Go into any bicycle store, and pretty much all of the bikes in there will have frames made from metal tubes or carbon fiber. A few manufacturers have gotten a bit more adventurous, offering frames made of bamboo or wood, while some have even experimented with things like aramid panels and nylon. A trio of San Francisco-based entrepreneurs, however, have created a prototype bicycle using yet another frame material – hand-folded sheet metal. They claim that their product is lighter, stronger and cheaper to produce than an aluminum-tube frame, and they’re hoping to be able to sell you one.
Rob, Mark and Andy are three mechanical engineers, who make up the company known as Ronin Metal Masters. They have devised a patented system for cutting lines of perforations into laser- or punch-cut pieces of sheet metal, that allows those sheets to be folded by hand. In the folding process, if desired, some sheets can be curved into pre-stressed self-reinforcing tubes. The individual folded sheets are then riveted together, or glued using automotive chassis epoxy. This allows them to be formed into items such as bracket joints for sheds, funky furniture ... and now, a street bicycle.
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After some experiments using heavy stock paper, the current prototype was built out of 0.024 inch (0.6 mm)-thick 6061-T6 aluminum. The entire process took less than three weeks, and the frame itself weighs under three pounds (1.4 kg). According to the designers, it delivers a spritely, rigid ride.
While the frame certainly has a unique “iron bridge” look to it, the choice of material goes beyond aesthetics. Because no welding is required, there is no risk of weakening the metal where welds are applied – a definite concern when building conventional metal frames. It also means that the frames wouldn’t have to be built in factories with industrial-strength welding equipment. Instead, it is hoped that the perforated sheets could eventually be “printed” at local outlets, then glued and riveted on location. This approach would greatly reduce transportation costs for Ronin (which would presumably be reflected in the price tag), although it would no doubt introduce some logistic complications, such as making sure that all the outlets had the proper machinery and metal stock.
Presently, the three bike-builders plan on offering buyers five options for the type of metal used: regular or high-end steel or aluminum, or a single grade of titanium. Estimated prices range from US$199 for a regular steel frame, to $999 for a titanium model. The first model that they plan on producing, made from high-end aluminum, should be priced around $499 – frame only.
They are currently raising funds on Kickstarter, to finance an initial run of 100 frames. A pledge of $300 will get you an unpainted frame, when and if they reach production, while $1,000 will score you a complete painted bicycle.
More information is available in their pitch video below.
Source: Ronin Bicycle Works