I have been working on a method
to construct a carbon frame. It consists of having carbon laid in a female
mold half section, and then adding polyurethane expanding foam of a 2
lb/cubic ft. density and allowing the assembly to cure. I have built a
number of molds and have become somewhat proficient at it, at least enough
to convince myself that a light weight frame could be constructed. Here
are some of my results.
Here
is my most recent piece. This one measures 2.4 inches wide by 2.9 inches
high and the piece is 18 inches long. The thickness of the carbon (4
layers) was approximately 0.040. This piece weighs 365 grams.
This
is an end view of same. Note the "spine" of carbon. This will be
clearer in another photo. The right and left separately made sections are
epoxied together.
This
is a photo of a different earlier piece half section where the carbon is
put in a mold and allowed to overlap. This overlap is epoxied to the
corresponding side to form a spine. This adds to the strength and
stiffness.
Here are a
few of the 20 odd pieces that got me where I am today. Note some pieces
with foam only. I wanted to see how it distributed in the mold. The
shorter piece in my right hand was interesting (next photo also) and was
intended to be a very thin wall section of carbon and foam. This proved to
be very difficult to work with. The piece under my left arm was like the
first piece shown except a little larger and with flat sides. Has
potential.
A close up
of the shorter piece mentioned. Very difficult to make and the small
gluing surface area of the two halves would probably fail.
Photo
showing mold for a half section. In left hand is the female mold where the
carbon is laid in. The top of the mold (in right hand) is then secured
with a fastener where each hole is marked. Foam is then vacuum sucked into
mold and allowed to expand and cure. It expanded in seconds and cured
overnight. Tremendous pressure is built up in mold. I have broken earlier
molds. One good thing is when laying in the carbon and removing the excess
resin, even more resin is squeezed out by the expanding foam. Even more
than in vacuum bagging. A tremendous amount of time in mold building and
fabrication but the mold will yield multiple frames.
