3D Printing Entombed-Core Tube Transitions for Composite Bike Frame

Current thinking is to 3D print PLA tube transitions and entomb them into the frame. The shapes can be printed with an extremely low fill density making them surprisingly light. So they would act, essentially, as scaffolding for the first layer of carbon. And they would be left inside the frame permanently. Printing a test transition (seat tube to top tube):
3D printing a PLA core for composite layup

Under 25 grams for that junction.
Weight of printed core

Testing the transition core in the frame jig. It fits as expected joining the seat tube, top tube, and link pivot.
Fitting printed seat tube to top tube core

Fitting printed seat tube to top tube core

Fitting printed seat tube to top tube core

Fitting printed seat tube to top tube core

Printing a test entombed core for the bottom bracket area:
Printing the bottom bracket transition core


Test fitting the bottom bracket core.
Fitting the bottom bracket transition core

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