2008 AFS/ECS casting competition: Carley Foundry's shiny blue oil tank took home this year's prize for Casting of the Year, but not just because it was pretty

Modern Casting, May, 2008

[ILLUSTRATION OMITTED]

Castings aren't always aesthetically pleasing, but when they are, it's worth taking a closer look. The 2008 Casting of the Year (pictured) is one of the beautiful ones. But the other eight prize winners in the 2008 AFS/ECS Casting Competition are all beautiful in their own way, whether they exhibit the benefits of the casting process, show marketability or simply satisfy their customers' needs impeccably.

The oil tank shown fits on a Harley Davidson motorcycle; other industries that benefitted from this year's award winners were material handling, agriculture, energy production, military, heavy truck and automotive. It was those customers who were the real winners.

Casting of the Year

[ILLUSTRATION OMITTED]

Harley-Davidson Oil Tank Carley Foundry Inc., Blaine, Minnesota

Material: A356-T6 aluminum.

Process: Semi-permanent mold.

Weight: 9.25 lbs.

Dimensions: 14 x 10 x 8 in.

Application: Oil reservoir and style item.

Converted From: Plastic.

* The design beat out a plastic oil tank initially conceived by the customer, as well as a multi-piece fabrication.

* By casting in oil circulation tubes, the metalcaster helped make the oil reservoir more efficient and reduced the number of components in the assembly.

* Using a unique surface finishing technique and subcontracted machining and painting, the metalcaster delivered a complete part to the customer.

Harley and Carley Team Up for Design Tag

Harley-Davidson's Softail family of motorcycles aren't made out of plastic.

When Ron Hurth and the rest of the design team for the world-renown motorcycle designer remembered that fact, the door was opened for a metalcaster to design the oil tank for the new Harley Rocker motorcycle.

"[The oil tank] started out as a plastic inner tank with a cosmetic outer shield, but they couldn't make it look good enough for the Softail standard, which incorporates metal for most components," Hurth said. "The thing about Harley is that a lot of the stylists still want to stick with metal, so they didn't like the way the plastic looked."

Plus, the plastic tank would have required considerable one-time tooling costs, and doubts remained about its ability to withstand the high heats it would be exposed to on the body of the motorcycle.

Pouring A356 aluminum into semi-permanent molds, Carley Foundry Inc.. Blaine, Minn., offered a solution to the majority of the problems presented by the plastic design, as well as a fabrication proposed immediately thereafter. The solution led them to the 2008 AFS Metal Casting of the Year award.

"What [semi-permanent mold] does, basically, is combine all the features of both the other tanks," Hurth said. "You get heat resistance, the look of metal and a cost reduction from not having to assemble the internal parts. Everything is cast and machined into one piece, so it consolidated everything."

A Pretty Piece

The Harley Rocker motorcycle has several kinds of visible metal pieces. Some provide the brawn--the drive-train and structural supports--and others offer the beauty.

At first, Harley designers thought the oil tank could be lumped in with the stronger group, the parts that need only to be shot blasted to achieve the desired surface finish. After all, the oil tank is a mission critical part and hardly just a nice looking piece of jewelry. But because of its location and visibility, it later became clear that the oil tank would complement the other more decorative pieces nicely.

"We knew it had to be cosmetic and pressure tight," said Randy Oehrlein, Carley's vice president of engineering. "It had to be pretty, but a more effective part."

The metalcaster couldn't just blast the casting in the traditional manner and expect to achieve the fine surface finish it desired. To solve the problem, Carley employs a variant of a vibratory deburring process, which makes the critical cosmetic casting surfaces as smooth as the paneling on a luxury automobile.

Carley then subcontracts several different painting processes to give the smooth casting its color and sheen. For black, blue, pearl and red bikes, a wet spray is employed. Powder coat dresses up satin stainless bikes.

[ILLUSTRATION OMITTED]

"We are responsible for the part as the Tier One supplier," Oehrlein said. "Even though we don't do machining and painting in-house, we were responsible for finding the sources. The multi-step manufacture of the assembly is controlled by Carley straight to the bike."

More Than Pretty

The Harley Rocker's oil tank had to do more than just look good. The success of the bike's circulatory system depended on an effective part. "To build such a part, Harley and Carley engaged in a vigorous game of design tag.

However, the team played a game of tag that is more familiar in the world of wrestling than in the schoolyard. The object is to tag your partner when you need help, rather than to make them "it." And when the metal casting your team is working on wins Casting of the Year, you've defeated the other tag-team wrestlers.

Once the initial plastic design was rejected in-house by Harley engineers, they next considered a multi-piece assembly that involved an upper and lower die casting and a separate manifold. The design also required the use of gaskets. However, concerns remained that the assembly would leak--the oil level would reach above the split line between the two castings--and cost too much due to its elevated level of complexity.