3-engine dynamic properties.ppt

8/20/2019 3-Engine dynamic properties.ppt

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Reciprocating engine dynamic properties

Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science

1. Combustion engines main principles and definitions

2. Reciprocating combustion engines architecture

3. Reciprocating engines dynamic properties

4. Engine components and systems

5. The engine management system for gasoline and Diesel engines

. The emission Re!uirements " Technology

#. Engine $ehicle integration

#.1 Engine layout and mounting

#.2 Engine%$ehicle cooling system

#.3 &nta'e system

#.4 E(haust system


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Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science 2

1. Engine operation forces

2. Engine E(citation )echanisms *+ingle Cylinder Engine,

3. -ey issue on masses balancing

In line 4 cylinder engine balance

Flat 4 cylinder engine balance



V60 6 cylinder engine balance

V!0- "0cran# o$$set 6 cylinder engine balance

V!0 % cylinder engine balance

V!0 - $lat cran#sha$t % cylinder engine balance

Reciprocating engines dynamic properties

ohn /ey0ood &nternal Combustion Engine undamentals )cra0%/ill Charles . Taylor The internal Combustion Engine in Theory and ractice The ).&.T. ress 6utomoti$e /andboo' 7 R. 8osch+6E 6d$anced engine technology */ein9 /eisler, 7 8utter0orth/einemann

:ight and /ea$y ;ehicle Technology *)..


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The purpose of the piston-connecting rod-crankshaft assembly in the reciprocating piston-

engines is to transform the gas forces generated during combustion within the working cylinder into

a piston stroke, which the crankshafts converts into useful torque available at the flywheel. Thecyclic operation leads to unequal gas forces, and the acceleration and deceleration of the

reciprocating power-transfer components generate inertia forces.

The mass inertia properties of the piston-connecting rod-crankshaft assembly are a composite of

the rotating mass of the crankshaft about their axis and the reciprocating masses in the cylinder

direction.

The inertial properties of a single cylinder engine are determined by the piston mass

e(clusi$ely oscillating mass the cran'shaft mass e(clusi$ely rotating mass and the

corresponding connecting%rod mass components usually assumed to amount to 1/ for rotating

and to !/ for oscillating mass.

The inertia force components are identified as inertial forces of the 1st 2 nd 4th order ,

depending upon their rotational frequencies, relative to engine speed" in general only the 1 st and !nd-

order components are significant.

#n the case of multi-cylinder engines, free moments of inertia are present when all the complete

crankshaft assembly$s inertial forces combine to generate a force couple at the crankshaft.

Engine operation forces


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Il Motore come sorgente di vibrazioni e rumore Fig. 1.1

Eccitanti alterne di inerzia in un motore alternativo monocilindro

Eccitanti alterne di inerzia in un motore alternativo monocilindro

IIIa FFaccmForce

dtd

racc

+==

=

+=

*

/

)]2cos(cos**2

θ

θ

Massa

alterna ma

The alternate motion of the con rod % cran' system

&nertia or mass forces


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Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science !

The gas forces are generated by the fuel combustion acting on the piston to betransferred to the crankshaft by connecting- rod through the expansion stroke"

therefore during the complete cycle they depend on the crankshaft position.

%hen multiplied by the crank radius, the gas forces produce a periodically

$ariable tor!ue $alue.

Il Motore come sorgente di vibrazionie rumore Fig. 1.3

L’effetto delle combustioni in un motore alternativo monocilindrico

L’effetto delle combustioni in un motore alternativo monocilindrico

F gas = P * A

F tot = F gas + F rec

F n = F tot * sin

T e = F n * x

Coppia

media

erogata

Gas pressure

Inertial effect

Resulting

pressure

The diagram shows the curve of the engine

torque as a function of crankshaft position" this

is one of the most important characteristics in

assessing the dynamic engine beha$ior .

Considerations on gas forces


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Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science "

Considerations on gas forces

#n multiple cylinder engines, the torque curve of the individual cylinders are

superimposed with a phase shift dependent on the numbers of cylinders theirconfiguration cran'shaft design and firing se!uence. The resulting composite

curve is characteristics of the engine design and covers a full working cycle.

&armonic analysis can lead to a 'torsional harmonics( by a series of sinusoidal

oscillations featuring whole-number multiples of the basic frequencies.

The cyclic tor!ue fluctuation leads to a variations of the

crankshaft$s rotation speed, called cyclic $ariation and

defined as"

Energy storage de$ices, as the fly0heel and the clutch

spring , must be design to adequately compensate for the

variations of rotation speed in normal applications.

min

minma#

ω

ω ω δ

−=


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)oncetti generali

Progettazione meccanica motori * +lessandro iccone !/!

$

Engine Orders

&ngine orders are si'(ly the a'(litudes o$ the $re)uency co'(onents *hich are the 'ulti(les

o$ the rotating $re)uency+ &ngine orders, *hich are deter'ined by an order analysis are

etensively used in the vibration and noise *or# to identi$y the source o$ ecitation .order/ and,

hence, its $re)uency o$ an engine induced (roble'+ For ea'(le, a $our cylinder in-line engine

*ill al*ays has its second order co'(onent as the do'inant ecitation+

2E

In $our-cylinder $our-stro#e engines this notation is o$ten used to denote an engine order

*here the $re)uency is t*o ti'es the engine rotational s(eed+

3E

asic $iring $re)uency o$ a si-cylinder $our-stro#e engine+

4E

*o ti'es engine $iring $re)uency o$ a $our-cylinder $our-stro#e engine+ It is the basic

$iring $re)uency o$ an eight-cylinder $our-stro#e engine+

Engine order meaning


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Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science %

Engine E(citation )echanisms *+ingle Cylinder Engine, 15

&nertia orce - he dis(lace'ent o$ the (iston *ith res(ect to cran# angle can be derived $ro' si'(le

trigono'etry+ his can then be di$$erentiated to yield velocity and acceleration o$ the (iston+ he e(ressions

obtained tend to be very co'(licated and can be si'(li$ied into the e(ression containing only $irst order

.once (er revolution/, second order .t*ice (er revolution/, and a negligible $ourth order .

*hereF

i Inertia $orce 3

R&7

Reciprocating mass .(iston 'ass (lus a((roi'ately 28" conrod 'ass/

9 7ran# angle .:ero at to( dead centre/R Cran'shaft radius 3' ; Conrod length 3'

Rotational s(eed 3r('

ote< i$ R8;=0+" it is accurate enough to use >ust the

$irst t*o ter's+

Inertia $orce is obtained by 'ulti(lying the (iston acceleration by the reci(rocating 'ass and acts only

in the line of the cylinders+


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Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science

as orcing

he rate o$ rise and (ea# cylinder (ressure o$ the diesel .1"?a at a((roi'ately 20 a$ter D7/ are

a((roi'ately t*ice that o$ the gasoline *ith the angle the (ea# occurs at ty(ically 5 earlier+Diesel and gasoline co'bustion is rando' even at $ull load, *orse at (art load and (articularly (oor at

idle+ here$ore, it is nor'al to tal# about the average (ea# cylinder (ressure .? 'a 'ean

/ and standard

deviation o$ ? 'a

+ his variability both cycle to cycle and cylinder to cylinder is one source o$ hal$ order

ecitation+

Il Motore come sorgente di vibrazionie rumore Fig. 1.3

L’effetto delle combustioni in un motore alternativo monocilindricoL’effetto delle combustioni in un motore alternativo monocilindrico

F gas = P * A

F tot = F gas + F rec

F n = F tot * sin

T e = F n * x

Coppia

media

erogata

Gas pressure

Inertial effect

Resulting

pressure

E!uilibrium of orces

The gas force that acts on the piston also acts on

the cylinder head + he $orce on the (iston s(lits intot*o co'(onents, one acting do*n the rod and one

acting side*ays on the cylinder *all+ he $orces are

reacted at the 'ain bearing but a couple e(ists

bet0een the hori9ontal reaction at the bearing

and the piston side force. his cou(le is e)ual to

the cran#sha$t out(ut tor)ue, so the cran'shaft

tor!ue is reacted by forces on the engine

structure.he gas $orce co'(onents o$ the vertical $orce at the

bearing is e)ual and o((osite to the $orce acting on

the cylinder head, but o$ course the inertia

co'(onent is unbalanced+



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Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science 1&

or)ue resulting $ro' (iston 'otion alone $or a single cylinder engine+

Torsional E(citation of Cran'shaft and Engine +tructure - he total tor)ue acting on the cran#sha$t o$

the single cylinder engine results $ro' the e$$ect o$ the gas and inertia $orces on the cran# slider

'echanis'+he tor!ue resulting from piston motion is o$ten called the I&RI@ tor)ue and is

re(resented by the e)uation<

*here

t i Inertia tor)ue 3'



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or)ue resulting $ro' gas (ressure alone $or a single cylinder engine.

he tor!ue resulting from gas pressure alone is re(resented by the e)uation<

*here

t g Aas tor)ue 3'

? g Aas (ressure 3'-2

@ @rea o$ to( o$ (iston 3'-2



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otal tor)ue $or a single cylinder engine

The total tor!ue is $ound by su''ing these t*o co'(onents+

ote that the tor)ue $ro' gas (ressure do'inates .$or the engine $iring case/+

The sum of the inertia and the gas tor!ues is present at the fly0heel and

has to be reacted by the engine structure



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rimary inertia forces. These arise from the force that must be applied to accelerate the piston over the

first half of its stroke, and similarly from the force developed by the piston as it decelerates over the second

half of its stroke. %hen the piston is around the mid-stroke position it is then moving at the same speed asthe crankpin and no inertia force is being generated. For an engine to be acce(table in (ractice, the

arrange'ent and nu'ber o$ its cylinders 'ust be so contrived that the (ri'ary inertia $orces generated in

any (articular cylinder are directly o((osed by those o$ another cylinder. %here the primary inertia forces

cancel one another out in this manner, as for example in an in-line or a hori0ontally opposed four-cylinder

engine with the outer and inner pair of pistons moving in opposite directions, the engine is said to be in

primary balance.

+econdary inertia forces. These are due to the angular variations that occur between the connecting rodand the cylinder axis as the piston performs each stroke. +s a consequence of this departure from straight-

line motion of the connecting rod, the piston is caused to move more rapidly over the outer half of its stroke

than it does over the inner half. That is, the piston tra$el at the t0o ends of the stro'e differs for the

same angular mo$ements of the cran'sha$t+ The resulting inequality of piston accelerations and

decelerations produces corresponding differences in the inertia forces generated. %here these differing

inertia forces can be both matched and opposed in direction between one cylinder and another, as for

example in a hori0ontally opposed four-cylinder engine with corresponding pistons in each bank moving

over identical parts of their stroke the engine is said to be in secondary balance. #t is not always

practicable for the cylinders to be arranged so that secondary balance can be obtained, but fortunately the

vibration effects resulting from this type of imbalance are much less severe than those associated with

primary imbalance and can usually be minimi0ed by the flexible mounting system of the engine. This is

confirmed by the long-established and popular in-line four-cylinder engine, which possesses primary

balance but lacks secondary balance. &owever, the continuing search for greater refinement of running with

this type of engine led, in the mid 12s, to a revival of interest in the use of twin counterbalancing shafts

for cancelling out these secondary inertia forces. 3http"//www.epi-eng.com/piston4engine4technology/piston4motion4basics.htm5

+implified understanding of rimary and +econdary inertia forces


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6ome measures are employed to get partial or complete compensation of the forces

and moments of inertia generated from the crankshaft assembly.

6ll masses are e(ternally balanced 0hen no free inertial forces or moments are

transmitted to the outside through the cylinder bloc'. &owever, the remaining internal

forces and moments apply various loads and deformative-vibratory stresses to the engine

mounts and block.

The simplest way to balance rotating mass is to use counterweights to generate anequal force to oppose the centrifugal one.

The 1-st order inertial forces are propagated at crankshaft speed, while the periodicity

of the !nd-order forces is twice the crankshaft7s rotational rate. These forces are

compensated by a counter0eight balance system designed for opposed rotation at

a rate e!ual to or t0ice that of the cran'shaft. The balance forces$ magnitudes must

equal those of the rotating inertial force vectors acting in the opposite direction.

#n multiple cylinder engine, the mutual counteractions of the various components in the

crankshaft assembly are one of the key factor determining the crankshaft configuration

and consequently the engine design. The inertial forces are balanced if the common

center of gra$ity for all mo$ing components lies at the cran'shaft midpoints" i+e+ if

the cran'shaft is symmetrical .

-ey issue on masses balancing


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Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science 1!

iring se!uence

engine design con$iguration uni$or'ity o$ ignition intervals ease o$ cran#sha$t 'anu$acture 'ini'i:ation o$ cran#case load (atterns

The firing sequence is the sequence in which combustion is initiated in thecylinders.

The arrangement of the crankthrows is determined by the requirements for

even firing intervals of the cylinders and for spacing the successive power

impulses as far apart as possible along the crankshaft, so as to reduce torsional

deflections or twisting effects. 8or any four-stroke engine the firing intervalsmust, if they are to be even, be equal to 2!9 divided by the number of

cylinders.

The firing sequences determines the position of the crankthrows and is

defined considering"

R i i i d i i


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Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science 1"

2r r

mr

F

cos2r am1F ⋅

2cos2r am2F ⋅

1%st and 2%nd order free forces and

moments for the most common

engine configurations

R i ti i d i ti


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Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science 1$

2r r

mr

F

cos2r am1F ⋅

2cos2r am2F ⋅

1%st and 2%nd order free forces and

moments for the most common

engine configurations

R i ti i d i ti


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Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science 1%

500 1000

2Cil

3Cil

4Cil

Cil

!Cil

1500 2000 2500 3000 3500 4000

5Cil

=ptimum cylinder number $s engine displacement

R i ti i d i ti


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Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science 1'

&n line 4 cylinder engine

The "nline#four engine or $traig%t#four engine is an internal combustion engine with all four cylinders

mounted in a straight line, or plane along the crankcase.

For in-line $our-cylinder engines the $irst and $ourth cran#thro*s are there$ore indeed on one side o$ thecran#sha$t and the second and third thro*s on the other side . The firing order of these engines, numbering

from the front, may then be either 1---! or 1-!-- at 1:9 intervals.

The inline-four is not a fully balanced configuration. +n even-firing inline-four engine is in primary balance

because the pistons are moving in pairs, and one pair of pistons is always moving up at the same time as

the other pair is moving down. Bo*ever, (iston acceleration and deceleration are greater in the to( hal$ o$

the cran#sha$t rotation than in the botto' hal$, because the connecting rods are not in$initely long, resulting

in a non sinusoidal 'otion+ +s a result, two pistons are always accelerating faster in one direction, while the

other two are accelerating more slowly in the other direction, which leads to a secondary dynamic

imbalance that causes an up-and-down vibration at t0ice cran'shaft speed . This imbalance is tolerable in

a small, low-displacement, low-power configuration, where alternate weight and stroke are moderate, but the

vibrations get worse with increasing si0e and power. +bove !. ;, most modern inline-four engines now use

balance shafts to eliminate the second-order harmonic vibrations. #n a system invented by


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Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science 2&

lat 4 cylinder engine *bo(er,

+ flat#4 or %orizontallo''osed#4 is a flat engine with four cylinders arranged hori0ontally in

two banks of two cylinders on each side of a central crankcase. The pistons are usually

mounted on the crankshaft such that o((osing (istons 'ove bac# and $orth in o((osite

directions at the sa'e ti'e, somewhat like a boxing competitor punching their gloves togetherbefore a fight, which has led to it being referred to as a bo(er engine.

Bo*ever, the $lat-4 does have a less serious secondary i'balance that causes it to rotate

bac# and $orth around a vertical ais t*ice (er cran#sha$t revolution .2 nd order $ree 'o'ent/+

his is because the cylinders cannot be directly o((osed, but 'ust be o$$set so'e*hat so the

(iston connecting rods can be on se(arate cran# (ins, *hich results in the $orces being

slightly o$$-centre+ he vibration is usually not serious enough to re)uire balance sha$ts+

The configuration is characteri0ed by a low centre of gravity, and a very short engine length,

however the two overheads imply a higher production cost and a higher complexity of the

intake and exhaust system layout> generally the ground clearance of the bottom side can be a

problem.



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+>86R>


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The straig%t#five engine or inline#five engine is an internal combustion engine with five

cylinders aligned in one row or plane, sharing a single engine block and crankcase.

+ five-cylinder engine gets a power stroke every 1 degrees 32!9 ? @ 195. 6ince

each power stroke lasts 1: degrees, this means that a power stroke is always in effect.

Aecause of uneven levels of torque during the expansion strokes divided among the five

cylinders, there is increased secondary-order vibrations. +t higher engine speeds, there isan uneven third-order vibration from the crankshaft which occurs every 1 degrees.

Aecause the power strokes have some overlap, a five-cylinder engine may run more

smoothly than a non-overlapping four-cylinder engine, but only at limited mid-range speeds

where second and third-order vibrations are lower.

In conclusion the 'ain disadvantage is that a straight-$ive design has $ree 'o'ents

.vibrations/ o$ the $irst and second order on the cylinder (lane< the $irst one 'ay be

balanced by a balance sha$t, rotating in o((osite directions at the cran#sha$tCs s(eed, and

by (ro(er *eight .rotational co'(onent/ on the cran#sha$t itsel$+

8iring order can be 1-!--- or 1----!" with the last one the !9 order free moment is

lower while higher the first one.

&nline 5%cylinder engine



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&nline cylinder engine

The straight%si( engine or inline%si( engine is a six cylinder internal combustion engine with all six

cylinders mounted in a straight line along the crankcase. The single bank of cylinders may be oriented

in either a vertical or an inclined plane with all the pistons driving a common crankshaft.

he cran#thro*s are s(aced in (airs *ith an angle o$ 120 bet*een the' " hence, the first and sixth

crankthrows are paired, as are the second and fifth, and likewise the third and fourth. The firing order

may then be such that no two adBacent cylinders fire in succession> that is, either 1---C-!- or 1--!-

C-- at, of course, 1!9 intervals.

+n inline si( engine is in perfect primary and secondary mechanical balance . The engine is inprimary balance because the $ront and rear trio o$ cylinders are 'irror i'ages , and the (istons 'ove in

(airs> that is, piston D1 balances DC, D! balances D, and D balances D, largely eliminating the polar

rocking motion that would otherwise result. 6econdary imbalance is avoided because an inline six

cylinder crankshaft has six crank throws arranged in three planes offset at 1!9. The result is that

differences in piston speed at any given point in rotation are effectively canceled.

Cran'shafts on si( cylinder engines generally ha$e either four or se$en main bearings" larger

engines and diesels tend to use the latter because of high loadings and to avoid crankshaft flex.

=any of the more sporty high%performance engines use the four bearing design because of

better torsional stiffness 3e.g., A=% small straight C7s, 8ord7s Eephyr C5. The accumulated length of

main bearing Bournals gives a relatively torsionally flexible crankshaft. The four main bearing design

has only six crank throws and four main Bournals, so is much stiffer in the torsional domain. +t high

engine speeds, the lack of torsional stiffness can make the seven main bearing design susceptible to

torsional flex and potential breakage.



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+ ) engine is a F engine with six cylinders mounted on the crankcase in two banks of three cylinders,

usually set at either a right angle or an acute angle to each other, with all six pistons driving a common

crankshaft.Due to the odd nu'ber o$ cylinders in each ban#, V6 designs are inherently unbalanced, regardless o$

their V-angle+ @ll straight engines *ith an odd nu'ber o$ cylinders su$$er $ro' (ri'ary dyna'ic

i'balance, *hich causes an end-to-end roc#ing 'otion+ Gach cylinder bank in a FC has an odd number

of pistons, so the FC also suffers from the same problem unless steps are taken to mitigate it. #n the

hori0ontally-opposed flat-C layout, the rocking motions of the two straight cylinder banks offset each

other, while in the inline-C layout, the two ends of engine are mirror images of each other and

compensate every rocking motion. 7oncentrating on the $irst order roc#ing 'otion, the V6 can be

assu'ed to consist o$ t*o se(arate straight-" *here counter*eights on the cran#sha$t and a counter

rotating balancer sha$t co'(ensate the $irst order roc#ing 'otion+ +t mating, the angle between the

banks and the angle between the crankshafts can be varied so that the balancer shafts cancel each

other 9 FC 3larger counter weights5 and the even firing C9 ; 0ith ?@ flying arms 3smaller counter

weights5. The second order rocking motion can be balanced by a single co-rotating balancer shaft.

The most efficient cylinder ban' angle for a ; is ? degrees minimi9ing si9e and $ibration.

%hile C9 FC engines are not as well balanced as inline-C and flat-C engines, modern techniques for

designing and mounting engines have largely disguised their vibrations. Hnlike most other angles, Cdegree FC engines can be made acceptably smooth without the need for balance shafts. %hen ;ancia

pioneered the C9 FC in 1, a C-throw crankshaft was used to give equal firing intervals of 1!9.

&owever, more modern designs often use a -throw crankshaft with what are termed $lying ar's

between the crankpins, which not only give the required 1!9 separation but also can be used for

balancing purposes. )ombined with a pair of heavy counterweights on the crankshaft ends, these can

eliminate all but a modest secondary imbalance which can easily be damped out by the engine mounts.

Two firing order are possible" 1---C-!- or 1-!--C--.

;?@ % cylinder engine



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Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science 2!

he uic# V6 *as notable because it introduced the conce(t o$ uneven $iring, as a result o$ using the

!0 V% cylinder angle *ithout ad>usting the cran#sha$t design $or the V6 con$iguration+ Rather than

$iring every 120 o$ cran#sha$t rotation, the cylinders *ould $ire alternately at !0 and 150, resulting in

strong har'onic vibrations at certain engine s(eeds+ hese engines *ere o$ten re$erred to by

'echanics as sha#ers, due to the tendency o$ the engine to bounce around at idle s(eed+ o

overco'e the (roble' o$ uneven $iring intervals *ith a !0 V6 engine, uic# in @'erica retained three-

thro* cran#sha$t but ingeniously re(laced the co''on, double-length, cran#(ins by ad>acent single

cran#(ins that *ere staggered by "0 in o((osite directions to (roduce a so-called Es(lit-(in cran#sha$t+

)ore modern A?@ ; engine designs a$oid these $ibration problems by using

cran'shafts 0ith offset split cran'pins and often by adding balancing shafts to

balance the 1st order free moment. Gxamples include the later versions of the Auick FC,

and earlier versions of the =ercedes-Aen0 FC and +H


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Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science 2"

6>D& 7 ;A?@ as engine

3?@+plit cran' pin

;A?@ 3?@ offset % cylinder engine 8alancing shaft to balancethe 1st order free moment



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Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science 2$

There are two classic types of F:s which differ by crankshaft"

The cross%plane or t0o%plane cran'shaft 3crank pins at a 9 angle5 is the configuration used in most F: road cars. The

first and last of the four crank pins are at 1:9 with respect to each other as are the second and third, with each pair at 9 to

the other, so that viewed from the end the crankshaft forms a cross. he last cylinder is not in the sa'e (osition as the $irst, so

there is end-to-end vibration again, *hich can be solved by adding counter*eights to the cran#sha$t *hich balance the $orced

created by the (istons This ma'es the cross%plane ;B a slo0%re$$ing engine that cannot speed up or slo0 do0n $ery

!uic'ly compared to other designs because of the greater rotating mass + %hile the firing of the cross-plane F: is

regular overall, the firing of each bank is ;I;;I;II. #n stock cars with dual exhausts, this results in the typical F: burble

sound that many people have come to associate with +merican F:s, #n all-out racing cars it leads to the need to connectexhaust pipes between the two banks to design an optimal exhaust system, resulting in an exhaust system that resembles a

bundle o$ sna#es as in the 8ord JT. This complex and encumbering exhaust system has been a maBor problem for single-

seater racing car designers, so they tend to use flat-plane crankshafts instead.

The flat%plane or single%plane cran'shaft 3crank pins at 1:95 % #n its simplest form, it is basically two straight- engines

sharing a common crankshaft. %hen the engine runs, the pistons shoot up and down, the first and last pistons of the bank

occupying matching positions on either end of the array, so that the force on both ends is equal and the system is balanced.

&owever, this simple configuration, with a single-plane crankshaft, has the same secondary dynamic imbalance problems

as t0o straight%4s, resulting in vibrations in large engine displacements. The induced vibrations can be eliminated by the useof balance shafts, with a counter rotating pair flanking the crankshaft to counter second order vibration transverse to the

crankshaft centerline. 6s it does not re!uire counter0eights for the primary balance the cran'shaft has less mass and

thus inertia allo0ing higher rpm and !uic'er acceleration. The design was populari0ed in modern racing with the

)oventry )limax 1. ; 3K! cu in5 F: that evolved from a cross-plane to a flat-plane configuration. 8lat-plane F:s on road cars

come from 8errari, 3every F: model they ever made, from the 12 "0% A4, to today7s F4"0 and 7ali$ornia5, ;otus 3the

Gsprit F: 5, and TFI 3the 6peed Gight5. This design is popular in racing engines, the most famous example being the

)osworth


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Scuola di Dottorato di Ricerca 2010 - Road vehicle and engine engineering science 2%

A=%* F:/9 =otorsport

;A?@ % B cylinder engine



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!

! cil )*0+# Cross#'lane cran,s%aft

;A?@ % B cylinder engine

3-engine dynamic properties.ppt

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