Bicycles and Bicycling - Introduction History evolution of bicycles Cycling as a sport and as an exercise - Reference: Faria and Cavanagh. The physiology and biomechanics of cycling - Muscles and movements - Physiological demands Design objectives: - Distribute rider’s weight appropriately - Ensure transfer of power from rider to machine - Points of contact must fit the rider: • handlebars • seat • pedals
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Bicycles and Bicycling - Introduction n History evolution of bicycles History evolution of bicycles n Cycling as a sport and as an exercise -Reference:
Other Frame Types; :Ladie’s Frame Top tube is sloped considerably
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Bicycles and Bicycling - Introduction History evolution of bicycles Cycling as a sport and as an exercise
- Reference: Faria and Cavanagh. The physiology and biomechanics of cycling
- Muscles and movements- Physiological demands
Design objectives: - Distribute rider’s weight appropriately- Ensure transfer of power from rider to machine - Points of contact must fit the rider:
Important parts: Front triangle (tubes), rear triangle (stays), fork, lugs, bottom bracket, head tube
Types of bicycles: (1) Road bike (10-speed) - touring, racing, and sport; (2) mountain, or all-terrain; and (3) hybrid
Other Frame Types; :Ladie’s Frame
Top tube is sloped considerably
Design Features - Height Height of bottom bracket (bike’s center of
gravity)- Lower for more stability- Higher for more pedal clearance
Height measurements determine size of rider
Frame size - length of seat tube and top tube
Design Features - Bike Length Wheelbase length - (Fig 12.6)
- Shorter for quicker response, longer for more stability (varies from 38 to 44 in)
Chainstay length- Shorter chainstays are used on racing bikes for more direct transfer of power
Design Features: Frame Angles
Head tube - steeper for rougher ride, more efficient power transfer; shallower for handling ease and shock absorbing, but less responsive
Rake (amount of bend in fork blades) and trail affect steering stability. More trail equals more stability
Design Features on Different Types of Bicycles
Road bicycles (10-speeds)- Touring, or comfort - long wheelbase, shallow
angles, fair amount of trail (21 speeds)- Racing - short wheelbase, steep angles, little trail(18 gears)- Sport/triathlon and cross bikes - in between (100
or more miles at high speed) Mountain, or all-terrain
- Fat, knobby tires, upright, sturdy frame, suspension systems
Hybrid - Cross between road and mountain
Bicycles - Frame Materials Important characteristics are elasticity, stiffness, and strength (esp
st/wt ratio) Butted and splined tubing - thicker at ends than in the middle, with
ribs inside Steel - most widely used on cheaper bikes. Reliable, inexpensive,
durable, predictable in handling - but is relatively heavy Aluminum alloys - light, shock absorbent, comfortable. Newer
alloys have improved properties of stiffness and strength (e.g., zirconium on trek bikes (trekbikes.com)
Titanium alloys - stiff, strong, lighter, more shock absorbent - but is expensive hard to weld and hard to machine
Composites - greatest strength/wt & stiffness/wt ratio - but expensive, bonding problems. Used mainly in front fork and stays. May fail catastrophically in other areas of frame.