In yet another attempt to mold bearing race seats into a head tube, I designed this mock head tube cross section for a tapered 1.5"-1.125" steerer tube.
The idea was to manufacture this shape using RTM. The yellow female clamshell mold would form the exterior shape, and the green insert caps would form the internal bearing seat surfaces. The blue shape is a plug around which I would wrap an inflatable bladder. The carbon (shown translucent here) would be laid-up dry over the bladder and fitted into the mold with inserts. Air pressure would be applied (blue) to the bladder forcing the carbon against the dimensional surfaces of the mold and inserts, the entire assembly would be put into a vacuum bag, and vacuum would infuse resin (red) into the cavity wetting the dry carbon thereby forming the composite matrix. Air pressure would then be increased to compress the matrix to await cure.
That was the plan. But I walked myself right into a textbook example of over-thinking details in CAD without enough practical application experience. Here is the plug over which I wrapped a latex condom and then passed it through the cap (this worked okay).
And then I tried wrapping the dry carbon:
It was impossible to form the carbon into the small details. I tried wrapping and tying with string, I tried using glue to hold it in place, I tried tape (as bad as that would have been for the layup). I just couldn't get the damn carbon into place.
Was the part too small? Was my uni too thick? Did I just need more patience and experience setting the carbon? Did I cut the fabric too large? I couldn't even prepare the pre-form for RTM. This dissuaded me from using the method for a functional/structural element of the project.
The idea was to manufacture this shape using RTM. The yellow female clamshell mold would form the exterior shape, and the green insert caps would form the internal bearing seat surfaces. The blue shape is a plug around which I would wrap an inflatable bladder. The carbon (shown translucent here) would be laid-up dry over the bladder and fitted into the mold with inserts. Air pressure would be applied (blue) to the bladder forcing the carbon against the dimensional surfaces of the mold and inserts, the entire assembly would be put into a vacuum bag, and vacuum would infuse resin (red) into the cavity wetting the dry carbon thereby forming the composite matrix. Air pressure would then be increased to compress the matrix to await cure.
That was the plan. But I walked myself right into a textbook example of over-thinking details in CAD without enough practical application experience. Here is the plug over which I wrapped a latex condom and then passed it through the cap (this worked okay).
And then I tried wrapping the dry carbon:
It was impossible to form the carbon into the small details. I tried wrapping and tying with string, I tried using glue to hold it in place, I tried tape (as bad as that would have been for the layup). I just couldn't get the damn carbon into place.
Was the part too small? Was my uni too thick? Did I just need more patience and experience setting the carbon? Did I cut the fabric too large? I couldn't even prepare the pre-form for RTM. This dissuaded me from using the method for a functional/structural element of the project.
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