Frog Bikes Tadpole - Inspection of Composite Frame, Fork, and Components

frogbikes.com
Frog Bikes
Owner’s Manual
3
rd
Edition
2014
Fatigue
Fatigue is not a perfectly predictable science, but here are some general factors to
help you and your stockist determine how often your bike should be inspected. The
more you t the “shorten product life” prole, the more frequent your need to inspect.
The more you t the “lengthen product life” prole, the less frequent your need to
inspect.
Factors that shorten product life:
• Hard, harsh riding style
• “Hits”, crashes, jumps, other “shots” to the bike
• High mileage
• Higher body weight
• Stronger, more t, more aggressive rider
• Corrosive environment (wet, salt air, winter road salt, accumulated sweat)
• Presence of abrasive mud, dirt, sand, soil in riding environment
Factors that lengthen product life:
• Smooth, uid riding style
• No “hits”, crashes, jumps, other “shots” to the bike
• Low mileage
• Lower body weight
• Less aggressive rider
• Non-corrosive environment (dry, salt-free air)
• Clean riding environment
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 bres are strong and light, but when crashed or overloaded,
carbon bres do not bend, they break.
What are composites?
The term “composites” refers to a part or parts made up of dierent components or
materials. You’ve heard the term “carbon bre bike.” This really means “composite
bike.” Carbon bre composites are typically a strong, light bre in a matrix of plastic,
molded to form a shape. Carbon composites are light relative to metals. Steel weighs
7.8 grams/cm3 (grams per cubic centimeter), titanium 4.5 grams/cm3, aluminium
2.75 grams/cm3. Contrast these numbers with carbon bre composite at 1.45
grams/cm3.
The composites with the best strength-to-weight ratios are made of carbon bre in a
matrix of epoxy plastic. The epoxy matrix bonds the carbon bres together, transfers
load to other bres, and provides a smooth outer surface. The carbon bres are the
“skeleton” that carries the load.
Why use composites?
Unlike metals, which have uniform properties in all directions (engineers call this
isotropic), carbon bres can be placed in specic orientations to optimize the structure
for particular loads. The choice of where to place the carbon bres gives engineers
a powerful tool to create strong, light bikes. Engineers may also orient bres to suit
other goals such as comfort and vibration damping. Carbon bre composites are
very corrosion resistant, much more so than most metals. Think about carbon bre
or breglass boats. Carbon bre materials have a very high strength-to-weight ratio.
What are the limits of composites?
Well designed “composite” or carbon bre bikes and components have long fatigue
lives, usually better than their metal equivalents. While fatigue life is an advantage
of carbon bre you must still regularly inspect your carbon bre frame, fork, or
components. Carbon bre 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 bre or carbon bre 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 bre 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 if the impact is hard enough the fork or
frame may be completely broken. Note the signicant dierence in behaviour between
carbon and metal. See Section 2. A, Understanding metals in this Appendix. Even
if a carbon frame is 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
bike 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 bike or component that has any signs of delamination. These are some
delamination clues:
1. A cloudy or white area. This kind of area looks dierent 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.
3. A dierence 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 dierent sound, usually
duller, less sharp.
APPENDIX B