Core Design for Practice Bottom Bracket Carbon Fiber Layup

Back to SolidWorks. Working off the same head tube practice layup model, I designed a practice bottom bracket core assembly. The core can be printed in 2 parts and bonded together onto a printed stand-in bottom bracket and main pivot. The surfaces are rough and basic: the exercise is to practice wrapping carbon fiber over cores not make perfect surfaces. Besides, the core surface is the inside and only generally determines the final exterior shape.
Design of transition core for bicycle frame bottom bracket area

 Half of the bottom bracket core
Half of the core oriented as 3D printed

The BB shell and pivot were printed in ABS and the core halves were printed in PLA.
3D printed bike frame transition core assembled into tubes

Bottom bracket area of practice composite bike frame ready for carbon layup

The cores will not be solvable. PLA is cheap, accurate, inexpensive, and very easy to print, but it takes a bit of doing to dissolve it. Sodium Hydroxide (Lye) is effective, but that will also attack the carbon/resin composite. So, for this practice layup, the core will simply be entombed and not removable. It is only to practice the composite process.


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