Bsi bs au 210 2 1994 (1999)

BRITISH STANDARD BS AU 210 2 1994 Drawbars for caravans and light trailers — Part 2 Specification for the design of aluminium drawbars and chassis UDC [629 11 43 + 728 76] 629 11 011 1 BS AU 210 2 199[.]

Drawbars for caravans

U C [ 62 1 -4 + 7 8.7 ]6 9.1 0 1.1

This Bri sh Stan ard, ha ing

b en pre ared u der the

directonof the Automo ile

Stan ards Policy Commi e ,

waspublished u der the

authoriyof the Stan ards

Bo rdan comes

into efect on

1 July1 9

© BSI 1 -1 9

The folowing BSI references

relate to the work on this

stan ard:

Commi e reference AUE 8

Draft for comment 9 7 3 6 DC

ISBN 0 5 0 2 3 4 8

The prep ration of this British Stand rd was entrusted b the Automobi e

Stand ards Pol cy Commit e ( AUE/-) to Tech ical Commit e AUE/8, upon

which the fol owing bod ies were represented :

Association of Traier Man facturer

British Compres ed Air Society

Carav an Club

Dep rtment of Transport

National Carav an Cou ci Limited

Society of Motor Man facturer and Tra er Ltd

Co pted member

Am endm ents is ued sinc publ cation

Pag e

Fig ure 2 — Curv es relating ma imum stres an stres ratio

for 10 8

This Part of BS AU2 0 was prep red u der the d irection of the Automobie

Stand rd s Polcy Commit e Since the drawb r is only one p rt of the chas is of

a carav an or lg ht traier, and as the chas is can be ma e ofmaterials other than

ste l, or ev en be of composite construction, this Part of BS AU2 0 aims to set out

requirements for the desig n of aluminium chas is for carav ans and lg ht trai er

A British Stand ard d oes not purport to includ e al the neces ary prov isions of a

contract User of British Stand rd s are responsible for their cor ect a plcation

Com pl anc with a British Standard does not ofitself confer im m unity

f om leg al o l g ations

Sum m ary of pag es

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

p g es1 to8, an inside b ck cov er an a b ck cov er

This stand rd has be n up ated ( se copy rig ht d ate) an ma hav e ha

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

insid e f ont cov er

1 Scope

This Part of BS AU2 0 specifies:

a) a procedure for determining the mechanical

streng th of drawb r for carav ans and lg ht

traier where the v ertical static for e on the

couplng head is not les than24 N and not

g reater than7 5N;

b) req uirements for the mechanical d esig n of the

chas is for carav ans an lg ht trai er

This stand rd a pl es to aluminium chas is of

carav ans and lg ht trai er prov ided they are not of

weld ed construction It also cov er the aluminium

elements of chas is of composite construction, ag ain

prov id ed the aluminium p rts hav e not be n

welded

NOT The method for calculaton of the mechanical streng th of

ste l drawb r for cara ans an lig ht trailer is co ered in

BSAU2 0-1

2.1 Normative referenc s

This Part of BS AU2 0 incorporates, b reference,

prov isions f om specific editions of other

publcations These normativ e references are cited

at the a propriate points in the text and the

publ cations are l sted on the inside b ck cov er

S bsequent amendments to, or rev isions of, any of

these publ cations a ply to this Part of BS AU2 0

only when incorporated in it b upd ating or rev ision

2.2 Inform ative referenc s

This Part of BS AU2 0 refer to other publcations

that prov id e information or g uid nce Editions of

these publcations cur ent at the time of is ue of this

stand rd are l sted on the insid e b ck cov er, but

reference should be ma e to the latest ed itions

3 Definitions

For the purposes of this Part of BS AU2 0, the

d efinitions g iv en in BS81 8 a ply , tog ether with

the fol owing

3.1

chas is

the element, includ ing the d rawb r, betwe n the

a le as embly and the bod of the carav an or lg ht

traier

3.2

drawbar

that p rt of the chas is which ena les the

con ection of the carav an or l g ht traier to the

towing v ehicle

For the purposes of this Part of BS AU2 0, the

folowing sy mbols are used

l is the distance ( in mm) f om the v ertical

ax is of the coupl ng dev ice to the fir t point

on the traier fame ( se Fig ure 1)

l is the distance ( in mm) f om the v ertical

a is of the coupl ng d ev ice to the drawb r

section cor esponding to the ma imum

strain rate ( se Fig ure 1)

e is the distance ( i mm) fom the horiz ntal

a is of the coupl ng d ev ice to the drawb r

neutral a is at the fir t fixing point on the

trai er f ame ( se Fig ure 1)

e

x

is the distance ( i mm) fom the horiz ntal

a is of the coupl ng d ev ice to the drawb r

neutral a is at the c os section

cor esponding to the ma imum strain rate

( se Fig ure 1)

d is the ma imum deflection ( in mm) at the

couplng dev ice relativ e to the fir t fixing

point ( se Fig ure 1)

P is the man facturer’s total mas ( in kg ) of

the carav an or l g ht traier ( se ISO723 )

D is the v alue d etermined b calculation for

the long itudinal for e ( i N) oc ur ing

betwe n the tractor v ehicle an the traier

( se ISO3 5 )

E

is the modulus of elasticity ( in N/mm

2

); its

v alue v aries ac ord ing to the aloy

( se Ta le 1)

I

is the moment of inertia ( in mm

4)

) of the

section

g

is the ac eleration due to g rav ity ( i m/s

2

)

( se ISO3 5 )

Fig ure 1 — Drawb r referenc dim ensions

— 2

8 8

5 Resistance ca lcula tion for dra wba rs

5.1The calculation for resistance for drawb r shal

be car ied out ov er the whole leng th l of the

drawb r, taking into ac ou t d istances l and e

x

in

ord er to determine the ma imum strain rate The

strain rate shal be checked at the position wher e

the ma imum bending moment oc ur when l = l

and e = e

x

5.2 The ma imum bend ing moment M

f ( in N·mm)

for the drawb r with e/l<0.15 an e

x /l

x

<0.15 shal

be calculated as fol ows

NOT Only fle ure is taken into ac ou t for the calculaton

— For braked trai er :

M

f

= 0.3 Pgl

— For u braked traier :

M

f

= 0.24 Pgl

5.3 The ma imum bending moment ( i N·mm) for

the drawb r with e/l>0.15 and e

x /l

x

>0.15 shal be

calculated as fol ows

NOT Only fle ure is taken into ac ou t for the calculaton

Thre bending moments M

f , M

fD

fR shal be

calculated and the larg est v alue of the thr ee shal be

used for the calculation of the ma imum a mis ible

fma

— For braked trai er :

M

f

= 0.3 Pgl

M

fD

= 0.8 D e

x

M

fR

= 0.7 ( M

f + M

fD )

— For u braked traier s:

M

f

= 0.24 Pgl

M

fD

= 1.0 D e

x

M

fR

= 0.7 ( M

f + M

fD )

5.4 The permis ible stres rates B, calculated for the

whole leng th of the drawb r, shal not exce d the

alowed stres B

bc ( se Ta le 2)

where

NOT I is as umed in this stan ard that aluminium she t,

plate or strip conforming to BS1 7 or b r , e tru ed rou d tub

or sectons conforming to BS1 7 are used This do s not pre ent

other, suia le an fi for purp se, aluminium alo s b ing used

The pro ertes of some aluminium alo s are shown inTa le 1

an Ta le 2

6 Deflection calculation

6.1The deflections d

f , d

fD and d

fR shal be calculated ,

at the same time as the resistance calculation in

clause5, as folows

— For braked traier :

d

fR

= 0.7 (d

f + d

fD )

— For u braked trai ler :

d

fR

= 0.7 (d

f + d

fD )

The v alue shal not exce d that defined in6.2

N T Because of the inc e sed fle ibiliy of aluminium

comp red to ste l, i should not b taken for g ranted that the

d rawb r desig n is suficiently stf wihout p rorming a

d eflecton calculaton

6.2 The permis ible d eflection d at the couplng

d ev ice shal not exce d:

to a ma imum of25mm

7 Fatig ue

Because of the constraints on manufacture, al

d rawb r shal be considered to hav e ty pe1

clas ification as d efined in BS81 8-1:19 1

Using the curv es inFig ure 2,the fatig ue l fe shal be

predicted

N T

I/V

is the section modulus ( in mm

3

), of the

d rawb r c os section cor esponding to the

max imum bending moment

B

min

is the minimum stres ,which is the lower n merical

v lue of the stres in a stres cycle

B

ma

is the ma imum stres , which is the hig her n merical

v lue of the stres in a stres cycle

is the stres rato, which is the rato of the minimum

to ma imum stres in a stres cycle, tensile stres

b ing considered p si v an compres iv stres

neg atv

W hen these p ints are ploted onFig ure 2 ) an Fig ure 2 ),

the alwa s oc ur on the curv or in the are defined as

“ac e ta le”

d l

7

=

Ö

min

Ö

ma

Table 2 — Perm is ible stres es for aluminium al o s

Allo BS or

inte national

no

a

T ick es

Axial b

Bearing c

t B

c B

bt B

bc

B

q

B

b

2

N/mm 2

N/mm 2

N/ mm 2

N/ mm 2

N/ mm 2

ex trusions

2 2

she t an

plate

2 2

drawn tube

2 2

5 8

M

ex trusions —

15 d

she t an

plate

O

ex trusions —

15 d

she t an

plate

6 6

15 d

15 d

2014A

TF

7 20

TB

she t an

plate

TF

she t an

plate

a

Se BS 1 7

b

Applies only when buckling is not the cierion;se BS8 1 -1

c

J ints in sing le she r

d

For rou d tub an holow sectons the p rmis ible stres es do not a ply a ov e7 mm

F

8 Mecha nica l desig n ofcha ssis

8.1 Bolted joints

8.1.1 Minimum sp cing betwe n b lt hole

The sp cing betwe n the centres of the bolts shal

not be les than2.5 times the bolt diameter

8.1.2 Edge distanc

W ith extrud ed , roled or machined ed g es, the

distance to the ed g e, measured f om the centre of

the bolt hole shal not be les than1.5 times the bolt

d iameter I, on the beating side, it is les than2

times the bolt diameter, the permis ible beating

streng th shal be reduced as folows:

where

8.1.3 Web st ifne s

The web stifnes shal be demonstrated b

calculation as detaied in BS81 8-1:19 1, b test or

both

8.1.4 B olt material

Ste l bolts conforming to BS EN24 14:19 2 and

n ts to BS EN24 32:19 2 shal be used Both the

bolts and n ts used shal be rend ered cor osion

resistant b zinc plating to BS3 82-2:19 1

W asher shal be prov ided u d er al bolt hea s and

n ts an these washer shal be zinc plated to

BS17 6:19 0 Fe/ Zn8 and p s iv ated The leng th of

the u threa ed p rt of the bolt shal be such that as

far as pos ible no p rt of the threa is within the

thick es of the member The threa shal project

bey on the n t b a minimum of two turns A form

of locking dev ice shal be used

NOT Other suia le ant-corosion co tng s ma b used that

ade uately protect the jointed p rts ag ainst electrolytc

cor osion

8.2 J ints with ste l or cast iron ( se also8.3)

For such composite joints, the ste l or cast iron

elements shal be either:

a) zinc plated to BS17 6:19 0 Fe/ Zn 8; or

b) hot dip g alv aniz d to BS729:19 1; or

c) p inted with priming coat with an in ibiting

pig ment containing not les than20% b weight

of zinc chromate or other a prov ed chromate in a

suita le water resisting v ehicle The priming coat

shal not contain any cop er or mer ury

compou d s, g ra hite or carbonace us materials,

or lea ; or

d) sep rated b the use of a continuous

membrane of non-reactiv e material e.g plastic

NOT A joint made b any other me ns not detailed in this

stan ard ma b used pro ided that is lo d carying ca aciy

an life e p ctancy can b shown to b satsactory

8.3 Contact with timber

Aluminium suraces in contact with timber, u les

the timber is ful y seasoned and the env ironment

d ry and u pol uted , shal be p inted Timber in

contact with aluminium shal not be treated with

preserv ativ es containing cop er sulfate, zinc

chloride or mer uric salts

NOT 1 Other preserv tv s ma b used pro ided that i can

b shown that the tmb r so tre ted is not harmful to the

aluminium

NOT 2 Oak, chestn t an western red cedar are likely to b

harmful to aluminium p rtcularly where there are throug h

fastening s,u les the tmb r is wel se soned

9 Chas is streng th

The chas is man facturer shal demonstrate, either

b test or b calculation, or both, that al elements

of the chas is are fit for their d eclared purpose with

reference to BS81 8:19 1

10 Joining ofbody to cha ssis

The chas is man facturer shal prov ide, in writing ,

instructions in respect of streng th an fixing

ar ang ements for the at achment of the carav an or

l g ht traier bod to the chas is There shal be no

fix ing directly or indirectly throug h the top or

bot om flang es of the d rawb r at the foremost bod

fixing position

P

BM

is the modified bearing streng th;

P

B

is the bearing streng th g iv en inTa le 2;

r

a

is the actual ratio of edg e distance to bolt

diameter;

r is the ratio of edg e distance to bolt

diameter

List ofreferences ( se claus 2)

BSI publ cations

B ITISH STANDARDS INSTITUTIO , Lon on

BS 729:19 1, Spe ifica tion f r hot d ip ga lva nized coa tings on ir on a nd ste l a r ticle

BS 17 6:19 0, Method fr spe ifing ele tr opla ted coa tings o zinc a nd ca d mium, on ir on a nd ste l

BS 3 82, Spe ifica tion f r ele tr opla ted coa tings on thr ea d ed components

BS 3 82-1 & BS 3 82-2:19 1, Ca d mium on ste l components Zinc on ste l components

BS 81 8, Str uctur a l us o a luminium

BS 81 8-1:19 1, Cod e o pr a ct c f r d esign

BS 81 8-2:19 1, Spe ifica tion f r ma ter ia ls, wor kma nship a nd pr ote ton

BS EN 24 14:19 2, Hexa gon hea d bols — Pr od uct gr a d es A a nd B

BS EN 24 32:19 2, Hexa gon n ts, style 1 — Pr od uct gr a d es A a nd B

BSI publ cations

B ITISH STANDARDS INSTITUTIO , Lon on

BS AU 2 0, D r a wba r s fr ca r a va ns a nd lght tr a iler s

BS AU 2 0-1:19 7, Method o ca lcula tion f r the me ha nica l str ength o ste l d r a wba r s

BS 14 0:19 7, Spe ifica tion fr wr ought a luminium a nd a luminium a llo s f r gener a l engine r ing

pur pos s: pla te, she t a nd str ip

BS 14 4:19 7, Spe ifica tion fr wr ought a luminium a nd a luminium, a llo s f r gener a l engine r ing

pur pos s: ba r s, extr ud ed r ou d tube a nd s ctons

ISO 723 :19 1, R oa d vehicle — Ma ss s a nd d imensions o ca r a va ns — Ter ms a nd d efini ions

ISO 3 5 :19 7, R oa d vehicle — Ca r a va ns a nd lght tr a iler s — Towing br a ckets a nd couplng ba lls —

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