Combining materials for better bicycles

Bicycle manufacturer HIA Velo (Little Rock, Ark., U.S.), founded in 2016, makes carbon fiber bikes in the U.S. (HIA means Handmade in America), without relying on the typical business model of overseas manufacturing. The company recently introduced the brand name Allied Cycle Works, as well as its Alfa bicycle models.

Sam Pickman, HIA Velo’s director of engineering, who came to the company from Specialized Bicycle Components, says, “Designing and making carbon fiber bikes involves compromises that you try to overcome. You must balance stiffness and handling with rideability, comfort and durability.” Allied Cycle Works’ Alfa frames are typically made with six plies of Mitsubishi Chemical Carbon Fiber & Composites Inc.’s (Irvine, Calif., U.S.) unidirectional carbon fiber prepreg, both 130-gsm standard modulus carbon and 110-gsm intermediate modulus carbon, prepregged with Mitsubishi’s Newport 301 epoxy resin and supplied in 1-meter-wide rolls. Pickman also reports that the company is investigating 114-gsm TeXtreme spread-tow woven material supplied by Oxeon (Boras, Sweden), as an alternative to unidirectional prepreg.

Pickman acknowledges, however, that lightweight carbon fiber frame tubes can be damaged when riders crash, particularly during racing: “And typically the damage is unseen, so riders get back on, and the unseen damage causes the frame to unexpectedly come apart.” To add durability to its frames, HIA Velo worked with Innegra Technologies (Greenville, S.C., U.S.) to incorporate Innegra S high-modulus polypropylene fabrics, sized for compatibility with epoxy resin, to discrete areas of the Alfa bike frames to improve frame durability. “The woven biaxial Innegra provides flex — it is very ductile and damps vibrations, so it increases ride comfort. And it’s tough and absorbs impact, so we use it in frame areas that are potentially damage-prone,” says Pickman. Those areas include the seat stays, the top tube where the handlebars could impact the tube, and the fork crown.

The company typically incorporates the Innegra plies in the center of the tube layup, encapsulated by carbon fiber plies, with the Innegra often forming the innermost ply of the tube. “The polypropylene adds weight without stiffness,” explains Pickman. “We have to pick and choose where to have the flex and ductility.” Models incorporating the Innegra reinforcements include the Alfa road racer with rim brakes, and the Alfa all-road model.