CAKRAWALA CAKRAWALA ELECTRIC VEHICLE
Suspension Design Cakrawala Formula Elektrik Danny Kusuma & Rama Primadi
Buku ini merupakan kumpulan reerensi mengenai !esain suspensi ken!araan !arat" k#ususn$a ken!araan %alap& Dasar reerensi terse%ut !igunakan untuk !esain suspensi ken!araan %alap !alam rangka lom%a Formula SAE&
C'(TE(TS Contents&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&) Rules * S+oring Dis+ussion&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&, Datar Literatur&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&Books&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&'t#er .ni/ersities Design&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&We%sites&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&Intro!u+tion&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&0 Aim o t#e work&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&0 Competition '%1e+ti/e&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&0 T#e !$nami+ e/ents&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&& 0 W#at is Suspension2&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&3 Design Aspe+t&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&4 Ve#i+le D$nami+s&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&4 Modeling & Vibration Mechanics&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&& &&&&&&&&&&&&&&& &&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&4 &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&4 Coordinate System&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&)5 Ride & Handling&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&)) Lateral Dynamics&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&), Longitudinal Dynamics&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&)-
Terminolog$&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& Terminolog$&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&& &&&&&&&&&&&& &&&&&&&&&&&&& &&&&&&&&& && )4 The heelbase&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&)4 Trac! &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&65 &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&65 Ride Height&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&6) KingPin & Scrub Radius&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&66 Caster & Trail&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&6Camber&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&63 Toe&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&,5 "nti #eatures&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&,) $nstant Centre & Roll Centre&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&,, Tie Rod Location&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&,0 "nti%Rol ar&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&,3 Damper&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&,7 Spring&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&,8
Design Step&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&-5 Rules&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&& && -5 9): 65)0 Formula SAE; Rules&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&-5 96: FSAE
Suspension T$pes&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&-6 Verti+al D$+nami+s =Ri!e*Han!ling > ?it+#*Boun+e@&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&-, Lateral D$nami+s > Cornering ?erorman+e&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&-, Stea!$ State Cornering > Ski!pa!" Stea!$ Turn&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&-, Transient Transient Rollo/er Rollo/er > Slalom" Rapi! steering&&&&&&&&&&&&&&&&&&&&&&& steering&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&& &&&&&&&&&&&& &&&&&&&&&&&&& &&&&&&&&&&&&& &&&&&&&& &&-, -, Suspension eometr$&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&-, Anti Roll Bar !esign&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&-, Tire ?erorman+e&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& ?erorman+e&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&& -, Longitu!inal D$nami+s&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&-, Desain Suspensi Cakrawala Formula Ele+tri+&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&-?enetuan DR*'&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&-Data Ken!araan&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&-?er#itungan Kekakuan ?egas&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&-Set a$a ?ere!aman Bertingkat&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&-?enentuan eometri Suspensi&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&-?erorma Stea!$ State Cornering&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&-?erorma Transient Cornering&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&-?er#itungan Kekakuan Anti Roll%ar&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&--
REFERE(CES B''KS Ber!asarkan 9,: illespie" Fun!amentals o Ve#i+le Dunami+s Ber!asarkan 9-: aar" Ve#i+le Dunami+s T#eor$ an! Appli+ation Ber!asarkan 90: Dion" T#e S#o+k A%sor%er Han!%ook Ber!asarkan 93: iliken" Ra+e Car Ve#i+le D$nami+s Ber!asarkan 97: Reimpell" Reimpell" T#e Automoti/e C#assis Engineering ?rin+iple Ber!asarkan 94: 94: a#$u!!in" An!i Isra& Design Cal+ulation o o Ve#i+le Ve#i+le Suspension S$stem& SAE ?aper 6& Ber!asarkan 98: T#ean!er" Design o a Suspension or a Formula Formula Stu!ent Ra+e Car Ber!asarkan 9)5: Su%eng" Laporan ?eran+angan FSAE us#ika ITB Di/isi Suspensi
' THER . (IVERSITIES D ESI( WEBSITES VIDE'S
I(TR'D.CTI'( AI
'F THE W'RK
T#e aim o t#is t#is t#esis work is to !esign t#e t#e suspension suspension geometr$ or or a Formula Stu!ent ra+e +ar& T#e !esign s#all meet t#e !eman!s +ause! %$ t#e !iGerent !iGerent !$nami+ e/ents in t#e +ompetition&
C'?ETITI'( ' BECTIVE T#e o%1e+ti/e o o t#e +ompetition +ompetition is or stu!ents stu!ents to +on+ei/e" !esign" !esign" a%ri+ate a%ri+ate an! +ompete wit# small ormulast$le ra+ing +ars& T#e !esign o t#e +ar rame an! engine are restri+te! in or!er to +#allenge t#e knowle!ge" +reati/it$ an! t#e imagination o t#e stu!ents 9):&
THE
D(AIC EVE(TS
J A++eleration J Ski!?a! J Auto+ross J En!uran+e an! Fuel E+onom$ 1.4.1 Acceleration Event The objective of the acceleration event is to evaluate the car’s acceleration in a straight line on at pavement. The cars will be staged 0.3m behind the starting line and when the cars cross the starting line the time will start. The goal is located 75m ahead of the starting line. Each team will have two drivers who can do two runs each a total of fo ur runs. This is the event were the suspension design is of least importance among the dynamic events, but not negligible.
1.4.2 Sid!"ad Event The objective of the s!id"pad event is to mea sure the cornering abilit# of the car on a at surface while ma!ing a constant"radius turn. The s!id"pad la#out will consist of two circles with a diameter of $5.%5m separated b# $&.%5m. The driving path will be 3m wide. The la#out of the s!id"pad and driving directions are showed in 'igure $.$.
The procedure of the event is as follows( the cars will start b# entering the right circle completing one lap. )e*t lap will be timed and immediatel# after the left circle is entered for the third lap. The fourth lap will be timed. Then the driver has the option to ma!e a second run immediatel# after the +rst. Each team will have two drivers who can do two runs each. The design of the suspension and steering geometr# will inuence the performance much.
1.4.# Autocross Event
The objective of the autocross event is to evaluate the car’s manoeuvrabilit# and handling ,ualities on a tight course. The autocross course will combine the performance f eatures of acceleration bra!ing and cornering. The la#out of the autocross trac! is made to !eep the speeds from being dangerousl# high average speeds should be between -0!mh and -&!mh. The la#out is speci+ed as follows( / traights 1 )o longer than 20m with hairpins at both ends or no longer than -5m with wide turns on the ends. / onstant Turns 1 %3m to -5m in diameter. / 4airpin Turns 1 inimum of 6m outside diameter. / laloms 1 ones in a straight line with 7.2%m to $%.$6m spacing. / iscellaneous 1 hicanes multiple turns decreasing radius turns etc. The minimum trac! width will be 3.5m / ength 1 8ppro*imatel# 0.&05!m. Each team will have two drivers entering the event. E ach driver will drive two timed laps and the best time for each driver will stand as the time for that heat.
1.4.4 Endurance and $uel Economy Event To evaluate the overall performance and to test the car’s reliabilit# an endurance event is performed. This event is combined with a fuel econom# event impl#ing that the fuel econom# will be measured during the endurance event. 8 single %%!m heat is made during which the teams will not be allowed to wor! on their cars. 8 driver change must be made during a three"minute period at the mid point of the event. The la#out of the endurance trac! is similar to the la#out of the autocross trac!( / traights 1 )o longer than 77m with hairpins at both ends or no longer than 2$m with wide turns on the ends. There will be passing 9ones at several locations. / onstant Turns 1 30m to 5-m in diameter. / 4airpin Turns 1 inimum of 6m outside diameter. / laloms 1 ones in a straight line with 6m to $5m spacing. / iscellaneous 1 hicanes multiple turns decreasing radius turns etc. The minimum trac! width will be -.5m. %n both the autocross event and the endurance event the suspension design and steering geometry is of ma&or importance. A well woring design helps the drivers perform at the edge of their capacity. The layout of the 2''# event endurance trac can be viewed in $igure 1.2.
WHAT
IS S'SP()S$*)2
T#e suspension on $our +ar #as two main un+tions& Its rst 1o% is to smoot# t#e ri!e o $our +ar& A++or!ing to r& (ewton an! #is ame! laws o p#$si+s" all or+es o motion
#a/e %ot# a magnitu!e an! a !ire+tion& A %ump in t#e roa! +auses t#e w#eel to mo/e up an! !own perpen!i+ular to t#e roa! sura+e& T#e %igger t#e %ump en+ountere!" t#e %igger t#e mo/ement& T#e mo/ement eperien+e! %$ t#e w#eel is +alle! /erti+al a++eleration&
Wit#out an inter/ening stru+ture" all o t#e w#eels /erti+al energ$ is transerre! to t#e rame" w#i+# tries to mo/e in t#e same !ire+tion& In su+# a situation t#e w#eels +an lose +onta+t wit# t#e roa! +ompletel$& T#en" un!er t#e !ownwar! or+e o gra/it$" t#e w#eels +an slam %a+k into t#e roa! sura+e& W#at $ou nee! is a s$stem t#at will a%sor% t#e energ$ o t#e /erti+all$ a++elerate! w#eel allowing t#e rame an! %o!$ to ri!e un!istur%e! w#ile t#e w#eels ollow %umps in t#e roa! an! sta$ in +onta+t wit# t#e asp#alt&
The suspension shall help to !eep the tires in constant contact ith the ground
so t#at t#e tires +an %e use! to t#e limit o t#eir +apa+it$& +ill the tires stay in satis,actory contact ith the road under all conditions-
T#is +ategor$ o+uses primaril$ on t#e unsprung masses o t#e /e#i+le" parti+ularl$ t#ose relate! to roa! #ol!ing an! !ire+tional +ontrol& To pro.ide good ride and handling per,ormance
>/erti+al +omplian+e pro/i!ing +#assis isolation >ensuring t#at t#e w#eels ollow t#e roa! prole >/er$ little tire loa! Mu+tuation /To ensure that steering control is maintained during maneu.ering
>w#eels to %e maintaine! in t#e proper position wrt roa! sura+e /To ensure that the .ehicle responds ,a.orably to control ,orces produced by the tires during
>longitu!inal %raking >a++elerating or+es" >lateral +ornering or+es an! >%raking an! a++elerating torNues >t#is reNuires t#e suspension geometr$ to %e !esigne! to resist sNuat" !i/e an! roll o t#e /e#i+le %o!$ /To pro.ide isolation ,rom high ,re0uency .ibration ,rom tire e1citation
>reNuires appropriate isolation in t#e suspension 1oints >?re/ent transmission o Oroa! noiseP to t#e /e#i+le %o!$
DESI( AS?ECT R.LES 9): 65)0 F'R.LA SAE; R.LES )& T23434 'n+e t#e /e#i+le is appro/e! to +ompete in t#e !$nami+ e/ents" t#e '(L mo!i+ations permitte! to t#e /e#i+le are t#ose liste! %elow& T#e$ are also reerre! to in ?art S o t#e Formula SAE Rules > Stati+ E/ent Regulations& "d5ustment o, the suspension w#ere no part su%stitution is reNuire!" =e+ept t#at springs" swa$ %ars an! s#ims ma$ %e +#ange!@ "pa!ah suspensi a!an didesain Re,erensi apa yang mendu!ung-
ad5ustable
atau
tida!-
Mengapa-
6& T63732 To keep t#e !ri/erPs legs awa$ rom mo/ing or s#arp +omponents" all mo/ing suspension an! steering +omponents" an! ot#er s#arp e!ges insi!e t#e +o+kpit %etween t#e ront roll #oop an! a /erti+al plane )55 mm =- in+#es@ rearwar! o t#e pe!als" must %e s#iel!e! wit# a shield made o, a solid material3 o/ing +omponents in+lu!e" %ut are not limite! to springs" s#o+k a%sor%ers" ro+ker arms" antiroll
,& T83232 T#e +ar must %e eNuippe! wit# a ,ully operational suspension s$stem wit# s#o+k a%sor%ers" ront an! rear" wit# usa%le w#eel tra/el o at least 05&4 mm =6 in+#es@" 60&- mm =) in+#@ 1oun+e an! 60&- mm =) in+#@ re%oun!" wit# !ri/er seate!& T#e 1u!ges reser/e t#e rig#t to !isNuali$ +ars w#i+# !o not CCC serious attempt at an operational suspension s$stem or w#i+# !emonstrate #an!ling inappropriate or an auto+ross +ir+uit& "pa itu heel tra.el- "pa itu rebound & 5ounce- Parameter apa yang mempengaruhi nilai tersebut-
-& T83634 T#e steering s$stem must #a/e positi/e steering stops t#at pre/ent t#e steering linkages rom lo+king up =t#e in/ersion o a our%ar linkage at one o t#e pi/ots@& T#e stops ma$ %e pla+e! on t#e uprig#ts or on t#e ra+k an! must pre.ent the tires ,rom contacting suspension" %o!$" or rame mem%ers !uring t#e tra+k e/ents& agaimana desain stops(rac di upright-
0& T223232 All t#rea!e! asteners utilie! in t#e !ri/erPs +ell stru+ture" an! t#e steering" %raking" !ri/erPs #arness an! suspension s$stems must meet or e+ee!" SAE ra!e 0" etri+ ra!e 4&4 an!
,asterner-
agaimana
6. T22343< All sp#eri+al ro! en!s an! sp#eri+al %earings on t#e steering or suspension must %e in double shear or +apture! %$ #a/ing a s+rew<%olt #ea! or was#er wit# an '&D& t#at is larger t#an sp#eri+al %earing #ousing I&D&
agian mana sa5a yang harus memili!i double shear 5oint-
7& S83234 T#e +ar t#at illustrates t#e %est use o engineering to meet t#e !esign goals" a +ost eGe+ti/e #ig# perorman+e auto+ross +ar" an! t#e %est un!erstan!ing o t#e !esign %$ t#e team mem%ers will win t#e !esign e/ent& Comment Teams are remin!e! t#at FSAE is an engineering !esign +ompetition an! t#at in t#e Design E/entQ teams are e/aluate! on t#eir !esign& Components an! s$stems t#at are in+orporate! into t#e !esign as nis#e! items are not e/aluate! as a stu!ent !esigne! unit" %ut are onl$ assesse! on t#e teamPs sele+tion an! appli+ation o t#at unit& For eample" teams t#at design and ,abricate their on shoc!s are e.aluated on the shoc! design itsel, as well as t#e s#o+kPs appli+ation wit#in t#e suspension s$stem& Teams using +ommer+iall$ a/aila%le s#o+ks are e.aluated only on selection and application wit#in t#e suspension s$stem& agaimana pengambilan !eputusan ma!e=buy setiap part suspensiagian mana sa5a yang didesain sendiri=beli- Mengapa-
96: FSAE
6& Bagaimana pula mem%uatn$a2 ,& Bagaimana +ara /ali!asi n$a2 =tes@ !an meto!e per%aikann$a2 -& Integrasi apa $ang !i%utu#kan suspensi !engan setiap di.isi lain2 =!esain uprig#t !ari steering" penempatan sensor !ari telemetri@ 0& Apaka# kemu!a#an per%aikan !an akses 1uga akan !ipertim%angkan !alam men!esain2 Ease of repair: ub"s#stems accessibilit# parts interchangeabilit# manufacturing comple*it#: 4ave fasteners been standardi9ed: 8re special tools re,uired to diagnoseservice vehicle:
3& Apaka# a!a i!e %aru terkait !esain suspensi2 Atau #an$a mengikuti !esain $ang %iasa !ipakai2 Bagian mana !ari suspensi $ang %enar%enar !esain %aru2 ;ill this car cause a rules change: 4ave the judges learned something new:
7& ?enting !alam penilaian !esain Design 9>46?;@ Assessment o !esign pro+ess use! %$ team& Is t#is a new
!esign" e/olution" or +omplete +arr$o/er2 Were !iGerent !esign options +onsi!ere!2 Were appropriate pre%uil! anal$ses perorme!2 uild 9>46?;@ Does t#e p#$si+al spe+imen presente! reMe+t t#e earl$ !esign work2 Is it reMe+te! in !esign report2 I not" w#$ not2 W#at spe+ial manua+turing +onsi!erations were en+ountere!2 ReAnement=Validation 9>46?;@ How t#oroug# an! #onest #as t#e team %een a%out testing2 Was a test plan !e/elope! an! ee+ute!2 Were !is+repan+ies %etween pre!i+te! an! teste! results !o+umente! an! a+te! upon to impro/e nal %uil!2 'nderstanding 9>46?;@ Is t#e team t#at presents t#e +ar at +ompetition trul$ intimate wit# t#e !esign2 Can t#e$ Nui+kl$ gi/e !etaile! answers a%out an$ su% s$stem2 'r !o t#e$ #a/e to go ask someone else2 4& Apaka# mengerti tentang Vehicle dynamic un!amental2 Apa sa1a $ang %er#u%ungan !engan suspensi2 Harus seperti apa2 8& Bagaimana pemilihan ban !an ukurann$a2 )5& Apaka# mengerti tentang ini understanding of failure modes and critical limp!home re,uirements should be addressed as well. This is !nown as robustness. ))& Bagaimana handling !ari !esain suspensi kita2 =respons !an traksi@ )6& Bagaimana +ara menentukan !an menganalisis wheel base weight distribution c.g. height front and rear trac! widths roll a*is location =static and d#namic> camber gain curves lin! lengths 8c!erman anti"s,uatdive !ing pin inclination scrub radius bump steer and other geometr#!inematics: ),& Bagaimana menentukan beban punca! untuk !esain2 )-& Bagaimana pemilihan material2 ?erluka# #eat treatment<+oating2 )0& Apaka# attachment su!a# !ianalisis2 )3& Bagaimana desain damper2 Bagaimana mekanisme katupn$a2 )7& Bagaimana menetukan heel rate dan roll resistance2 )4& Apa sa1a $ang !ilakukan untuk mengurangi berat unsprung mass2 )8& Bagaimana !esain suspensi agar %isa di%ad5ust2
65& Bagaimana sistem riksi
VEHICLE D (AICS M*D(L$)B & V $R"T$*) M (CH")$CS
C**RD$)"T( S ST(M 2
) illespie" Fun!amentals o Ve#i+le D$nami+s
R$D( & H ")DL$)B 4
T#e ri!e o a /e#i+le is t#e #ea/ing" pit+#ing an! rolling motion in or+e! /i%ration +ause! %$ roa! roug#ness& T#e purpose o t#e suspension in t#is +ontet is to minimise t#e !is+omort o t#e passengers" w#i+# o%/iousl$ in/ol/es a minimisation o some measure o t#e /e#i+le %o!$ motion" %$ +#oi+e o t#e springs an! !ampers" Figure ,&,&)& T#e optimum /alues will o +ourse %e !epen!ent upon t#e Nualit$ o roa!s o/er w#i+# a /e#i+le is epe+te! to operateQ t#e %est suspension parameters or #ig#spee! +ruising on goo!Nualit$ roa!s ma$ %e Nuite !iGerent rom t#e %est o/er +o%%lestones& Anot#er important a+tor to %ear in min! is t#at" alt#oug# t#e ri!e motions +an %e measure! a++uratel$" ri!e Nualit$ is reall$ a su%1e+ti/e opinion" an! as su+# !epen!s /er$ mu+# upon t#e in!i/i!ual& .ltimatel$" t#ereore" t#ere is signi+ant /ariation o opinion on optimum suspension !esign" or %ot# stiGness an! !amping" %ut espe+iall$ o t#e latter& Han!ling is t#e Nualit$ o a /e#i+le ena%ling it to %e +ontrolle! %$ t#e !ri/er in a sae an! pre!i+ta%le manner" so t#at it is eas$ to maintain a !esire! +ourse" an! eas$ to +ontrol t#e /e#i+le at #ig# longitu!inal an! lateral a++elerations" s#oul! t#is %e nee!e!& Dampers un!ou%te!l$ pla$ an important role in t#is" partl$ %e+ause %a!l$ +ontrolle! ri!e motions +ause se/ere pro%lems !uring +ornering or %raking" %ut also %e+ause t#e /ariations o a++eleration +ause pit+# an! roll angles to !e/elop" an! t#is must o++ur in a +ontrolle! wa$& T#e Nualit$ o ri!e an! #an!ling o a /e#i+le is +ertainl$ inMuen+e! %$ man$ a+tors" in+lu!ing t#e springs an! !ampers& In t#e +ase o ri!e" too sot a spring will gi/e a /er$ low natural reNuen+$ w#i+# lea!s to passenger tra/el si+kness& Too stiG a spring wit# a #ig# reNuen+$ gi/es too #ig# a transmissi%ilit$ o #ig#er reNuen+ies& For #an!ling" a sot spring allows e+essi/e pit+# an! roll angles in a++eleration" w#ilst a /er$ stiG spring !oes not permit t#e w#eel to mo/e a!eNuatel$ relati/e to t#e %o!$ an! +onorm to t#e roa! s#ape" so t#e t$re grip %e+omes worse& Consi!ering some sort o Nualit$ rating UR or ri!e an! UH or #an!ling" plotting t#ese against spring stiGness" spe+i+ stiGness" or natural reNuen+$" gi/es Figure T#e optimum stiGness or ri!e is less t#an t#at or optimum #an!ling& Hen+e t#ere is e/i!entl$ a +ompromise to %e ma!eQ t#e wellknown ri!e>#an!ling +ompromise& ?ra+ti+al /alues o stiGness will lie %etween K R)" t#e %est or ri!e" an! K H)" t#e %est or #an!ling" !epen!ing upon t#e t$pe o /e#i+le& ?lotting UR against UH gi/es a polar plot along t#e lines o Figure ,&))&6& Here it is +lear t#at aroun! t#e %est ri!e" wit# stiGness K R)" an in+rease o stiGness will gi/e a su%stantial =rstor!er@ in+rease o #an!ling wit# little loss o ri!e Nualit$ =se+on!or!er@& (ear to optimum #an!ling" wit# stiGness K H)" a re!u+tion o stiGness gi/es su%stantial impro/ement o ri!e wit# little !eterioration o #an!ling&
6 Dion" T#e S#o+k A%sor%er Han!%ook
Hen+e" or passenger /e#i+les t#e pra+ti+al range o +#oi+e lies wit#in a range somew#at less t#an K R) to K H)& Realisti+ /alues o natural reNuen+ies range rom aroun! ) H or large passenger +ars =kSS -5 ( m )
ReNuire! /alues o t#e !amping ratio /ar$ in a somew#at similar wa$ to stiGness& 'ptimum /alues !epen! /er$ mu+# upon parti+ular +on!itions" an! espe+iall$ on personal preeren+es" %ut t#e ri!e o a passenger +ar will generall$ %e %est at a !amping ratio aroun! 5&6" an! t#e %est #an!ling ma$ reNuire an a/erage !amping ratio aroun! 5&4& Hen+e /alues +#osen in pra+ti+e are likel$ to %e in t#e range 5&60>5&70" Figure ,&))&,& For eample" in a stu!$ o /aria%le !amping or a small passenger +ar" using a simple #ea/e mo!el" Sugasawa et al& =)840@ oun! t#eoreti+all$ a !amping ratio o 5&)7 to %e t#e ri!e optimum =minimum spe+tral energ$ o %o!$ #ea/e motion@ an! a ratio o 5&-0 t#e optimum or roa! #ol!ing =minimum t$re or+e /ariation@& In more !etail" t#e /alue oun! or optimum ri!e in or!inar$ !ri/ing was 5&)3" a /alue o 5&-, to minimise O%oun+$ eelP" a /alue o 5&-- or roa! #ol!ing on roug# roa!s" an! a /alue o 5&7) or roll an! pit+# minimisation wit# +ontrol inputs& T#e anal$ti+al mo!el or t#is !i! not in+lu!e t$re stiGness&
L"T(R"L D )"M $CS < Low Spee! Turning > A+kerman Hig# Spee! Cornering
, illespie" Fun!amentals o Ve#i+le D$nami+s
L*)B$T'D$)"L D )"M $CS
- illespie" Fun!amentals o Ve#i+le D$nami+s
S.S?E(SI'( T ?ES
TERI('L' TH(
+H((L"S(
6
l" is t#e !istan+e %etween t#e +entre o t#e ront ale an! t#e +entre o t#e rear ale& T#e
w#eel%ase #as a %ig inMuen+e on t#e ale loa! !istri%ution& A long w#eel%ase will gi/e less loa! transers %etween t#e ront an! rear ales t#an a s#orter w#eel%ase !uring a++eleration an! %raking a++or!ing to ENuation 6&) an! Figure 6&)&
A longer w#eel%ase will t#ereore %e a%le to %e tte! wit# soter springs an! will in+rease t#e le/el o +omort or t#e !ri/er& 'n t#e ot#er #an! a s#orter w#eel%ase #a/e t#e a!/antages o smaller turning ra!ius or t#e same steering input" see se+tion 6&4 9,:& A +ar wit# too s#ort w#eel%ase ma$ a+t ner/ousl$ on +orner eits an! in straig#t line !ri/ing& Anti eatures +an %e %uilt into a suspension an! t#ese will also aGe+t t#e longitu!inal loa! transer" see se+tion 6&7& ,&6 W#eel%ase3 T#e w#eel%ase l" measure! rom t#e +entre o t#e ront to t#e +entre o t#e rear ale =Fig& 3&)@" is an important /aria%le in t#e /e#i+lePs ri!e an! #an!ling properties& A long w#eel%ase relati/e to t#e o/erall lengt# o t#e /e#i+le makes it possi%le to a++ommo!ate t#e passengers easil$ %etween t#e ales an! re!u+es t#e inMuen+e o t#e loa! on t#e ale loa! !istri%ution =see Se+tion 0&,&3@& T#e s#ort %o!$ o/er#angs to t#e ront an! rear re!u+e t#e ten!en+$ to pit+# os+illations an! make it possi%le to t sot springing" normall$ asso+iate! wit# a #ig# le/el o ri!e +omort& A s#ort w#eel%ase" on t#e ot#er #an!" makes +ornering easier" i&e& gi/es a smaller swept turning +ir+le or t#e same steering input =see Se+tion ,&7&6@& Ve#i+le !esigners seek to a+#ie/e a long w#eel%ase on %ot# rontw#eel !ri/e passenger +ars an! on +on/entional !esigns& Howe/er" t#is !epen!s on t#e %o!$ s#ape& =See Se+tion )&) in Re& 94: an! Re& 965:@& A #at+#%a+k estate saloon =Figs )&34 an! )&76@
0 T#esis A!am T#ean!er 3 Buku Reimpel #al )0)
+an %e o a more +ompa+t !esign" gi/ing a longer w#eel%ase relati/e to t#e /e#i+le lengt# t#an not+#%a+k saloons an! t#e estate +ars !e/elope! rom t#em& T#e ratio w#eel %ase
TR"CK 434 Trac! +idth T#e tra+k wi!t#7 is o ma1or importan+e w#en !esigning a /e#i+le& It #as inMuen+e on t#e /e#i+le +ornering %e#a/iour an! ten!en+$ to roll& T#e larger t#e tra+k wi!t# is t#e smaller t#e lateral loa! transer is w#en +ornering an! /i+e /ersa a++or!ing to ENuation 6&6 t#at s#ows t#e loa! transer or a rear ale 9,:&
A larger tra+k wi!t# #as t#e !isa!/antage t#at more lateral mo/ement o t#e /e#i+le is nee!e! to a/oi! o%sta+les& A++or!ing to t#e regulations t#e smallest se+tion o t#e Skip ?a! ma$ not %e smaller t#an ,m an! t#e Auto+ross an! En!uran+e tra+ks no smaller t#an ,&0m 9):& T#e amount o lateral loa! transer wante! !epen!s on tires tte! on t#e +ar" see se+tion 6&8& I t#e +ar #as antiroll %ars t#ese will also aGe+t t#e l oa! transer&
It s#oul! %e as large as possi%le %ut +annot e+ee! a +ertain /alue relati/e to t#e /e#i+le wi!t#& 'n t#e ront ale t#e +ompressing" ull$ turne! w#eel ma$ not +ome into +onta+t wit# t#e w#eel #ouse =ar+#@ =Fig& 6&4@ an! on t#e !ri/en ale =regar!less o w#et#er ront" rear or %ot#@ t#ere #as to %e enoug# spa+e or snow +#ains to %e tte!& W#en t#e w#eels +ompress or re%oun!" t#e$ must not +ome into +onta+t wit# an$ part o t#e +#assis or t#e %o!$work&4
The advantages of a relatively long wheelbase are increased straight line stability, reduced longitudinal load transfer and pitching moments, somewhat easier reduction of the polar moment of inertia and more room to put things in. The advantages of a relatively short wheelbase are reduced overall weight and increased maneuverability. The advantages of wide track widths are reduced lateral load transfer for a given amount of centrifugal acceleration and room for longer suspension links. The major disadvan_ tage is increased frontal area. When we get into aerodynamics,we will see that, at least on open wheeled cars the importance of frontal area is overrated.
7 T#esis A!am T#ean!er 4 Reimpell" T#e Automoti/e C#assis" )06
Very basically, the racing car with a long wheelbase and relatively narrow track widths will be very stable in a straight line at the epense of cornering power and maneuverability. The vehicle with a shorter wheelbase and wide tracks will be less stable, more maneuverable and will develop more cornering power. ! believe that the front track should be considerably wider than the rear track. The wider the front track, the more resistance there is going to be to diagonal load transfer and the lesser will be the tendency for the car to "trip over itself# on corner entry and$or to push into the wall from the effect of the drive on the inside rear wheel when the power is applied.
R$D( H ($BHT
Depen!ing on t#e ea+t roa! or ra+ing en/ironment" generall$ speaking t#e suspension s#oul! %e as low as possi%le to t#e Moor wit# out t#e t#e +ar %ottoming out = w#eel" +#assis or groun! making +onta+t wit# ea+# ot#er@& T#ere are goo! reasons or re!u+ing t#e ri!e #eig#t8 •
•
•
Lower +enter o gra/it$re!u+ing weig#t transer le/els an! ai!ing #an!ling +#ara+teristi+s on t#e limit& In+rease! aero!$nami+ !ownor+e" t#e ront s#oul! alwa$s %e slig#tl$ lower t#en t#e rear to gain a rake eGe+t =re!u+ing lit@ to ai! !ownor+e& Re!u+ing !rag an! in+reasing uel e+onom$&
A!1ustments will reNuire tting o a!1usta%le +oilo/ers" !ampers" or s#orter springs& Care must %e taken in lowering t#e +ar as it #as a !i/erse eGe+t on ot#er suspension geometr$ an! t#is +oul! en! up #in!ering t#e perorman+e potential&
8 www&rapi!ra+er
K $)B P$) & S CR' R "D$'S
T#e Kingpin)5 ais is !etermine! %$ t#e upper %all 1oints" .B" an! lower %all 1oints" LB" on t#e outer en! o t#e Aarms& T#is ais is not ne+essar$ +entre! on t#e tire +onta+t pat+#& In ront /iew t#e angle is +alle! Kingpin in+lination an! t#e !istan+e rom t#e +entre o t#e tire print to t#e ale +entre is +alle! S+ru% or S+ru% ra!ius& T#e !istan+e rom t#e kingpin ais to t#e w#eel +entre plane measure! #oriontall$ at ale #eig#t is +alle! Spin!le lengt#& Figure 6&6 s#ows t#e kingpin geometr$& T#ere are numerous o eGe+ts !ue to t#e /alues o t#ese a+tors" t#e eGe+ts +onsi!ere! to in t#is work are oun! in 96:" 9,: J
J
J
I t#e spin!le lengt# is positi/e t#e +ar will %e raise! up as t#e w#eels are turne! an! t#is results in a in+rease o t#e steering moment at t#e steering w#eel& T#e larger t#e kingpin in+lination angle is t#e more t#e +ar will %e raise! regar!less o w#i+# wa$ t#e ront w#eels are turne!& I t#ere is no +aster present t#is eGe+t is s$mmetri+al rom si!e to si!e& T#e raise o t#e +ar #as a selaligning eGe+t o t#e steering at low spee!s& Kingpin in+lination aGe+ts t#e Steer +am%er& W#en a w#eel is steere! it will lean out at t#e top" towar!s positi/e +am%er i t#e kingpin in+lination angle is positi/e& T#e amount o t#is is small %ut not to negle+t i t#e tra+k in+lu!es tig#t turns& I t#e !ri/ing or %raking or+e is !iGerent on t#e let an! rig#t si!e t#is will intro!u+e a steering torNue proportional to t#e s+ru% ra!ius" w#i+# will %e elt %$ t#e !ri/er at t#e steering w#eel&
Kingpin in+lination)) a!ala# su!ut $ang !i%entuk garis sum%u /ertikal !engan sum%u %all 1oint atas !an %awa# %ila !ili#at !ari tampak !epan ken!araan& .ntuk meminimalisasi s+ru% ra!ius" kita #arus mengatur kingpin in+lination antara 5)5 !era1at& Besar su!ut kingpin se%esar -5& crub radus$% a!ala# 1arak pa!a tampak !epan antara kingpin ais !an garis tenga# %an
ketika ke!uan$a se+ara teoritik %ersentu#an !engan tana#& S+ru% ra!ius #arus !iatur antara 5 sampai )5 mm agar !apat meminimalisasi #awing moment $ang !itim%ulkan )5 T#esis A!am T#ean!er )) Laporan Steering usika
karena a!an$a per%en!aan resistansi antara %an kanan !an %an kiri ter#a!ap permukaan 1alan& am%ar geometri %an !apat !ili#at pa!a gam%ar !i%awa#& Besar s+ru% ra!ius $ang !i!apat se%esar ) mm& ?a!a geometri kingpin !iatas" terli#at a!an$a kingpin ais& Kingpin ais atau steering ais merupakan garis %u1ur $ang akan memutar uprig#t !an ro!a& omen $ang ter1a!i pa!a kingpin ais !apat !i+ari !engan rumus !i%awa# ini = +os X sin(+ @ Keterangan
%&' ( momen Steering ais )*m+ ( traksi roda ( -besar gaya normal roda /koefisien gesek01 )*+ d ( scrub radius )m+ v ( sudut caster )derajat+ 2 ( kingpin inclination )derajat+ Td ( torsi pada ale )*m+ 3 ( kemiringan tie rod terhadap sumbu hori4ontal )derajat+
T#e initial !e+ision o ero !egree kingpin in+lination), #a! to %e re+onsi!ere! sin+e t#e 03 mm o s+ru% ra!ius resulte! is large an! will gi/e an e+essi/e ee!%a+k to t#e !ri/er& T#ereore - !egree kingpin in+lination is to %e %uil! in t#e ront uprig#t !esign t#at will result in an amount o s+ru% ra!ius o ,5mm +al+ulate! or last $ear w#eel oGset& Sin+e t#is amount is still grater t#an )5Y o t#e t#rea! wi!t# =Heisler )848@" new w#eels wit# less oGset #a/e %een oun! t#ereore t#e resulting s+ru% ra!ius is a%out 65 mm t#at is t#e amount we aime! or&
)6 Laporan Steering usika ), Desertasi Cristina Elena
C"ST(R & T R"$L In t#e si!e /iew t#e kingpin in+lination is +alle! aster angle&)- I t#e kingpin ais !oesnPt pass t#roug# t#e +entre o t#e w#eel t#en t#ere is a si!e /iew ?ingpin o@set present& T#e !istan+e rom t#e kingpin ais to t#e +entre o t#e tire print on t#e groun! is +alle! Trail or aster o@set & See Figure 6&6 or t#e si!e /iew geometr$& T#e +aster angle an! trail is o importan+e w#en !esigning t#e suspension geometr$& T#e eGe+ts +onsi!ere! in t#is work are 96:" 9,: J J
J
J
T#e larger t#e trail is t#e #ig#er steering torNue is nee!e!& Caster angle will +ause t#e w#eel to rise an! all wit# steer& T#is eGe+t is opposite rom si!e to si!e an! +auses roll an! weig#t transer& Lea!ing to an o/ersteering eGe+t& Caster angle #as a positi/e eGe+t on steer+am%er& Wit# positi/e +aster angle t#e outsi!e w#eel will +am%er in a negati/e !ire+tion an! t#e inner w#eel in a positi/e !ire+tion" +ausing %ot# w#eels to lean into t#e turn& T#e sie o t#e me+#ani+al trail !ue to +aster ma$ not %e too large +ompare! to t#e Aneumatic trail rom t#e tire& T#e pneumati+ trail will approa+# ero as t#e tires rea+#es t#e slip limit& T#is will result in lowering t#e sel+entring torNue t#at is present !ue to t#e le/er arm %etween t#e tires rotation point at t#e groun! an! t#e point o atta+k or t#e lateral or+e& T#is will %e a signal to t#e !ri/er t#at t#e tire is near %reakawa$& T#is %reakawa$ signal ma$ %e lost i t#e me+#ani+al trail is large +ompare! to t#e pneumati+ trail& • •
•
•
Caster)0 a!ala# su!ut $ang !i%entuk ketika teering ais !imiringkan ke !epan atau %elakang ketika !ili#at !ari samping& ika teering ais !imiringkan ke %elakang =%agian atas !iposisikan !i %elakang %agian %awa#@" maka !ise%ut +aster positi" 1ika !imiringkan ke !epan" maka !ise%ut +aster negati& Caster trail atau me+#ani+al trail !igunakan untuk meningkatkan sta%ilitas teering& e+#ani+al trail 1uga mengaki%atkan momen teering& omen ini !irasakan ole# pengemu!i melalui sistem kemu!i& Caster !apat melawan peru%a#an +am%er $ang !ise%a%kan ole# kingpin i n+lination& Besaran su!ut !an trail menurut literatur reerensi a!ala# Caster angle approimatel$ - !eg& Caster trail approimatel$ 65 mm& Besar su!ut !an trail $ang !ipakai pa!a mo%il us#ika56 a!ala# Caster angle , !eg& Caster trail ),&, mm&
T#e amount o +astor angle)3 was set to ,&0 !egree an! is also %uil! in t#e ront uprig#ts& Howe/er" +astor angle +an %e a!1uste! %$ a!1ustment o t#e upper wis#%one& T#is reNuires t#at one arm o t#e wis#%one to %e s#ortene! w#ile lengt#ening t#e ot#er arm %$ s+rewing in or out t#e a!1usta%le sp#eri+al ro! en!s& Anot#er possi%le a!1ustment is to
)- T#esis A!am T#ean!er )0 Laporan Steering usika )3 Desertasi Cristina Elena
assem%le t#e uprig#t in an in+line! position on t#e #u% ale %ut t#is is not a #an!$ met#o! o a!1ustment&
T#e Caster angle)7 is t#e a%ilit$ o t#e ront suspension s$stem to sel +enter un!er +ornering loa!s& Too mu+# +aster an! t#e ront o t#e +ar will un!ersteer more positi/e +aster@" too little an! $ou will get o/ersteer #an!ling +#ara+teristi+s =negati/e +aster@& Improper a!1ustment will result in steering inputs reNuire! %ot# into an! out o a +orners" resulting in a +ar w#i+# is !iZ+ult to keep on a straig#t line& A large positi/e +am%er setting =w#eel a+ing orwar! o ais@ is goo! or #ig# spee! sta%ilit$ %ut +an make it more !iZ+ult or turning t#e steering" e+essi/e amounts will in+rease t$re
=
Caster angle)4 intro!u+es a new element& T#e +aster angle reers to t#e longitu!inal in+lination o t#e steering ais& It +reates a sel+entering or+e t#at is somew#at !iGerent rom t#e one +reate! %$ t#e lateral steering ais in+lination& A positi/e +aster is esta%lis#e! w#en t#e steering ais meets t#e groun! a#ea! o t#e +enter point o t#e +onta+t pat+# =a point !ire+tl$ un!er t#e ale@& ost passenger +ars #a/e a positi/e +aster on t#e or!er o 5 to 0 !egrees& A positi/e +aster +auses t#e w#eel to trail %e#in! t#e steering ais& W#en t#e /e#i+le is steere!" t#e +aster angle !e/elops an opposing or+e t#at ten!s to steer t#e /e#i+le out o t#e turn Anot#er eGe+t o +aster angle is t#at it +auses t#e +am%er angle to +#ange w#en t#e w#eels are steere!& W#en t#e /e#i+le is steere!" t#e insi!e w#eel p rogresses into a positi/e +am%er an! t#e outsi!e w#eel progresses into a negati/e +am%er& Consi!ere! in!epen!entl$ o steering ais in+lination" t#e eGe+t o +aster in a turn is to !rop t#e si!e o t#e /e#i+le on t#e outsi!e o t#e turn an! to raise it on t#e insi!e o t#e turn&
)7 www&rapi!ra+er
C"M(R Cam%er angle)8 is t#e angle %etween a tilte! w#eel plane an! a t#oug#t /erti+al plane& ?ositi/e +am%er is !ene! as w#en t#e w#eel is tilte! outwar!s at t#e top relati/e to t#e +ar& T#e +am%er angle #as inMuen+es on t#e tires a%ilit$ to generate lateral or+es& A +am%ere! rolling pneumati+ w#eel pro!u+es a lateral or+e in t#e !ire+tion o t#e tilt& T#is or+e is reerre! to as Cam%er t#rust w#en it o++urs at ero slip angles& Cam%er also aGe+ts t#e aligning torNue !ue to !istortion o t#e tire print& T#e eGe+t o t#is is rat#er small an! ten!s to %e +an+elle! wit# in+reasing slip angle& Cam%ering t#e w#eel also lea!s to a raise in t#e lateral or+e pro!u+e! %$ t#e w#eel w#en +ornering& T#is is true in t#e linear range o t#e tire& I t#e linear range is e+ee!e! t#e a!!iti/e eGe+ts o t#e +am%er in+lination !e+reases" t#is eGe+t is +alle! RolloG& T#ereore t#e !iGeren+e in lateral or+e w#en +omparing a +am%ere! w#eel an! a non+am%ere! w#eel is small" aroun! 0)5Y at maimum slip angle& T#e !iGeren+e is mu+# larger at ero !egrees slip angle !ue to t#e +am%er t#rust& T#e eGe+ts o +am%ering t#e t$re are %igger or a %ias pl$ t$re t#an a ra!ial pl$ t$re& For ra!ial t$re t#e +am%er or+es ten!s to all o at +am%er angles a%o/e 0[ w#ile t#e maimum or+e !ue to +am%er or a %ias pl$ ra+ing t$re o++urs at smaller angles&
(egati/e Cam%er65 in+reases t#e +ornering grip o t#e t$re< tire !uring +ornering" #elping to maimise grip an! pro/i!ing %etter tra+tion& Too mu+# (egati/e Cam%er will in+rease t#e insi!e t$res
)8 T#esis A!am T#ean!er 65 www&rapi!ra+er
?ositi/e Cam%er use! more or oG roa! appli+ations" espe+iall$ wit# agri+ultural /e#i+les as t#is setting #elps t#e w#eels to turn wit# lig#ter steering eGort reNuire!&T#e outsi!e w#eel un!er etreme +ornering loa!s will %enet" %ut +am%er le/els are normall$ linke! = mig#t %e a +onsi!eration or o/al tra+ks@&
Cam%er6) is t#e lateral in+lination o t#e w#eel& I t#e w#eel leans out at t#e top" awa$ rom t#e /e#i+le" it #as a positi/e +am%er angle& Wit# a negati/e +am%er angle" t#e w#eel leans inwar! at t#e top& Cam%er+#anges o++ur w#en t#e %o!$ leans !uring a turn an! w#en t#e w#eels mo/e /erti+all$ t#roug# 1oun+e an! re%oun!& A w#eel set at a +am%er angle pro!u+es \+am%er t#rust"\ w#i+# is a lateral or+e generate! in t#e !ire+tion o t#e lean& T#e magnitu!e o +am%er t#rust is su%stantiall$ less t#an t#e or+es generate! %$ slip angle =!ire+tion in w#i+# t#e tire is rolling@& Bias pl$ tires pro!u+e signi+antl$ greater +am%er t#rust t#an !o ra!ial tires& ] As a general rule" t#e /e#i+le will #an!le well i t#e +am%er angle meets +ertain +riteria& At t#e ull$ la!en ri!e #eig#t" t#e ront w#eels s#oul! assume a ero or slig#tl$ positi/e +am%er angle& During 1oun+e" as t#e w#eel mo/es upwar! t#roug# its ar+" +am%er s#oul! progress to a negati/e angle in relation to t#e /e#i+le& T#e pur pose o t#e negati/e +am%er angle is to maimie +ornering or+es %$ keeping t#e outsi!e tire uprig#t or at a slig#tl$ negati/e +am%er angle as t#e %o!$ leans to t#e outsi!e o t#e turn& T#e se+on! purpose o negati/e +am%er is to minimie lateral mo/ement" or tire s+ru%%ing" at t#e +onta+t pat+#& W#en w#eels mo/e t#roug# t#e ar+ pres+ri%e! %$ t#e suspension linkages" t#e$ ma$ %e !ragge! laterall$ in%oar! an! out%oar! as t#e$ mo/e up an! !own& Lateral mo/ement +auses a s+ru%%ing a+tion at t#e +onta+t pat+#" w#i+# re!u+es a!#esion an! s#ortens tire lie& Se/ere lateral s+ru%%ing +an also +ause a +on!ition known as \%umpsteer&\ A suspension s$stem wit# a large s+ru%%ing a+tion will +ause t#e /e#i+le to /eer to one si!e w#en a!#esion or /erti+al w#eel mo/ement is not eNual at %ot# si!e%$si!e w#eels& 6) www&rNrile$&+om
I!eall$" t#e +am%er angle will +#ange !uring 1oun+e enoug# to +ompensate or t#e suspensionin!u+e! lateral mo/ement at t#e #u%& Cam%er +#ange s#oul! also +ompensate or %o!$ roll to keep t#e outsi!e w#eel rom lean awa$ rom t#e turn& Tire s+ru%%ing =+#anges in t#e trea!@ s#oul! %e minimie! %$ goo! suspension !esign" an! +am%er +#anges s#oul! %e minimal as well& Consi!eration o +am%er angle #as tra!itionall$ emp#asie! t#e ront w#eels& Wit# t#e prolieration o in!epen!ent rear suspension s$stems" t#e eGe+ts o +am%er angle #a/e %e+ome 1ust as important at t#e rear o t#e /e#i+le& Rear w#eel +am%er +#anges +an augment +ornering or+es" an! t#e$ +an inMuen+e t#e %alan+e %etween o/ersteer an! un!ersteer&
T*( Toe66 a!1ustment +an %e use! to o/er+ome #an!ling !iZ+ulties in t#e +ar& Rear toeout +an %e use! to impro/e t#e turnin& As t#e +ar turns in t#e loa! transer a!!s more loa! to t#e outsi!e w#eel an! t#e eGe+t is in an o/ersteer !ire+tion& T#e amount o stati+ toe in t#e ront will !epen! on a+tors su+# as A+kermann steering geometr$" ri!e an! roll steer" +omplian+e steer an! +am%er& inimum stati+ toe is !esira%le to re!u+e rolling resistan+e an! unne+essar$ t$re #eating an! t$re wear +ause! %$ t#e tires working against ea+# ot#er& Toe In or Toe out6, is anot#er important suspension setting" it aGe+ts t#e #an!ling o t#e +ar in terms o t$re< tire wear" straig#t line an! +ornering +#ara+teristi+s& In terms o t#e %est %raking an! a++eleration +apa+it$ or t#e t$res< tires" it is %est to #a/e neutral toe settings& •
Too mu+# toe in +auses t#e outsi!es o t#e t$res< tires to wear out&
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Too mu+# toe out +auses t#e insi!es o t#e t$res< tires to wear out&
66 T#esis A!am T#ean!er 6, www&rapi!ra+er
")T$ # ("T'R(S
T#e anti eGe+t6- in a suspension !es+ri%es t#e longitu!inal to /erti+al or+e +oupling %etween t#e sprung an! unsprung masses& It results rom t#e angle o t#e si!e /iew swing arm" s/sa& Anti eatures !o not +#ange t#e stea!$state loa! transer at t#e tire pat+#Q it is onl$ present !uring a++eleration or %raking& T#e longitu!inal weig#t transer !uring stea!$ a++eleration or %reaking is a un+tion o w#eel%ase" C #eig#t an! a++eleration or %reaking or+es as !es+ri%e! in Figure 6&-& T#e anti eatures +#anges t#e amount o loa! going t#roug# t#e springs an! t#e pit+# angle o t#e +ar& Anti eatures are measure! in per+ent& A ront ale wit# )55Y anti !i/e will not !eMe+t !uring %raking" no loa! will go t#roug# t#e springs" an! a ront ale wit# 5Y anti !i/e will !eMe+t a++or!ing to t#e stiGness o t#e springs tte!Q all loa! is going t#roug# t#e springs& It is possi%le to #a/e negati/e anti eGe+ts& T#is will result in a gain o !eMe+tion& ENuation 6&- gi/es t#e per+ent o anti!i/e in t#e ront o a +ar wit# out%oar! %rakes& Anti Di/e ^ =Y ront %raking@ _ = tan `@ _ =)<#@ B$ su%stituting Y ront %raking wit# Y rear %raking an! tan F tan wit# R in ENuation 6&t#e amount o anti lit +an %e +al+ulate!& T#e wa$ t#at %rake an! !ri/e torNue is rea+te! %$ t#e suspension alters t#e wa$ to +al+ulate t#e amount o anti present& I t#e +ontrol arms rea+t torNue" eit#er rom t#e %rakes or rom !ri/e torNue" t#e antiPs are +al+ulate! %$ t#e IC lo+ation relati/e to t#e groun! +onta+t point& I t#e suspension !oesnPt rea+t !ri/e or %rake torNue" %ut onl$ t#e orwar! or rearwar! or+e" t#en t#e antiPs are +al+ulate! %$ t#e IC lo+ation relati/e to t#e w#eel +entre& For a rearw#eel !ri/en +ar t#ere are , !iGerent t$pes o anti eatures J Anti !i/e" w#i+# re!u+es t#e %ump !eMe+tion !uring orwar! %raking& J Anti lit" w#i+# re!u+es t#e !roop tra/el in orwar! %raking& J Anti sNuat" w#i+# re!u+es t#e %ump tra/el !uring orwar! a++eleration& Figure 6&0 s#ows t#e +onguration or +al+ulating t#e anti eatures or a +ar wit# out%oar! ront %rakes an! in%oar! rear %rakes& 6- T#esis A!am T#ean!er
$)ST")T C ()TR( & R *LL C ()TR( Instant +entre60 is t#e momentar$ +entre w#i+# t#e suspension linkage pi/ot aroun!& As t#e suspension mo/es t#e instant +entre mo/es !ue to t#e +#anges in t#e suspension geometr$& Instant +entres +an %e +onstru+te! in %ot# t#e ront /iew an! t#e si!e /iew& I t#e instant +entre is /iewe! in ront /iew a line +an %e !rawn rom t#e instant +entre to t#e +entre o t#e tirePs +onta+t pat+#& I !one or %ot# si!es o t#e +ar t#e point o interse+tion %etween t#e lines is t#e Roll +entre o t#e sprung mass o t#e +ar& T#e position o t#e roll +entre is !etermine! %$ t#e lo+ation o t #e instant +entres& Hig# instant +entres will lea! to a #ig# roll +entre an! /i+e /ersa& T#e roll +entre esta%lis#es t#e or+e +oupling point %etween t#e sprung an! t#e unsprung masses o t#e +ar& W#en t#e +ar +orners t#e +entriugal or+e a+ting on t#e +entre o gra/it$ +an %e translate! to t#e roll +entre an! !own to t#e tires w#ere t#e rea+ti/e lateral or+es are %uilt up& T#e #ig#er t#e roll +entre is t#e smaller t#e rolling moment aroun! t#e roll +entre is& T#is rolling moment must %e restri+te! %$ t#e springs& Anot#er a+tor is t#e #oriontal/erti+al +oupling eGe+t& I t#e roll +entre is lo+ate! a%o/e t#e groun! t#e lateral or+e generate! %$ t#e tire generates a moment a%out t#e instant +entre" w#i+# pus#es t#e w#eel !own an! lits t#e sprung mass& T#is eGe+t is +alle! a+king& I t#e roll +entre is %elow t#e groun! le/el t#e or+e will pus# t#e sprung mass !own& T#e lateral or+e will" regar!ing t#e position o t#e roll +entre" impl$ a /erti+al !eMe+tion& I t#e roll +entre passes t#roug# t#e groun! le/el w#en t#e +ar is rolling t#ere will %e a +#ange in t#e mo/ement !ire+tion o t#e sprung mass&
T#e +am%er +#ange rate is a un+tion onl$ o t#e ront /iew swing arm lengt#" /sa lengt#& Front /iew swing arm lengt# is t#e lengt# o t#e line rom t#e w#eel +entre to t#e instant +entre w#en /iewe! rom ront& T#e amount o +am%er +#ange a+#ie/e! per mm o ri!e tra/el woul! %e as !es+ri%e! in ENuation 6&, an! Figure 6&,& !egrees
60 T#esis A!am T#ean!er
T$( R *D L *C"T$*) T#e lo+ation o t#e tie ro!s63 is o ma1or importan+e& T#e lo+ation s#all %e su+# t#at Bump steer eGe+ts are kept at a minimum& Bump steer is t#e +#ange in toe angle !ue to w#eel tra/el& A +ar wit# mu+# %ump steer will #a/e a ten!en+$ to +#ange its mo/ement !ire+tion w#en t#e ront w#eels runs o/er an o%sta+le& T#e aGe+ts o t#is +an %e #aar!ous w#en running on an une/en tra+k& T#e simplest wa$ to minimie %ump steer is to lo+ate t#e tie ro! in t#e same plane as eit#er t#e upper or lower Aarms& Anot#er a+tor to keep in min! is t#e +am%er +omplian+e un!er lateral or+e& I t#e tie ro!s are lo+ate! eit#er a%o/e an! %e#in! or %elow an! in ront o t#e w#eel +entre t#e eGe+t on t#e steering will %e in un!ersteer !ire+tion& I t#e Aarms are stiG enoug# t#e eGe+ts will %e small an! t#ere%$ minimie t#e risk o o/ersteering eGe+ts !ue to +omplian+e in t#e A arms& T#e lengt# o t#e le/er arm rom t#e outer tie ro! en! to t#e upper %all 1oint !etermine toget#er wit# t#e steering ra+k ratio t#e total ratio rom t#e steering w#eelPs angle to t#e w#eelPs steering angle&
63 T#esis A!am T#ean!er
")T$ %R *L "R AntiRoll
.n!ersteer re!u+e ront or in+rease rear antiroll< swa$ %ar settings&
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'/ersteer in+rease ront or re!u+e rear antiroll< swa$ %ar settings
67 www&rapi!ra+er
D"MP(R Dampers64 work in +on1un+tion wit# springs to orm t#e %asis or +ar suspension" t#e$ are sometimes in+orre+tl$ reerre! to as s#o+k a%sor%ers& I a +ar was onl$ tte! wit# spring an! not !ampers" t#en an$ mo/ement in t#e +ars suspension in t#e /erti+al plane" woul! eGe+ti/el$ keep %oun+ing up an! !own until t#e kineti+ energ$ is !ispla+e!& T#is woul! make t#e +ar /er$ !iZ+ult to !ri/e rom a perorman+e point o /iew" as t#e geometr$ woul! %e +onstantl$ +#anging& Dampers eGe+ti/e #elp to !issipate an$ /erti+al mo/ement in t#e suspension an! keep t#e springs mo/ements +ontrolle!" also t#e$ #elp t#e w#eel keep ull motion un!er !iGerent loa!s" w#ile keeping t#e w#eel in +onta+t wit# t#e groun!& •
2%+ay ad5ustable Suspension@ re%oun!
a!1usta%le onl$& •
4%+ay ad5ustable Suspension@ %ump
an! re%oun! a!1usta%le& •
%+ay ad5ustable Suspension@ #ig#
an! low spee! %ump setting " #ig# an! low spee! re%oun! settings =#ig# spee! or %umps" low spee! or +orners an! %raking@& It is possi%le to a!1ust t#e !ampers to gi/e !iGerent #$!rauli+ resistan+e to ne tune t#e #an!ling o t#e suspension or gi/en +on!itions" t#e mo/ement is %roken !own into %ump =+ompression@ an! re%oun! =etension@ motions& Dampers !ont +ontrol loa! le/els" %u t aGe+t t#e spee! o #ow ast t#e suspensions rea+ts to loa! +#anges an! #ow ast t#e t$re< tires +onta+t pat+# re+ei/es t#ese loa!s& •
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StiGer ront !amping =%ump an! re%oun!@" in+reases grip at t#e rear o t#e +ar" in+reasing un!ersteer +#ara+teristi+s& StiGer rear !amping =%ump an! re%oun!@" in+reases grip at t#e ront o t#e +ar" in+reasing o/ersteer +#ara+teristi+s&
ump During %ump" t#e !ampers an! springs a%sor% t#e upwar! mo/ement rom +ornering or roa! irregularities =t#e springs store some o it@" t#e !ampers t#en goes into re%oun!& I t#ere isnt enoug# !amping t#en t#e +$+le %egins again until t#e +ar returns to t#e original ri!e #eig#t" wit# a %oun+ing motion to t#e +ar& Anot#er trait o un!er !amping is t#at loa!s go into t$re< tire an! suspension relati/el$ slowl$" t#is +om%ine! wit# t#e %oun+ing eGe+t means a +onstant /ar$ing !ownloa! or+e& A++eleration" %raking or +ornering in t#is state wit# also /ar$ !ue to t#e /arious !ownloa! rates" so it is important to #a/e enoug# %ump stiGness to %e a%le to !eal wit# une/en sura+es& I t#ere is too mu+# !amping" t#en it is eGe+ti/el$ like running no suspension an! an$ upwar! motion will %e transmitte! !ire+tl$ to t#e +#assis& '/er !amping will result in a in+rease in t#e loa!s a+ting on t#e suspension an! t#e t$res
/er$ #ars# an! #ar!" t#is will eGe+t street !ri/ing in terms o +omort le/els" so mig#t not %e !esire! or a !ail$ !ri/e& T#is is un!esira%le in %ot# un!er an! o/er !amping settings as it will re!u+e t#e #an!ling o t#e +ar an! will aGe+t a++eleration" %raking an! +ornering loa!s&
Rebound During re%oun! =ollowing t#e %ump +ompression p#ase@ t#e !ampers eten! %a+k to t#eir original positions" using up t#e store! energ$ rom t#e springs& T#e re%oun! stiGness nee!s to %e set at a #ig#er /alue t#en t#e %ump setting as t#e store! energ$ is %eing release!& I t#ere is not eGe+t !amping on t#e re%oun!" t#e w#eel will Nui+kl$ return t#roug# t#e stati+ le/el an! start to %ump again" wit# t#e %oun+ing eGe+t unsettling t#e suspension wit# little +ontrol& I t#ere is too mu+# re%oun! stiGness" t#en t#e w#eel +oul! #ol! longer in t#e w#eel ar+# t#en nee!e!" eGe+ti/el$ losing +onta+t wit# t#e roa! as t#e or+e to pus# t#e w#eel %a+k !own is slower to respon! to t#e +#anging sura+e le/el& T#is state is again ar rom i!eal an! it is %est to make sure a goo! le/el is set or optimal t$re
Damping (Eect *n Cornering@ ump
Front Bump In+rease^ Front Bump De+rease^ Rear Bump In+rease^ Rear Bump De+rease^
.n!ersteer& '/ersteer& '/ersteer& .n!ersteer&
Rebound
Front Re%oun! In+rease^ .n!ersteer& Front Re%oun! De+rease^ '/ersteer& Rear Re%oun! In+rease^ '/ersteer& Rear Re%oun! De+rease^ .n!ersteer&
SPR$)B
Spring Rate It is a ratio in!i+ating t#e resistan+e o a spring !uring %ump or re%oun! =+ompression or epansion@&Also known as suspension rate" it is +riti+al or setting t#e +orre+t ri!e #eig#t an! is proportionate to t#e mo/ement o t#e lengt# o +omponent tra/el in its stoke p#ases& As we know t#e w#ole 1o% o suspension is to keep t#e w#eels an! t$res in +onta+t wit# t#e groun! at all times" or total perorman+e& B$ #a/ing t#e a%ilit$ to +#ange t#e spring rate" #ea/ier /e#i+les +an #a/e a #ig#er setting to stop t#e suspension %ottoming out un!er etreme loa!s" or i t#e +ar #as %ig !ownor+e generation a%ilities& Soter spring rates +oul! %e an a!/antage in roug#er terrains or raise! ker%s at apees& I #a/e seen a +ar 1ump o a ker% at spee!" t#an lower spring rates are nee!e!& .nless o +ourse $ou en1o$ %oun+ing !own t#e tra+k" or e/en oG t#e tra+k in worse +ase eamples& Sometimes people +omplain w#en !ri/ing sports or tra+k o+use! +ars wit# +ompetiti/e suspension on normal roa!s" t#is is %e+ause o #ig#er spring rates& ost springs will #a/e ratings on ater market upgra!es an! unless $ou #a/e ra!i+all$ re!u+e! weig#t o t#e +ar or re/ise! t#e aero!$nami+ pa+kage" it is %est to keep to t#e manua+tures re+ommen!ations& Spring rates +an %e measure on a ma+#ine or alternati/e t#e ollowing ormula ma$ #elp
here d is the ire diameter: B is the springFs Shear Modulus 9,or e1ample about 24:GGG:GGG lb,=in4 or 7G BPa ,or steel;: and ) is the number o, raps and D is the diameter o, the coil3
W#eel Rate Similar to spring rate %ut measure! at t#e w#eel instea! o at t#e suspension linkage o t#e spring& Also it is important to know t#at t#e w#eel rate woul! alwa$s normall$ %e less t#an t#e spring rate" as t#e w#eel will tra/el a larger !istan+e t#roug# +ompression or epan!ing t#an t#e spring& +heel Rate is the Motion Ratio s0uared times the Spring Rate@ +heel Rate Spring Rate I 9Motion Ratio J 4; I Spring "ngle Correction
S.S?E(SI'( E'ETR T.(E T' WI( > C ARR'L SITH •
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T#e geometr$ o an$ w#eel suspension s$stem !etermines t#e linear an! angular pat#s t#at w#eel an! tire will ollow w#en it is !ispla+e! rom its stati+ position& T#e s#ape o t#ese w#eel pat# will !epen! on t#e realati/e lengt#s an! in+linations o suspensions links We want to +ontrol +#ange o w#eel +am%er angle an! +#ange o tra+k !imension wit# w#eel an! sprung mass mo/ement In or!er to a+#ie/e t#e maimim ootprint area an! an e/en pressure pattern so t#at we +an realie maimum tire tra+ti/e eGort un!er %raking * a++elerating We wis# t#e w#eel to remain uprig#t w#en t#e suspension is su%1e+te! to /erti+al mo/emnet o t#e sprung mass +ause! %$ longitu!inal loa! transer We want %ot# t#e in%oar! an! out%oar! w#eels to remain /erti+al to t#e tra+k sur/a+e as t#e sprung mass rolls !ue to +entriugal a++eleration We also !o not want t#e tra+k !imension at t#e +onta+t pat# to +ange un!er an$ o t#ose +on!ition as t#at woul! +ause t#e tire to %e s+ru%e! si!ewa$s a++ros t#e ra+e tra+k It woul! %e ni+e i t#e roll +enters at ea+# en! o t#e +ar were to remain a +ontant !istane awa$ rom t#eir respe+ti/e +entre o mass so t#at we +an retain our linear rate o roll generation an! lateral loa!
?ARALEL * EU.AL LE(TH •
no camber change ith .ertical mo.ement& T#ere is" #owe/er" +onsi!era%le
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+#ange in tra+k wi!t#w#i+# is not goo!& W#en t#e +#asis rolls" t#e w#eels an! tires +#ange +am%er %$ t#e ea+t amount o +#assis rollwit# t#e outsi!e w#eel +am%ering in t#e positi/e !ire+tion& T#is is not goo! un!er an$ +on!ition an!" t#e wi!er t#e tire in/ol/e!" t#e less goo! it is& We +an re!u+e t#e amount o tra+k +#ange or a gi/en amount o /erti+al motion %$ t#e simple epe!ient o lengthening the suspension lin!s: as in Figure =60@& Wit# t#is +#ange" a gi/en amount o /erti+al w#eel or +#assis mo/ement results in less angular !ispla+ement o t#e w#eel an! t#ereore in less +#ange in t#e tra+k !imension
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?ARALEL * .(EU.AL LE(TH (ow" in /erti+al tra/el" t#e upper link #as a s#orter ra!ius t#an t#e lower w#i+# •
results in the heel assuming a negati.e camber angle in both bump and either negati.e or positi.e camber droop& I t#e w#eels are allowe! to •
tra/el /er$ mu+#" t#e +am%er +ur/es will %e+ome /er$ steep in!ee!& At an$ rate" t#e roll +enter wit# uneNual %ut parallel links stays pretty constant in relationship to the center o, mass3 T#ereore t#e roll moment remains more or less +onstant" w#i+# is a goo! t#ing&
.(EU.AL A(D ('( ?ARALLEL LI(KS B$ in+lining t#e link pi/ot aes wit# respe+t to ea+# ot#er we +an place the roll centers here.er e please an! we an! ,urther reduce the positi.e camber o t#e la!en w#eel in roll& W#at #as #appene! is t#at t#e in+lination o t#e upper link is too steep" resulting in a /er$ s#ort instantaneous swing arm wit# t#e atten!ant /er$ steep +am%er +ur/es& B$ raising t#e in%oar! points o %ot# t#e upper an! t#e lower links we •
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woul! a+#ie/e ar better camber cur.es hile maintaining the roll center in the same static location&
BASIC TR.THS =)@ W#ile it is possi%le to +ontrol w#eel +am%er eit#er !uring /erti+al mo/ement or !uring +#assis roll" it is not possible to achie.e .ery good camber control •
under the combined condition •
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=6@ T#e longer we make t#e suspension links" t#e less angular and linear heel displacement will result rom a gi/en amount o +#assis or w#eel mo/ement& =,@ In /erti+al mo/ement" t#e roll +enter mo/es wit# t#e +enter o gra/it$" ten!ing to keep t#e roIl moment +onstant& =-@ $ncreasing the eEecti.e sing arm length !e+reases t#e amount o camber change !ue to /erti+al w#eel mo/ement" !e+reases t#e amount o .ertical roll center mo/ement relati/e to t#e e&g& an! in+reases t#e amount o lateral roll center mo.ement
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=0@ E+ept in t#e +ase o eNual lengt# an! paraIlellinks long eGe+ti/e swing arms !ont sta$ long w#en t#e w#eel mo/es into t#e %ump position or" or t#e la!en w#eel" w#en t#e +#assis rolls& =3@ In+reasing t#e in+lination o t#e upper link =or s#ortening its relati/e lengt#@ results in more negati/e +am%er in %ump" less positi/e +am%er on t#e la!en w#eel in roIl an! a !e+rease in t#e amount o w#eel or +#assis mo/ement %eore we lose +am%er +ontrol&
C'?R'ISE =)@ T#e present generation o ra+ing tires is relati/el$ insensiti.e: wit#in reasona%le limits" to camber change3 =6@ Load trans,er characteristics are more important to tire perorman+e an! /e#i+le %alan+e t#an +am%er +ur/es =,@ DiGerent !esign p#ilosop#ies ten! to e/en out in terms o lap timet#e +ar w#ose geometr$ ten!s to limit its a%osolute +ornering power ma$ well put t#e power !own%etterhat you gain on the straights you lose in the corners an! soon •
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.IDELI(ES •
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T#e ,ront camber cur.e should !eep t#e la!en w#eel more upright in roIl t#an t#e rear& =6@ T#e ront roll +enter will alwa$s %e lower t#an t#e rear& If it is too mu+# lower" we will #a/e a +ar t#at !oes not enter +orners well an! w#i+# eits +orner on t#ree w#eels& The big tric! here is to !eep the ,ront and rear roll center mo.ements appro1imately e0ual to each other%and in the same direction
=,@ We +an +ontrol w#eel +am%er wit#in narrow limits o +#assis roll an! rat#er more %roa! limits o /erti+al mo/ement& At some point in t#e generation o roll or /erti+al mo/ement" t#e geometr$ will go to #ell an! t#e w#eel pat#s will start to +#ange /er$ rapi!l$3 The longer that e ma!e the suspension lin!s: the
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more mo.ement can ta!e place be,ore e lose camber control%and the less heel displacement e ill suEer per unit o, chassis mo.ement& Ve#i+le %alan+e or !ri/ea%ilit$ is
more important in terms o lap time an! winning ra+es t#an ultimate +ornering power& So& I eel t#at we s#oul! !esign t#e geometr$ o our
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suspensions to minimie rapid changes o, camber and relati.e ,ront to rear roll center mo.ement as t#e +ar goes t#roug# its transitions rom %raking to +ornering a++eleration restri+t +#assis rol = I@ We +an use #ig# roll +enters w#i+# result in low roll moments& We !o not want to ollow t#is approa+# %e+ause we will t#en #a/e poor +am%er +ur/es an! #ig# 1a+king or+es& =6@ We +an use antiroll %ars at ea+# en! o t#e +ar stiG enoug# to restri+t roll to our !esire! maimum& =,@ We +an use t#e suspension springs to restri+t rolleit#er %$ making t#em stiGer" w#i+# is a %a! i!ea" or %$ optimiing t#eir pla+ement so t#at we get maimum linear spring tra/el per !egree o roll generate!& =-@ We +an use longer suspension links to re!u+e t#e amount o +am%er +#ange generate! per !egree o roll&
C'(SIDERATI'( • • • •
?ower to weig#t ratio =6@ Aero!$nami+ !ownor+e to %e generate! an! range o/e#i+le spee!s =,@ Tire wi!t# an! +#ara+teristi+s =-@ Tra+k +#ara+teristi+ssmoot#ness" +orner spee!" !egree o %anking present an! t#e amount o %raking t#at will take pla+e&
T#e u%iNuitous Formula For! eatures low engine power" low gross weig#t" narrow tires" /irtuall$ no !own or+e generation" an! +ra$ !ri/ers& T#e$ !o not a++elerate /er$ #ar! %e+ause t#e$ !ont #a/e mu+# torNue& Sin+e t#e$ are not allowe! to run wings" t#e operating ri!e #eig#t !oes not +#ange mu+# wit# roa! spee!& T#e narrow tires will tolerate a air amount o +am%er& W#at Formula For!s nee! rom t#e suspension geometr$ is ma1imum bra!ing poer and ma1imum cornering poer3 T#e$ nee! t#e %raking power" %e+ause one o t#e ew pla+es or a Formula For! to get %$ anot#er one is in t#e %raking area& T#e$ nee! t#e +ornering power" %e+ause t#e$ +annot aGor! to slow !own an$ more& We get t#e %raking power %$ keeping t#e& ,ront heels as upright as possible in bump and not allomg the rear heels to go into positi.e camber in droop3 T#is
means long links wit# not mu+# in+lination at t#e ront& At t#e rear" we !ont nee! to worr$ a lot a%out t#e eGe+ts o sNuat sin+e we wont #a/e enoug# torNue to +ause mu+# o it& We !o" #owe/er" #a/e to worr$ a%out t#e +am%er o t#e la!en w#eel& As no limite! slip !iGs are allowe!" we also #a/e to a/oi! insi!e rear w#eelspin w#i+# means lots o !roop tra/el" a.oidance o, e1treme negati.e camber generation on the inside heel and minimum lateral load trans,er at the rear3
I %elie/e t#at it is a #ell o a lot more important to get the roll center locations and mo.ements happy ith each other and ith the mass centroid a1is than it is to get the camber cur.es per,ect If $ou !e+i!e to make t#e links longer" take a reall$
goo! look at t#e stru+tural a+tors in/ol/e!t#e$ will ne+essaril$ #a/e to %e stiGer" parti+ularl$ at t#e ront" !ue to t#e %rake torNue loa!s %eing rea+te! o/er a longer !istan+e& Raising or lowering pi/ot points" at t#e ront" is simpl$ a +ase o making spa+ers or t#e %all 1oints" or o re!u+ing t#e #eig#t o t#e uprig#ts& It is alwa$s easier to !o it out%oar! t#an in%oar!e+ept on pro!u+tion +ars& T#e opposite +on!ition eists at t#e rear w#ere t#e out%oar! pi/ots are prett$ well e! in t#e #u% +arrier !esign %ut t#e in%oar!s are %olt on stru+tures or +ross mem%ers w#i+# +an %e prett$ easil$ repla+e! or mo!ie!
I(TER(ET S'.RCE R 'LL C E(TRE ? 'SITI'( #ttp<
? 'SITI'( E FFECT I roll +entres set too low" t#ere will %e more %o!$ roll an! stiGer %ars will %e reNuire! at %ot# en!s" t#at will eGe+t w#eel rates an! tra+tion on %umps w#en +ornering" an! espe+iall$ on slipper$ sura+es& Low roll +entres an! stiG %ars =wit# t#e #ig#er w #eel rate !uring +ornering t#is +reates@ will make it /er$ ast in t#e !r$ %ut it will sli!e mu+# too easil$ in t#e wet& T#is is t#e one %ig reason pro!u+tion +ars #a/e mo!eratel$ #ig# roll +entres& Roll +entres set ar too #ig# will +ause 1a+king an! pro!u+e minimal %o!$ roll w#i+# makes t#e antiroll %ars mu+# less sensiti/e" an! %asi+all$ makes t#e +ar untuna%le&
A D.STI( #ttp<
+am%er& T#is will gi/e $ou sta%le stea!$ state +ornering an! get %ot# en!s o t#e +ar working& T#e net step is to start a!1usting t#e roll ais in+lination or %est TRA(SIE(T response& Loa! will transer aster at t#e en! o t#e +ar as t#e roll ais #eig#t is in+rease! at t#at en!& A low roll +entre will ee! t#e lateral loa! transer pro!u+e! rom %o!$ roll mainl$ t#roug# t#e springs an! %ar& Bo!$ roll is not instantaneous" an! eit#er will %e lateral loa! transer at t#at en!" response will %e slower& A #ig# roll +entre will pro!u+e less %o!$ roll" %e+ause most o t#e lateral loa! transer goes !i re+t t#roug# t#e suspension links" it respon!s aster to su!!en +#anges in !ire+tion& W#at we want is a sta%le /e#i+le wit# astest possi%le response& We !o t#is %$ %uil!ing in some stea!$ state un!ersteer =t#i+ker ront antiroll %ar@& An! gi/ing it 1ust a %it o transient o/ersteer =#ig#er rear roll +entre@& I it is !one rig#t" it will %e ast an! sta%le aroun! a +#i+ane" w#ere $ou rapi!l$ turn rst one wa$ t#en t#e ot#er& All t#is assumes t#ere are no %ump or roll steer pro%lems to +ompli+ate t#ings& E/er$ time $ou mo/e one o t#e roll +entre #eig#ts" $ou i!eall$ nee! to t#en re%alan+e t#e +ar on a ski! pa! %eore testing or a +#ange in transient response& Ve#i+les wit# etreme or unusual weig#t !istri%ution +an reNuire un+on/entional roll +entre in+linations" t#e ront roll +entre is not alwa$s lower t#an t#e rear" %ut it usuall$ is& T#e astest wa$ to get rom one stea!$ state +on!ition to anot#er is wit# 1ust a %it o o/ers#oot& T#at is w#ere t#e transient o/ersteer +omes in& It will not +ause insta%ilit$" unless t#ere is ar too mu+#& W#at it !oes is spee! up t#e response& 'ne more t#oug#t on roll +enters& T#ere are two t$pes o weig#t transer" geometri+ an! elasti+& eometri+ weig#t transer is weig#t transerre! t#roug# t#e linkages =pan#ar! %ar or a+o%s la!!er@ an! Elasti+ Weig#t Transer is weig#t transerre! t#roug# t#e springs& As we raise our roll +enter we are in+reasing t#e amount o eometri+ Weig#t Transer an! re!u+ing t#e amount o elasti+& T#e issue wit# geometri+ weig#t transer is it #appens instantaneousl$" wit# elasti+ it #appens slower %e+ause we #a/e to wait or t#e spring to +ompress& As t#e roll +enter is raise!" t#e ri!e %e+omes more #ars# an! t#e +ar +an get a tenan+$ to #op an! also !oes not a%sor% t#e ruts an! %umps as well& T#is kin!s goes against our wanting to loosen t#e +ar up or keep t#e +ar rom rolling %$ raising roll +enters in t#e rear on a roug# or wet tra+k to loosen t#e +ar&
R EADI( A(D A (ALI( C ABER C .RVES #ttp<
? ARTS 'F THE C ABER RA?H
T#e num%ers on t#e let si!e o t#e grap# represent t#e up an! !own tra/el o a w#eel or suspension& T#e line in t#e mi!!le la%ele! \stati+\ is t#e w#eel =or suspension@ position w#en t#e ra+e +ar is at rest or stan!ing still& T#e negati/e =@ num%ers represent t#e +on!ition w#ere t#e w#eel mo/es !ownwar! rom t#e rame& T#is +oul! #appen w#en t#e tire !rops into a pot#ole" or w#en t#e insi!e o t#e +#assis lits as !uring %o!$ roll in a +orner& T#e positi/e num%ers a%o/e t#e stati+ line are w#ere t#e w#eel #as mo/e! up in relation to t#e +#assis& T#is +an %e a +ase w#ere t#e tire is going o/er a %ump or w#en t#e outsi!e o t#e rame !rops as !uring %o!$ roll in a turn& T#e num%ers on t#e %ottom o t#e grap# are use! to i!enti$ t#e w#eels +am%er +#ange& T#e +ur/ing line on t#e grap# is t#e +am%er +#ange or ea+# position o t#e w#eels /erti+al mo/ement& .sing t#e stati+ line an! t#e \5\ +am%er line" t#e grap# +an %e !i/i!e! into Nua!rants =top let" top rig#t" %ottom let" %ottom rig#t@& T$pi+all$" it is !esira%le to #a/e a +am%er +ur/e t#at is in t#e top let an! %ottom rig#t Nua!rants& Sto+k +ar suspensions rom t#e 35s an! 75s oten #a! +am%er +ur/es t#at ran rom t#e top rig#t t#roug# t#e %ottom let Nua!rant& T#is is almost alwa$s un!esira%le or #ig# perorman+e #an!ling&
D ESIRED S HA?E 'F L I(E T#e net step in anal$ing an! impro/ing $our +am%er +ur/e ater getting t#e line in t#e proper Nua!rants =or i $ou were lu+k$ to #a/e it in t#e proper Nua!rants to start@" is to a+#ie/e a spe+i+ line s#ape on t#e +am%er grap#& Depen!ing on t#e t$pe o tra+k an! +ar $ou will #a/e !iGerent reNuirements& 'n a Mat tra+k wit# small or no swa$ %ars" generall$ $our +am%er +ur/e s#oul! %e less o a +ur/e an! more o a straig#t line& I!eall$ t#e line woul! slope uniorml$ rom t#e top let to t#e %ottom rig#t o t#e grap#& 'n %ig %ar sot spring setups t#e let an! rig#t si!es ma$ nee! !iGerent +am%er lines an! oten a /er$ steep sloping line works %etter t#an a Matter slope! line&
''D A(D B AD ? ARTS 'F L I(E an$ sto+k +ar suspensions will #a/e a +am%er +ur/e t#at looks like t#e one in t#e eample& T#e #ook part o t#e line w#ere t#e arrow \A\ is pointe! is un!esira%le i $ou #a/e a lot o re%oun! =or etention@ o t#e i nsi!e suspension w#en +ornering& I $our +ar sNueals t#e insi!e ront tire in a +orner" t#ere is a goo! +#an+e $ou #a/e a +am%er +ur/e wit# a #ook& S#ort tra+k ra+e +ars t#at #a/e a +am%er +ur/e =like t#e eample@ oten reNuire larger amounts o positi/e +am%er in t#e let ront tire in or!er to keep t#e +ar rom pus#ing in t#e mi!!le o t#e turns&
Again" t#e region o t#e line marke! B is t$pi+all$ a !esira%le s#ape& (oti+e t#at #ere t#e line it is Matter an! less +ur/e! t#an at t#e opposite en! o t#e line& W#en anal$ing $our suspension" i $ou are limite! to mo!i+ations !ue to rules" $our #an!ling +oul! %e impro/e! %$ lowering or raising $our rame #eig#t& 'ne wa$ o t#inking a%out t#is is t#at lowering or raising t#e ri!e #eig#t will mo/e t#e +am%er +ur/e to a !iGerent stati+ spot on t#e grap#& T#is +an %ring t#e %etter portion o t#e +ur/e to t#e operating range in t#e +orners& I $ou want a s+ienti+ wa$ to set +am%er +ur/es it nee!s to %e !one on t#e %a+k o testing& Atta+# some inrare! t$re temp sensors to $our +ar an! go running& ou will n! t#at t#e t$pe o t$re matters& T#e si!ewall stiGness is /er$ important& 'ne eample rom our testing is t#at t#e oo!$ear t$res are /er$ wear sensiti/e to +am%er e/en i t#e$ are a little aster& T#e t#ing to learn rom t#at is to take t#e t$re test !ata wit# a grain o salt& (ot#ing %eats ontra+k testing& Anal$sing t#e !ata to n! out w#at $ou s#oul! %e running is a w#ole new topi+& A reall$ simple wa$ is to %reak $our !ata !own into +orners t#at represent low" me!ium an! #ig# spee! +orners an! look at $our temperature !istri%ution in ea+# o t#em& Remem%er to keep a reeren+e o $our steering angle or t#e ront as it will #a/e a great aGe+t or t#e +astor angles most o t#ese +ars run& ou s#oul! %e a%le to !iGerentiate %etween t#e eGe+t o stati+ +am%er an! !$nami+ +am%er& I woul! not o/erestimate t#e eGe+t o geometr$ on a ski!pan& ost o our time gains on t#e ski!pan were ma!e t#roug# !amper work an! !ri/er training& Ha/e a look at t#e !ata o a ski!pan run an! noti+e #ow mu+# lateral gs are !roppe! or 1ust a small steering or t#rottle +#ange& Also note #ow !iZ+ult it is to #ol! +onstant t#rottle an! steering on a reall$ %ump$ tra+k&
L'AD T RA(SFER L'(IT.DI(AL LATERAL
DESI( S TE? READ
A(D .(DERSTA(D
T#is is t#e rst step $ou s#ol! take %eore !esign an$ti#ing& .n!erstan!ing w#at a FSAE ra+e is an! ea+# rule o it is /er$ important t#ing& T#ese knowle!ge #elp $ou !etermine t#e rig#t !esign o $our ormula +ar" espe+iall$ or t#is kin! o ra+e& istake on $our !esign not also make a %a! +ar" %ut $ou +an not ra+e e/entuall$& T#e S+rutineers inspe+t e/er$ aspe+t o $our +ar %eor ra+e& I an$t#ing go wrong" t#e$ or%i! $ou ra+e& T#e winner o t#is +ompetition is not t#e +ar t#at #as %est engine or t#e lig#test weig#t" %ut ot#er t#ings matters&Suspension itsel !o a great inMuen+e to t#e perorman+e o +ar& Suspension !etermine perorman+e o a +ar w#en w#eels #it a %ump" +orner in a turn" an! also a++elerate an! %rake& A goo! suspension sta%ilie t#e +ar in e/er$ roa! +on!ition& W#eel %ase" tra+k" roll +entre" anti roll %ar" transient !$nami+" natural reNuen+$" weig#t !istri%ution" an! man$ ot#er aspe+t !etermine #ow $our suspension perorm& How on eart# $our suspension will work well i $ou !onPt k#ow t#ese t#ings2 A goo! setting o suspension +an gi/e responses to t#e !ri/er so t#at #e know #ow to steer t#e w#eel an! w#en to pe!al t#e gas or %rake& ItPs also /er$ important t#at t#e suspension team un!erstan! w#at t#e !ri/er nee!& King pin" +am%er" +aster" trail" toel" roll %ar stiGness" spring stiGness" !amper stiGness" an! ot#er settings +#ange #ow t#e suspension respons t#e or+e rom roa!& As I sai!" !ri/er +an +ontrol #is +ar %$ a parti+ullar suspension settings t#at gi/e #im a goo! response& How on eart# $ou +an set t# suspension parameter i $ou !onPt un!erstan! t#ose parameters an! t#e eGe+ts2 So" gu$s" !o a lot o rea!ingb
DESI( R EU.IREE(T
A(D 'BECTIVES
' +or+es" t#is is amiiar or t#ose w#o #as take ?eran+angan +lass& It is a set o Nuali+ation o our !esign
Can operate in 0 #our wi# %atteries Can !o a lot o program simultaneousl$ Lig#t an! #an!$ Has Anti s+rat+# LCD Et+
I TERATIVE
?R'CESS
Designing is an iterati/e pro+ess& Basi+all$" itPs imposi%le to a+#i/e all reNirements in a one s#ot !esign& Espe+iall$" w#en !esigning a +omple pro!u+t su+# as a ormula +ar& W#et#er $ou are a genius or 1ust an +oin+i!ent& Analiing t#e /e#i+#le !$nami+s reNuires t#e !imensions o $our suspension !esign" lengt# og pus# ro!" arms" et+& '#trewise" %eore !raw t#e ,D soli! $ou nee! t#e !imension !ata t#at gi/es %est /e#i+le !$nami+s perorman+e& So" w#i+# one we !o rst2 Dreamingb
VERTICAL D C(AICS =R IDE *H A(DLI( > ? ITCH*B '.(CE@ )& Colle+ting Ve#i+le Spesi+ation Centre o ra/it$" W#eel%ase" ass" Ra!ius o g$ration" Weig#t !istri%ution 6& Determining Uualit$ o Ri!e * Han!ling Desire! natural reNun+$" !amping ratio" ,& Cal+ulating ?it+#*Boun+e reNun+$ 'lle$ +riterion" ront
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