TRACTORS AND THEIR POWER UNITS

FOURTH EDITION

TRACTORS AND THEIR POWER UNITS John B. Liljedahl Professor Emeritus Agricultural Engineering Department Purdue Cniyersity

Paul K. Turnquist Professor and Head Agricultural Engineering Department Auburn Cniyersity

David W. Smith Research Engineer Technical Center Deere & Company

Makoto Hoki Associate Professor Department of Agricultural Machinery Mie Cni\'ersity, Tsu, Japan

An AVI Book

Published by Van Nostrand Reinhold, New York

An AVI Book (AVI is an imprint of Van ;-';ostrand Reinhold) Copyright © 1989 by Van Nostrand Reinhold

Softcover reprint of the hardcover 1st edition 1989

FOlRTH EDlTIO:\

Library of Congress Catalog Card Number 88-14907

ISBN-13: 978-1-4684-6634-8

All rights reserved. No part of this work covered by the copyright hereon may be reproduced or used in any form or by any means-graphic, electronic, or mechanical, including photocopying, recording, taping, or information storage and retrie\'al systems-without written permission of the publisher.

Van ;-';ostrand Reinhold 115 Fifth Avenue :\ew York, :\ew York 10003

Van :\ostrand Reinhold International Compan~ Limited I I :\ e\\' Fetter Lane London EC4P 4EE, England

Van Nostrand Reinhold 480 La Trobe Street :\Ielbourne, Victoria 3000, Australia

:\lacmillan of Canada Division of Canada Publishing Corporation 164 Commander Boule\'ard Agincourt, Ontario MIS 3C7, Canada

16 15 14 13 12 II 10 9 8 7 6 5 4 3 2

Library of Congress CataIoging-in-PubIication Data

Tractors and their power unitslJohn B. Liljedahl ... let aLl.-4th ed.

p. cm. "An AVI book." Includes bibliographies and index.

\. Tractors-:\Iotors. L Liljedahl, John B. TL233.T658 1989 629.22'5--dcI9 88-14907

ISBN-13: 978-1-4684-6634-8 001: 10.1007/978-1-4684-6632-4

e-ISBN-13: 978-1-4684-6632-4

CONTENTS

PREFACE

ACKNOWLEDGMENTS

1 DEVELOPMENT OF THE TRACTOR Tractor Tvpes Some \r orId \' ariations in Tractors Functions of a Farm Tractor Sources of Energ\ Energy Conversion Devices The Future Engine Trends in Tractor Design

2 THERMODYNAMIC PRINCIPLES OF INTERNAL­COMBUSTION ENGINES

xi

xiii

1 4 8 8

13 14 16 16

20 Specific Heat 22 Entropy 23 Energy Changes 23 Constant-Volume Changes 24 Constant-Pressure Changes 24 Isothermal Changes 25 Adiabatic or Constant-Entropv Changes 26 General or Polytropic Changes 28 Changes in an Adiabatic Expansion of a Perfect Gas 28 Determination of the Value of 11 from an Actual Compression Line 31 Equations for KonHow Processes 33

3 INTERNAL-COMBUSTION ENGINE CYCLES Simplifying Assumptions The Ideal Air-Standard Otto Cvcle The Ideal Air-Standard Diesel Cycle Actual Cycles and Causes for Deviation from the Ideal

4 FUELS AND COMBUSTION Sources of Fuels Chemical Composition of Petroleum Petroleum Refining Combustion Gasoline Tests and Their Significance Antiknock Quality

37 37 38 41 43

48 48 48 51 54 56 57

\'I

Factors Affecting the Octane l'\umber Requirement Volatility Distillation Reid Vapor Pressure Test Sulfur Content Corrosion Test Gum Content Gravity Heating Values Gasoline Additives Diesel Fuel Tests and Their Significance Cetane l'\umber Heating Value of Diesel Fuel Viscosity Carbon Residue Flash Point Pour Point and Cloud Point Ash Content Diesel Fuel Additives Alternate Fuels

5 ENGINE DESIGN Engine Design-General Stroke-to-Bore Ratio Crankshafts and Firing Orders Tractor Engine Valve Design Valve Materials, Design, and Application Valve Timing Valve Clearance Adjustment Valve Seats Valve-Opening Area Cams Combustion Chamber Design Effect of Compression Ratio Piston Crank Kinematics Inertia Force of Connecting Rod Inertia Force of Single-Cylinder Engines Crank Effort Flywheels Balance of Single-Cylinder Engines Balance of M ulticylinder Engines Principles of CI Engine Operation Construction of Diesel Engines Combustion Chamber Design Fuel- Injection Systems

CO:\TE~TS

58 59 61 62 64 65 65 65 66 67 67 69 72 72 72 72 73 73 73 74

77 78 78 80 82 83 85 87 90 91 91 93 94 94 95 98

100 101 102 104 106 110 III 112 116

COl'\TENTS Vll

Fuel Injectors 119 Turbochargers 120 Matching of Turbocharger to Engine 122 Aftercooling 129 Engine ]\; oise 129

6 ELECTRICAL SYSTEMS 134 Battery 134 Starting Motor 137 Electrical Charging 139 Battery Ignition System with Breaker Points 140 Magneto Ignition System 145 Ignition Timing 145 Spark Plugs 148 Sensors 149 Environmental Problems Ei2

7 ENGINE ACCESSORIES 156 Speed Control 156 Principles of Centrifugal Governor Action 157 Spark Arresters 160 Mufflers 162 Air Cleaners 163 Air Inlet Location 163 Precleaners 164 Dry-Type Air Cleaner 164 Dust Composition 165 Air Cleaner Tests 166 Engine Cooling Systems 166 Cooling Load 167 Heat Transfer 170 Air Cooling 170 Radiator Design 171 Radiator Construction 174 Temperature Control 174 Antifreeze Materials and Coolants 175 Corrosion and Radiator Deposits 177 Pressure Cooling 178 Quantity of Air 178 Fans 179 Engine Cooling Summary 181

8 LUBRICATION 183 Tvpes of Lubricants 183 Properties of Lubricants 183 Viscosity 184 Classification of Oil bv Viscosity 188

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Classification by Service Cniversal Tractor Oils Oil Additives Journal Bearing Design Oil Contamination Oil Filters Lubricating Oil Systems

9 HUMAN FACTORS IN TRACTOR DESIGN Operator Exposure to Environmental Factors Operator Exposure to Noise Operator Exposure to Vibration The Operator-Machine Interface Noise and Vibration Control Operator Seating Sound Control in Operator Enclosures Spatial, Visual, and Control Requirements of the Operator Rollover Protection for Wheeled Agricultural Tractors Thermal Comfort in Operator Enclosures Safety

10 TRACTION Traction Mechanics Mohr-Coulomb Failure Criteria Traction Performance Equations Traction Prediction from Dimensional Analysis Performance of Four-Wheel, Tandem, and Dual Tires Tire Size, Load, and Air Pressure Relationship Radial-Ply Construction Tread Design Effect of Lug Spacing Traction Improvement Tracks Tire Testing Traction Devices for Paddy Fields

11 MECHANICS OF THE TRACTOR CHASSIS Simplifying Assumptions Equations of Motion Static Equilibrium Analysis-Force Analysis Static Equilibrium Analysis-Maximum Achievable Drawbar Pull Static Equilibrium Analysis-Four-Wheel-Drive Longitudinal Stability The Tractor as a 2-Degree-of-Freedom Vibratory System Transient and Steady-State Handling Lateral Stability in a Steady-State Turn Three-Dimensional Static Analysis

CO~TE~TS

193 194 194 195 198 199 201

203 203 206 210 214 216 21i 224 226 231 233 234

240 240 240 243 24i 254 25i 258 259 263 263 265 265 265

272 2i2 2i3 2i8 280 282 283 285 289 295 29i

CO]\:TEi\TS IX

Center of Gravitv Determination 303 Moment of Inertia Determination 306

12 HYDRAULIC SYSTEMS AND CONTROLS 314 Hydraulic Component Svmbols 314 Hvdraulic Components 314 Motor Performance 315 Accumulators 319 Valves 321 Hvdraulic Fluids 323 Classification of H vdraulic Controls 328 Draft Sensing 329 Automatic Control 330 Complete H\'draulic System 332 PO\\'er Steering 333 r\oise in Hvdraulic Systems 350 Hitches 350 Tractor Kinetic Energy 351 Integral Hitch Systems 353 Three-Point Hitches 353 Quick-Attaching Coupler for Three-Point Hitches 355

13 TRANSMISSIONS AND DRIVE TRAINS 360 Complete Drive TraiIl 362 Transmission Types 364 Friction Brakes and Clutches 371 Spur and Helical Gears 377 Bevel Gears 377 Gear Design 378 Planetary Gear Systems 383 Differentials 389 Transmission Drive Shafts 390 Antifriction Bearings 391 Drive Train Speeds and Loads 392 Electronic Transmission Controls 392 Torsional Vibration 393 Computer Simulation 397

14 TRACTOR TESTS AND PERFORMANCE 403 Tractor Performance Criteria 403 Power Measurement Methods 404 Absorption DYIlamometers 406 Electric Direct Current Dynamometers 409 Shop-Type Dynamometers 410 Drawbar Dynamometers 411 Torsion Dynamometers 413 Chassis Dynamometer 413

x

Power Estimating-Field Method Air-Supply Measurement Engine Pressure Indicators Fuel Flow Meter The Nebraska Tractor Tests Globalization of the Tractor Industry Correction for Atmospheric Conditions Torque Curves Engine Performance Efficiency of Tractor Engines Actual Power Output and Fuel Consumption Tractor Reliability

CONTENTS

415 416 418 420 420 432 433 435 435 435 436 438

APPENDIXES A Standards for Agricultural Tractors 447 B Standard Graphical Symbols 451 C Agricultural Tractor Tire Loadings, Torque Factors, and Inflation

Pressures-SAE j709d 453 D Conversion Factors 457

INDEX 459

PREFACE

At the time of the writing of the fourth edirion of this textbook, the agricultural economy in the United States and Canada was depressed. The prices paid to farmers for their grain crops were very low, and consequently most farmers in North America could not afford to buy a new tractor when needed; there­fore, the sales of tractors and other farm machines were much below normal. The farmer who was the victim of the depressed economy was forced to "make do." Instead of purchasing a new tractor when the old one needed to be replaced, the farmer usually purchased a used or second-hand tractor or repaired the old one. In a strict sense, tractors usually do not wear out; instead, they become obsolete. The farmer who owns an obsolete tractor would prefer to replace it with one having more power, more speeds, more conveniences, a better hydraulic system, lower operating cost, or all of the above.

But farmers in the United States, Canada, and other industrial nations will continue to want to purchase tractors that have all of the features, in­cluding microprocessors, found on other vehicles.

The authors have tried to make this textbook more international in scope, and it is partly for that reason that a new co-'author from Japan has been added. Makoto Hoki, through his experience in the Philippines, Malasia, and other Third World countries, brings to this textbook broad experience in the mechanization of agriculture. To a farmer in a Third World country, a tractor is likely to have less than 10k W of power, only three forward speeds, and a single cylinder engine, and the farmer is fortunate indeed if the tractor has a seat on which to ride.

The primary purpose of this book is as a text for engineering seniors and graduate students. A secondary intended use for this book is as a ref­erence.

Measurements in this edition, as in the previous edition, are in SI units. In a few instances (e.g., tire sizes) customary units remain because of their continued international use. Conversion factors are included in Appendix D. We give credit to Dr. Hussam Al-Deen of the John Deere Werke, Mannheim, West Germany, for most of the conversion factors from customary to SI units.

Xl

ACKNOWLEDGMENTS

We pay tribute here to three previous authors. Each made significant con­tributions to the farm power literature both in farm power research and leaching. Dr. E. G. McKibben, now deceased, was a pioneer in farm power research and teaching, especially in matters relating to tractor stability and traction. E. L. Barger, now retired, is widely recognized for his contributions to transport and traction literature and for his leadership in farm power and machinery economics. With others, they also played a significant part in es­tablishing the Ferguson Foundation Agricultural Engineering Series in co­operation with Harold Pinches of the original Ferguson Foundation, without which this book and others in the original Ferguson Foundation Series would likely not have been written. Dr. W. M. Carleton, now retired, also had a distinguished career in teaching, research, and service. Dr. Carleton's atten­tion to details insured that the first ~dition was properly organized and written.

Credit is due Purdue University for providing the time and space to write this edition.

Special thanks go to the Society of Automotive Engineers and the Amer­ican Society of Agricultural Engineers from whose literature came much of the new information in this edition.

Many educators have been helpful, especially those who participated in the Power and Machinery Textbook Conference at the ASAE Meeting at Bozeman, Montana, in June 1982. Their report helped in the reorganization of this book.

Many engineers in industry contributed information. Special thanks must go to Richard A. Michael and William H. Lipkea of the John Deere Product Engineering Center in Waterloo, Iowa, for their editorial work on Chapters 2,3, and 13. Other engineers who contributed represented Massey-Ferguson Ltd.; Case IH; Ford Tractor Operations; Duetz Allis; Perkins Engines Group, England; Cummins Engine; Caterpillar; Kubota Ltd., Japan; Fiat Trattori, Italy; Versatile, Canada; and Yanmar, Japan.

Speciallhanks to H.arriet Liljedahl for patiently proofreading this edition.

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TRACTORS AND THEIR POWER UNITS