Contents

Preface vii... Acknowledgements Vlll Introduction ix

1 Crown wheel and 1 at rear axles 4 Vehicle performance torque 5 Axle torque (from maximum engine torque through the lowest ratios) Axle torque - from wheel slip Drive pinion torque Stress determination and scoring resistance Bending stress Contact stress

2 Internal running gear 16 Shaft stressing for size 16 Input shaft 19 Intermediate shaft 19 Output shaft 19 Internal 20 Lubrication system 22 Gear engagement 22 Interlock system 26 Reverse gear 27 Differential 27 Bearing arrangement and casing 30

3 Lubrication of gears 33 Principles of gear lubrication 36 Group A 36 Spur gears 36 Helical gears 37 vi Contents

Bevel gears 38 Crossed helical gears 38 Group B 39 Worm gears 39 Hypoid gears 40 Tests for lubricating oils 46

4 Gear tooth failures 50 Gear tooth failure 52 Tooth fracture 53 Tooth surface failures 54

5 Crowa wheel and pinion designs 61 Klingelnberg palloid spiral calculations 66 Basic conception 66 Terminology 67 Bevel gear calculations 67 ‘0’-bevel gears 80 Bevel gear V drives 82 Tooth profiles 83 Gear blank dimensions 84 Formulae for the determination of the external forces 88 Strength of teeth 96 Rules for the examination of the tooth profile by the graphic method 100 Example of design 106

6 Oerlikon cycloid spiral bevel gear calculations 113 Design features 113 Production features 113 Gear calculation with standard En cutters 117 Strength calculation 1 30

7 Gearbox design - rear-engined racing 134 Basic aims 134 In-line shaft arrangement 135 Internal gear arrangement 137 Face-dog selectors 137 Bearhg arrangement 139 Crown wheel and pinion layout 141 Differential location and type 143 Transverse-shaft arrangement 148 Selector system 150 Selector interlock system 152 Lubrication method 155 Gearbox casing 157 Materials guide 158

Index 161 Preface

This book has been written in an effort to put down on paper some of the experience I have gained during my forty-five years in the design field, thirty-one years of which was designing Formula One gearboxes, and the last five years before retirement with Lotus Engineering as Chief Designer - Transmissions. Knowing of no other book that covered this subject made me more determined to proceed with it. I have attempted to work through the design procedure in the same order used on the many gearbox designs I have been involved with. Alternative types of crown wheel and pinion designs to the widely used Gleason system are covered, that is, Klingelnberg and Oerlikon. Various types of differential are described along with interlock systems which prevent the selection of more than one gear at a time. It contains a wide coverage of gear failures, their causes and requirements to prevent further failures, together with an engineering understanding of lubrication and its application. The book also includes a list of materials along with the heat treatment applied and race-proven in the B.R.M. Formula One Racing Transmissions as a guide to the designer. A. Stokes

vii

Introduction

The purpose of this book is to provide both the student and young professional design engineer with an overall guide to the amount of work involved in the design of a manually operated automotive gearbox, and the problems that can be encoun- tered both during the design stages and in operation. I am unaware of any other book which gives such information and at the same time attempts to provide a methodical system of solving what appears to be a fairly straightforward engineering design problem to the majority of people, but often turns into one re