Frame Materials
Historically, the most common material for the tubes of a bicycle frame has been steel. Steel frames can be very inexpensive carbon steel to highly specialised using high performance alloys. Frames can also be made from aluminum alloys, titanium, carbon fiber, and even bamboo. Occasionally, diamond (shaped) frames have been formed from sections other than tubes. These include I-beams and monocoque. Materials that have been used in these frames include wood (solid or laminate), magnesium (cast I-beams), and thermoplastic. Several properties of a material help decide whether it is appropriate in the construction of a bicycle frame:
- Density (or specific gravity) is a measure of how light or heavy the material per unit volume.
- Stiffness (or elastic modulus) can in theory affect the ride comfort and power transmission efficiency. In practice, because even a very flexible frame is much more stiff than the tires and saddle, ride comfort is in the end more a factor of saddle choice, frame geometry, tire choice, and bicycle fit. Lateral stiffness is far more difficult to achieve because of the narrow profile of a frame, and too much flexibility can affect power transmission, primarily through tire scrub on the road due to rear triangle distortion, brakes rubbing on the rims and the chain rubbing on gear mechanisms. In extreme cases gears can change themselves when the rider applies high torque out of the saddle.
- Yield strength determines how much force is needed to permanently deform the material (for crash-worthiness).
- Elongation determines how much deformity the material allows before cracking (for crash-worthiness).
- Fatigue limit and Endurance limit determines the durability of the frame when subjected to cyclical stress from pedaling or ride bumps.
Tube engineering and frame geometry can overcome much of the perceived shortcomings of these particular materials.
Read more about this topic: Bicycle Frame
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