Carbon fiber frame construction

[blanclui]

Are you interested in learning how to build a carbon fiber frame? I would like to show you how I built my own carbon fiber frame, from raw material to taking it out for a ride. I would like to mention that I learned how to do all this after attending the carbon fiber frame building course ran by Dave Bohm from Bohemian cycles (Tucson, Arizona).

 

[blanclui]

Hello, my name is Luis and I build bike frames made out of carbon fiber. I would like to show the process that I follow to design and build such framesets. I'm about to finish a road frame and I will be posting notes on how I'm progressing (including photos). I hope it is informative for you and I hope I can also get help from some of the members of this forum.

 

[blanclui]

To begin the construction of a carbon frame, I'll show you how I make the main tubes (down, top and seat tubes). I use a mandrel which is just a solid aluminum cylinder, the diameter required on each tube and wrapped with strips of unidirectional carbon fiber. I use unidirectional carbon so that I can control the direction of maximum tensile strength and compression (that is the direction in which the filaments of the carbon fiber have been arranged). This results in different layers wound on the mandrel with directions ranging from 0 °, + 45 °, -45 ° to 90 °. In this way I make sure that the tube will respond well to forces in tension, compression and torsion (with the fibers at 45 °). In the picture below, you can see how the strip 45 ° is wound onto the mandrel.

 

[blanclui]

This is the final result after wrapping all layers,

 

[blanclui]

The tube is then placed inside a vacuum bag and subsequently cured in an oven. By the way, I almost forgot to say that I only use carbon fiber that has been pre-impregnated with epoxy resin (pre-preg) as it facilitates the handling of the material lot.

 

[blanclui]

And this is the 3 main tubes look like once baked and removed from the vacuum bag. As you can see, the surfaces of the tubes are a bit rough. This is due to the type of material used for wrapping the tubes for curing. This is dealt with relatively easily by subsequent sanding but I am in favor of sanding as little as possible because, invariably when sanding, carbon fibers are broken and, in a way, the integrity of the tube is compromised. Now I'm trying molds that will leave an outer surface of the tubes completely smooth. The last step is the removal of the aluminum mandrel from inside the tubes. This is done very easily if you have cleaned the mandrel with release agent before the wrapping of the carbon strips. If you forget this step, then I can assure you that you will never be able to take off the mandrel form the inside of the carbon tubes.

 

[blanclui]

In my next "chapter", I'll show you how I make chain stays, dropouts and the rear brake bridge, all out of molds. See you soon.

 

[sharkantropo]

Interesting. Please go ahead and write all the step by step carbon fiber frame constuction by chapters.