Table Of ContentTRACTORS 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 e-ISBN-13: 978-1-4684-6632-4
001: 10.1007/978-1-4684-6632-4
CONTENTS
PREFACE xi
ACKNOWLEDGMENTS xiii
1 DEVELOPMENT OF THE TRACTOR 1
Tractor Tvpes 4
Some \ro rId \' ariations in Tractors 8
Functions of a Farm Tractor 8
Sources of Energ\ 13
Energy Conversion Devices 14
The Future Engine 16
Trends in Tractor Design 16
2 THERMODYNAMIC PRINCIPLES OF INTERNAL
COMBUSTION ENGINES 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 37
Simplifying Assumptions 37
The Ideal Air-Standard Otto Cvcle 38
The Ideal Air-Standard Diesel Cycle 41
Actual Cycles and Causes for Deviation from the Ideal 43
4 FUELS AND COMBUSTION 48
Sources of Fuels 48
Chemical Composition of Petroleum 48
Petroleum Refining 51
Combustion 54
Gasoline Tests and Their Significance 56
Antiknock Quality 57
\'I CO:\TE~TS
Factors Affecting the Octane l'\umber Requirement 58
Volatility 59
Distillation 61
Reid Vapor Pressure Test 62
Sulfur Content 64
Corrosion Test 65
Gum Content 65
Gravity 65
Heating Values 66
Gasoline Additives 67
Diesel Fuel Tests and Their Significance 67
Cetane l'\umber 69
Heating Value of Diesel Fuel 72
Viscosity 72
Carbon Residue 72
Flash Point 72
Pour Point and Cloud Point 73
Ash Content 73
Diesel Fuel Additives 73
Alternate Fuels 74
5 ENGINE DESIGN 77
Engine Design-General 78
Stroke-to-Bore Ratio 78
Crankshafts and Firing Orders 80
Tractor Engine 82
Valve Design 83
Valve Materials, Design, and Application 85
Valve Timing 87
Valve Clearance Adjustment 90
Valve Seats 91
Valve-Opening Area 91
Cams 93
Combustion Chamber Design 94
Effect of Compression Ratio 94
Piston Crank Kinematics 95
Inertia Force of Connecting Rod 98
Inertia Force of Single-Cylinder Engines 100
Crank Effort 101
Flywheels 102
Balance of Single-Cylinder Engines 104
Balance of M ulticylinder Engines 106
Principles of CI Engine Operation 110
Construction of Diesel Engines III
Combustion Chamber Design 112
Fuel-Injection Systems 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
Vlll CO~TE~TS
Classification by Service 193
Cniversal Tractor Oils 194
Oil Additives 194
Journal Bearing Design 195
Oil Contamination 198
Oil Filters 199
Lubricating Oil Systems 201
9 HUMAN FACTORS IN TRACTOR DESIGN 203
Operator Exposure to Environmental Factors 203
Operator Exposure to Noise 206
Operator Exposure to Vibration 210
The Operator-Machine Interface 214
Noise and Vibration Control 216
Operator Seating 21i
Sound Control in Operator Enclosures 224
Spatial, Visual, and Control Requirements of the Operator 226
Rollover Protection for Wheeled Agricultural Tractors 231
Thermal Comfort in Operator Enclosures 233
Safety 234
10 TRACTION 240
Traction Mechanics 240
Mohr-Coulomb Failure Criteria 240
Traction Performance Equations 243
Traction Prediction from Dimensional Analysis 24i
Performance of Four-Wheel, Tandem, and Dual Tires 254
Tire Size, Load, and Air Pressure Relationship 25i
Radial-Ply Construction 258
Tread Design 259
Effect of Lug Spacing 263
Traction Improvement 263
Tracks 265
Tire Testing 265
Traction Devices for Paddy Fields 265
11 MECHANICS OF THE TRACTOR CHASSIS 272
Simplifying Assumptions 2i2
Equations of Motion 2i3
Static Equilibrium Analysis-Force Analysis 2i8
Static Equilibrium Analysis-Maximum Achievable Drawbar Pull 280
Static Equilibrium Analysis-Four-Wheel-Drive 282
Longitudinal Stability 283
The Tractor as a 2-Degree-of-Freedom Vibratory System 285
Transient and Steady-State Handling 289
Lateral Stability in a Steady-State Turn 295
Three-Dimensional Static Analysis 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 CONTENTS
Power Estimating-Field Method 415
Air-Supply Measurement 416
Engine Pressure Indicators 418
Fuel Flow Meter 420
The Nebraska Tractor Tests 420
Globalization of the Tractor Industry 432
Correction for Atmospheric Conditions 433
Torque Curves 435
Engine Performance 435
Efficiency of Tractor Engines 435
Actual Power Output and Fuel Consumption 436
Tractor Reliability 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
