230 likes | 475 Views
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
E N D
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
Anatomy of Diamond Frame • 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.
Tubing design and Construction Methods • Lugs no longer used: • Laser mitering • Butted tubes – varying wall thickness • Splined tubes • Diameter and shape changes
Suspension systems • Front, rear, and seat • Simple spring • Air coil/springing systems • Travel and stiffness may vary
Bicycle Accessories • Drive Train -Crank, chainrings (front driving cogs), freewheel, derailleurs (indexed and automatic shifting are recent innovations) • Shoes and pedals - clipless or with clips?
Accessories (cont’d) • Rims, tires, brakes • Saddles • Stems & handlebars
Accessories (cont’d) • Helmets • Gloves, shorts
Websites on Bicycles • How to select a bicycle http://www.primusweb.com/fitnesspartner/library/equipment/equip.htm • Manufacturer’s websites • Trek • Schwinn • Specialized
Assignment for Thursday, 10/21 • Go to one of the bicycle manufacturer’s websites (slide 23) and select a bicycle to suit your purposes • Read article on suspension systems and submit 2 questions for clarification or discussion