Building
A Custom Carbon Bike Part 4
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| December
5, 2002 |
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| Since
the last progress report, the front (main frame) and the rear stays have
been joined, faired together, strengthened at the junction and rear brake,
and the hole drilled for the headrest. The frame has been coated with a
filler material to close the millions of pinhead holes that form when
carbon is fabricated. Obviously, the frame will be painted rather then
clear coated. There emerged what I "perceived" as a flaw. I took
the necessary steps to Rectify it. Since this is my first project, I have
no way of knowing how stiff the frame should be. I conducted a rudimentary
test. I suspended the frame at the rear dropout and the nose (far more
severe than normal), and stood on the middle. I thought there was more
flex then there should be (not very scientific), so I built up the center
section (see comparison in a few photos) to make it deeper. I should have
known better being an engineer that maximum bending stress is at the
center of a beam. This cost me some added weight. Will be discussed later. |
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| The
next step was to install the headset tube. I machined a two-part headrest
sleeve, which will be bonded into the frame. It had to be in two parts to
install from the top and bottom and, and mate within the frame. This
picture shows the entire assembly. |
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| This picture
shows the two parts removed from each other. The larger piece on the right
is inserted into the bottom of the frame, and the smaller piece from the
top and bonded. What is not shown here is that 3 layers of CF sleeve were
added? The wall thickness of the tube was kept at a minimum to save
weight. Bad photo…sorry |
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| This photo shows
the method used to strengthen the junction where main frame and rear stays
join. Two layers of CF plate (each .100 inch) were used. This is on the
top of the frame. |
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| This photo shows
the bottom of the frame. Along with the two layers as on top, an
additional cross member is installed where the brake will be mounted. |
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| Rear quarter view
of joined frame |
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| This photo shows
the depth of the subject frame relative to an unmodified one. Since the
mold was already made and I would have to go through the whole process to
change the shape, I added depth by using the positive mold process (vs.
negative). I built up the depth to a desired level with balsa wood and
filler, then added multi-layers of CF and a great deal of hand finishing.
This added weight. More will be said on this later. |
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| This photo shows
the strengthened frame at slightly different angle. |
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| This photo shows
the headset sleeve, and the fixture that was constructed to insure that it
would be bonded straight (from side to side) when inserted in the frame. |
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| This is what I
mean. |
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| This photo shows
some of the components coming together. The headset sleeve is bonded into
the frame and an old Spinergy wheel is on the rear (note that this wheel
will not be used). On the front is my modified fork (see my site
"building a custom 20 inch carbon fork) loosely installed (the
bearings are not pressed in yet). This combination will be used on the
bike. This photo only serves to show form. |
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| Same but shown
from rear left. |
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| Shown from front
right. Keep in mind that the nose must be cut and a sleeve built so that
the boom will be adjustable. |
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| Shown here is a
close up of my custom carbon fork, and how I used an M5 mono hub in a
stereo application. Note that when I cut the standard 650 fork to fit the
406 wheel, the distance between dropouts turned out to be 80 mm (vs.100
standard). I machined a shaft to fit that dimension. I then realized that
I have only 1 wheel (of the custom dimension) so I ordered another hub
from Ed Deaton (Fools Crow Cycle) to build another wheel as a spare. |
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| I got to think
(while waiting for delivery of hub) that the assembly could be a lot
narrower then 80mm. Shown is a vernier set at 60 mm. The fork could be
modified (by being cut higher up), and the dropouts narrowed to 60mm. This
solves a lot of chain line management problems. Note that the red dye
aluminum is my machined shaft. |
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| The new hub
arrives and some things have changed at M5 (all good). While the overall
width of the hub (with bearings installed) remains the same at the 45mm,
it is lighter and is drilled for 24 spokes rather then 18. I purchased a
24-hole rim and will mate it to this hub. Makes for a slightly stronger
wheel. |
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| Now a sleeve must
be constructed so that the boom can be made to be adjustable. Some 3
layers of CF sleeve was laid around the curvature of the front boom, but
slit from front to rear so it could be removed. After it was removed, more
layers were added off the frame. Next, the front of the boom was cut off,
separating the nosepiece from the frame. That really was a "pucker
factor." That turned out to be a 2-scotch night! A hole was drilled
for the bottom bracket shell (previously made) and then the shell was
bonded to the nosepiece. A "belt" of CF was added toward the
rear of the shell where the clamp will be attached. |
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| Now here is where
I am in construction. The nosepiece is added to the main frame. Also, the
handlebar and tiller, the seat and the HED Alps rear wheel. |
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| A rear quarter
view of it. Note that additional holes were drilled near the seat pivot,
and the dropouts. In all cases, a carbon tube is installed and bonded. |
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| Shown with Murray
adjustable cranks. |
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| Detailed area of
main frame/rear stays. Carbon tubes bonded into the frame tie everything
together. |
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| Front view of it. |
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| Rear view. |
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| Front, right side
of cranks. These cranks are extremely thin. Not only are they aerodynamic,
but they offer the availability of not only adjusting crank length, but
relative crank length. One of my legs is shorter then the other. My
"doctor" cycling friends tell me it is not uncommon in someone
of my age. Want to determine if different lengths can make my spin
smother. |
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| Another view of
semi-completed bike. I am not on as solid a weight schedule as I would
have liked. Not too far off, but I don't have a cushion. The biggest fault
is my error. The frame is now at 5 pounds and is just about complete,
except for paint. The extra weight came in the added material to the
mid-section and the extra layers I put in the rear stays. Both I attribute
to the fear factor as this is my first bike. I will know after I ride it
if all was necessary. My goal was a 4 1/4-pound frame. Another reason was
the HED rear wheel. The advertised weight was 800 grams. The actual weight
was 860. I am thinking that I might have to drill out (lightning holes)
the seat. I am still confidant that I can get it at 20 lbs. or slightly
below, but I might have to shell out big money for carbon brakes (half the
weight of normal) and I might have to consider down tube shifters. Next
step is putting it all together. |
