BRIEF
The object of this project was to convert a truck with a 6x4 configuration (1) to an 8x4: that is, to add an additional steering axle to a vehicle with only one. As this had never been done to this make and model of vehicle TSV was contracted to engineer the solution, working with specific guidelines from the client.

DESIGN PROCESS
The first step was to simulate the steering geometry in a 3D modeling package (2) to check that the vehicle had the correct Ackermann angles (the relationship of the wheels complementing each other wheel negotiating an corner, ie turned at a specific angle which corresponds to the circle diameter of that specific tyre).
The simulation established that ‘off the shelf’ items would not provide to correct ackermann angles for the  desired wheel base and axle spacing, so it was decided to remanufacture the main steering box Pitman arm to meet the design need. The original arm was copied with the addition of the required features.

The first step was to create a geometrically correct 3D model (3).
This was analysed for strength using a Finite Element Analysis (FEA) package (4).
The 3D model was then refined to avoid any ‘hot spots’.

MANUFACTURE
TSV also managed the manufacturing. A foundry with full CAD/CAM capability was selected, and given a 3D model of the casting (5), in an oversize condition, which then could be machined off the models geometry by a suitable CNC mahine.  The same company was able to perform the machining, using data converted from the 3D model. A tapered spline was machined into the larger bore by another subcontractor.
TSV supervised the fitting of the arm and its corresponding retrofitted components. The installation was inspected and tested on completion (6). TSV also certified the installation met LTSA requirements.

BUDGET
The project was completed with a design cost less than 50% of traditional hand based methods.

KEY BENEFITS