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.

Frame Materials used by Trek

Schwinn Frame Technology

TrekRacingFrame

Schwinn Suspension Frame

Trek Mountain Suspension Bike

Fisher Suspension Bike

Recumbent Bikes

Tubing design and Construction Methods

•Laser mitering•Butted tubes – varying wall thickness•Splined tubes•Diameter and shape changes

•Lugs no longer used:

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