ISO INTERNATIONAL STANDARD 7642 Second edition 1991-04-01 Caravans and light trailers .-. Trailers of categories O, and O, with overrun brakes Inertia bench test methods for brakes Caravanes et remorques legeres - Remorques des categories O et O2 a freins a inertie -- Methodes d'essai des freins sur banc a masse d'inertie Reference number ISO 7642:1991(E) Not for Resale ISO 7642:1991(E) Foreword Iso (the International Organization for Standardization) is a worldwide federation of national standards bodies (isO member bodies). The work of preparing International Standards is normally carried out through Iso technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, govern- mental and non-governmental, in liaison with iso, also take part in the work. Iso collaborates closely with the International Electrotechnical Commission (lEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committees' are circulated to the member bodies for voting. 'Publication as an inter- national Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard IsO 7642 was prepared by Technical Committee IsO/TC 22, Road vehicles. This second edition cancels and replaces the first edition 7642:1983), of which certain values have been altered, the previous clause 8 deleted and references updated. ISO1991 All rights reserved, No part of this publication may be reproduced or utllized In any form or by any means, electronic or mechanical, including photocopying and microfilm, wlthout permisslon in writing from the publisher. Internatlonal Organlzation for Standardization Case Postale 56 · CH-1211 Geneve 20 · Switzerland Printed In Switzeriand ii t license from IHS Not for Resale ISO 7642:1991(E) INTERNATIONAL STANDARD Caravans and light trailers - Trailers of categories O, and O, with overrun brakes -- Inertia bench test methods for brakes N'2 is the actual rotational frequency meas- Scope 7 ured during the heating of the brakes, in reciprocal minutes. This International Standard specifies test methods for type approval testing of the overrun brakes on 2.2 For mechanical brakes trailers. It should therefore be used in connection with the pertinent regulation.1) Po is the force of the brake, in newtons; NOTES P is the force applied on the brake control In order to understand fully the requirements of this lever, in newtons, to obtain a braking International Standard and to ensure that the test pro- torque Mt; cedures are correctly applied, it is recommended that the regulation is studied before application of this Inter- P2 is the force applied on the brake, in national Standard. newtons, to obtain a braking torque Mta with cold brakes; 2 Onty S! units are used in this Internationat Standard. P3 is the force applied on the brake, in These test methods apply to the type approval of newtons, for the strength test: categories O1 and Oz1) trailers with inertia brakes by testing on an inertia dynamometer. They relate P3 = 1,8P to mechanically and hydraulically operated braking systems. For hydraullc brakes 2.3 Po is the input pressure in the brake cylin. 2 Symbols and definitions der, in kilopascals; is the pressure applied in the brake cyl- p1 2.1 For all brakes inder, in kilopascais, to obtain a braking torque Mt: N, is the theoretical rotational frequency calculated for tests with cold brakes, in is the pressure applied in the brake cyl- P2 reciprocal minutes; inder, in kilopascais, to obtain a braking torque Mta with cold brakes; N't is the actual rotationai frequency meas- ured during the tests with cold brakes, in is the pressure applied in the brake cyl- ps reciprocal minutes; inder, in kilopascals, for the strength test: is the theoretical rotational frequency N2 p3 = 1,8pt calculated for the heating of the brakes, T in recipr