Linear plain bearings for bus trailer steering systems

Bus trailers are becoming increasingly important both economically and ecologically. This is because the ability to detach it from the towing vehicle during off-peak periods reduces wear and fuel consumption, important arguments in times of rising energy prices and particulate matter regulations. Extremely high demands are placed on the safety of passenger trailers. In the course of the implementation of competition-orientated EU regulations and the energy law reform, as well as increasing cost pressure, all transport companies are required to review their profitability and efficiency in all areas and align their investment decisions with these framework conditions. At present, exemptions still have to be obtained for the registration of bus trailers. For approval reasons, the trailer is based on a purely mechanical steering system, for which durable and high-quality bearings were sought that must fulfil the requirements of everyday operation. Safety and comfort, easy handling, and problem-free maintenance: these were the most important key points in the development of the trailer, which has four-wheel steering.

Open and closed drylin R linear plain bearings from igus SE & Co. KG in Cologne have been used in bus trailers right from the start. The product range is based on highly wear-resistant polymers specially developed for linear technology. The dimensions are compatible with standard ball bushings. Their special geometry guarantees robustness even under extreme environmental conditions. The linear guides with polymer sliding elements for the steering system help to keep the trailer safely on track at all times without grease or oil and even in very dirty conditions. They are virtually resistant to dirt. They offer a very high level of safety even in the coarsest dirt. The absence of lubricants and the special design of the bearing surface with its individual raceways and the interruptions between them have a particularly favourable effect here. Even if damp dirt hits the shaft, it is wiped off the individual raceways and pushed back into the non-contact tracks. The crossbars of the running surfaces of the bearings then slide on the track that has been wiped free of all dirt. A total of fourteen drylin R linear plain bearings are installed in the steering system of each trailer. They transmit the steering movement from the front to the rear wheels. An extra guide system was selected, which can easily absorb misalignments due to the crowning in the centre of the housing in order to take edge loads from the push rod. In addition to their design advantages, the linear bearings are particularly impressive due to their material features. They are corrosion-free, wear-resistant, have a low coefficient of friction, run quietly, are lightweight and cost-effective. An in-house development would never have been worthwhile. Some time ago, the first authorised trailer came to Augsburg for a general overhaul. The bearings in particular were analysed and no obvious defects were found. Even flash rust had not attacked the bearings.

The redundant push rod system developed and patented by the company plays an important role in the overall solution. It transmits the steering movements of the front axis to the rear axis purely mechanically. It consists of several rods and two slewing ring plates at the ends. Depending on the application profile and customer requirements, different steering angles of the rear axis can be specified. Using the trailers is good for the environment and the budget. Calculations show that fleet operation can reduce fuel costs by more than 30% per year. This leads to savings well into the six-figure range. But the calculations go even further. As the linear plain bearings are lubrication-free, there is no need for expensive centralised lubrication, which is also very harmful to the environment.