Brake Pedal Force Determination

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The c o n t e n t s o f t h i s r e p o r t r e f l e c t t h e v iew s

o f t h e Highw ay S a f e t y R es e ar ch I n s t i t u t e w h ic h

s

r e s p o n s i b l e f o r t h e f a c t s and t h e a c cu ra c y

o f t h e d a t a p r e s e n t e d h e r e i n The c o n t e n t s d o

n o t n e c e s s a r i l y r e f l e c t t h e o f f i c i a l v ie w s o r

p o l i c y o f t h e D e p ar tm e nt of T r a n s p o r t a t i o n .

T h is r e p o r t d oe s n o t c o n s t i t u t e a s t a n d a rd

s p e c i f i c a t i o n o r r e g u l a t i o n


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s y s t e m d ~ e s i g n a r i a bl e s

3

Recipient s Catalog No.

i

. Report No.

I

un i ve r s i t y o f - Michigan

Ann Ar bo r, Mic hig an 48105

2. Government Accession No.

7

Author(s)

R.G.

Mortimer,

L.

S e g e l ,

H

Dugoff,

J . D .

Campbell, C.M. Jo rgeson ,

R W

Murphy

9. Performing Organization Name and Address

Highway Safe ty Research I n s t i t u t e

11. Contract or Grant No .

FH-11-6952

8.

Perform~ng Organization Report No.

HuF- 6a

10.

Work

Unit No.

N z t i o n a l ~ i ~ h w a ~afety Bureau

Washington, D .C . 20591

12 . Sponsoring Agency Name and Address

Federal Hiahwav Administrat ion

.

14.

Sponsoring Age.ncy Code

13. Type of Report and Period Covered

Summary Final Report

I

Ju ly 1 , 1968-Apr i l 10 , 1970

i

I

1 5

Supplementary Notes

--

16

Abstract The o b j e c t i v e o f t h i s s t u d y was t o d e f i n e t h o s e b ra ke c h a r a c t e r i s t i c s ,

wi t h in th e space bounded by t he r e l a t i on sh ip between b rake peda l fo rce and

v e h i c l e d e c e l e r a t i o n , wh ic h l e a d t o a c c e p t a b l e d r i v e r - v e h i c l e p er fo rm an ce . A

d r i v e r - v e h i c l e b r a k i n g t e s t was pe rf or me d i n w hi ch t h e d e c e l e r a t i o n / p e d a l f o r c e

i

r a t i o , t h e pe d al d i sp la c em en t , t h e s u r f a c e - t i r e f r i c t i o n , and d r i v e r c h a r a c t er i s - l

t i c s a g e , w ei g ht ) were s y s t e m a t i c a l l y v a r i e d i n o r d e r t o d e te rm in e t h e i n f l u e n c e ,

of

the se v a r i a b l es upon minimum s topp i ng d i s t a nc e and o the r pe rformance va r i ab le s :

The t e s t s t h a t

were

performed on a low coe f f i c i e n t o f f r i c t i o n su r f a ce showed

t h a t h i g h v a l u e s o f d e c e l e r a t i o n / p e d a l f o r c e g a i n r e s u l t i n l a r g e number of w he el 1

lockups and lower mean de ce le r a t io n i n b r ing ing th e veh ic l e t o a s to p , compared

I

t o i n t e r m e d i a t e o r low d e c e l e r a t i o n / p e d a l f o r c e g a i n l e v e l s . Te s t s c on du c te d on ;

i n t e r m e d i a t e a nd h i g h c o e f f i c i e n t of f r i c t i o n su r f a c e s showed t h a t h i g h an d

i n t e r m e d i a t e d e c e l e r a t i o n / p e d a l f o r c e g a i n s pr od uc ed g r e a t e r mean d e c e l e r a t i o n s

and gr ea te r f requ enc ies of wheel lockups than lower ga in systems. The f requency

of l o s s of l a t e r a l c o n t r o l was s i g n i f i c a n t l y g r e a t e r w i th t h e h ig h d e c el e r a t io n /

peda l fo rce ga in b rakes on a l l su r f ac es than wi th lower ga ins . There were minor

~ e n e f i t s f 2 . 5 i n c h p e d a l d i sp l a ce m en t compared t o ze r o i n ch e s . P o t e n t i a l

b r a k e f a i l u r e s a nd t h e i r e f f e c t s upon p e d a l f o r c e r e q u ir e m e n t s w er e a na l yz e d .

The i m p l i c a t i o n s o f t h e f i n d i n g s f o r a v e h i c l e b r a k i n g s t a n d a r d w er e shown i n

terms

o f d e c e l e r a t i o n / p e d a l f o r c e q a i n a nd p e d a l f o r c e .

1 7

Key Words

BRAKING DECELERATION, STOPPING DISTANCE,

DRIVER BRAKING

PEDAL FORCE, PAVEMENT

FRICTION, BRAKE FAILURE.

19. Sectulty Classif.tof this report)

20. Security Classif.(of this

page)

18.

Distribution Statement

A v a i l a b i l i t y i s unlimited. Document

may be r e l ea sed t o th e Clea r inghouse

f o r F e d er a l S c i e n t i f i c and T e c hn i ca l

Inform at ion , Sp r i ng f i e l d , Va. 22151

f o r s a l e t o t h e p u bl ic

21. No. of Pages

u n c l a s s i f i e d

22. Pr~ce

u n c l a s s i f i e d

22 i-v


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TABLE

CONTENTS

L i s t o f T a b l e s a n d F i g u r e s

b j e c t i v e s

Summa ry o f Ta sks

i t e r a t u r e ~ e v i e w

o o t F o r c e C a p a b i l i t y o f D r i v e r s

D r i v e r B r a k i n g P e r fo r m a n c e a s a F u n c t i o n o f

e d a l F o r c e a n d P e d a l .D i s p l a c e m e n t

r i v e r B r a k in g P r a c t i c e

a i l u r e A n a l y s i s

i n d i n g s

a x imum Foo t Forc e

r i v e r V e h i c l e B r a k in g T e s t

D e c e l e r a t i o n M a g ni tu de F re qu e n cy D i s t r i b u t i o n

a i l u r e A n a l y s i s

o n c l u s i o n s


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LIST

O FIGUR S

i g u r e 1 F o o t p e d a l f o r c e m e a su re m en t b u ck .

2

i g u r e 2. B r a k e

t e s t

i n p r o g r e s s .

i g u r e

3

C u m u l a t i v e p e r c e n t p e d a l f o r .c e f o r 276 f e m a l e s .

6

F i g u r e

4 .

C u m u la t i ve p e r c e n t p e d a l f o r c e f o r 3 23 m a l e s . 6

F i g u r e

5

G e o m e tr ic mean d e c e l e r a t i o n a s a f u n c t i o n

of

d e -

e l e r a t i o n / p e d a l f o r c e g a i n s p e e d an d s u r f a c e .

8

F i g u r e 6 . M e a n n u m b e r o f w h e e l l o c k u p s a s

a

f u n c t i o n o f

e c e l e r a t i o n / p e d a l f o r c e g a i n a n d s p e ed . 1 0

F i g u r e 7 . Mean n um ber o f w h e e l l o c k u p s a s a f u n c t i o n o f

d e c e l e r a t i o n / p e d a l f o r c e g a i n a nd s u r f a c e . 10

F i g u r e 8 . M ean w h e e l l o c k u p time a s a f u n c t i o n o f d e c e l e r -

a t i o n / p e d a l f o r c e g a i n a nd s u r f a c e . . 1 2

F i g u r e 9 . P e r c e n t w h ee l lo c k u p t i m e / t o t a l b r a k i n g t i m e

a s a f u n c t i o n o f d e c e l e r a t i o n / p e d a l s u r f a c e . 1 2

F i g u r e 1 0 . Mean c o n t r o l l a b i l i t y r a t i n g f o r 28 s u b j e c t s

a s a f u n c t i o n o f d e c e l e r a t i o n / p e d a l

f o r c e

g a i n a nd p e d a l d i s p l a c e m e n t . 1 4

F i g u r e 11 Mean r a t i n g o f f o r c e r e q u i r e d f o r 28 s u b j e c t s

a s a f u n c t i o n o f d e c e l e r a t i o n / p e d a l f o r c e g a i n

n d d i s p l a c e m e n t . . 1 4

F i g u r e 1 2 . C u t- of f PFG v a l u e s f o r s a t i s f a c t o r y d r i v e r - v e h i c l e

r a k i n g p e r f o rm a n c e . 1 6

F i g u r e 13 . C u m u la t i ve p e r c e n t o f d e c e l e r a t i o n s f o r m an ua l

n d p ow er b r a k e s . 1 7

F i g u r e 1 4 . C u m ul at i ve p e r c e n t o f v e h i c l e s w i t h l ow e r g a i n :

M a n u a l b r a k e s . 1 8

F i g u r e 1 5 . C u m ul at i ve p e r c e n t o f v e h i c l e s w i t h l ow e r g a i n :

P ow er b r a k e s . . 8

F i g u r e 1 6 . C u m u la ti v e p e d a l f o r c e d i s t r i b u t i o n s f o r f r o n t

a x l e b r a k e c i r c u i t f a i l u r e i n a l o a d e d s e d a n

w i t h m a nu al b r a k e s . . 1 9

F i g u r e 1 7 . T he recom mended d e c e l e r a t i o n / p e d a l f o r c e s p a c e . . 2 1

LIST OF TABLES

TABLE 1 RANK ORDER OF DECELERATION/PEDAL FORCE GAINS

DIFFERING SIGNIFICANTLY I N

D R I V E R

VEHICLE

BRAKING DECELERATION 9

TABLE

2 . PERCENT^ O T RIAL S INVOLVING LOSS O F LATERAL

CONTROL

AS A FUNCTION OF

BRAKE

SYSTEM SPEED

AND

SURFACE

11

v


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O B JE C T IV E

The ma jo r o b j e c t i v e o f t h i s s t u d y was t o d e f i n e t h e

e nve l ope e nc l os i ng t h e r e l a t i on sh i p betw ee n ve h i c l e de c e l e r -

a t i o n a nd b r a ke pe da l e f f o r t which g i ve s r i s e t o good d r i v e r -

veh ic le b rak ing pe r formance .

H a v i ng de r i ve d a su i t a b l e

s e t

of

l i m i t i n g c o n d i t i o n s upon t h e d e c el e r a t i o n / pe d a l f o r c e g a i n a s

a fun c t i on o f pe da l d i sp l a c e m e n t i t

was

a l so de s i r e d t o recom-

mend an a p p rop r i a t e s e t of ob j e c t i ve t e s t i ng a nd c ompli ance

procedures .

The e f f e c t of v a r i ous t ype s o f b r a ke f a i l u r e s upon

t h e b r ak e p e da l f o r c e r e q u i r e d t o o b t a i n a g i v en l e v e l o f d e c el -

e r a t i o n was a l s o i n v e s t i g a t e d i n o r d e r t o d e r i v e a methodology

by which dec el er at io n/ pe da l fo rc e r a t i o s may be recommended f o r

a b rake f a i l u r e mode.

SUMMARY OF TASKS

I n o r d e r t o meet t h e o b j e c t i v e s o f t h i s program f i v e m aj or

e x p er i m en t a l and a n a l y t i c a l t a s k s w ere c a r r i e d o u t .

LITER TURE REVIEW

r ev ie w o f t h e l i t e r a t u r e was c a r r i e d o u t p e r t i n e n t t o an

a n a l y s i s

of

t h e d e c e l e r a ti o n / p e d a l f o r c e c h a r a c t e r i s t i c s of an

a ut om ot ive ve h i c l e . The f a c t o r s c ons i de re d i m por t a n t i n t he

review were brake system desi gn brak e usage skid ding brake

t e s t i n g and d r i v e r c h a r a c t e r i s t i c s and b r ak e m od ul at io n.

FOOT FORCE C P BILITY OF

RIVERS

The brake peda l on convent iona l ve h i c l es

i s

a c t u a t e d by t h e

f o o t o r b ot h f e e t o f t h e d r i v e r . Fo r t h i s r ea so n

t

i s impor-

t a n t t o know t h e f o o t f o r c e c a p a b i l i t i e s o f i n d i v i d u a l s c om pr is -

in g th e dr iv in g popu la t io n. procedure was developed by which

l e f t and r i g h t fo o t maximum forc e ex e r t i on could be measured

f o r a sample of female and male dr iv er s .

The pe dal fo rc e measur-

ing buck shown i n Figu re was used i n th es e t e s t s . Male and


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igure

1

oot p edal fo rc e measurement

buck


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fema le su b j ec t s were s e l e c te d a t random f rom ind iv id ua l s i n a

lo ca l shoe s t o r e and a d r iv e r l i cen s in g o f f i ce . Two measure -

ments of maximum fo o t f or ce were taken wi th t h e r i g h t and t he

l e f t f o o t , e ac h. The i n s t r u c t i o n s on t h e f i r s t and second t r i a l s

were v a r i e d suc h t h a t i n t h e s ec on d t r i a l t h e su b j e c t was a ske d

t o ex er t th e ab so lu te maximum e f f o r t . Maximum fo ot f or ce f o r

t h e r i g h t a nd l e f t f o o t , wei gh t and ag e f o r e a c h su b j e c t were

ob ta ined .

DRIVER

BRAKING

PERFORMANCE AS

A

FUNCTION OF PEDAL-FORCE

AND

PEDAL-DISPLACEMENT

An exper ime nta l t e s t veh ic l e was con st r uc te d in which va r ia -

t i o n s i n d e c e l e r a t i o n / p e d a l f o r c e g a i n and p ed a l d isp la c em e n t

could be re ad i l y made. brakin g t e s t was devise d i n which a

d r i v e r was r e q u i r e d , upon a s i g n a l , t o b r i n g t h e c a r t o a s t o p

a s r a p i d l y a s p o s s i b l e w i t h i n a l a n e t e n f e e t wide d e l i n e a t e d by

r ub be r t r a f f i c c on es F i gu r e

2

The t e s t was conducted on

t h r e e su r f a c e s : a d r y a sp h a l t , wet a sp h a l t and a we t- pa in te d

s u r f a ce . The r o l l i n g t i r e f r i c t i o n c o e f f i c i e n t s of t h es e s u r -

f a c e s w er e, r e s p e c t i v e l y :

86

.71 and

.40.

Stops were made

from

35

mph and 5 mph. The 2 8 t e s t su b je c t s were randomly

se l e c t e d on t h e b a s i s of t h r e e we ig ht c a t e g o r i e s and f i v e a ge

groupings, wi th an upper

l m t

of 6 0 y e a r s .

Measurements t aken f rom th e s t a r t o f b rak ing con s i s t ed o f

the braking d is ta nc e , brakin g t ime, number of wheels locked,

du ra t io n of wheels locked, number of l os s of c on t r o l runs , pedal

force and speed,

DRIVER

BRAKING PRACTICE

The d e c e l e r a t i o n l e v e l s t h a t d r i v e r s u se d i n no rmal d r i v i n g

co nd it io ns were measured by means of an ins tru men ted veh ic le .

The vehicle was driven by personnel engaged

on

Un i v e r s i t y b u s i -

ness . Measurements were made of th e dec e le ra t ion le ve ls t h a t

were used by d r i ve rs and t he maximum de ce ler a t ion i n each ap pl i -


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i gu r e 2

Brake

t s t in progress


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c at io n of th e bra kes was rec orde d, By t h i s means a frequenc y

d i s t r i bu t io n of th e peak dec e le ra t io ns employed i n everyday

dr iv in g , on c i t y , r u r a l roads and expressways , were ob ta ined ,

Such d a t a we re r eq u i r ed i n o rd e r t o p ro v id e i n form a t io n o f

demands imposed upon th e s er v i ce brake and t he p ro ba bi l i ty wi t h

which a given l ev e l of d ece le r a t i on

s

des i re d by d r iv er s . The

l a t t e r d a t a were r e qu ir e d f o r a p p l i ca t i on i n t h e f a i l u r e a n a l y s i s

p hase of t h e p ro j ec t .

FAILURE ANALYSIS

An an a ly s i s was con du ct ed t o d et e rm ine t h e e f f ec t of v a r i -

o us f a i l u r e s i n t h e b rakin g s ys tem, s uch a s f ro n t and r ea r brak e

c i r c u i t f a i l u r e , b o o s t e r f a i l u r e and b ra ke f a d e upon t h e p e da l

f o r c e r e q u ir e d t o d e c e l e r a t e t h e v e h ic l e .

FINDINGS

M X I M U M

FOOT

FORCE

The maximum fo rc e exer ted wi th t he r i g h t fo ot f or

2 7 6

f em ale d r i v e r s i n t h e s t and a rd1 ' m o t iva t i on ( t r i a l -1 ) and t h e

induced mot iva t ion ( t r i a l - 2 ) cond i t i ons a r e shown i n th e form

of a cu m ula ti ve p e rcen t d i s t r i b u t i o n of fo rc e i n F ig u re 3 The

ana lo go us d a t a f o r t h e

3 3

male su bj ec ts a r e shown i n Figure 4

The 5 th pe rc en t i l e fo r ce f o r females was

7 0

and 100 l b s i n th e

two t r i a l s , and f o r m ale s

1 4 0

and 185 lbs.

These da t a could be considered t o be over-es t imates of

f o r c e l e v e l s t h a t may be a t t a i n e d i n

a

v eh ic l e s ea t , wh ich h as

cons iderab le compl iance , because a hard s e a t was used i n th e

t e s t f i x t u r e , On th e o th e r hand t h e s t r e s s of an emergency s i t u -

a t i o n has been a rgu ed t o enab l e d r i v e r s

t o e x e r t h i gh p ed al

fo rc es . An in t er me dia te l e v e l between th e s tan dard motiva-

t i o n and i nd uced m o t iv a t i o n p ed al fo rce l e v e l s fo r t h e 5 th p e r-

c e n t i l e female would app ear t o be a r easo nabl e maximum for ce

l e v e l t h a t d r i v e r s s h o uld be exp ect ed t o

e x e r t t o d e r i v e a h ig h


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PED L FORCE lbs)

Figure 3 Cumulative percent pedal force

for

2 7 6 females

PED L

FORCE

1b.S)

Figure 4 Cumulative percent pedal force

f o r

3 2 3 females


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l e v e l o f d e c e l e r a t i o n from t h e v e h i c l e . f o r c e o f 85 l b s i s

th e r e f or e sugges ted by th es e d a t a a s t he maximum brake peda l

e f f o r t f o r a v e h i cl e d e ce l er a t io n i n t h e o r d e r of 0 . 7 5 g.

DRIVER VEHICLE BRAKING TEST

The m aj or i n t e r e s t i n t h e b r a k in g t e s t was t o d e te r mi n e

t h e e f f e c t o f t h e r e l a t i o n s h i p between d e c e l e r a t i o n and p ed a l

f o r c e a nd p ed a l di s pl ac e me n t upon t h e a b i l i t y o f d r i v e r s t o

minimize s t o p p i n g d i s t a n c e s , w h i le r e t a i n i n g c o n t r o l o f t h e

v e h i c l e .

The s t opp i ng d i s t a n c e s a c h i e ve d i n e a ch run du r i ng t h e t e s t

we re c onve rt e d t o t he a ve ra ge de c e l e r a t i o n .

An a n a l y s i s of

va r i a nc e c a r r i e d o u t upon t h e a ve ra ge de c e l e r a t i on da t a showed

t h a t t h e r e were no s i g n i f i c a n t e f f e c t s due t o t h e p e da l d i sp l a ce -

ment va r i ab le .

Thus, performance was s im i l ar f o r a pedal having

a maximum displacement of 2 . 5 i n c he s , a t ab ou t 1000 p s i i n t h e

bra ke l i n e , and one which had zer o in ch es disp lace ment . Mean

d e c e l e r a t i o n s were s l i g h t l y f a v o r a b l e t o t h e p ed a l which d i s -

p la ce d d u ri n g b ra ki ng . S t a t i s t i c a l l y s i g n i f i c a n t e f f e c t s were

found due t o th e dec ele ra t ion /pe dal fo rc e gai n . The mean dece l -

e r a t i o n s on ea ch o f t h e t h r e e s u r f a c e s , a t t h e two i n i t i a l sp e ed s ,

f o r t h e de c e l e r a t i on / pe da l f o r c e ga i n l e ve l s a r e shown i n F i gu re

5 . The h i g he s t ga i n de f i ne d a s h i gh de c e l e r a t i on / pe d a l f o r c e

i n g / l b , o r a s p e da l f o r c e / d e c e l e r a t i o n i n l b s / g ) c o n fi g u r a-

t i on d i d no t p rov ide optimum per formance i n any of th e sur fac e

x speed combinatio ns. On t h e dr y and wet su rf ac es performance

was

a l s o p oo r a t low g a i n s .

On t h e wet-painted s ur fa ce t h e low

and in te rmed ia te ga in co nf i gu ra t ion s prov ided be s t per formance .

Table shows t h e f in di n g s of Newman-Keuls t e s t s conducte d

i n e ac h o f t he s u r f a c e and spe ed c ond i t i ons a c ross t he de c e l -

e r a t i o n / p e d a l f o r c e g a i n l e v e l s .

Values which a r e i n pa ren thes es

i n d i c a t e t hose l e ve l s o f c on t ro l gai n which provi ded sup e r i o r


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5

mph

5

mph

Dry

Wet

--. -. - ------

El -

etopainted

w -

Figure

5.

Geometr ic mean dec el er at io n a s

a

f u n c t i o n

of

d e c e l e r a t i o n / p e d a l f o r c e

ga i n speed and su r fa ce .


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TABLE

1

RANK

ORDER

OF DECELERATION/PEDAL FORCE GAINS

DIFFERING SIGNIFICANTLY I N DRIVER VEHICLE

BRAKING

DECELERATION

Dry Wet Wet-Painted

PFG 3

5 5

35

5

35

5

Rank

Level g / l b ) MPH MPH MPH MPH

MPH MP

Sum

[Those v a l u e s b lo c ke d o f f i n d i c a t e t h e p e d a l f o r c e g a i n s

p r o vi d i ng s i g n i f i c a n t l y g r e a t e s t mean d e c e l e r a t i o n u nd er

e a ch s ur f a c e- s p e ed c o n d i t i o n ] .

p er fo rm an ce t o o t h e r l e v e l s . The numbers w i t h i n t h e t a b l e i n d i -

c a t e t h e

r a n k i n g s o f e a ch o f t h e d e c e l e r a t i o n / p e d a l f o r c e g a i n

l e v e l s i n t er ms of s i g n i f i c a n t d i f f e r e n c e s wi t h o t h e r l e v e l s .

The mean f req uen cy wi th which whe els were l ocked up du r ing

e ac h ru n a s a f u n c t i o n of t h e i n i t i a l s pe ed and t h e p ed a l f o r c e

g a i n

i s

shown i n Fi gur e

6 .

There

i s

a c l e a r r e d u c t i o n i n wh ee l

l oc k up f r e qu e nc y a s t h e g a i n i s decreased . There were s l i g h t l y

l e ss w h ee l l o ck up s w i t h t h e

2 . 5

inch maximum displacement pedal

t h an t h e d i s p l acem en t o n some o f t h e p ed a l f o r c e g a i n l e v e l s .

There was a co ns id er ab le e f f e c t upon mean number of wheel

lockups of

t h e p a v e m e n t

s u r f a c e , w i t h f a r g r e a t e r f re qu en cy of

whee l lockups occ u r r ing on the wet -pa in ted su r f ac e than on

e i t h e r t h e w et a nd t h e d r y which i n c u r r e d s i m i l a r f r e q u e n c i e s

F i g u r e

7


18/32

F i g u r e 6 Mean number o f wh eel loc ku ps a s a

f u n c t i o n o f de c e l e r a t i o n /p e d a l f o r c e

ga in and speed

I

Wet \

P a i n t e d ,

0.065 0.037 0.0 21 0.012

0.007 0.004

1)

2 )

3)

4 )

5 ) 6)

DECELERATION/PEDAL FORCE GAIN g/lb)

F i g u r e

7

Mean number of wheel lockups as a

f u n c t i o n of d e c e l e r a t i o n / p e d a l f o r c e

g a i n an d s u r f a c e

10


19/32

The mean time f o r which wheels were locked up as a fun ct ion

of t he pavement su r fa ce and the peda l fo rc e ga in

i s shown i n

F ig u re

8 .

The mean

time

of wheel lockup

i s

g r e a t e s t on t h e

wet-

p a in t ed s u r face . The re

i s

a co n s i s t e n t r ed u c t i o n i n wheel l ock-

up

t i m e

a s t h e p e d al f o r c e g a i n

i s

reduced. The pr op or ti on of

t h e b r a k i n g

t i m e

du ri ng which one o r more wheels were locked on

e ac h o f t h e t h r e e s u r f a c e s

i s

shown i n Fi gur e 9 i n d i c a t i n g

t h a t f o r as much as 60 percen t o f th e b rak ing

time,

on t h e wet-

pai n te d su rf ac e, one or more wheels were locked.

Loss of co n t ro l t r i a l s (Tab le 2 ) o ccu r red m ost o f t en w i th

t h e h i g h e s t b ra ke pe da l ga i n . T he re a r e s m a ll d i f f e r e n c e s a t t r i -

TABLE

2.

PER ENT^ OF

TRIALS

INVOLVING LOSS O

LATERAL CONTROL AS

A

FUNCTION OF BRAKE

SYSTEM, SPEED

AND

SURFACE

Ped a l

D i s -

Deceler at ion/Pedal Force Gain (g / lb)

p lacement Surface MPH 0.065 0.037 0.021 0 . 0 1 2 0.007 0.004

ry

Wet

Wet-

Pa in t ed

Dry

Wet

Wet-

Pa in t ed

Mean

p e rcen t Los s o f C o n t ro l T r i a l s i n a Tes t C o n di t i on

To ta l (Su cces s ful Los s of C o n t ro l ) T r i a l s i n a

x

1 0 0

Tes t Cond i t ion


20/32

PEFCENT WHEEL LOCKUP TIE E/

TOTAL

BR KING

TIME

t

rn DJ

c a r

Y

D

Q

nJ rD

D

ME N WH L LOCKUP TTVE s e c )

-.

C O

E g

- ?

2:

z

m

g -?

xz

*1

w

?

e:

z

-

0

.

.

t lo-

u

-0

- 4

.

r 0

-0

3

R) w

r

w

1

I I

0

w

z

Y O

Y

ID

Documents

Brake Pedal Force Determination