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During wet weather operating conditions, tire hydroplaning can occur, potentially altering the handling characteristics of a vehicle. The rear tires of the vehicle run in a path previously cleared by the front tires under some operating conditions. Although path clearing has been previously demonstrated both analytically and qualitatively, it is difficult to estimate the changes in the tire/road coefficient of friction resulting from path clearing because of the complexity of the hydroplaning flow regime. In the present work, we utilize wheelspeed information captured from the vehicle CAN bus and photography to examine potential variations in tire/road coefficient of friction that result from path clearing. Results suggest that differences in friction availability may result from such path clearing. Maneuvers performed include steady-state cornering tests, straight-line braking and ISO lane change maneuvers.

Many vehicles are equipped with independent suspension systems on the front and/or rear axle. As opposed to a DeDion or beam axle, independent suspension systems have the potential to generate camber and toe changes as the suspension strokes from full jounce to full rebound. Each vehicle suspension design presents unique camber and toe curves to the tire. To improve handling, manufacturers often set static camber on such vehicle suspension systems to nonzero values so that when cornering, the outside suspension will deflect so as to maximize cornering power and vehicle stability. Then, under straight driving conditions, the tires tend to predominantly wear their inside shoulder edges, producing the phenomenon known as camber wear.

We employ theoretical and experimental means to examine driver control strategies for use in emergency brake-and-steer maneuvers using ABS-equipped vehicles, and show that the admonition to simply “stand on the brakes” does not necessarily produce the desired vehicle response because the full maneuver envelope of the vehicle is not utilized. Rather, judicious use of vehicle braking in its non-ABS mode is preferred for portions of some maneuvers where maximum lateral control is desired.

Many modern vehicles utilize so-called “space-saver” spare tires. Such tires are not fitted to the vehicle and driven on until a tire problem has arisen with a service tire, and are limited in the mileage and speed at which they can operate. They also may have quite different characteristics (rolling radius, tread pattern, contact patch width and length, aspect ratio, stiffnesses, self-aligning torques, etc.) than the service tires with which the vehicle is equipped. As such, they have the potential for presenting significantly different handling signatures to the driver when they are fitted.. In the present work, we present force and moment characteristics for two disparate space-saver spare tires. The tires were tested at the T.I.R.F. (TIre Research Facility), Calspan Corporation, Buffalo, NY.

Hydroplaning behavior of a single tire running in stationary, undisturbed water of constant depth is a well-studied phenomenon, and has been examined both theoretically and experimentally. Most experimental tire studies have been conducted on drum or flat-track test machines or with towed tires, and correlative expressions for hydroplaning of a single tire have been developed from such tests. Vehicle testing, on the other hand, has typically involved full-scale, proving ground experiments in which gross vehicle motion and behavior were of interest without regard to individual tire contributions. In the present work, we examine the behavior of a vehicle with rear tires running in a path partially cleared by the front tires. Under such conditions, it can no longer be assumed that the rear tires are experiencing the same hydrodynamic conditions as the front tires, nor does their behavior correlate well with conditions obtained from individual tire testing.

In the present work, we study motorcycle dynamics under conditions where the motorcycle-rider combination encounters either a step or a channel parallel to the direction of travel. Analyses are presented from the points of view of geometric, analytical and experimental approaches. As with passenger cars and trucks which encounter so-called “edge drop-offs,” the results depend on the magnitude and shape of the step or channel, velocity of the motorcycle and control input(s) of the rider, if any. Results show than for many common disturbance situations, difficulties may be experienced by the rider.

The subject of qualitative and quantitative evaluation of vehicle handling has received emphasis and study since the first automobiles were constructed. Handling quality can be divided into three distinct regimes: (a) resistance to rollover, (b) steady-state behavior, and (c) transient behavior. Additionally, handling of a modern race car can and often must also be separated into handling characteristics due to mechanical grip and characteristics due to aerodynamic performance. For modern racing cars, rollover solely due to lateral acceleration is unlikely except for a few specialized types of racing cars (e.g., Bonneville). In the present work, we discuss handling from the perspectives of human control performance, vehicle metrics and handling test development. We show that from the point of view of the human operator, certain vehicle characteristics are important if emergency and high-g handling maneuvers are to have a chance of being properly executed by drivers.

Speed trials have been conducted on the Bonneville Salt Flats for more than 50 years. In many ways, land speed racing represents the ultimate in freedom, ingenuity and creativity for engineers and constructors. Most of the rules associated with the various classes (and there are literally hundreds of classes) are safety-related, while the rules associated with the design and construction of the vehicle itself are extremely free, with streamliner and lakester classes being the most uninhibited of all. This freedom of design leads to widely disparate attempts to solve the Bonneville riddle. To successfully race at Bonneville requires the engineer to possess expertise in a number of aspects of vehicle design and construction rarely seen in other forms of racing competition. We begin with an overview of the nature of land speed racing competition, and continue to a discussion of the engineering aspects and fundamental requirements of car design and behavior.

A number of simplistic formulae, based on particle dynamics, energy, and momentum methods are routinely employed by accident reconstructionists to calculate vehicle speeds immediately prior to impact. It is almost always the case that scene evidence and other information regarding important variables involved in such equations must either be estimated or can be measured only in an approximate way. In the present work, we examine the sensitivity of such standard calculations to variations in the measured or estimated values of the independent variables needed for calculation. The traditional methods of the calculus are employed. Example problems illustrate the difficulties faced by accident reconstructionists as they grapple with incomplete and/or estimated values for important variables, and with the inherent sensitivity of some of the calculations to seemingly small variations in variable magnitudes.

The very high speeds achieved by IndyCars at the 1992 Indianapolis 500-Mile Race and practice have led to a complete reconsideration of the safety implications involved in the sport. The present work describes calculations performed in order to totally redesign and reconstruct the outer concrete retaining wall and fence structure at Indianapolis Motor Speedway (IMS), to ensure spectator safety. Car capabilities were first examined to ascertain energies involved in realisticcollisions with the wall at racing speeds. A series of practice and race accidents was examined via frame-by-frame video analysis, and further calculations performed to refine energy calculations. Calculations and actual accident analyses indicate that a substantial amount of kinetic energy is lost before car-to-wall impact can occur through aerodynamic drag and tire scrub. Wall strength requirements and estimates of impact forrealistic car speeds, spectator visibility and construction were also computed.