BICYCLES
Builders boost the bamboo bike frame
By Ben Coxworth March 19, 2014
The tubing in this frame may look like it's made from regular ol' bamboo ... but it isn't
It wasn't that long ago that bamboo-framed bikes were thought of as a weird rarity. Thanks to its combination of durability, stiffness and vibration-damping characteristics, however, the material has been gaining popularity in recent years. That being said, some designers still find that the random nature of pure bamboo makes it a little too unpredictable for producing frames of a consistent character and quality. That's why two frame builders have developed some interesting work-arounds.
The LamBoo model is part of Mereš' B-8 line of frames HeroBIKE's woven bamboo frame A close look at the woven bamboo/carbon fiber tubing HeroBIKE uses the same process to make its bamboo-slat tubing –
Bamboo, meet LamBoo
Slovakian mechanical engineer Braňo Mereš, who previously brought us the eye-catching X-9 Nighthawk concept bike, is now starting to make frames out of what he calls "LamBoo."
The LamBoo model is part of Mereš' B-8 line of frames
To produce his LamBoo tubes, he starts by wrapping thin sheets of epoxy-covered bamboo veneer around a cylindrical steel form known as a mandrel. He then places it in a mold, where it's subjected to 25 tons (22.7 tonnes) of pressure. Once it's removed from the mold and the mandrel is withdrawn, the result is a laminated bamboo tube that reportedly has the same good qualities as regular bamboo, but with a much more uniform and tweakable composition.
"I was building frames using natural bamboo, and it was quite difficult finding suitable pieces, because every one has different wall thicknesses, different properties," Mereš told us at the North American Handmade Bicycle Show, where his frames were on display. "Now I can design the properties, I can have 100 frames with the same properties."
Weaving it all together
HeroBIKE's woven bamboo frame
Elsewhere on the showroom floor, Alabama-based HERObike was showing off its own unique wares. Among those was a bamboo composite frame made by Lance Rake, a professor of industrial design at the University of Kansas.
Instead of laminated layers of bamboo, he used thin strips of the material that were woven together into flat mat-like sheets. Each sheet was then rolled into a tube shape, with an uncured cylindrical carbon fiber "sleeve" inside of it, and a sealed-ended length of bicycle inner tube inside of it. The whole tube-within-a-tube-within-a-tube combo was then placed in a cylindrical mold.
When the inner tube was subsequently inflated, the air pressure caused it to press against the carbon fiber, pushing it up against the inside surface of the woven bamboo. Once the carbon fiber had set, the mold was opened and the inner tube was pulled out, resulting in a rigid tube made of woven bamboo on the outside, bonded to carbon fiber on the inside.
A close look at the woven bamboo/carbon fiber tubing
According to Rake, the flexible woven bamboo can be pulled or compressed before curing to alter the diameter of the tube, plus it can be molded into tube shapes that aren't completely straight or cross-sectionally round. Although the one prototype frame is currently all that there is, he hopes to make a whole line of woven bamboo bikes.
"A lot of the things I wanted to find out, I'm finding out," he said. "I think the construction is viable, the direction's good, the weight's great ... I like it."
Company pages: BME Design, HeroBIKE
http://bmedesign.eu/
http://www.herobike.org/
http://www.gizmag.com/bamboo-bicycle-frame-alternatives/31292/
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Aramid/carbon-framed X-9 Nighthawk looks like the stealth fighter of bicycles
By Ben Coxworth March 29, 2012
The X-9 Nighthawk is a prototype bicycle with a frame made from aramid/carbon fiber sandwi...
Slovakian mechanical engineer Braňo Mereš has created some pretty nifty one-off bicycle frames over the past several years. Some of his construction materials have included riveted-together strips of titanium, a woven bamboo fiber/epoxy resin composite, and carbon fiber rods. With his latest creation, the X-9 Nighthawk, he has taken yet another approach – the frame is made from sandwich panels that have an aramid core and carbon fiber skins.
The X-9 Nighthawk complete bicycle, on display in BerlinThe aramid honeycomb material, used in the X-9's panelsThe X-9 Nighthawk frame weighs in at about 1.4 kilograms (3.09 lbs)The X-9 Nighthawk also features a custom carbon fiber fork, stem and handlebarsView all
Aramid is a tough, heat-resistant synthetic fiber that is used in products such as body armor fabric. The panels used for the X-9 are made of an aramid-based material produced in an open honeycomb pattern, allowing for a balance between structural integrity and low weight. Mereš used a water jet to cut these panels to size, connected them to one another, then laminated sheets of carbon fiber over top.
The completed frame weighs approximately 1.4 kilograms (3.09 lbs), although Braňo told us that weight wasn’t his primary concern with this project. “The goal of the experiment was mainly to design the first bicycle frame ever using honeycomb sandwich panels,” he said. “This material is widely used in the aircraft industry and offers a very good stiffness/weight ratio compared to pure carbon composites. The weight could be much lower if using more suitable and lighter epoxies, which I had unfortunately no access to.”
The X-9 Nighthawk also features a custom carbon fiber fork, stem and handlebars
To build the frame into a complete single-speed bike, Mereš added a carbon fiber fork, stem and handlebars, which he created specifically for the X-9. He also equipped it with a saddle of his own design, along with off-the-rack wheels, disc brakes, and a belt-drive drivetrain. He told us that it rides well, although he plans on test-riding it more in the near future.
The X-9 Nighthawk had its first public display earlier this month at Berlin Fahrradschau 2012 (The Berlin Bicycle Show), where it was reportedly well-received. Should anyone be wondering, incidentally, Braňo assures us that the images of the X-9 accompanying this article are all photographs, not renderings.
Source: Braňo Mereš Engineering and Design via Bicycle Design
http://bmeres.com/nighthawk.htm
http://bicycledesign.net/2012/03/brano-meres-nighthawk-and-more/
http://www.gizmag.com/x9-nighthawk-sandwich-panel-bicycle/22000/
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