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While many composite monocoque and semi-monocoque chassis have been built there is very little open literature on how to design one. This paper considers a variety of issues related to composite monocoque design of an automotive chassis with particular emphasis on designing a Formula SAE or other race car monocoque chassis. The main deformation modes and loads considered are longitudinal torsion, local bending around mounting points, and vertical bending. The paper first considers the design of elements of an isotropic material monocoque that has satisfactory torsional, hardpoint, and vertical bending stiffness. The isotropic analysis is used to gain insight and acquire knowledge about the behavior of shells and monocoque structures when subjected to a vehicle's applied loads. The isotropic modeling is then used to set initial design targets for a full anisotropic composite analysis.

The validity and usefulness of low-complexity “fast-turnaround CFD” for motorsports design is investigated using results from three different combined experimental and CFD analyses of racing or high-speed vehicles. Analyses using both wind tunnel experiments and CFD simulations (with commercial software and moderate computing resources) found good agreement in some aspects of interest over a variety of applied situations. Key results were the ability for relatively simple CFD models to consistently predict CL in complex flows within 15-25% of experimental findings, predict the effect of design changes on flow, and accurately show qualitative flow phenomenon. However, CD values were not accurately predicted with the low-complexity simulations. Simulations were run using the commercial Fluent© 6.3 application. Experimental results were performed in the Cornell University 4 by 4 foot wind-tunnel.

Results are presented from a study on the use of Computational Fluid Dynamics (CFD) for automotive underbody design. A diffuser-equipped bluff body with endplates was examined in ground effect at varying ride heights in configurations with and without wheels. The study was performed using commercial CFD, Fluent© 6.3.26. CFD data is compared to experimental work done with similar bodies by Cooper et al. [1, 2], George et al. [3, 4], Zhang et al. [5, 6], and others [7, 8, 9]. Emphasis is made on the study of vortex structures in bluff body flow. Various mesh geometries and solvers were explored with computational models designed to operate on single-processor workstations or small networks. Steady-state solutions were modeled for all cases; boundary layers were approximated with wall functions. CFD results for lift coefficient measured within 15-25% of experimental cases, dependent on solver. Qualitative results matched well with experimentally measured flow structures.

This paper summarizes an experimental study of an isolated bluff body in ground effect and the same body with the addition of nearby non-rotating wheels. First, theoretical and experimental trends relating to ground proximity and diffuser mechanics are reviewed. Next, experimental forces and flow patterns for a body alone were found, resulting in a maximum lift coefficient of approximately 0.80. Subsequently, the addition of stationary wheels, not attached to the body, significantly diminished the downforce generation by as much as 65%. Quantitative trends as well as tuft and neutrally buoyant bubble flow observations were carried out to infer the appropriate flow physics. Specifically, it is concluded that the wheels decrease body downforce by impeding the creation of strong vortices in the diffuser, deflecting flow in a potential manner, and introducing energy dissipating wake turbulence into the diffuser.

The goal of this project was to improve the understanding of various joints available for use in high performance small-scale automotive suspensions. The data and conclusions from this effort can be more widely applied to any instance where positive motion control is required with minimal or controlled levels of friction and compliance. This project involved testing and analysis of a series of mechanical joint samples obtained from the Aurora Bearing Company. The particular joint focused on for the majority of the testing is commonly known as a rod end. Ten different samples of varying materials and construction styles were tested and compared. They were evaluated for both compliance and friction over a range of loads to approximate their behavior under normal use. This data was obtained using an Instron tension-compression machine and a selection of appropriately designed and constructed fixtures.

For many racing teams the use of Computational Fluid Dynamics (CFD) as a design tool could mean a very expensive investment. CFD analysis of the complex separated flows associated with a race car would typically require extensive resources. Through the design of aerodynamics for a Formula SAE race car, this paper illustrates the use of less extensive CFD along with the wind tunnel as a tool that reduces design time. Various meshing techniques are analyzed that do not require extensive computational resources and are fairly simple to implement. The results obtained from these methods are compared to experimental results from wind tunnel tests. For the design of wings the results show that the coefficient of lift can be predicted fairly accurately to within 10% of the experimental value, but the coefficient of drag is not predicted very well. It is also shown that the design of an effective aerodynamics package can be accomplished with these fairly simple techniques.

This paper is taken from work completed by the first author as a member of the 1999 Cornell University Formula SAE Team and discusses several of the concepts and methods of frame design, with an emphasis on their applicability to FSAE cars. The paper introduces several of the key concepts of frame design both analytical and experimental. The different loading conditions and requirements of the vehicle frame are first discussed focusing on road inputs and load paths within the structure. Next a simple spring model is developed to determine targets for frame and overall chassis stiffness. This model examines the frame and overall chassis torsional stiffness relative to the suspension spring and anti-roll bar rates. A finite element model is next developed to enable the analysis of different frame concepts. Some modeling guidelines are presented for both frames in isolation as well as the assembled vehicle including suspension.

This paper demonstrates the methods used to design an automobile engine cooling system. Basic terminology associated with the cooling system is defined. Topics covered include the radiator, fan, and coolant. The radiator is described in detail. The advantages of aluminum over copper/brass radiators are discussed, as well as the numerous tube, fin, and core designs of automobile radiators. Finally, experimental methods used in radiator and cooling fan selection are discussed. The experimental methods include dynamometer testing and the development of radiator/fan pressure drop vs. volumetric flow rate curves. Experimental data for radiator/fan curves of a typical racing car cooling system are presented. In addition, analytical techniques used to determine the maximum cooling capacity of radiators used for the Comell University Formula SAE Racing Car Team 1996 are described.

The transmission of sound through automotive glazing materials was investigated. The sound transmission loss in one-third octave bands of several different automobile windows was measured at a testing laboratory. The materials tested included monolithic (single-layer) glass, monolithic polycarbonate, and a double glazing with an air gap in between the two panes. The experimental data are given in the paper. Subsequently, a computer spreadsheet program was written and developed to predict the sound transmission loss of single-layer glazing materials, using empirical equations found in the literature. The predicted sound transmission loss values showed good agreement with the experimental values. The sound transmission loss spreadsheet is a useful, easy-to-use tool to predict the acoustic performance of automobile window glazing materials.

The transmission of aerodynamically-generated noise through panels in automobiles has become of more pressing interest in recent years. As automobile engines, transmissions, and tires have become quieter, wind noise has become more noticeable, particularly at higher speeds. Hence, an automobile manufacturer would like to know how to design the automobile to minimize the wind noise levels heard by the passengers. In this investigation, both experimental and analytical methods were applied to the problem. A simplified model of an automobile side window was subjected to wind tunnel tests. The effects of window thickness and edge conditions on the transmitted wind noise level were investigated. An attempt was made to analytically predict the transmitted noise level by using a simple Statistical Energy Analysis (SEA) model, which used an empirical expression for the fluctuating wall pressure on the window of an automobile.

As engine, tire, and other automobile noise is reduced and as driving speeds increase, aerodynamic noise sources on ground vehicles are becoming relatively more important. They often dominate at cruise speeds of 65 mph. Aspiration and leak noise are strong sources but generally can be controlled by known methods. Turbulent pressure fluctuations due to separated and vortical flows are also strong sources. Much interior noise is caused by transmission of these external pressure fluctuations through windows and other surfaces. The paper presents the variety of aeroacoustic sources on automobiles and reviews the state of experimental data, of analysis methods, and noise reduction principles. A new correlation method for predicting external fluctuating pressures in separated regions is presented.

As engine, tire, and other automobile noise is reduced and as driving speeds increase, aerodynamic noise sources on ground vehicles are becoming relatively more important. They often dominate at cruise speeds above 60 mph. Aspiration and leak noise are strong sources but generally can be controlled by known methods. Turbulent pressure fluctuations due to separated and vortical flows are also strong sources. Much interior noise is caused by transmission of these external pressure fluctuations through windows and other surfaces. The paper presents the variety of aeroacoustic sources on automobiles and reviews the state of experimental data, of analysis methods, and noise reduction principles. A new correlation method for predicting external fluctuating pressures in separated regions is presented.