February 4, 2013

OarCycle: Tacked Front Triangle

I finished mitering the carbon fiber tubes, and tacked the frame's front triangle together.  Before doing so, I put a layer of fiberglass composite over the outside of the bottom bracket shell and head tube.  I attempted to vacuum bag the tubes, but I forgot about all the volume on the inside of the tubes when making the vacuum bags.  When I turned on the vacuum pump, all the bagging was sucked into the centers of the tubes, which caused the bagging to leak.  To avoid having to run the pump constantly to maintain the vacuum while the epoxy cured, I went back to the electrical tape method of compressing the composite.

To fill some gaps due to imperfect mitering and to fillet the intersections of the tubes, I made some epoxy filler by shredding carbon fiber tow.  The resulting mixture was smoothed over all the joints:

Because Carbon Fiber, the frame is much lighter than it looks, with the front triangle weighing in at 720 grams.  For the complete frame, I am aiming for something just above 1 kg, making  this frame under half the weight of my bamboo frame.

I made dropouts track fork ends to hold the rear wheel out of scrap 1/4" aluminum plate.  The two dropouts were roughed out independently, and then clamped together for final machining.  The non-right-angles were done by some creative clamping on the mill.

I touched up the dropouts on the belt sander, to round off some sharp corners and make them shiny:

Who needs a waterjet cutter....

Next up:  the rear triangle.  This bit is going to take much longer, because a) IAP is over, and b) I am out of pre-made carbon fiber tube.  I plan on making some sort of form for the seat stays and chain stays out of foam, and laying up the tubes from carbon fiber cloth myself.

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