I have built this carbon composite MTB frame four years ago using simple building method which is described in this Instructable. Of course, this method is not suitable for mass production, but if you plan to build just one or two frames for yourself, it is sufficient and you can build your own frame of a high quality. The feeling of riding a self-made frame is great!
After years of riding, the frame is still okay and I am still alive too, although I prefer riding my bike equipped by the bamboo/carbon frame, which I have built using the same method described here. Until now, several frames have been built by this method in the world.
Step 1: Few Important Things You Need for Building the Carbon Frame
1. Frame jig - it is used to hold all parts in their exact position. I have built the frame jig from scrap wooden rods and some lathed parts and connected with screws. You can also build e.g. adjustable aluminum jig, where you can make the frame geometry according your needs. As a template of a frame dimensions for construction of a jig, I have used my bike frame that I rode before. The completed jig was stiff enough and guaranteed the position and the alignment of the metal parts during the construction of the foam core.
2. Metal parts - they include an aluminum bottom bracket shell, head tube, short seat tube, cable stops, rear dropouts and a rear brake bosses. The used thin walled tubes and cable stops were made on a lathe, for the carbon frame I have purchased rear dropouts and brake bosses from the bike parts supplier. I have made them by water-jet cutting for the bamboo frame. I prefer to use 7075 Alloy for the metal parts. It is good to have all aluminum parts anodized, as then you do not need to wrap a light layer of fiberglass around the aluminum tubes and part of the rear dropouts as an insulation between the aluminum and the carbon against galvanic corrosion.
3. Foam core - I have used polystyrene foam to make the core of the carbon frame. But it is better to use extruded polystyrene, or polyurethane foam, which is more rigid. Later I have used the polyurethane foam which is normally used for insulation of the outer walls of buildings.
4. Materials for laminating - I have chosen a bi-directional woven carbon cloth (180 grams per square meter). I have used MGS's L285 epoxy resin with hardener 285 for laminating. For the carbon frame I used about 3.8 sq.m of the fabric, for the bamboo frame about 2.0 sq.m. You can also use uni-directional carbon for the base layers and use the bi-directional carbon just for the outer layer.
5. Supplies - I used plastic kitchen foil for covering the workbench during the wetting out the carbon, latex gloves, a small digital scale for weighing of the exact volume of resin and hardener, cups for mixing, paint brushes for wetting out, lots of electrical tape, sand paper and a good respirator during sanding.
6. Patience - the more the better