Bicycle Design and Construction

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ME240/105S: Product Dissection

From Ref. 5, used by permission ofRodale Press, ©1994, all rights reserved

Bicycle Design andConstruction



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Diferent Frame

Construction Philosophies

Cannondale !elded aluminum frames, hand "rafted

#pe"iali$ed !elded steel or "hromemoly %a steel alloy&

're( glued aluminum frames, or !elded steel

)i"y"le "ompanies tend to have different designphilosophies, to give them a uni*ue mar(et +ni"he-



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FrameComponen

tsfrom Ref. , used !ith permission of /orling 0indersley, ©199, all rights reserved



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Joining Processes or Frame

Tubing

from Ref. , used !ith permission of /orling 0indersley, ©199, all rights reserved

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Cannondale Factory Tour -

CAD 2ll of Cannondale3s bi"y"le frames are

designed on highte"h C2/ systemsin the R/ department at the )ethel,Conne"ti"ut head*uarters.

e! frame designs are then sent viamodem to the Cannondale fa"tory in

)edford, Pennsylvania.

'he follo!ing are e6"erpts from http-77!!!."annondale."om7fa"toryb7f.html

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Cannondale Factory Tour - Ra

Tubing 8ith the e6"eption of "arbon

fiber7aluminum Raven models, allCannondale bi"y"les are built fromlight!eight ::: series aluminumtubes !ith different diameters, shapes,and !all thi"(nesses.

::: series aluminum is used be"auseit "an be shaped and ma"hined mu"heasier than ;::: series aluminum ormetal matri6 aluminum "ompounds.



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Cannondale Factory Tour - !aser

Cutting Computer guided lasers are used to

pre"isely "ut aluminum frame tubes tothe proper length.

#ele"ted tubes are also mitered to!rap around ad<oining tubes.

'he lasers provide a "leaner "ut thantraditional "utting methods and ensurein"redibly tight toleran"es for greater!eld integrity and a stronger frame.



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Cannondale Factory Tour - Tabs "

#lots 'he tubes on Cannondale frames

feature a uni*ue, patented taband"orrespondingslot design that aligns

the tubes for !elding. )y eliminating the need to build

numerous produ"tion fi6tures for ea"hsi$e and every ne! frame style, thistabandslot system dramati"allyredu"es preprodu"tion engineering"hores and allo!s Cannondale to bringinnovative ne! models to mar(et !ithama$ing speed.



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Cannondale Factory Tour - T$%

&elding 'he ::: series aluminum frames are

then '=> !elded together by hand.

8elding the thin!alled ::: seriesaluminum tubing used in "uttingedgebi"y"le frames is a surprisingly diffi"ultart to master.



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Cannondale Factory Tour - 'eat

Treating Cannondale then heattreats their

frames to restore the tubes to theiroriginal strength after !elding.

2 frustratingly diffi"ult %and e6pensive&pro"ess to perfe"t, heattreating allo!sCannondale to a"tually use lessmaterial to a"hieve the ne"essarylevels of strength.

?any other manufa"turers use thi"(er!alled tubing or reinfor"ing gussets,both of !hi"h add !eight.



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#anding )eyond the obvious aestheti" benefit,

smooth, sanded !elds help preventstressrisers !hi"h "an o""ur at the

outer edge of an unfinished !eld,!here the !eld abruptly ends and thetube !all is suddenly thinner and moreprone to a""umulated stresses.

'he gradually tapering !alls "reated by properlyfinished !elds, ho!ever, disperse stresses over a!ider area, allo!ing Cannondale to use thinner

!alled tubes for a lighter frame.



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For the most even, most "onsistent"overage possible, Cannondale paintstheir frames ele"trostati"ally !hereby

the frame "arries a small ele"troni""harge that a"tually attra"ts individualpaint parti"les.

2fter painting, ea"h frame has itsde"als applied and is "lear"oated !itha durable, prote"tive finish.



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Testing Cannondale has invested over a

million dollars in their @Aab, an inhouse testing fa"ility for bi"y"le

frames and "omponents. 2 ne! frame design typi"ally spends

more than t!o months undergoingfive different batteries of tests-

1. fatigue testing,. impa"t testing,. finite element analysis testing,4. "omputeri$ed field testing, and

5. brittle"oat testing.



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!oo( at one #imple

#ubsystem - Frame Tubing Frame design is an e6"ellent e6ample of the tradeoffs inherent in

the design pro"ess and the sometimes arbitrary de"isions %i.e., not <ustifiable based on purely analyti"al terms& !hi"h are often made

'here are lots of possibilities %variables& for frame design- B material %steel, aluminum, titanium, "omposite, ...&

B "ross se"tion shape

shape %s*uare, round, oval or other&

hollo! or solid

"onstant "ross se"tion, or variable

Do! do you handle all this information and ma(e a proper"hoi"e E



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Design Process

1. 'he first step in design ASK QUESTIONS

B intended use of produ"t

B desired or important performan"e *ualities

for bi(e lo! !eight, riding effi"ien"y, "omfort, durability,lo! "ost ...

B potential failure modes

B ho! does the part fit into overall system

. =dentify design variables %things you as thedesigner "an spe"ify&



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Design Process -

continued . @uantify the performan"e *ualities in terms of

the design variables

4. =dentify the "onstraints based on potential failuremodes and performan"e *ualities

5. Formulate a measure of the design3s +goodness%*uantitative if possible&



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. 2pply an appropriate design method for "hoosing thea"tual values of the design variables-

B 'rial and error %0 for simple problems& B Past e6perien"e %e6trapolation or interpolation&

B =ntuition, dumb lu"(

B umeri"al optimi$ation methods %a ne"essity if the number of designvariables and "onstraints are large&

Design Process -

continued



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Bac( to the Frame Tube

Aet3s assume that the most important *ualities ofthis tube are its- B Ao! Fle6ibility %G high stiffness&

B Ao! 8eight %!ant as light as possible&

B Digh )ending and Crush #trength

B Aong Aife

/esign Hariables- B ?aterial

B 8all thi"(ness

B 'ube /

B Ioining method %!eld, glue, bra$e&



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Bi(e Tubing

)etter tubes arethi"(er at ends togive greaterstrength at <oints

plain gage tube

single-butted tube

double-butted tube

triple-butted tube

From Ref. 5, used by permission of Rodale Press, ©1994, all rights reserved

ME240/105SP d D



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)aterial Design $ssues

8hy does Cannondale use aluminumE

8hat are its advantages and disadvantagesE

ther possibilities- B #teels

Ao! Carbon, Digh Carbon, Chromemolybdenum,#tainless ...

B 'itanium B ?agnesium

B Carbon fiber "omposite %Carbon Fiber, 0evlar&

ME240/105SP d tDi ti



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$mportant )aterial

Properties 8eight %density&

#tiffness %elasti" modulus&

#trength %tensile strength, enduran"e limit&

=mpa"t resistan"e %hardness&

Corrosion resistan"e

Ioining methods

Re"y"ling potential




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Comparison o )aterial

Properties

Elastic Yield TensileMaterial Modulus Strength Strength

[Mpsi] [Kpsi] [Kpsi] [lb/in] !ardness

2luminum :1 ' 1: 4: 45 .1: 95 J1J.5: ;:;5 ' 1: ; K .1: 15: JJ.:#teel 1:4: DR %med "arbon& : 4 ; .K 149 J:.5J1 1:4: C/ : ;1 K5 .K 1;: + 414: DR %"hrome7moly& : 9: .K 1K; +

414: C/ : 9: 1: .K +'itanium 4 1.5 1:15: 1:1: .1 72 J1J9:

>raphite7Lpo6yM 1: 15: ::: .: 72 J5J;

DR G Dot Rolled C/GCold /ra!nM 2"tual properties depend on the type and amount of reinfor"ing material




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#tatic #trength

Results from a typi"al tensiletest of a steel sample

from ?anufa"turing Lngineering and 'e"hnology, by #. 0alpaa(<ian,used by permission of 2ddison 8esley, ©199, all rights reserved

ME240/105SProdctDissection



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Fatigue *Cyclic+ #trength

Fatigue properties are verydependent on material type.

#teels have an enduran"e

limit a stress level !hi"h "anbe endured for an unlimitednumber of "y"les %no fatigue&.

2luminum does not have an

enduran"e limit and fatiguesno matter !hat the stresslevel. 'herefore, an aluminumbi(e must be built !ith e6trastrength to a""ount for fatigueeffe"ts.

1045 Steel

Endurance Limit

2014-T6

Aluminum alloy

Number of Cycles, N

S

t r e s s A m p l i t u d e ,

S ( M P a )

K p s i

80

500

0

103 1010

0

ME240/105S:ProductDissection



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Cannondale TubeCannondale uses aluminum tubing, 1.;5 /, .:K5 "onstant !all

thi"(ness a good "ompromise bet!een !eight and fle6ibility

WALL THICKNESS - inches

0 0.05 0.1 0.15 0.2 0.25

WEIGHT

FLEXIBILITY

OD - 1.75”

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Bicycle Design and Construction