Bsi bs au 164 1977 (2000) iso 3784 1976

BRITISH STANDARD AUTOMOBILE SERIES BS AU 164 1977 ISO 3784 1976 Specification for Measurement of impact velocity in collision tests on road vehicles UDC 629 113 614 864 531 66 531 112 082 L ic e n s e[.]

BRITISH STANDARD AUTOMOBILE SERIES

164:1977

U C 6 9.1 3:6 4.8 4:5 1.6 :5 1.1 2.0 2

This Bri shStan ard, ha ing

b en pre ared u der the

directonof the Automo ile

Stan ards Commi e ,was

published u der the authoriy

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The folowing BSI references

relate to the work on this

stan ard:

Commi e reference AUE/ -/ 1/6

Draft for comment7 / 73 5 DC

ISBN 0 5 0 0 9 0 3

This BritishStand rd was prep red u der the authority of the Automobie

Stand ards Commit e and is identical with ISO3 8 :19 6 “ R oa d vehicle —

Mea sur ement o impa ct velociy in colision te ts”, prep red b Tech ical

Commit e ISO/ TC2 , Roa v ehicles, of the International Org anization for

Stand ardization

Term inolog y and conventions The text of the International Stand rd has

be n ac epted as suita le for publcation, without dev iation, as a

BritishStand ard Certain terminolog y and conv entions are used, howev er,

that are not strictly a propriate in a BritishStand rd , an at ention is

therefore d rawn to the fol owing

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a pear, they should be interpreted as “BritishStand rd”

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Sum m ary of pag es

This d ocument comprises a f ont cov er, an insid e font cov er, p g esi andi ,

p g es1 to3 and a b ck cov er

This stand rd has be n upd ated ( se copy rig ht d ate) and ma hav e had

amend ments incorporated This wi l be indicated in the amendment ta le on

the inside f ont cov er

Am endm ents is ued sinc publ cation

Amd No Date of is ue Comments

Pag e

b

1 Scope and field ofappl cation

This International Stand rd lay s down the ac uracy

of measurement of the imp ct v elocity in col ision

tests on roa v ehicles In ad dition, some ty pical

method s suita le for the measurement of this

imp ct v elocity are des ribed in the Annex These

method s are intended to faci itate the comp rison of

d ata obtained in simi ar tests b d iferent

la oratories

2 Per ormance

2.1 The ac uracy of v elocity measurement shal

be±1%

2.2 The imp ct v elocity measurement shal be ma e

within0,2 s prior to imp ct

3 Methods ofmea sur ment

Ty pical methods for measuring imp ct v elocity are

d es ribed in the Annex.Other method s ma be used

prov id ed they me t the req uirements of2.1and2.2

© BSI 0 -2 0

AnnexTypica l methods of

Velocity measurement method s can be clas ified in

thre general categ ories:

a) Dop ler efect method;

b) summation of the u its of d istance in a g iv en

time ( fifth whe l method );

c) measurement of the time ne ded to cov er a

g iv en distance

A.1 Do pler efe t m etho

This efect uti z s the a p rent f equency v ariation

of a wav e in motion This v ariation is proportional to

the spe d of the bod in relation to the observ er and

is g ov erned b the fol owing formula:

where

f is the a p rent f eq uency ;

f

0

is the emit ed feq uency ;

v

1

is the spe d of the wav e emit ed in an

ambient medium;

v

2

is the spe d of the v ehicle

The emit ed electromag netic wav es which are

g eneraly used are situated in two d iferent

wav eleng th b nds:

a) centimetric wav es: ra ar with an ac uracy that

is only of the ord er of2%;

b) mic ometric wav es: the laser

The laser sy stem, more perected than the rad ar

sy stem, permits measurements with an er or les

than1 % It should be noted , howev er, that the cost

of this ty pe of eq uipment is v ery hig h

A.2 Summ ation of the units of distanc in a

g iven time (fifth whe l m etho )

A whe l at ached to the rear ofthe v ehicle b an

articulated y oke is maintained in contact with the

g rou d b a spring Mounted a ial y on this whe l is

a dis containing sl ts sp ced reg ularly arou d the

cir umference A photo lectric transmit er-receiv er

sy stem is located on either side of the dis

Pas ag e of the slts in f ont of a photo lectric cel

activ ates a series of impulses cor esponding to the

distance cov ered The summation of these d ta

permits direct rea ing fom a g alv nometer, or a

recording on an ultra-v iolet os i og ra h Careful

machining permits an ac uracy of the order of1 %

An alternativ e method is to use an induction

proximity sensor in place of the photo lectric

receiv er Its a v antag es are simpler as embly and

resistance to weather

A further v ariation inv olv es at aching the

transmit er d irectly to a rear whe l of the v ehicle

instead of the fifth whe l In this case it is d ificult

to cal brate the sy stem and there must be no ty re

slp at the road sur ace Howev er, the calbration

must be car ied out careful y

A.3 Measurem ent of time ne ded to co er a

g iven distanc

The folowing ty pical method s are in g eneral use:

A.3.1 Syst em using a phot oele tric bar ier

A transmit er an a receiv er are located on either

sid e of a sh t er in a U-sha ed ar ang ement fixed

rig idly on the v ehicle

The transmit er consists of a lamp emit ing a l g ht

beam with es entialy p ral el ray s which

i uminate a photo lectric cel which constitutes the

receiv er

S c es iv e cut ing of the l g ht beam b the arms of

the U start an stop a d ig ital chronometer

The transmit er is placed a proximately1 m f om

the receiv er A d ia hrag m can be placed on the

receiv er to l mit p rasitic reflections

The cut ing of the beam is efected b means of a

sh t er in a U sha e mou ted on the side of the

v ehicle This mou ting should be v ery rig id in order

to av oid any d eflection tend ing to spread or ti t the

two arms, th s altering their sep ration The

sp cing betwe n the arms of the U should be k own

within a proximately0,2% The U is p inted mat

black to av oid any reflections

The p s ag e of the fir t arm of the sh t er throug h

the b r ier prod uces a v ariation in v oltag e at the

amplfier This d iference in potential a pled at

entrance A of a dig ital chronometer whose time b se

is reg ulated to10

– 5

s, initiates the time record ing

W hen the second arm obs ures the receiv er, it

prod uces a new v oltag e v ariation at entrance B of

the chronometer, stop ing the record ing

The ac uracy with this sy stem is v ery hig h an can

be bet er than1 %

A.3.2 Sy stem with induction pr x imit y s nso

The receiv er is of a cy lindrical form and has

dimensions of a proximately6 mm in leng th with

a d iameter of1 mm The receiv er includ es an

electronic amplfier within the sensor

The sensor is an os i lator which is stop ed when a

metal c bod p s es in f ont of the activ e extremity

of the receiv er The power sup ly required b this

receiv er is24V d.c The output cur ent can

at ain4 mA f om a receiv er hav ing a resistance

of6 07, with a response time of15 Ès A dig ital

chronometer is started and stop ed b the metal c

bod p s ing close by

f

v

1

f

0

v

1

v

2 –

=

The ac uracy of this sy stem is bet er than1 %

Dura i ity is also v ery g ood d ue to the fact that

there is no direct contact

This procedure can only be uti z d if the v ehicle is

per ectly g uid ed , the ma imum detection distance

being5mm

A.3.3 Equipment uti izing ele tr magnetic

beam bar iers

Two centimetric transmit er and two receiv er are

located on each sid e of the test track at an interv al

of at least1m Pas ag e of the v ehicle inter upts the

beams

Inter uption of the fir t beam actuates the cir uit of

the chronometer; inter uption of the secon stops

the cir uit.The major drawb ck of this sy stem is its

hig h cost

Assuming that the a es of the beams f om the two

transmit er are perectly p ral el, the princip l

sour e of er or comes f om measurement of the

sp cing of the receiv er

It is considered that this sy stem prov id es an

ac uracy bet er than1 %

A.3.4 Cinematographic pr c dure

The imp ct v elocity can also be measured b use of

hig h-spe d cinematog ra hy , of the ord er of5 0

to20 0 imag es per second

A clearly v isible targ et is placed on the v ehicle and

its displacement in relation to a g rou d targ et is

measured on a certain n mber of fim imag es The

time is deriv ed on the b sis of the camera time

b sed on an impres ion on the margin of the fi m of

a smal flash ev ery0,01s or0,0 1s, conting ent on

the fim spe d chosen To obtain the time

measurement, another method can be uti iz d b

fi ming a d is operated b a smal sy nchronous

motor

The ac uracy of this proced ure depend s on:

a) the g rain of the fim, which can cause blur ing

of the imag e;

b) the time b se of the camera

Analy sis of the fi ms must be efected with

eq uipment permit ing positioning of the fi m

within±15Èm, a resolution of1/ 20mm in Xand Y

and2 ½ of ang le inÚ

In order to minimiz p rala er or , the cameras

must be positioned as far awa as pos ible and be

eq uip ed with long focal leng th lenses comp tible

with the field to be fimed

To obtain ac uracies of1 %, v ery d etaied at ention

to eq uipment and tech iq ue is required

A.3.5 Syst em o plat es actuated by t he vehicle

whe ls

A.3.5.1 Meta llc pla te

Two flexible metal ic plates, sep rated f om each

other and ar ang ed ac os the test track, are put in

contact b the pres ure of the f ont whe ls of the

v ehicle Coupled with a direct cur ent g enerator,

this contact actuates a d ig ital chronometer

Thep s ag e of the rear whe ls re-closes the contact

and stops the chronometer Knowing the time

required to cov er a g iv en d istance,

i.e.thewhe lb se of the v ehicle, it is simple to

d eriv e the v elocity This proced ure is not v ery

precise owing to the disp rity of the pres ures

eng endered b the f ont whe ls an the rear whe ls

This drawb ck lead s to the use of a v ariation of this

procedure which consists in placing two identical

sets of plates ac os the track The actuation and

stop ing of the chronometer are then caused b the

f ont whe ls alone

I the contact is subjected to repeated actuation and

wear is not a p rent, it is pos ible that after sev eral

tests the v elocity measurement would be afected b

er atic release

A.3.5.2 Pneuma tic pla te

In this v er ion, the receiv er consists of a rub er tube

closed at one end Pas ag e of the v ehicle ov er the

tube produces a pres ure v ariation, which actuates

an electrical contact formed f om a mov able element

and a stationary element

Time measurement is achiev ed in the same manne

as with the metal c plates eq uipment

ISO 3784:1976

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