By Shannon Wetzel, Senior Editor

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The Polaris Victory Core concept motorcycle started as a sketch dreamed up a few thousand feet in the air on a flight from Arizona to Minnesota. Michael Song, Polaris lead industrial designer for Victory Motorcycle, had been visiting with motorcycle enthusiasts who were riding stripped down versions of the Polaris Victory Vision touring bike. Song, who was building his own custom bobber—a raw, basic bike in which everything not needed to run is eliminated—was inspired by the transformation of Polaris’ complex touring bike into a simple bare-bones machine.

Back at Polaris’ industrial design department in Medina, Minn., Greg Brew, director of industrial design at Polaris Industries, was easily sold on the idea.

“We were interested in the minimalistic approach because it is really hard to do,” Brew said. “It’s easy to make something look modern when it is complex.” Polaris wanted to produce a modern-looking bike that was at the same time stripped of the excess.

Part of the answer to achieving the minimalist design was hidden within the Victory Vision touring bike. The large production bike features a cast aluminum frame, and the design team knew the casting process was capable of incorporating further part integration, which would be just the ticket for a bobber-style bike.

“The Victory Vision was our first application of a cast frame, but the Victory Core incorporates five or six more things,” Brew said. “We wanted to show there was a lot more you could do with casting technology.”

With the help of Craft Pattern and Mold, Maple Plain, Minn., an experienced supplier of prototype plastic and metal components, Polaris was able to make the Core idea a reality. The backbone frame casting—one of five castings that makes up the concept motorcycle’s cast aluminum frame—serves as the main structural component and incorporates the gas tank, air inlet, air intake box, electrical routing, and seat and motor mounts. The casting process afforded the bike superior design opportunities over typical steel fabrication and assembly, leading the backbone part to be named this year’s Casting of the Year by Metal
Casting Design & Purchasing and the American Foundry Society.

Complexity Made Simple

Before Brew and Song could think about sourcing the Polaris Core’s cast components, however, they had to convince the powers-that-be that the parts should be cast in the first place. Steel fabrications and tubing weldments are the standard for much of what Polaris makes—from its snowmobiles to its ATVs and motorcycles.

“It was a big jump for the company to go from a welded fabrication to a casting, and it took a lot of pushing from the design and engineering team,” Brew said. “But tube frames have a high part count and are difficult to weld and assemble. We wanted to show the aesthetic of the metalcasting process. Also, it is one of the least expensive manufacturing methods.”

The backbone casting consolidated what would have been a 20-piece steel fabrication into a single part. The integration resulted in a 30-35% weight savings, as well as significant cost savings in tooling and piece price. “It would take, for instance, $1.2 million to tool a gas tank,” Brew said. The tooling for the backbone casting, which incorporates the gas tank, along with several other critical features, was engineered and produced by Craft Pattern and Mold for less than $15,000.

“The process and cost-savings are really intriguing,” Brew said. “The impact of it is that the Core looks like a custom bike—everything is hidden in the frame—yet it could be the least expensive bike in our lineup.”
Craft Pattern and Mold’s team of machinists were able to fixture the casting and control critical part features and tolerances using CAD-CAM technology and CNC machining techniques, all of which led to improved downstream secondary processing and assembly efficiency.

“Casting reduces the tolerance variation, so we start with a more accurate base,” Brew said.
In addition to part consolidation and cost savings, the cast aluminum frame increased the rigidity of the bike, improving its resistance to the twisting force pulling on the front and rear wheels. According to Brew, tube frames have more flex, so when the bike is taking a hard corner, the frame bends, causing the two wheels to move in different directions from each other. The cast frame’s inherent rigidity prevents that from happening.

“The other thing I love about the casting is that it gives fantastic validity to the front end of the bike,” Brew said. “It has a certain mass and polished spine that is really just amazing. Only because we cast the bike were we able to do that. The overall feel of the cast frame is very powerful and solid.”