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Concrete Carbon Parts
Concrete Carbon sells carbon fiber bicycle seatposts. Carbon fiber is the ideal material for this application because of its lightweight, ability to dampen road vibrations and the ability to structurally engineer the material for the specific application. Concrete Carbon will offer one diameter for the seatposts, 27.2, the most standard size. For bicycles that use odd sizes, Concrete Carbon will offer shims. The post is made in 250 mm and 400 mm lengths for road bikes and mountain bikes respectively. It will also come in three weight classes, a post for rider weights of <150 lbs, 150-190 lbs, and >190 lbs. The unit will come with a five year warranty. The post will utilize a carbon fibre shaft with a CNC (computer numeric controlled) machined head by Paul Components. CNC is the perfect fabrication technique because it allows small production runs, precise manufacturing, and there are plenty of subcontractors that can provide the machining. The head will be bonded to the shaft using a Loctite brand adhesive. The shaft will be made to specifications by Advanced Composite Technologies. Both vendors were chosen based on prior relationships/networking that Josh has developed. Since Josh owns the technical designs and specifications of his products, if necessary he would be able to take his design to different subcontractors.
As mentioned earlier, a CNC machining is the perfect fabrication technique. CNC uses a computer controlled lathe that is able to take a block of aluminium and through 3D machining, turns the chunk of metal into whatever the computer design indicates. Production runs can be as low as a couple and modifications can be made within a production run. Forged aluminum heads are only cost effective when production runs are double digit thousands.
All of the products and designs have undergone rigorous product torture testing. The product testing has served two distinct functions. The first goal is that it aids the design development because it provides invaluable information as to where and how the post will fail under adverse conditions. This information is then taken back to the design board. It also serves as an inexpensive way to significantly minimize the risk of a product liability suit. Engineering the product so it does not fail is key to the survival of this business.
Carbon fiber construction is the ideal manufacturing technique because of the high strength, the ability to design in structural elements as a function of the different resins used, and the orientation of the lay up. Carbon fiber (sometimes called graphite fiber) possesses both high fiber modulus (<33 to 120+ Msi), and high fiber strength (<200 to 1000+ Ksi). Carbon fiber can be made from a variety of organic or petroleum polymer fibers. Most commonly, it is made from either of two precursor materials: pitch or polyacrylonitrile (PAN). Most intermediate modulus fiber is made from PAN, while pitch is used for the production of high modulus fibers. The precursor material is spun into fibers and processed in three steps: oxidation, carbonization, and graphitization. This processing forms a turbostratic graphitic structure in which graphitic crystallites are aligned with the fiber axis and intermingled with each other.
The processing of carbon fibers produces three types of fiber: “High Modulus” fibers with marginal strength and marginal elongation to failure, “Intermediate Modulus, Intermediate Strength” fibers with higher elongation to failure, and “High Strength” fibers with marginal modulus and marginal elongation to failure.
The fibers themselves are manufactured by extruding some precursor or melt material through tiny orifices to form a fiber, and then stretching and heat or chemically processing the fibers to orient the microstructure and produce the desired properties. The fibers are then bundled into rovings, which can consist of many thousands of individual fibers, and the rovings are spooled or woven into. The cloth or roving can be impregnated with the uncured matrix material to form prepreg.