Dellner Couplers (now known as Dellner Train Connection System) is a manufacturer of couplers for passenger trains with their headquarters located in Vika, between Falun and Borlänge in Dalarna. For this thesis project Dellner had a wear problem of parts in the support and centering (SCD) device. This device is placed under the coupler, mounted to the pivot anchor in the rear and to the buffer tube in the center section, to support and center the coupler so that a coupling can be made without any manual work. When coupling has been made the SCD does not fill any function and wear issues occur due to hilltops and curves along the railroad which causes the coupler to move both vertically and horizontally. These movements cause the dampers to move in a linear fashion through the support damper holes in the front bracket and this leads to worn-out bushings/sleeves placed at the dampers. The problem is that the sleeves are worn-out after approximately four years while the normal maintenance interval is eight years.
The project has investigated the wear problem to find the root cause and tried to investigate possible solutions in order to develop suitable concepts to solve the wear-out problem. The project is based on the product development process as given by Ulrich & Eppinger (2012) and the purpose and goal have been to apply this method to develop one or more concepts.
After the analysis several ideas for different kinds of solutions were generated and some of these were picked for concept screening. For the concept screening eight possible concepts were included and presented as they possibly could act as the beginning of a new product or solution to solve the current problem with worn-out sleeves. Four concept ideas for an older type of bracket with an old interface, and four concept ideas for a newer bracket type with a new interface were presented.
The conclusions are that the angular displacements between the axis of the damper (the strut) and the support damper holes are one root cause for the current problem as well as the movement of the dampers in the support damper holes. It is clear that this problem with worn-out sleeves is solvable within reasonable limits regarding time, complexity and economy. With more time, concept scoring followed by a final selection, final specifications and a detailed design would have been done and so are suggested as further work.