Using Reverse Engineering To Get 1952 Race Car Running Again

The #28 Cummins Diesel Special shocked the racing world in 1952 when it captured the pole position at the Indianapolis 500 (Indy 500) with the fastest lap time in history. This feat, along with the car’s many other innovations, won it a prominent place in racing history.

Challenges:

The original water pump was a unique design specific to the #28 car, which meant no spare production parts would fit the bill.

Sixty-five years later, #28 was invited to the Goodwood Festival of Speed in the United Kingdom to participate in the legendary Goodwood Hillclimb along with hundreds of modern and heritage cars. While preparing #28, the Cummins engineers discovered that the water pump was so corroded it would probably not survive the event. If the #28 car was to make it to Goodwood in working order, it needed a new water pump.

They had to ship #28 within a matter of weeks, which ruled out traditional sand-casting methods as infeasible for a replacement part given an estimated lead time of 10 weeks.

Solutions:

Cummins engineers turned to reverse engineering and metal additive manufacturing (AM) using a ProX DMP 320 metal 3D printer by 3D Systems.

The baseline method for building a new pump housing is the same method that is used to build the original pump: machining a plastic or wood pattern and using it to form a sand mold for casting. Using this method, it would have taken about 10 weeks to build a single housing, ruling out a run at Goodwood. The lead time for the new water pump housing could have been reduced by 3D printing the new casting pattern or even 3D printing the sand casting mold itself, but the greatest productivity gains available came from bypassing the casting process altogether and using reverse engineering and 3D printing to produce the final part directly in only five weeks—50 percent faster.

Scanning

Cummins engineers began by scanning the existing water pump housing with a CT scanner. They selected a CT scanner because the pump contained many undercuts and other internal geometries that would have been impossible to capture with a laser scanner or other line-of-sight imaging tool.

Inspecting

To verify that the scan data was accurate before moving forward, the engineers imported the point cloud data generated by the CT scanner into Geomagic Control X inspection and metrology software where they separated and aligned the internal and external geometry of the pump.

“For a project like this, we typically separate out the internal volute geometry from the body so we can model it as a core and do a comparison back to the point cloud data to be sure all our work is accurate,” said Chris George, master CAD model team leader for advanced system design for Cummins.

Reverse Engineering

With good scan geometry to jump-start its design work, Cummins used Geomagic Design X reverse engineering software to convert the point cloud to a nonparametric solid model to perform CAD fit checks. These checks helped the Cummins team determine the right assembly dimensions for the impeller and shaft and how everything would ultimately fit and seal together.

According to George, Cummins uses Geomagic Control X and Geomagic Design X as its primary software for point cloud manipulation. “The 3D Systems Geomagic software provides a complete solution for processing and inspecting scan data and converting it to a solid model,” he says. “We use them for every reverse engineering project we do, which often requires geometric reconciliations, finite element analyses of structure and flow, and model-to-scan comparisons reported to our engineering customers.”

Designing

Due to the significant corrosion of the original part, Cummins could not use the model created from the scanned data as the basis for 3D printing. Instead, Cummins engineers imported the nonparametric model into PTC Creo^® 3D CAD software to act as a template for creating a parametric model. In light of the physical damage to the scanned pump, the Cummins team had to make informed decisions as they 3D modeled the replacement to achieve a functional final model.

3D Printing

The file was sent for cleaned up, analyzed it for optimal print orientation, and assigned supports for stable printing. The file was further sliced and hatched the part to define the movement of the laser during the build.

Although the original water pump housing had been made of magnesium to help reduce weight, magnesium’s susceptibility to corrosion following extended water and coolant exposure was a large factor in the problem Cummins was trying to solve. The final 3D-printed part was manufactured using LaserForm 316-L stainless steel material on a ProX DMP 320 metal 3D printer.

Benefits:

The new water pump was 3D printed in only three days and the entire process took five weeks instead of 10.

“The larger build volume of the ProX DMP 320 enabled us to have some additional options with part orientation, which helped us optimize supports, and the print speed allowed us to get the print done in the time we had,” said Bob Markley, president of 3rd Dimension. “The ProX DMP 320 also does not use a binder to join the material, which means the output is a pure alloy that performs like real metal—because it is real metal. This is a benefit to the final part performance given the operational environment.”