Aramid/carbon-framed X-9 Nighthawk looks like the stealth fighter of bicycles
By Ben Coxworth
March 29, 2012
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.
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.”
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.