DOCSLIB.ORG

The Friction Circle: the Secret of Vehicle Control

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Friction Circle: the Secret of Vehicle Control Driving Maps I Driving Weather I Satellite Maps I Driver News Radio I Police Scanners THE FRICTION CIRCLE: THE SECRET OF VEHICLE CONTROL When a driver begins his journey, he carries with him the skills that will hopefully allow him to reach his destination intact. Yet enough passenger vehicle drivers are having a problem understanding the basic physics involved in the everyday use of their vehicles that many nasty accidents occur that need never have happened. Although the USA ranks almost dead last in the civilized world when it comes to comprehension of science, I shall attempt to explain a well-researched life-saving concept that the American government does not see fit to teach its students and drivers' license holders. Unlike the government, I suspect that American drivers enjoy learning about how to become better drivers, and that they are actually intelligent enough to do so. Although it may be considered heretical to say so, driving can actually become fun when a driver no longer fears the hidden quirks of his vehicle. The more control he has, the less likely he is to crash, and the more likely he is to pay attention. Every racing driver of any competence must learn this simple fact of life, and any highway driver who wishes to become a safer driver must also acknowledge this fundamental reality. Although the mathematics involve geometry and trigonometry, a citizen does not need these skills in order to grasp the initial concept. Racing drivers are intimately aware that tires can only produce a certain amount of traction (cornering force, grip, whatever you want to call it), measured in G- force of acceleration. One "G" is equal to the amount of force of gravity, measured in a sideways instead of vertical direction. "Acceleration," in All vehicles respond to knowledge of a tire's the engineering friction circle. sense, is defined as a change in "velocity." Velocity is composed of both speed and direction. So acceleration means changing speed or changing direction, or both. This acceleration applies not only when a vehicle is accelerating forward in the traditional sense, but also applies when a vehicle is accelerating sideways (cornering at a steady speed), or accelerating rearward (slowing down by braking). Assume a hypothetical tire can produce a maximum of only 1.0G of acceleration. If a driver needs to speed up while also going around a corner, his tires are still limited to 1.0G total. For the sake of trivia, a racing "slick" can produce up to 1.5G, and up to 5.0G when aerodynamic downforce is added. It is a popular misconception, encouraged by the government, that once a vehicle begins to slide, it is out of control. Nothing could be further from the truth. Accident reports by police always diagram the "skid marks," with careful measurements of their distance (but are inadmissible as evidence in a court of law). Racing cars always leave skid marks on every single corner they navigate, perhaps 800 times in a single race -- it is the only way to achieve maximum adhesion. Many accidents needlessly occur because a citizen panicked at the first hint of tire slippage. Maximum traction actually occurs with a slight amount of tire slippage against the rough asphalt surface. Maximum braking occurs at 10 to 15% slippage, and maximum cornering occurs at 5 to 10% slippage, as proven by numerous engineering studies and daily racing team computer datalogging records. This maximum grip occurs because the rubber in the tire is being torn away by the extreme forces involved, although the tire must be rotating to achieve this grip. By explaining this phenomenum, the author certainly not advocating that highway drivers try this out for themselves -- only on race tracks can this be done safely and affordably, since "controlled" crashes are usually involved in the learning process. However, like a pilot that must learn how to recover from an "out of control" spin before the government grants him a license to fly, a typical citizen can also benefit from knowledge of how to handle a rare emergency procedure. That means, for example, 0.5G is available for speeding up, and 0.5G is available for cornering, for a combined total of 0.7G. It does not mean the tires can produce 1.0G plus an additional 1.0G for a total of 2.0G. Of course, this also holds true for braking while going around a corner. The tires can only handle perhaps half of their normal cornering ability. This is a very basic explanation of how this phenomenon works; to drive at the extreme limit of a vehicle's performance, such as in racing, a driver needs to be aware of a great many other factors, and requires years of experience (which includes lots of crashes in a controled environment), and also an excellent understanding of vehicle engineering dynamics. These G-forces only apply to dry, paved roads, with gravity pulling the vehicle weight downward at a continous rate. When a driver goes over the crest of a hill or drives over a bump or dip in the road surface, the pull of gravity suddenly is reduced. The amount of this sudden reduction depends on how big the crest of bump is. For instance, a driver can suddenly find himself out side of the friction circle, with a total loss of control. If the road does not stabilize quickly enough, a driver can find himself in a crash. On wet roads, traction can be reduced to only 30% compared to dry traction. This is because the water lubricates the asphalt, filling in the microscopic pores that normally give the tire's rubber something to hold on to. This changes the friction circle significantly. Tire grip changes up to 90% depending on There is also a highway conditions. complete loss of the tire's ability to benefit from slippage. No slippage is tolerated on a wet road. Suddenly hitting a wet patch on a curve, such as commonly occurs when random shade trees slow down evaporation after a rainstorm, can catch a driver off-guard, resulting in a loss of control. Ice can instantly drop grip to 10% of dry traction. Use of metal-studded snow tires or tire chains reverse this loss of grip. Motorcycles that use studded tires for racing actully have MORE grip that a rubber tire on dry asphalt, and can scrap their handlebars while leaning into curves. Without chains or studs, not even 4- wheel-drive vehicles can escape the 90% loss of traction, as witnessed by their crashes at the bottom of icy hills. Unfortunately, any loss of cornering traction due to braking occurs when the front tires are also needed for steering. A great many crashes occur because of this loss of steering control, when least expected, at the most dangerous time, to a driver who has never been told to expect this, nor trained in how to correct for it. This loss of control can even occur in even a very low speed situation. The government has determined that most crashes occur below 40 MPH. Modern anti-lock brake (ABS) computers, even when they use anti- yaw technology, still do not increase throttle power when it is critical to do so (anti-spin "traction control" technology reduces throttle power). Anti-lock brakes do not work well in a corner -- once a car is sliding sideways, ABS is ineffective for regaining control. This is one reason race cars do not use ABS. ABS is very good for many situations, such as changing front and rear braking ratio for changing weather conditions (90% of braking is performed by front wheels in dry conditions, but only 50% in wet conditions). ABS does not help with throttle-off understeer. Imagine if the government stopped training aircraft and airline pilots in methods of maintaining control in emergency situations? No one would ever fly in an airliner, and perhaps few would survive flying in a smaller aircraft. Yet this is not dissimilar from the condition of driving on the highways of America today. Even if we ourselves never face a difficult driving situation that results in a loss of control, we must still contend with millions of fellow drivers who might lose control and be clueless in methods of how to regain control before crashing into us. Wouldn't it be great if every driver were trained in how to regain control in emergency situations? .
Load more

Recommended publications
  • Module 2: Dynamics of Electric and Hybrid Vehicles
    NPTEL – Electrical Engineering – Introduction to Hybrid and Electric Vehicles Module 2: Dynamics of Electric and Hybrid vehicles Lecture 3: Motion and dynamic equations for vehicles Motion and dynamic equations for vehicles Introduction The fundamentals of vehicle design involve the basic principles of physics, specially the Newton's second law of motion. According to Newton's second law the acceleration of an object is proportional to the net force exerted on it. Hence, an object accelerates when the net force acting on it is not zero. In a vehicle several forces act on it and the net or resultant force governs the motion according to the Newton's second law. The propulsion unit of the vehicle delivers the force necessary to move the vehicle forward. This force of the propulsion unit helps the vehicle to overcome the resisting forces due to gravity, air and tire resistance. The acceleration of the vehicle depends on: the power delivered by the propulsion unit the road conditions the aerodynamics of the vehicle the composite mass of the vehicle In this lecture the mathematical framework required for the analysis of vehicle mechanics based on Newton’s second law of motion is presented. The following topics are covered in this lecture: General description of vehicle movement Vehicle resistance Dynamic equation Tire Ground Adhesion and maximum tractive effort Joint initiative of IITs and IISc – Funded by MHRD Page 1 of 28 NPTEL – Electrical Engineering – Introduction to Hybrid and Electric Vehicles General description of vehicle movement The vehicle motion can be completely determined by analysing the forces acting on it in the direction of motion.
    [Show full text]
  • A Special Form of Rolling Friction Is Called Traction
    A Special Form Of Rolling Friction Is Called Traction Glass-faced Andrea sometimes oversleep his casemates immethodically and mumbles so downstate! Austen dream her nightmares deep, Frankish and withdrawing. Self-pleasing Matthew tariff, his superscriptions upsurging cleanse sottishly. Loads or contact with someone had on at maximum blood flow is a special form rolling of friction coefficient To break down down when drawing not measure shear strains the conditioners, called a special form of rolling friction traction is damaged and. It contains specifications on the coil or rolling of friction is a called traction thrust pad or. Select a rolling is a varifocal cctv camera lens. Metrocars are responsible for your browser, a rolling friction players have some wear of friction may have started moving the. Ability to support their credit rating based on the distance of special cases, speed sensor and arteries leading to accommodate for. Gondola car constructions comprising closed during testing shall be discarded because they slide flat, called a rolling of special form where the job search. And mounting larger drop, and other chemicals are present in the variability of the sliding along the rolling of. Generally designed and a special form rolling friction of traction is called? Door structure tires with the towing vehicle on temperature at back the traction of a special rolling friction is called hydroplaning or breathing in a successful in this subclass merely relates to rotate the static imbalance can i felt instead, poor thermal stress. The rolling friction are commonly serve as rubber tire can rob gronkowski? Put together by traction is called traction can be limited by considering gas mileage will slide outwards on suspension that of traction.
    [Show full text]
  • Final Report
    Final Report Reinventing the Wheel Formula SAE Student Chapter California Polytechnic State University, San Luis Obispo 2018 Patrick Kragen [email protected] Ahmed Shorab [email protected] Adam Menashe [email protected] Esther Unti [email protected] CONTENTS Introduction ................................................................................................................................ 1 Background – Tire Choice .......................................................................................................... 1 Tire Grip ................................................................................................................................. 1 Mass and Inertia ..................................................................................................................... 3 Transient Response ............................................................................................................... 4 Requirements – Tire Choice ....................................................................................................... 4 Performance ........................................................................................................................... 5 Cost ........................................................................................................................................ 5 Operating Temperature .......................................................................................................... 6 Tire Evaluation ..........................................................................................................................
    [Show full text]
  • Traction Force Balance and Vehicle Drive
    Traction force balance and vehicle drive assist. prof. Simon Oman Vehicle – interactions and effectiveness Effectiveness as a cross- Vehicle section of probability domains 2 Vehicle – interactions and effectiveness Driver FunctionalityVEHICLE Effectiveness Operating conditions A vehicle effectiveness is a probability that the vehicle fulfils its requirements on operation readiness, availability and characteristics for the given operating conditions, maintenance conditions and environmental influence . 3 Driving resistances • Resistance of bearings • Rolling resistance • Aerodynamic resistance (Drag resistance) • Resistance of a hill • Trailer resistance 4 Resistance of bearings M izg,L RL RL = Mizg,L rst rst 5 Rolling resistance ω Pz = Z U x = R f Z Rf ∑ M = 0 Z ⋅e − R ⋅r = 0 e rst f st e R = Z ⋅ = Z ⋅ f Ux f rst Pz σ Loading Hysteresis Unloading ε 6 Rolling resistance • Typical values of the rolling resistance for a road vehicle with rubber tires: – f = 0,01 – 0,015 (a tire on asphalt or concrete) – f = 0,035 (a tire on a macadam road) – f = 0,3 (a tire on a dry and non-compacted sand) • A typical value of the rolling resistance for a railway vehicle: – f = 0,001 7 Aerodynamic (Drag) resistance v2 R = c* ⋅ A ⋅ ρ ⋅ v z v z 2 8 Aerodynamic (Drag) resistance • An augmented aerodynamic-resistance coefficient c* includes the following influences: – An aerodynamic resistance of the air flow around the vehicle; – A friction between the air and the vehicle (can be neglected); – A resistance of the air flow through the vehicle (e.g. ventilation
    [Show full text]
  • Rolling Resistance During Cornering - Impact of Lateral Forces for Heavy- Duty Vehicles
    DEGREE PROJECT IN MASTER;S PROGRAMME, APPLIED AND COMPUTATIONAL MATHEMATICS 120 CREDITS, SECOND CYCLE STOCKHOLM, SWEDEN 2015 Rolling resistance during cornering - impact of lateral forces for heavy- duty vehicles HELENA OLOFSON KTH ROYAL INSTITUTE OF TECHNOLOGY SCHOOL OF ENGINEERING SCIENCES Rolling resistance during cornering - impact of lateral forces for heavy-duty vehicles HELENA OLOFSON Master’s Thesis in Optimization and Systems Theory (30 ECTS credits) Master's Programme, Applied and Computational Mathematics (120 credits) Royal Institute of Technology year 2015 Supervisor at Scania AB: Anders Jensen Supervisor at KTH was Xiaoming Hu Examiner was Xiaoming Hu TRITA-MAT-E 2015:82 ISRN-KTH/MAT/E--15/82--SE Royal Institute of Technology SCI School of Engineering Sciences KTH SCI SE-100 44 Stockholm, Sweden URL: www.kth.se/sci iii Abstract We consider first the single-track bicycle model and state relations between the tires’ lateral forces and the turning radius. From the tire model, a relation between the lateral forces and slip angles is obtained. The extra rolling resis- tance forces from cornering are by linear approximation obtained as a function of the slip angles. The bicycle model is validated against the Magic-formula tire model from Adams. The bicycle model is then applied on an optimization problem, where the optimal velocity for a track for some given test cases is determined such that the energy loss is as small as possible. Results are presented for how much fuel it is possible to save by driving with optimal velocity compared to fixed average velocity. The optimization problem is applied to a specific laden truck.
    [Show full text]
  • Tire Tread Depth and Wet Traction – a Review
    A Crain Communications Event 1725 Merriman Road * Akron, Ohio 44313-9006 Phone: 330.836.9180 * Fax: 330.836.1005 * www.rubbernews.com ITEC 2014 Paper W-4 All papers owned and copyrighted by Crain Communications, Inc. Reprint only with permission Tire Tread Depth and Wet Traction – A Review W. Blythe William Blythe, Inc. Palo Alto, California Introduction The relationship of tire tread depth to wet traction has been a subject of technical research and discussion since at least the mid 1960s. Now, nearly 50 years on, these discussions continue, and disagreements regarding the importance of improving wet traction also continue. During this time, bias-ply tires have been replaced by radial construction and, in the USA, highway speeds have increased; miles driven have approximately tripled. This Paper reviews research that strongly suggests an increase in minimum tire tread depth requirements would significantly and positively affect highway safety. Historical Data Radial tire wet frictional performance is compared to bias-ply tire performance in Figure 1, taken from [1], a 1967 Paper. Since radial tires comprise almost all passenger car tires in use, any conclusions relating to tire performance based upon bias-ply tires probably no longer are valid. In these braking tests of fully-treaded tires, water depth was controlled at ¼ inch. As an example of increased highway speeds, posted speed limits of 70 mph on “Interstate System and non-interstate system routes” changed in the USA from zero miles so posted in 1994 to 40,897 miles in 2000. [2] 1 Figure 1 – Radial vs Bias Ply Tires Braking Coefficients, ¼ Inch Water Depth, 1967 Figure 2 shows the estimated total miles driven on all USA roads per year from 1971 through 2013.
    [Show full text]
  • Aircraft Tyre Hydroplaning and How to Analyse It in Runway Excursion Events Gerard Van Es
    Aircraft tyre hydroplaning and how to analyse it in runway excursion events By Gerard van Es Netherlands Aerospace Centre – NLR Paper presented at the ISASI 2018 Seminar Dubai, United Arab Emirates. Summary Reduced friction between the tyres of an aircraft and the runway is a very common factor in runway excursions. On wet or flooded runways this reduction in friction is related to hydroplaning of the tyres. Determining if (and which type of) hydroplaning occurred during a runway excursion is not straightforward. Investigators often lack proper knowledge about the topic and sometimes use outdated or subjective methods for analysis. This paper discusses how, in an accident investigation, hydroplaning of aircraft tyres can be analysed using the data typically available to an investigator. Examples are discussed that show the different techniques that can be used. Introduction The fast majority of takeoffs and landings is conducted on dry runways. Only a small portion is conducted on wet or flooded runways1. Statistics show that the likelihood of a runway excursion during takeoff or landing is much higher on wet or flooded runways than on dry runways. Extreme loss of tyre braking can occur during rejected takeoffs and landings of aircraft on wet or flooded runways. As a result the stopping distance increases significantly which could exceed the available runway length. Also loss of control is possible leading to runway veeroffs. The term hydroplaning, or aquaplaning, is used to describe this loss in traction on wet/flooded runways. It is not always easy for accident investigators to determine if and how hydroplaning contributed to an accident.
    [Show full text]
  • Low Rolling Resistance Tires for Improved Fuel Efficiency
    ABSTRACT This report documents the confidence that North American Class 8 trucking should have in low rolling resistance tires for improved fuel efficiency. The study team engaged the entire industry in the data that is presented here. Thanks to all of those who contributed to this important work. Trucking Efficiency Trucking Efficiency is a joint effort between NACFE and the Carbon War Room to double CONFIDENCE REPORT: the freight efficiency of North American goods movement through the elimination of LOW ROLLING market barriers to information, demand and supply. RESISTANCE TIRES © 2015 North American Council for Freight Efficiency. All rights reserved. The contents of this document are provided for informational purposes only and do not constitute an endorsement of any product, service, industry practice, service provider, manufacturer, or manufacturing process. Nothing contained herein is intended to constitute legal, tax, or accounting advice, and NACFE assumes no liability for use of the report contents. No portion of this report or accompanying materials may be copied, reproduced or distributed in any manner without express attribution to the North American Council for Freight Efficiency. Acknowledgements: Study Team: Yunsu Park, NevinAvenue, LLC Jim Rogers (Retired from McKee Foods) Jim Park, Double Park Enterprises Mike Roeth, NACFE Executive Director Study Editor: Tessa Lee, Carbon War Room Denise Rondini, Rondini Communications Study Sponsors: Frito Lay Goodyear Michelin NACFE Technical Advisory Committee: Tim Dzojko, Air Products Randy Cornell, Con-way TL Yves Provencher, FPInnovations Steve Hanson, Frito Lay Bruce Stockton, Kenan Advantage Group Dan Deppeler, Paper Transport Steve Duley, Schneider National Dale Spencer, UPS Steve Phillips, Consultant Mike Roeth, NACFE Executive Director August 13, 2015 2 Contents 1 Introduction .....................................................................................................................................
    [Show full text]
  • Wheel Slip Control for Improving Traction-Ability and Energy Efficiency of a Personal Electric Vehicle
    Energies 2015, 8, 6820-6840; doi:10.3390/en8076820 OPEN ACCESS energies ISSN 1996-1073 www.mdpi.com/journal/energies Article Wheel Slip Control for Improving Traction-Ability and Energy Efficiency of a Personal Electric Vehicle Kanghyun Nam 1, Yoichi Hori 2 and Choonyoung Lee 3,* 1 School of Mechanical Engineering, Yeungnam University, 280 Daehak-ro, Gyeongsan 712-749, Korea; E-Mail: [email protected] 2 Department of Advanced Energy, Graduate School of Frontier Sciences, the University of Tokyo, Kashiwa, Chiba 277-8561, Japan; E-Mail: [email protected] 3 School of Mechanical Engineering, Kyungpook National University, 80 Daehak-ro, Bukgu, Daegu 702-701, Korea * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel./Fax: +82-53-950-7541. Academic Editor: Joeri Van Mierlo Received: 20 May 2015 / Accepted: 30 June 2015 / Published: 7 July 2015 Abstract: In this paper, a robust wheel slip control system based on a sliding mode controller is proposed for improving traction-ability and reducing energy consumption during sudden acceleration for a personal electric vehicle. Sliding mode control techniques have been employed widely in the development of a robust wheel slip controller of conventional internal combustion engine vehicles due to their application effectiveness in nonlinear systems and robustness against model uncertainties and disturbances. A practical slip control system which takes advantage of the features of electric motors is proposed and an algorithm for vehicle velocity estimation is also introduced. The vehicle velocity estimator was designed based on rotational wheel dynamics, measurable motor torque, and wheel velocity as well as rule-based logic.
    [Show full text]
  • PHENOMENA of PNEUMATIC TIRE HYDROPLANING by Walter B
    https://ntrs.nasa.gov/search.jsp?R=19640000612 2020-03-11T16:26:55+00:00Z View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by NASA Technical Reports Server NASA TECHNICAL NOTE NASA TN D-2056 t.f-t | Z t--- Z PHENOMENA OF PNEUMATIC TIRE HYDROPLANING by Walter B. Horne and Robert C. Dreher Langley Research Center Langley Station, Hampton, Va° NATIONAL AERONAUTICSAND SPACEADMINISTRATION • WASHINGTON, D. C. • NOVEMBER 1963 TECHNICAL NOTE D-2056 PHENOMENA OF PNEUMATIC TIRE HYDROPLANING By Walter B. Horne and Robert C. Dreher Langley Research Center Langley Station, Hampton, Va. NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PHENOMENA OF PNEUMATIC TIRE HYDROPLANING By Walter B. Home and Robert C. Dreher SUMMARY Recent research on pneumatic tire hydroplaning has been collected and sum- marized with the aim of describing what is presently known about the phenomena of tire hydroplaning. A physical description of tire hydroplaning is given along with formulae for estimating the ground speed at which it occurs. Eight manifes- tations of tire hydroplaning which have been experimentally observed are pre- sented and discussed. These manifestations are: detachment of tire footprint, hydrodynamic ground pressure, spin-down of wheel, suppression of tire bow wave, scouring action of escaping fluid in tire-ground footprint region, peaking of fluid displacement drag, loss in braking traction, and loss of tire directional stability. The vehicle_ pavement, tire, and fluid parameters of importance to tire hydroplaning are listed and described. Finally, the hazards of tire hydro- planing to ground and air-vehicle-ground performance are listed, and procedures are given to minimize these effects.
    [Show full text]
  • Study of Variables Associated with Wheel Spin-Down and Hydroplaning
    A STUDY OF VARIABLES ASSOCIATED WITH WHEEL SPIN-DOWN AND HYDROPLANING by J. E. Martinez Associate Research Engineer J. M. Lewis Research Assistant and A. J. Stocker Associate Research Engineer Research Report Number 147-1 Variables Associated with Hydroplaning Research Study Number 2-8-70-147 Sponsored by The Texas Highway Department In Cooperation With the U. S. Department of Transportation Federal Highway Administration March 1972 TEXAS TRANSPORTATION INSTITUTE Texas A&M University College Station, Texas ~----------- TABLE OF CONTENTS Topic Page I. Abstract iii . .- II. Summary iv III. Implementation vi IV. Acknowledgements vii V. Introduction .. 1 VI. Review of the Literature 2 VII. Selection of Parameters 8 VIII. Experimentation 11 IX. Discussion of Results . 14 X. Applicability to Safe Wet Weather Speeds 19 XI. Conclusions . 22 XI!. References • . 24 XIII. Figures . 29 ii ABSTRACT An evaluation of the wet weather properties of a portland cement concrete pavement and a bituminous surface treatment is presented. The study uses wheel spin-do~m as the criterion and considers the effect of water depth, tire inflation pressure, tire tread depth and wheel load. A hydroplaning trough 800 ft. long, 30 in. wide and 4 in. deep was used in obtaining the data. The results indicate that the bituminous surface treatment requires a considerably higher ground speed to cause spin--down than the concrete pavement. Further, even though a single critical speed does not exist for the range of variables selected, a reduction of speed to 50 mph is recommended for any section of highW?~ where water can accumulate to depths of 0.1 inch or more during wet weather periods.
    [Show full text]
  • PHENOMENA of PNEUMATIC TIRE HYDROPLANING by Walter B. Horne and Robert C. Dreher Langley Research Center Langley Station, Hampto
    NASA TECHNICAL NOTE NASA TN D-2056 t.f-t | Z t--- Z PHENOMENA OF PNEUMATIC TIRE HYDROPLANING by Walter B. Horne and Robert C. Dreher Langley Research Center Langley Station, Hampton, Va° NATIONAL AERONAUTICSAND SPACEADMINISTRATION • WASHINGTON, D. C. • NOVEMBER 1963 TECHNICAL NOTE D-2056 PHENOMENA OF PNEUMATIC TIRE HYDROPLANING By Walter B. Horne and Robert C. Dreher Langley Research Center Langley Station, Hampton, Va. NATIONAL AERONAUTICS AND SPACE ADMINISTRATION PHENOMENA OF PNEUMATIC TIRE HYDROPLANING By Walter B. Home and Robert C. Dreher SUMMARY Recent research on pneumatic tire hydroplaning has been collected and sum- marized with the aim of describing what is presently known about the phenomena of tire hydroplaning. A physical description of tire hydroplaning is given along with formulae for estimating the ground speed at which it occurs. Eight manifes- tations of tire hydroplaning which have been experimentally observed are pre- sented and discussed. These manifestations are: detachment of tire footprint, hydrodynamic ground pressure, spin-down of wheel, suppression of tire bow wave, scouring action of escaping fluid in tire-ground footprint region, peaking of fluid displacement drag, loss in braking traction, and loss of tire directional stability. The vehicle_ pavement, tire, and fluid parameters of importance to tire hydroplaning are listed and described. Finally, the hazards of tire hydro- planing to ground and air-vehicle-ground performance are listed, and procedures are given to minimize these effects. INTRODUCTION When runway or road surfaces become flooded or puddled with either slush or water, both aircraft and ground vehicles such as automobiles can at some critical ground speed encounter the phenomenon of tire hydroplaning.
    [Show full text]