This article discusses integration of handcrafted parts into computer-aided design (CAD)-designed bikes. The digital duplication process started when Harley Davidson sent Schaefer an assembly-ready Dyna Wide gas tank. It took two days of work to prepare the tank and scan it with an ATOS white-light 3D scanner, made by GOM mbH (for Gesellschaft fur Optische Messtechnik) in Braunschweig, Germany. Using Geomagic Studio, the software from Raindrop Geomagic, Advanced Design Concepts first converted the point cloud to a polygonal model. The 3D point cloud data were brought into Geomagic Studio, software from Raindrop Geomagic of Research Triangle Park, North Carolina. Using Geomagic, ADC first converted the point cloud to a polygonal model. The next step of processing created a non-uniform rational b–spline (NURBS) model. Digitizing the Dyna Wide gas tank represented the first time that Advanced Design Concepts had used Geomagic Studio on a Harley-Davidson job. According to an expert, the company now has three people devoted to working with the program.
It isn’t easy being a cultural icon. The role calls for equal shares of form and function, and the standards for them are exacting. Take Harley-Davidson, for instance: The name conjures up images of Peter Fonda in Easy Rider and buttoned-down executives putting on their colors for a weekend romance with the road.
The design of a Harley is intricate and each bike has been designed to be a classic. The company warehouses models, sculpted with clay, wood, or fiberglass, for parts from earlier generations of its motorcycles.
All that tradition can pose a challenge, especially when the company wants to integrate those older, handcrafted designs into a new CAD-engineered bike. To draw the exact look and feel of the curves of a signature Harley part—a 20-year-old gas tank, say—in a three-dimensional CAD system is difficult at best, and interpreting the shapes for a computer can be a time-consuming, expensive process of trial and error.
Legacy in the Gas Tank
When Harley-Davidson decided to incorporate a legacy part, the teardrop-shaped gas tank of the Dyna Wide Glide, into a newer motorcycle, the company turned to a consultant to carry out the reverse engineering.
This article was prepared by staff writers in collaboration with outside contributors.
For most vehicles, a gas tank is simply utilitarian. Not so for the Dyna Wide Glide. The teardrop tank, designed 20 years ago by Willie G. Davidson, is one of the distinguishing features of the motorcycle.
The Dyna Wide’s tank was originally sculpted in wood and its soft-curving shapes are too difficult to draw accurately in today’s computer-aided design software.
The company entrusted the job of reproducing the part to Mark Schaefer of Advanced Design Concepts, a 3-D modeling and CAD service bureau in Pewaukee, Wis., not far from Harley-Davidson’s hometown of Milwaukee.
The task at hand was to create computer surface models for the deceptively complex gas tank. Surface models would allow Harley-Davidson to integrate design and production of the gas tank with the rest of its CAD processes.
According to Schaefer, who has been handling jobs for Harley-Davidson for about 10 years, getting from sculpted piece to a CAD-compatible file usually took a week or more.
“We were familiar with the difficulty of this task,” said Schaefer, who started out using commercial surface modeling software. “Styling is what drives Harley-Davidson’s designs. Most of their styled models begin as clay models that need to be converted into CAD models for engineering design and manufacturing.”
For this assignment, he tried a new process that has changed the way ADC captures and duplicates Harley-Davidson legacy parts.
Dyna Wide Goes Digital
The digital duplication process started when Harley-Davidson sent Schaefer an assembly-ready Dyna Wide gas tank. It took two days of work to prepare the tank and scan it with an ATOS white-light 3-D scanner, made by GOM mbH (for Gesellschaft fur Optische Messtechnik) in Braunschweig, Germany.
The 3-D point cloud data were brought into Geomagic Studio, software from Raindrop Geomagic of Research Triangle Park, N.C. Using Geomagic, ADC first converted the point cloud to a polygonal model. The next step of processing created a NURBS model. NURBS, for non-uniform rational b-spline, is a technique for the mathematical representation of 3-D curves and surfaces that can reproduce complex shapes.
The final model was exported as a manufacturable IGES surface. The computer modeling steps together took a few hours, compared to three or four days with ADC’s previous surfacing tool.
In the final step, Pro/Engineer software from PTC Corp. of Waltham, Mass., was used to add parametric features such as mounting brackets to the model. The entire process was completed within four days.
ADC’s earlier surfacing methods made it tedious work to get the models within the accuracy range that is required by Harley-Davidson.
The surface accuracy of the model came within 0.003 inch of the original gas tank. “In the past, I had to work pretty hard to get models in the 0.010- to 0.015-inch range,” Schaefer said.
Raindrop Geomagic pitches the company’s product to potential customers by urging that a digital inventory of parts opens up enticing possibilities. Ping Fu, the company’s chief technology officer, said, “A digital inventory of parts saves warehousing costs and opens opportunities for design and reuse.”
According to Fu, the 3-D data can be used to spin off different designs, products, and applications with no duplication of effort. Substantial cost savings can be realized by having conceptual work, fit testing, and iterative redesign done on a computer. Replacement parts can be manufactured as needed, saving on warehousing costs, and at the same time, a manufacturer is able to avoid the risk of damage and deterioration of aging legacy parts.
Digitizing the Dyna Wide gas tank represented the first time that Advanced Design Concepts had used Geomagic Studio on a Harley-Davidson job. According to Schaefer, the company now has three people devoted to working with the program.