Bicycles and Bicycling - Introduction n Assignments: -Tuesday, 9/20: Ch 12 Kreighbaum & Smith. Sports & Fitness Equipment Design. Also, website: History and evolution of bicycles History and evolution of bicycles -Thursday, 9/22: Go to one of the bicycle manufacturer’s websites (slide 23) and select a bicycle to suit your purposes Read PDF bicycle review article posted on courses website. Submit 2 questions from article or other readings on bicycle design.

Bicyces & Bicycling Introduction n History and evolution of the bicycle -History and evolution of bicyclesHistory and evolution of bicycles n Cycling as a sport and as an exercise -Reference: Faria and Cavanagh. The physiology and biomechanics of cycling -Muscles and movements -Physiological demands

Bicycle Frame Design Objectives n Distribute rider’s weight appropriately n Performance - ensure transfer of power from rider to machine n Comfort – management of forces from machine to rider n Fit - points of contact must fit the rider: -handlebars -seat -pedals

Anatomy of Diamond Frame n Important parts: Front triangle (tubes), rear triangle (stays), fork, lugs, bottom bracket, head tube n 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 n Height of bottom bracket (bike’s center of gravity) -Lower for more stability -Higher for more pedal clearance n Height measurements determine size of rider n Frame size - length of seat tube and top tube

Design Features - Bike Length n Wheelbase length - (Fig 12.6) -Shorter for quicker response, longer for more stability (varies from 38 to 44 in) n Chainstay length -Shorter chainstays are used on racing bikes for more direct transfer of power

Design Features: Frame Angles n Head tube - steeper for rougher ride, more efficient power transfer; shallower for handling ease and shock absorbing, but less responsive n Rake (amount of bend in fork blades) and trail affect steering stability. More trail equals more stability

Design Features on Different Types of Bicycles n 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) n Mountain, or all-terrain -Fat, knobby tires, upright, sturdy frame, suspension systems n Hybrid - Cross between road and mountain

Bicycles - Frame Materials n Important characteristics are elasticity, stiffness, and strength (esp st/wt ratio) n Butted and splined tubing - thicker at ends than in the middle, with ribs inside n Steel - most widely used on cheaper bikes. Reliable, inexpensive, durable, predictable in handling - but is relatively heavy n Aluminum alloys - light, shock absorbent, comfortable. Newer alloys have improved properties of stiffness and strength (e.g., zirconium on trek bikes (trekbikes.com)trekbikes.com n Titanium alloys - stiff, strong, lighter, more shock absorbent - but is expensive hard to weld and hard to machine n 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

Trek Racing Frame

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 n Shock absorption, or suspension system consists of one or two elements: spring and dampener, both may be adjustable for both travel and stiffness. n A suspension system may be on front fork (FS), seat, or rear chainstay (DS) n Review article on courses website on suspension systems

Sports Med Article on Shock Absorption Systems n Introduction -Designed to improve bicycle comfort and handling by dissipating terrain-induced energy -May also dissipate cyclist’s energy through small oscillatory movements called “bobbing” -Three basic approaches to examine efficacy of these systems Engineer’s perspective – measuring or modeling estimates of power output loss of cyclist Exercise physiologist/biomechanist perspective – measuring energy consumption/expenditure (VO2)of cylist Behavioralist perspective –Ratings of comfort and perceived exertion to estimate stress

Suspension systems review article (cont’d) n Common suspension designs (Figure 2) n Engineer’s perspective (Figure 3 and 4) -DS resulted in 1.3% power loss, reduced to.7% when rear pivot location optimized (Figure 4) to same vertical height as top of chainring -When standing, power loss increased to 5% n Physiologist/biomechanist perspective -No sig diff in VO2 in smooth treadmill -DS better than FS and NS on bumpy treadmill -In time trials, FS performed better on level smooth track -On uphill courses, suspension systems seem to work better, although results of studies don’t also demonstrate this n Behavioral perspective -Suspension systems reduce RPE and comfort ratings

Bicycle Accessories n Drive Train -Crank, chainrings (front driving cogs), freewheel, derailleurs (indexed and automatic shifting are recent innovations) n Shoes and pedals - clipless or with clips?

Accessories (cont’d) n Rims, tires, brakes n Saddles n Stems & handlebars

Accessories (cont’d) n Helmets n Gloves, shorts

Websites on Bicycles n How to select a bicycle er/library/equipment/equip.htm er/library/equipment/equip.htm n Manufacturer’s websites -TrekTrek -SchwinnSchwinn -SpecializedSpecialized