process. Kopplow makes a clear and positive summary: “Integrated tracking adjustment has had a consistently positive influence on trailer production for decades. It also offers clear advantages when making tracking adjustments after more extensive repairs.”