146 7 Reverse Engineering in the Automotive Industry
to within 0.005. “It would probably have taken several months if we had to model it directly, and I’m not sure we would have been able to capture the com- plexity of the actual cast surfaces”, Kiziah said. “The finished model looks and measures the same as the real block.”
GM and its racing teams now have an accurate digital model of the SB2 en- gine for CFD tests to optimize cooling, and secondary machining simulations to check for clearances and fit of new parts. FEA simulations will be used to deter- mine where material can be removed in secondary machining without affecting the strength of the block.
Reverse engineering of the SB2 engine block could be just the start in RCR’s quest to digitize parts that do not have 3-D CAD models. The team is working on a digital model of a total car assembly, complete with surface models of the chas- sis and the entire engine.
except for the front bumper, the only part for which Prodrive had a CAD model.
The point cloud of the half car body contained 40 million points.
The eight scan files were read into reverse engineering software, where they were merged and triangulated into a watertight polygonal mesh. A mirroring function created the other half of the car body that was not scanned, and different Figure 7.5. Advanced CFD Model X with a Faro arm is used to capture half of the Ferrari 550 Maranello body. Copyright © Advantage CFD, Brackley, Northamptonshire, UK, www.advantage-cfd.co.uk. Repro- duced with permission.
Figure 7.6. Aligned and merged point clouds of Ferrari 550
Figure 7.7. Ferrari 550 Maranello body reverse engineered in Geomagic Studio software and assembled and visualized in Pro/E software
148 7 Reverse Engineering in the Automotive Industry
sections of the body were aligned and merged together. The software then auto- matically parameterized the polygonal mesh, computed the nonuniform rational B-spline (NURBS) surface, and output the surface in IGES file format. The IGES files were imported into a CAD assembly along with the front bumper data.
After assembling a complete CAD model of the car’s external geometry, engi- neers defined a surrounding fluid volume and created a hexahedral mesh ex- truded from the majority of the body surfaces. A structured hexahedral mesh was also used to resolve the critical rear-wing flow, the flow under the flat floor, and the wake behind the car. The remaining volume was filled with tetrahedral cells. The 3-D model was tested initially without a wing to assess flow curvatures around the rear of the car and through the volume where the rear wing is posi- tioned. Based on these findings, a 2-D analysis was done on a wide range of wing angles. The analysis showed that the center of pressure for the new wing section should be moved further back.
Figure 7.8. Visualized results from CFD analysis generated by CEI’s EnSight software. Copyright © Advan- tage CFD, Brackley, Northamptonshire, UK, www.advantage-cfd.co.uk. Reproduced with permission. A color reproduction of this figure can be seen in the Color Section (pages 219–230).
Figure 7.9. Manufacturing the rear wing. Copyright © Advantage CFD, Brackley, Northamptonshire, UK, www.advantage-cfd.co.uk. Reproduced with permission.
Several new wing designs were evaluated on the 3-D model, simulating per- formance at the same speed as used on track tests. Visualizations of the first few design iterations showed regions of flow separation caused by the original wing mounts. The wing mounting system was redesigned to address the issue, and further CFD tests were run.
A comparison of oil flow on the rear wings clearly indicated flow separation on the mounts of the original wing and significant improvement in this area with the new wing design. The new design had a small separation at the trailing edge, but that was removed when a 6-mm gurney was attached to the wing. The final CAD model was loaded into CNC machines to produce tooling blocks needed to manufacture the new wing.
A new rear wing was made in time for track tests 6 weeks after the project had begun. The track tests and further running at the Le Mans prequalifying event confirmed that the new wing reduced drag by 2.5% for the same level of downforce.
Lap times on Le Mans test day confirmed what the race itself would later prove: The Veloqx Prodrive Ferraris were easily the quickest cars in the GTS class–with both the new and old wings. Because of time constraints, the new wing could not be tested for durability, a key factor in the 24-hour race. Not wanting to risk going into the race without durability testing and knowing that its cars were still the fastest, Veloqx Prodrive decided to stick with the old wing design. The wisdom of the decision was borne out by the victory of the young racing team.
Buoyed by the success of the Le Mans project and continually looking for a competitive edge, Prodrive developed an additional rear wing for the Ferrari 550 Maranello. The goal this time was to provide greater downforce for the American Le Mans series. A similar design approach was used for the new wing, and once again, it went straight from computational flow analysis to the track for testing. The wing exceeded predictions from CFD analysis when tested on the car and was used for the rest of the season, as Prodrive teams won the GTS class in all three of the American Le Mans series races in which they competed.