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.

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

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    About the Author

    Ben Coxworth

    An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away.

    All articles by Ben Coxworth


    • Why not stamped sheet metal? They make even firearms that way!

      Edgar Castelo
    • I like that.......

      Rather than serving up the kids the usual packed crap for Hexmas, it would be good to say, "Heyyyy lets BUILD a bicycle!!!"

      I am a bit wary of pop rivets, especially on things that are subject to stress reversal, and I am frightened to death of bicycles coming apart underneath me, down hill at great speed.....

      But as I am a big fellow, if I could be satisfied that this frame would hold together for say 10 years without "loosening up" I'd endorse this.

      Partly because I like things "you get to do", partly because you can include other people in it, and partly because I like the "Built by people" look, over the factory blandness.

      I also like it because of all the rivets and "cleverness much", and one of my friends was the late great professor Charles Slack - who with Timothy Leary pushed the LSD in the 60's.

      And you know the while LSD does have some "unique" poroperties, all the drug users really talked out their rear ends, LSD isn't mind expanding - "LIFE is mind expanding, and life is a wonderful addiction - and there is so many fascination things to do - and this bike just reeks of endless fascination and while the stoners are sitting around on the couch - this bike and things like it - is where life is happening."

      I can just see myself "Oooo I want to do this too!" and just enjoying making them.....

      Dammit - it just LOOKS like something that you just HAVE TOO tinker with.... and polish and.....

      Mr Stiffy
    • Give it a tarnished copper color paint job, and voila! Steampunk Bicycle. Nice look.

      Matt Rings
    • Not sure what the point is here. The frames are expensive and need lots of hand work and have holes in them to allow water and other stuff inside the frame. I Love folded stuff, but this just looks like a solution for the problem of how to separate hipsters from their cash.

      Michael Crumpton
    • Cool concept, but isn't this what Orange has been doing with the Orange 5 frame for a number of years? As demonstrated by Guy Martin in this video http://www.youtube.com/watch?v=mlIYEdRFQu4 filmed at the Orange factory. Guy shows how a flat metal sheet is formed into the downtube of the bike, using a folding machine.

      Josie Herbert
    • Josies got it right; but pressed or hydroformed sheet-metal frames still require a weld to join the two shells together. However I fail to see how a piece of perforated, folded sheet-metal could have any strength advantage over a "weakened" welded frame. Good welds should only reinforce the strength of the structure it is holding together.

      But if I see this as a giant jigsaw puzzle with novelty as its core marketing tactic then I think it is pretty cool.

    • looks cool, and it could lead to all sorts of interesting styling too.

    • Why not just print the frame on your industrial 3-D printer (material notwithstanding)?

      In any event, I'd like to see a latticework frame and adjustable on-the-fly crank length.

    • Someone said it is very expensive but for it's weight it is fairly priced. I like it because it looks heavy but it is very light.

      The Hoff
    • I saw a recumbent bike built like this in the 1990's at an event in Long Beach. It worked.

      William Volk
    • Meh, it's not really that cool. In fact it's rather ugly and the way it's made is labor intensive and expensive, which goes to show in the ludicrously expensive price tag. Hipsters will still love to blow their wad on one before they "become cool" and this company will do well in the short run, but in the end I'm sure this will remain a novelty.

      Demian Alcazar
    • only way to assess the strength of this protototype is to give it a good stress test and a good beating, ride it down some rocky paths and make measurements of it compared to a normal aluminium frame. See if their pop rivets are strong enough compared to tubes when taking a battering. I think they should do all that and give us some results before talking about a production run! if they make the pop rivets very tenacious and spreading the load it should be a great bike?

      1.3 kilos is amazing for a bike frame, considering a carbon fibre race frame is 1.15-1.3 kilos also.

      The main advantage with this design, is that it makes titanium frames easy to make, because titanium can't be welded, that's why it costs so much, so if you can just fold together titanium frames, then you can make very strong frames that weigh 1-2 kilos using just the price of some folding gear and tools instead of investing millions in a titanium forging equipment, that's intersting.

      yeah they should do a bunch more prototypes and put them through some cross country settings and tell us how strong they are!

      Antony Stewart
    • Rivets very in quality. I have seen pop rivets that were one short step above gluing the pieces together with bubble gum, high end rivets are quality goods. Most aluminum airplanes are riveted together without any strength issues.

    • Ronin is so overused. Just Google the word, almost THIRTY MILLION hits. Lost in the noise just a bit.

      A lordless samurai, esp one whose feudal lord had been deprived of his territory. or A student who has graduated from middle school or high school but has failed to enter a school at the next level.

      The two most common definitions = FAILURE. Might want to rethink your company name.

      Gregg Eshelman
    • A word from our sponsor..

      Yes.. many people have been folding metal in many ways ever since sheet metal has been out there. What is our difference?

      Using our technique, we are able to fold sheet metal to a tolerance that is equal to that of an expensive die without one (inside radius of the bend is 10% of material thickness). We can fold any sheet metal which include Aluminum T6, Titanium Grade 4, Magnesium.. even Spring steel ! Without the need for costly dies or folding equipment, these parts can be produced in any shop with a laser/punch turret.

      The rivets are just there to hold the shape until the epoxy sets up.. so after, you can drill them out if you like. This bonding technique is very common in aircraft and high-end autos... No welding allows one not only to not weld but also to not un-heat treat the AL and the Ti... Look at where these frames usually crack.. just outside the weld zone for just that reason.

      So far, the FEA analysis shows that the stresses are pushed away from the corners allowing for a stronger frame than with bending.. and in bending you are creating a situation of high compression in the inner corners and high tension on the outside.. which explains why a tight radius on a titanium sheet material is not possible.. certainly not spring steel. The material in the corners are very healthy and as time permits, we are running our frame through a battery of fatigue tests to see the match with the FEA.

      Why fold? Well imagine a shop like the one shown above with all these different sizes of tubing on the shelf for all different applications. What our process allows you to do is just store flat sheets of metal and you can print out, via a turret press, any shape you like. Since cross section is the key to strength, we show just one application.. a square to a triangle .. and back to a square... not possible using conventional methods (unless you use expensive dies..). Not to mention that if you check our our blog, you can see how "complicated and expensive" the folding equipment would be. I assure you that creating our down tube would take you 5 minutes.. even if you never did it before.. Hopefully, we will be able to mail out frame sets in a box that you could fold at home.

      Also, curves are no issue, since all one has to do is lay in a curved bend line and .. ta da.. you can have a curved frame.. We are just offering this one due to money limitations at this time.

      Feel free to check out our website for more info: http://www.roninmetalmasters.com/

    • Looks too weak to me - seems like the rivets would cause a stress riser, under certain loads I could see those rivets failing in shear, ripping clean from the frame or reaming themselves loose resulting in 'slop' in the frame - but it works on aircraft and bridges, so maybe it would be ok after all, it's just that, speaking from experience having sheared a traditional aluminum frame myself, I could easily see myself folding one of these in half or shearing those rivets.

    • OK - after reading Ronins comment, I retract my statement about shearing rivets if they're using a metal bond process, that's just as good as a weld.

    • WOW! These frames are cheap. They will capture huge marketshare....

      To try and sell this from a low cost point of view is a pipe dream. The frame is a small part of the overall bike's cost. Or to think it will have a better strength-weight ratio of regular steel/aluminum/CF frames. At 3 pounds....meh.

      Different look though but it will be a niche product for hipsters. Nothing wrong with variety.

    • The riveted frame from bent titanium laser-cut sheets was already built a few years ago - http://bmeres.com/rivetedframe.htm

    • I believe that arc welding produces nanoparticle.....bad. It is good to have alternatives.

      Stewart Mitchell
    • @RoninMM...

      Welds (or near them) ONLY crack for 3 reasons.

      Improper welding techniques.

      Inadequate joint design (load bearing, stress reversals, stress flows, improper materials).

      Failure to heat treat the Heat Affected Zone (HAZ).

      @ Ampfni France - Titanium can be welded - it's welded day in and day out BUT some grades weld well, some don't, some grades are reasonably tolerant of stress reversals, some are not, some are terribly notch sensitive, some are not.....

      Titanium ought to only be welded in an inert atmosphere chamber..., with the frame being flushed in the process.

      It seems to me that what makes the best weight to strength ratio in titanium for a bike frame, does not make for the ideal bike and the properties of the available alloys - thus a compromise is reached.

      Mr Stiffy
    • Quoting Ronin;" in bending you are creating a situation of high compression in the inner corners and high tension on the outside.." Surely this principle applies to the bend achieved along the perforated (slotted) metal sheet, which is already weakened by having a proportion of material removed.

      The bike certainly has an "I made this myself" quality. It is very expensive in my opinion.

      People are criticising welding, and riveting, which are amongst the most widely used methods of joining metal parts. I feel it is stronger than glue, personally. Would you fly in a glued aeroplane?

    • @ Windykites...

      A PROPERLY designed metal to metal joint, for a specific application, using rivets and glue, with the correct surface treatments, bonding materials, rivet types etc., is a very good joint.

      All assembly techniques have their inherent strengths and weakeness's.

      All joints and material have their limitations.

      A properly designed joint, is a very good joint.

      Mr Stiffy
    • If it's not cheaper than traditional frame why bother? Just to say look at me I'm different? You can build a frame in a garage with a TIG welder, chopsaw, and pipe bender.

    • How about a follow up article? What happened to these guys as I believe they didn't get financing through KickStart.

    • Its interesting reading the comments from people who obviously dont have direct experience with the methods being used in either bike ie orange or ronin.

      And if you have flown in any commercial aircraft in the last oh 30 years they all have bonded parts and newer ones like the Dreamliner 787 is mainly bonded metal or composites.

      My only concern about the bonding is not about the initial strength but what process is used. If not done the bond will be stronger than anything else for about 30 days than will degrade in any humidity exposure over time. The higher the humidity the faster. The rivets on any bonded part are only there for anti-peel not strength. You could take them out and it wont notice them gone.


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