Electra Bicycle - Manual (Page 26)

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WARNING: Do not ride a bicycle or component with any crack, bulge
or dent, even a small one. Riding a cracked frame, fork or component
could lead to complete failure, with risk of serious injury or death.
B. Understanding composites
All riders must understand a fundamental reality of composites. Composite
materials constructed of carbon fibers are strong and light, but when crashed or
overloaded, carbon fibers do not bend, they break.
What Are Composites?
The term “composites” refers to the fact that a part or parts are made up of
different components or materials. You’ve heard the term “carbon fiber bike.” This
really means “composite bike.”
Carbon fiber composites are typically a strong, light fiber in a matrix of plastic,
molded to form a shape. Carbon composites are light relative to metals. Steel
weighs 7.8 grams/cm 3 (grams per cubic centimeter), titanium 4.5 grams/cm 3 ,
aluminum 2.75 grams/cm 3 . Contrast these numbers with carbon fiber composite
at 1.45 grams/cm 3 .
The composites with the best strength-to-weight ratios are made of carbon
fiber in a matrix of epoxy plastic. The epoxy matrix bonds the carbon fibers
together, transfers load to other fibers, and provides a smooth outer surface. The
carbon fibers are the “skeleton” that carries the load.
Why Are Composites Used?
Unlike metals, which have uniform properties in all directions (engineers call
this isotropic), carbon fibers can be placed in specific orientations to optimize
the structure for particular loads. The choice of where to place the carbon fibers
gives engineers a powerful tool to create strong, light bicycles. Engineers may
also orient fibers to suit other goals such as comfort and vibration damping.
Carbon fiber composites are very corrosion resistant, much more so than most
metals.
Think about carbon fiber or fiberglass boats.
Carbon fiber materials have a very high strength-to-weight ratio.
What Are The Limits Of Composites?
Well designed “composite” or carbon fiber bicycles and components have long
fatigue lives, usually better than their metal equivalents.
While fatigue life is an advantage of carbon fiber, you must still regularly
inspect your carbon fiber frame, fork, or components.
Carbon fiber composites are not ductile. Once a carbon structure is
overloaded, it will not bend; it will break. At and near the break, there will be
rough, sharp edges and maybe delamination of carbon fiber or carbon fiber fabric
layers. There will be no bending, buckling, or stretching.
If You Hit Something Or Have A Crash, What Can You Expect From Your
Carbon Fiber Bike?
Let’s say you hit a curb, ditch, rock, car, other cyclist or other object. At
any speed above a fast walk, your body will continue to move forward, the
momentum carrying you over the front of the bike. You cannot and will not
stay on the bike and what happens to the frame, fork and other components is
irrelevant to what happens to your body.
What should you expect from your carbon frame? It depends on many
complex factors. But we can tell you that if the impact is hard enough, the fork
or frame may be completely broken. Note the significant difference in behavior
between carbon and metal. See Section 2. A, Understanding metals in this
Appendix. Even if the carbon frame was twice as strong as a metal frame, once
the carbon frame is overloaded it will not bend, it will break completely.
Inspection of Composite Frame, Fork, and Components
Cracks:
Inspect for cracks, broken, or splintered areas. Any crack is serious. Do not
ride any bicycle or component that has a crack of any size. Delamination:
Delamination is serious damage. Composites are made from layers of
fabric. Delamination means that the layers of fabric are no longer bonded
together. Do not ride any bicycle or component that has any delamination.
These are some delamination clues:
1. • A cloudy or white area. This kind of area looks different from the ordinary
undamaged areas. Undamaged areas will look glassy, shiny, or “deep,” as if one
was looking into a clear liquid. Delaminated areas will look opaque and cloudy.
2. • Bulging or deformed shape. If delamination occurs, the surface shape may
change. The surface may have a bump, a bulge, soft spot, or not be smooth and
fair.
3. • A difference in sound when tapping the surface. If you gently tap the surface
of an undamaged composite you will hear a consistent sound, usually a hard,
sharp sound. If you then tap a delaminated area, you will hear a different sound,
usually duller, less sharp.
Unusual Noises:
Either a crack or delamination can cause creaking noises while riding. Think
about such a noise as a serious warning signal. A well maintained bicycle will
be very quiet and free of creaks and squeaks. Investigate and find the source
of any noise. It may not be a crack or delamination, but whatever is causing the
noise must be fixed before riding.
WARNING: Do not ride a bicycle or component with any
delamination or crack. Riding a delaminated or cracked frame, fork
or other component could lead to complete failure, with risk of
serious injury or death.
C. Understanding components
It is often necessary to remove and disassemble components in order to
properly and carefully inspect them. This is a job for a professional bicycle
mechanic with the special tools, skills and experience to inspect and service
today’s high-tech high-performance bicycles and their components.
Aftermarket “Super Light” components
Think carefully about your rider profile as outlined above. The more you fit
the “shorten product life” profile, the more you must question the use of super
light components. The more you fit the “lengthen product life” profile, the more