1、 Collection of SANS standards in electronic format (PDF) 1. Copyright This standard is available to staff members of companies that have subscribed to the complete collection of SANS standards in accordance with a formal copyright agreement. This document may reside on a CENTRAL FILE SERVER or INTRA
2、NET SYSTEM only. Unless specific permission has been granted, this document MAY NOT be sent or given to staff members from other companies or organizations. Doing so would constitute a VIOLATION of SABS copyright rules. 2. Indemnity The South African Bureau of Standards accepts no liability for any
3、damage whatsoever than may result from the use of this material or the information contain therein, irrespective of the cause and quantum thereof. ISBN 978-0-626-22229-1 SANS 570:2008Edition 1SOUTH AFRICAN NATIONAL STANDARD Directional stability performance of vehicles in the event of tyre failure P
4、ublished by SABS Standards Division 1 Dr Lategan Road Groenkloof Private Bag X191 Pretoria 0001Tel: +27 12 428 7911 Fax: +27 12 344 1568 www.sabs.co.za SABS SANS 570:2008 Edition 1 Table of changes Change No. Date Scope Foreword This South African standard was approved by National Committee SABS TC
5、22, Steering committee for construction of motor vehicles, in accordance with procedures of the SABS Standards Division, in compliance with annex 3 of the WTO/TBT agreement. This document was published in December 2008. Introduction When a tyre fails, the driver might lose directional control such t
6、hat the vehicle veers off its intended path and possibly impacts an obstacle, or spirals into such an acute turn that the vehicle broadsides and rolls. The tendency for this to happen would depend on many factors, both human and mechanical. Examples of human factors are as follows: a) driver alertne
7、ss; b) negotiating a bend or driving straight ahead; c) driver response time; and d) correctness of driver response. Examples of mechanical factors are as follows: a) correctness of tyre selection; b) period that the tyre has been seated on the rim; c) strength of tyre sidewall; d) change in rolling
8、 radius (a low-profile tyre gives less change); e) load distribution in the vehicle; f) play in steering; g) power steering; h) wheelbase; i) tyre run-flat design; j) electronic stability control; and k) rim design. This standard was developed as a performance standard to support legislation applied
9、 to minibuses, midibuses and buses that operate under an NLTTA operating licence for minibus-taxi type services. No attempt is made to assess durability or reliability of any product or of the ease or otherwise of any installation procedure since this is intended only as a design assessment standard
10、. The user of this standard is urged to keep in mind that the test driver referred to in this standard is an experienced driver who is fully prepared and alert and knows when and where to expect the tyre deflation to occur, and that the experience and alertness of the driver is such as to minimize t
11、he likelihood of exceptional departures from the intended vehicle direction. An inexperienced, unprepared or distracted driver may well allow irrecoverable deviations to occur before he/she begins to react. SANS 570:2008 Edition 1 1 Contents Page Foreword Introduction 1 Scope 3 2 Definitions 3 3 Req
12、uirements 3 4 Methods of test4 4.1 Preparation. 4 4.2 Procedure. 5 SANS 570:2008 Edition 1 2 This page is intentionally left blank SANS 570:2008 Edition 1 3 Directional stability performance of vehicles in the event of tyre failure 1 Scope This standard specifies requirements for directional stabili
13、ty performance for rigid passenger vehicles in the event of a tyre failure. It does not apply to articulated units, combinations of vehicles or failure of a tyre on a dual-wheeled axle. 2 Definitions For the purposes of this document, the definitions given in the national road traffic regulations an
14、d the following apply. 2.1 directional stability control device directional stability control system mechanism or arrangement fitted in a motor vehicle for the purposes of minimizing the risk of the driver losing control of the motor vehicle in the event of tyre failure or sudden loss of pressure 2.
15、2 vehicle model type of vehicle falling within the criteria of number of axles, load distribution, wheelbase and track as detailed in this standard 3 Requirements 3.1 General When a vehicle is tested in accordance with 4.2, it shall be possible to maintain the required direction of the vehicle withi
16、n a lane width of 5 m. 3.2 Steering force and steering angle limits During any manoeuvre in the tests given in 4.2, the forces and angles employed by the test driver on the steering wheel shall not exceed those which the test driver would be unwilling to repeat. 3.3 Ground contact In no test shall a
17、ny part of the body of the vehicle come into contact with the road surface. SANS 570:2008 Edition 1 4 3.4 Design data Sufficient data that describe equipment fitted to the vehicle which is responsible for, or which contributes to directional stability control, shall be provided to the test authority
18、 who shall verify its presence and that no other equipment relevant to stability is present. The design data shall include at least the following: a) the vehicle model designation; b) a drawing that shows the overall width, wheelbase, overhangs, centre of gravity and track, seating arrangements cove
19、red by the tests given in 4.2; c) details of wheel rims and tyres, any specific lip or offset dimension or other design feature(s) present that might be responsible for, or contribute to, directional stability after tyre failure; d) the presence of any electronic directional stability control device
20、 or system and whether this device or system is in operation during the test; and e) the presence of any other specific device or system that is considered instrumental in achieving the required performance. 4 Methods of test 4.1 Preparation 4.1.1 Selection of vehicle models 4.1.1.1 Select vehicle m
21、odels for the test after considering vehicle design, wheelbase, wheel size, tyre design, loading, centre of gravity, and wheel offsets and track. These vehicle models may be representative of the worst case such that the test result can be extended to cover other models within that range. 4.1.1.2 In
22、 cases where devices or other systems are added to the standard design of the vehicle model, the applicability of the result shall also apply to the model range in 4.1.1.1. 4.1.2 Selection of tyres 4.1.2.1 Ignore tyres that are fitted to dual axles or to dual wheels. 4.1.2.2 Ignore any imbalance in
23、wheel loadings from one side of the vehicle to the other. 4.1.2.3 Select a tyre on the side of the vehicle that offers the largest escape area for the straightaway test (see 4.2.2). 4.1.2.4 Select a tyre on the outer side of the vehicle for the semicircle test (see 4.2.3). 4.1.2.5 Except for dual wh
24、eels in 4.1.2.1, select a rear tyre in addition to the front tyre and in any sequence. 4.1.3 Loading Load the vehicle to its maximum permissible mass for one test run. SANS 570:2008 Edition 1 5 4.1.4 Selection of a test site The test site shall be such that a) other traffic is excluded and the road
25、surface is tar or concrete, b) there is a bend or circle of inner radius 40 m with a 5 m lane marked out at 40 m and 45 m and with a free space escape capability of 5 m outside of this lane. (i.e. a pan of 100 m diameter), and c) there is a straight reasonably level road of length at least 1 km such
26、 as to ensure safety, and with a width of not less than 8 m with a 5 m lane marked out and with an escape lane to one side of width not less than 3 m. 4.1.5 Safety considerations 4.1.5.1 The target performance of the vehicle is to traverse the bend at 40 km/h and to bring the vehicle to rest without
27、 deviating from the lane width of 5 m. 4.1.5.2 For safety reasons the procedure is structured to enable confidence to be developed by the test driver during screening tests before proceeding to the instantaneous deflation test. 4.1.5.3 If the test driver deems it unsafe to proceed, any test may be a
28、bandoned at any stage. 4.1.5.4 Conversely, the test driver may wish to eliminate a stage in the build-up procedure. 4.1.6 Tyre deflation 4.1.6.1 Ensure that qualified personnel are available in cases where detonators fixed to the sidewall of the selected tyre is the intended method to achieve rapid
29、deflation. 4.1.6.2 Other methods that produce similarly rapid deflation may be used. 4.2 Procedure 4.2.1 Familiarization runs 4.2.1.1 Complete the preparation processes in 4.1. 4.2.1.2 Load the vehicle to its maximum permissible mass in terms of the relevant national road traffic regulations with al
30、l tyres inflated to recommended pressures. 4.2.1.3 Drive the vehicle along the straight road and around the semicircle repeatedly to develop a feel for the vehicle and to assess that the lane widths and escape areas are sufficient for the tests. 4.3.1.4 During the above manoeuvres, observe and note
31、the steering forces and angles required to negotiate the tracks. Alternatively, use measurement and recording equipment. 4.2.2 Straightaway test 4.2.2.1 For the build-up, drive the vehicle along the straightaway at a speed acceptable to the test driver. 4.2.2.2 Instantaneously deflate the front tyre
32、 and establish whether the driver can bring the vehicle to rest under control. SANS 570:2008 Edition 1 6 4.2.2.3 Repeat 4.2.2.2 for increased speeds until the driver has gained sufficient confidence to travel up to 100 km/h or the maximum attainable speed or the speed limit relevant for that vehicle
33、. If sufficient confidence cannot be achieved, abandon the test. 4.2.2.4 When additional corroboration is required, perform the test by driving the vehicle at the maximum applicable speed established in 4.2.2.1. 4.2.2.5 Instantaneously deflate the front tyre and bring the vehicle to rest within a la
34、ne width. 4.2.2.6 Repeat 4.2.2.1 to 4.2.2.5 for a rear tyre deflation when the vehicle is fitted with single tyres at the rear. 4.2.2.7 Check for compliance with 3.1 and 3.2. 4.2.3 Semicircle test 4.2.3.1 For the build-up, repeat the speed build-up process in 4.2.2.1 to 4.2.2.3, if necessary, around
35、 the semicircle until a speed of 40 km/h is attained, or abandon the test. 4.2.3.2 When it is adjudged difficult to maintain a 5 m lane in the standard condition such as for a maximum length bus, increase the lane width to 6 m. 4.2.3.3 Whilst travelling at 40 km/h into the semicircle, instantaneousl
36、y deflate the front tyre during the first half of the semicircle. 4.2.3.4 Continue to traverse the remainder of the semicircle within the lane bringing the vehicle to rest in a straight line upon exiting the semicircle. 4.2.3.5 Repeat 4.2.2.1 to 4.2.2.5 for a rear tyre deflation when the vehicle is
37、fitted with single tyres at the rear. 4.2.3.6 Check for compliance with 3.1 and 3.2. SABS SABS Standards Division The objective of the SABS Standards Division is to develop, promote and maintain South African National Standards. This objective is incorporated in the Standards Act, 2008 (Act No. 8 of
38、 2008). Amendments and Revisions South African National Standards are updated by amendment or revision. Users of South African National Standards should ensure that they possess the latest amendments or editions. The SABS continuously strives to improve the quality of its products and services and w
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