Part 3 of Concept realization of an 4x4 Vehicle's Transfer case

  • April 13, 2015
  • Marcel Romijn

Continuing the demonstrator project at BRACE Automotive now the stage of development for a transfer case housing has been reached. Marc Fiedler; an intern from the Fontys Automotive Engineering Bachelor has been given a role in this step: The main task for the third stage of the Transfer case project is to design a housing for the mechanical concept that was established in the earlier stages.

To start with a housing the interfaces, that would exist between the mechanical parts and the housing, needed to be identified. By that, we mean the parts that actually ‘touch’, or pass through the housing itself. For example, the bearings, the axles and the shift shaft. These geometries were used to start the initial housing design.

For the concept housing design, the three bodies method was used. A general drawing of all the bodies needed for the way of designing was put on paper for visualization.

In this method, the bodies are subtracted from each other to create the housing. This approach helps in making complex objects and makes translation to the casting stage easier.

  1. Inner body
    This element was the first that was designed and represents the inside of the housing. Critical dimensions are based of the mechanical components, such as the gears and shafts.

  1. Outer body
    This is the second element designed. It containes the geometry and overall shape of the inside, plus an offset of 5 mm for the wall thickness. Ribs were applied for structural improvements where forces act on the housing. For example via the bearings but also via mounting points for e.g. the shift actuator.

  1. Base part
    This can be seen as a solid block were the inner and outer body will finally be subtracted from. It has roughly the same contour as the inner body, but it is marginally larger.

After all of the three bodies were created, an assembly for the housing was made by performing a so called ‘assembly cut’. What it basically means is that all of the bodies are subtracted from each other.
Starting with subtracting the outer body from the base part; This creates a solid body with the geometry of the outer body. Afterwards; the inner body is subtracted. What is left over is the housing.

Since the housing is designed to be build out of two sections to make assembly possible, these need to be mounted together. Therefore the process is repeated for the other side and finally the machining is done. This means drilling the holes for the bearings and bolts as well as skimming the flanges where the separate parts touch each other. The housings are designed such that all the machining can be done from one end; a simple cost-reduction idea that BRACE knows from experience.

When both parts of the housing are put together, the mechanical parts are loaded in, and the bolts and sealings are inserted. In the end a realistic model is established.

The next step in the project is to make the technical drawings, consider tolerances, etc. so that a 3D model of the housing can be made. Stay tuned for further updates.


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