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Vehicles running in wet conditions may experience hydroplaning of one or more tires. Hydroplaning can, and often does, change vehicle braking, acceleration and handling characteristics dramatically. Proper analysis of this behavior requires accommodating the clearing of paths for the rear tires that may result from the front tires engaging the water-coated surface first. In this work, a hydroplaning analysis is presented that examines steady-state cornering under potential hydroplaning situations and includes lateral weight transfer, tire load sensitivity and path clearing potential. The sensitivity of vehicle understeer/oversteer characteristics to path clearing and vehicle dimensional characteristics is also examined.

Coast down testing with full-scale vehicles on level and inclined roads offers an inexpensive approach to road load determination and, in particular, aerodynamic force evaluation, provided that drag component extractions can be accurately achieved under random instrumental disturbances and biased environmental conditions. Wind tunnel testing of large vehicles, especially truck/trailers, to establish their aerodynamic drag is costly and also may produce questionable results when the effects of the moving road, blockage, wake/diffuser interaction, and rotating tires are not properly simulated. On the road, testing is now conveniently and speedily carried out using GPS-based data acquisition and file storage on laptops, allowing instantaneous on-board data processing.

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 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.

The current performance of a top fuel (T/F) dragster racing car is very high. The cars can accelerate from a standing start to well over 330 mph (528 km/h) in < 4.6 seconds! The engine of a T/F dragster can make considerably more power than can be put down to the track surface. Intentional clutch slippage prevents wheelspin for most of the ¼-mile (0.4 km) standard length racing run. Even though the drive tires used are highly specialized and specifically designed for this type of racing environment, more traction is needed. To create more traction, especially during the second ½ of the run, external wings have been employed by the designers of such cars. The size and configuration of the wings is limited according to sanctioning rules. Recent wing failures and accidents have made other options for the creation of downforce appear attractive. In the present work, we consider the potential for using the shape of the car itself to create the required down-force.

For a number of years, racetrack designers have been considering various designs for energy-absorbing or “soft” walls. Moving walls, water-filled barrels, tire walls and walls coated with various materials have all been suggested or employed to varying degrees of success. In this paper, a new concept involving a series of slats placed outward from the walls is outlined. First, fundamental requirements for a soft wall design are laid down. Then the development of the slatted wall is presented, along with a series of design variables able to be adjusted for particular applications. The slats have multiple modes of energy dissipation and absorption, and calculations show that the concept has good promise. Evaluation of various design alternatives can be largely done computationally, rather than experimentally, a great advantage given the expense of full-scale barrier testing.

The various forms of professional and amateur motor sports all require barriers, fences and deceleration/run-off areas for driver and spectator safety. We examine the translational and rotational kinetic energies involved for various types of race vehicles, and present some comparisons to typical energies encountered in everyday situations. Stopping distance vs. deceleration rates are also calculated, and some simplified trajectory analyses are performed for parts potentially launched during racing accidents.

We examine the characteristics, properties and potential idealized delamination failure modes of tires in this work. Calculations regarding tire failure stresses during tire failure scenarios, as well as during normal operation, are made. The calculations, though idealized, indicate that large chassis loads can result from the idealized failures.

Vehicles running in wet conditions may experience hydroplaning of one or more tires. Hydroplaning can, and often does, change vehicle braking, acceleration and handling characteristics dramatically. Proper analysis of this behavior requires accommodating the clearing of paths for the rear tires that may result from the front tires engaging the water-coated surface first. In this work, tire overlap is calculated for vehicles in steady-state cornering maneuvers for generalized vehicle dimensions and tire characteristics.

Vehicles operating in wet conditions may experience hydroplaning of one or more tires. Proper analysis of this behavior requires accommodating the clearing of paths for the rear tires that may result from the front tires engaging the water coated surface first. An experimental program was developed to study tire/road behavior during straight line braking maneuvers on a wet surface. Wheel rpm values were measured with operating ABS via CAN bus data. The experiments allowed qualitative estimation and visualization of the effects of path clearing on rear tires.

Recent research into the phenomenon of tire hydroplaning has concentrated on the effects of possible path clearing of the rear tires by the front tires. When this occurs, the rear tire behavior and hydroplaning properties will be different from what would occur had the tire been running in an undisturbed flow field. In the present work, we modify rear tire properties to simulate the path clearing effect and utilize the SIMON/HVE suite of simulation programs with a standardized double lane change maneuver to examine path clearing potential during transient vehicle behavior.

This research compares the responses of a vehicle modeled in the 3D vehicle simulation program SIMON in the HVE simulation operating system against instrumented responses of a 3-axle tractor, 2-axle semi-trailer combination. The instrumented tests were previously described in SAE 2001-01-0139 and SAE 2003-01-1324 as part of a continuous research effort in the area of vehicle dynamics undertaken at the Vehicle Research and Test Center (VRTC). The vehicle inertial and mechanical parameters were measured at the University of Michigan Transportation Research Institute (UMTRI). The tire data was provided by Smithers Scientific Services, Inc. and UMTRI. The series of tests discussed herein compares the modeled and instrumented vehicle responses during quasi-steady state, steady state and transient handling maneuvers, producing lateral accelerations ranging nominally from 0.05 to 0.5 G's.

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.

Various mechanical and electromechanical configurations have been proposed for the recapture of vehicle kinetic energy during deceleration. For example, in Formula One racing, a KERS (Kinetic Energy Recovery System) was mandated by the FIA for each racing car during the 2011 World Championship season and beyond, and many passenger car manufacturers are examining the potential for implementation of such systems or have already done so. In this work, we examine the potential energy savings benefits available with a KERS, as well as a few design considerations. Some sample calculations are provided to illustrate the concepts.

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.

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.

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.

Traditional vehicle simulations use two methods of modeling driver inputs, such as steering and braking. These methods are broadly categorized as “Open Loop” and “Closed Loop”. Open loop methods are most common and use tables of driver inputs vs time. Closed loop methods employ a mathematical model of the driving task and some method of defining an attempted path for the vehicle to follow. Closed loop methods have a significant advantage over open loop methods in that they do not require a trial-and-error approach normally required by open loop methods to achieve the desired vehicle path. As a result, closed loop methods may result in significant time savings and associated user productivity. Historically, however, closed loop methods have had two drawbacks: First, they require user inputs that are non-intuitive and difficult to determine. Second, closed loop methods often have stability problems.

Enthusiasts, accident reconstructionists and racing personnel have always been interested in wheel torque and HP values for vehicles. Modifications to the engine and/or driveline cause factory data to be in error, and special racing engines have no such data available in any case. Engine dynamometers provide useful information, but require the engine to be removed from the car before any testing can occur. Of more interest, particularly in competition situations, is the effect of changes at the driving wheels. We focus here on a simple method of deriving rim torque and HP values from accelerometer data. The data can be acquired using nearly any sufficiently accurate accelerometer package, and the calculations involved can be done by hand or with a spreadsheet program. Unknown vehicle characteristics can be extracted from coastdown tests. Use of a chassis dynamometer is not required.