BODY IN WHITE or THE PARETO PRINCIPLE

The body-in-white of the TWIKE 5 is currently undergoing its foreseeable final development phase before it finally makes its way from the developers' CAD programs to the prototype workshop in a load-path and weight-optimized sheet metal shell construction. A positive aspect was that the chosen design allows relatively uncomplicated modifications. The accompanying simulation calculations also show that further improvements can be achieved in terms of weight, costs and rigidity.

In addition to all the advantages, however, the 80/20 Pareto rule also comes to mind: For although the additional 20% improvement is clearly noticeable, the associated efforts are also grueling and time-consuming. To our relief, we have to note that the revision was not so much driven by a pure striving for optimization, but was necessary because changes in the suspension and the positioning of the engine made it necessary. This is because the drive unit, which is now set for series production, has a slightly different form factor and this required an adjustment of all adjacent components (position of the rear axle tube, drive shafts, connection and type of engine mounts) and thus also of the bodyshell that connects everything.

The change in the position of the rear axle tube in turn required readjustment of the mounting location of the chargers. The dimensions of the chargers also had to be adjusted slightly, which was achieved by chamfering the edge of one side panel, which seemed simple in retrospect. Fortunately, the housing design of the charger was also in progress at this time, so that the corresponding modification was not critical in terms of time and cost. If there had been no available space under this housing wall of the charger, the rear design would have had to be tackled again. The associated change loops should not even be listed here, we are simply grateful that the optimization could be completed so invisibly.

The adjustment of the frame concept cost time, but allowed the weight and stiffness to be optimized once again. It was also possible to optimize the assembly concept once again in terms of time-saving workflows during installation but also during potential removal of the drive unit. The complete unit, consisting of motor, inverter, transmission, drive shafts, wheel carriers, trailing arms, wishbones and the de-pauly rear axle developed specifically for the TWIKE 5, now sits as a sub-assembly on a summarizing sub-frame. This sub-frame supports the pre-assembled sub-assembly and, once fitted to the vehicle frame, closes the rear end, thus making a decisive contribution to the rigidity of the overall structure. This now possible pre-assembly as a sub-assembly also helps to keep costs within the target window and promises to make the final assembly process more reliable.

Time-critical for the start of production (SOP) is currently the all-connecting frame (body-in-white), which is why there is currently the greatest pressure to act and we have therefore dedicated this news article to it.