Machine Design

Sheet-metal bikes

Ronin Metal Masters

The three mechanical engineers who make up the San Francisco-based Ronin Metal Masters have developed a method of cutting perforation lines in sheet metal using lasers or a punch press. The sheet metal can then be folded by hand into a variety of shapes, including prestressed, reinforcing tubes. Folded sheets can then be riveted or glued together with automotive chassis epoxy and turned into bracket joints or furniture. But the company has decided to concentrate on sheet-metal patterns that fold into bicycle frames.

“We can fold sheet metals into geometrically strong shapes, which is prohibitively expensive in small-to-medium runs using conventional methods, “ says Robert Hannum, CEO of Ronin Metal Masters. “There is no specialized tooling involved, which lets us come out with new and exciting designs whenever we chose.”

Their current prototype of a bike is made of 0.024-in.-thick 6061-T6 aluminum. It took about three weeks to cut the pattern and manually assemble it, and the resulting frame weighs under 3 lb. Because the bike is made without welding, there is no risk of the fastening method weakening the metal, a problem with welds. It also means frames can be assembled without the heavy-duty industrial welding equipment used in most bike factories. Instead, patterns might be created on sheet metal, then shipped to local assembly shops. This would cut transportation costs but could complicate overall logistics.

The company plans on offering five material options for buyers: low and high-end aluminum and steel, and a single grade of titanium. Estimates on prices range from $200 for a steel frame to $1,000 for the titanium version. And the high-end aluminum frame should be about $500. In an unusual scheme to get the production up to speed quickly, the company is accepting pledges of $300, which will get a person an unpainted frame, when and if the company gets enough orders to pursue production. A $1,000 pledge earns a completed and painted bike (again, if and when it goes into production).

© 2012 Penton Media, Inc.

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