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High Performance Executive Transport Design Employing Twin Oblique Lifting Surfaces

This paper presents a new Trans-Atlantic high performance executive transport suitability equipped to offer accommodation for 19 first class passengers. The unique feature of this conceptual design is application of Twin Oblique Lifting Surfaces or TOLS configuration. Minimum goals for the design included: similar maximum takeoff gross weight; satisfactory field performance; good stalling characteristics; and, competitive fuel burn qualities at high-transonic and low-supersonic speeds, i.e. M0.90–1.20, compared to contemporary M0.75–0.85 large and super-large business jets. The vehicle is to be powered by two medium by-pass derivative engines based on the BMW-Rolls Royce BR715 in an effort to maximize the likelihood of availability, ensure adequate en route performance efficiency and fulfillment of yet to be ratified Stage 4 noise compliance requirements.

Assessment of a Vehicle Concept Finite-Element Model for Predicting Structural Vibration

A vehicle concept finite-element model is experimentally assessed for predicting structural vibration to 50 Hz. The vehicle concept model represents the body structure with a coarse mesh of plate and beam elements, while the suspension and powertrain are modeled with a coarse mesh of rigid-links, beams, and lumped mass, damping, and stiffness elements. Comparisons are made between the predicted and measured frequency-response-functions (FRFs) and modes of (a) the body-in-white, (b) the trimmed body, and (c) the full vehicle. For the full vehicle, the comparisons are with a comprehensive set of measured FRFs from 63 tests of nominally identical vehicles that demonstrate the vehicle-to-vehicle variability of the measured FRF response.

A Method and Apparatus for Generating Full Vehicle Roof System Rain Noise for the Purpose of Development, Benchmarking and Interior Noise Performance Measurement

The direct excitation of a vehicle roof system by a repeatable method and the corresponding interior sound pressure level generated by that excitation can be a key characteristic of the total interior acoustic signature of a vehicle. After nine years of work and five design iterations, a test method and apparatus has been developed that exposes a vehicle to a repeatable and measurable artificial rain excitation. The test apparatus, method and performance data are reviewed. Performance data is shown for several different vehicles and roof systems.

Feasibility of Using Acoustic Room Models and Measured Sound Power to Estimate Vehicle Interior Noise

In this paper, interior noise of a heavy commercial truck was modeled with the room equation. This approach assumed that large truck cabins may be adequately modeled as a practical room as is done in architectural acoustics, where ray theory and statistical concepts are suitable, and where application of complicated wave theory may not be necessary. This simplifies computational requirements, making a semi-empirical scheme useful for timely product development. This study employed sound power measurements at thirty-four surface patches encompassing the interior cabin boundary. Each surface-patch constituted an individual interior noise source. Predicted and measured results correlated well, demonstrating the capability to estimate driver-position noise level from predicted periphery sound intensity changes.

New Developments on Glazings

Increase of size and bending of glazings, and general improvements concerning NVH, has made of glazings one of the weak points to be treated. No specific acoustic solutions existed. First question was to determine exactly concerning which problems glazings were involved, and then what and how solutions could be found. Main problems were found concerning booming noise, transmission of airborne external noise and aerodynamic noise. To dispose of good specifications concerning products, simulations had to be done and validated: finite elements code for low frequency behavior (booming and airborne), SEA and modal superposition concerning medium and high frequency (aerodynamic and airborne). This was done for monolithic and laminated glass with their shape, free-free and taking into account boundary conditions: glues, extrusion, encapsulation. The way it has been done is presented: measurements of the characteristics of components (interlayers, glues), use of FEM and FEM-BEM methods from CAD shapes, use of SEA. Validations are also presented. Problems to solve were mostly coupling between windshield eigenmodes and internal modes of the cavity excited by the engine (low frequency), and whistling due to coincidence frequency of glass concerning mostly aerodynamic noise. Solutions are found by using specific interlayer instead of standard PVB within the laminated glass, or by improving boundary conditions by using specific shapes and/or material of the joint, first defined by a specific software. Psychoacoustic criteria are used to optimize the solutions. Shape influence is also studied. Some specific studies concerning both problems are presented. Some glass solutions now exist to reduce NVH problems within cars, and/or to compensate reduction of weight, which is one main topic of car industry.

Noise and Vibration Reduction Technology in Hybrid Vehicle Development

The world's first mass production gasoline hybrid passenger car, the “Prius”, was introduced into the Japanese market in 1997. By the time it was introduced into the American and European markets in Mid-2000, its fuel consumption and exhaust emissions had been further improved while achieving superior NV performance compared with conventional vehicles with 1.5-liter engines even in these competitive markets. This paper describes NV reduction technology for problems peculiar to the hybrid vehicle such as engine start/stop vibration, drone noise and vibration at low engine speed and motor/generator noise and vibration. It also compares the overall NV performance of the hybrid vehicle with conventional gasoline engine vehicles.

Automatic Detection of Buzz, Squeak and Rattle Events

In the world of BSR (Buzz, Squeak and Rattle) testing, there is a high level of sophistication regarding the test machines employed to excite the items under test as well as the techniques used to ensure that the test is representative of real-life operating conditions. However, the object of the measurements, i.e., the identification of transient acoustic events classified as Buzz, Squeak or Rattle, is mostly a subjective procedure with classification in terms of Sound Pressure Level in dB(A) or Stationary Loudness. These “standard” metrics have proven, in general, unreliable in assessing the importance of individual transient events, and inappropriate to describe the vehicle signature from a BSR standpoint. This paper presents a methodology that has been developed for the BSR test of a vehicle using a road simulator to: 1 Demonstrate the feasibility of an automated system of detection of BSR events that can replace the “subjective” detection 2 To establish “vehicle BSR” indices that can be used to assess design targets and specifications.

Vehicle Wind Noise Analysis Using a SEA Model with Measured Source Levels

A series of tests have been performed on a production vehicle to determine the characteristics of the external turbulent flow field in wind tunnel and road conditions. Empirical formulas are developed to use the measured data as source levels for a Statistical Energy Analysis (SEA) model of the vehicle structural and acoustical responses. Exterior turbulent flow and acoustical subsystems are used to receive power from the source excitations. This allows for both the magnitudes and wavelengths of the exterior excitations to be taken into account - a necessary condition for consistently accurate results. Comparisons of measured and calculated interior sound levels show good correlation.

Condition Monitoring of a Gear Box Using Vibration and Acoustic Emission Based Artificial Neural Network

The objective of this study is to investigate and develop an Artificial Neural Network approach based on vibration and AE signals for the detection, and characterization of wear, damage, and malfunction of an experimental gearbox. Five artificial defects were introduced to the gearbox and these are; (1) tooth face wear, (2) full tooth breakage (missing tooth), (3) clearance or backlash, (5) axial gear looseness, and (5) single internal bearing race wear. The signals, collected from extensive experimentation, were analyzed using time-frequency harmonic wavelet transform, Power Spectral Density (PSD), and four statistical measures of the time domain that captured the salient features of the vibration and AE signals. The results of the time and frequency domain analysis were used in developing a neural network-based estimator for on-line monitoring of gearbox operational condition. The results strongly suggest that vibration and acoustic emission (AE) signals have tremendous promise for machine health monitoring and diagnostics. The proposed technique can be adopted for on-line monitoring of power train and Engine systems, which could be a second phase of this project.

A Comparison of NVH Treatments for Vehicle Floorpan Applications

Under the constraints of improved vehicle refinement, automotive OEMs are challenged to improve vehicle noise, vibration and harshness (NVH) characteristics, reduce vehicle weight, and streamline manufacturing and assembly processes. In support of these objectives, alternate methods of vehicle noise control are being investigated. This paper will address one area where alternate material strategies are being investigated to meet these requirements. Floorpan damping treatments are a primary component of the overall vehicle noise package. This paper will investigate three floorpan damping treatments. Comparisons will be made between asphaltic melt sheets, constrained layer dampers, and spray-on dampers. Performance of these treatments will be measured using laboratory methods and will feature a case study using a Body-In-White (BIW) to demonstrate performance of the different materials.

The Application of Direct Body Excitation Toward Developing a Full Vehicle Objective Squeak and Rattle Metric

In order to engineer Squeak & Rattle (S&R) free vehicles it is essential to develop an objective measurement method to compare and correlate with customer satisfaction and subjective S&R assessments. Three methods for exciting S&Rs -type surfaces. Excitation methods evaluated were road tests over S&R surfaces, road simulators, and direct body excitation (DBE). The principle of DBE involves using electromagnetic shakers to induce controlled, road-measured vibration into the body, bypassing the tire patch and suspension. DBE is a promising technology for making objective measurements because it is extremely quiet (test equipment noise does not mask S&Rs), while meeting other project goals. While DBE is limited in exposing S&Rs caused by body twist and suspension noises, advantages include higher frequency energy owing to electro-dynamic shakers, continuous random excitation, lower capital cost, mobility, and safety. Results show that almost all S&R issues found on the road and simulator are found on DBE. In many cases additional issues are discovered because of the lack of background noise. Initial data tends to show that using DBE to excite interior S&Rs is preferable to actual roads or to 4-post road simulators for making objective measurements.

Use of Layered Media for Noise Abatement in Automotive Interiors: A Balanced Approach

Concepts for dual density materials for usage as absorbers and decouplers are based on well-established layered media principles and have been applied for many years in non-automotive applications. Balancing the mass, air flow resistance, and thickness allows for improved noise attenuation in the low to mid frequency range which is of particular interest for automotive NVH management. Using these principles, products were tuned via mass and airflow resistance to reduce noise levels while also significantly reducing mass. Validation in various vehicles confirmed that up to a 55% reduction of a sound package's mass is possible. The considerable weight reductions of dash insulators and carpet systems are possible at the same times as the sound level in the vehicle interior is at least maintained and frequently improved. Product designs utilize non-woven fabrics and vertically and or horizontally lapped fibers to provide excellent fit and finish at low weight in an all-thermoplastic, recyclable product. Here, product development is described, which utilized computer modeling to provide a balance between transmission loss and absorption properties. Test results showing the effects of various properties on sound transmission loss and normal incidence absorption as well as in vehicle performance are given.

“Digital Prototype” Simulations to Achieve Vehicle Level NVH Targets in the Presence of Uncertainties

“Digital Prototype” simulations have been used at DaimlerChrysler to achieve vehicle level NVH objectives. The effectiveness of these simulations to guide the design when faced with vehicle parameter uncertainties is discussed. These uncertainties include, but are not limited to, material properties, material gauges, damping, structural geometry, loads, boundary conditions and weld integrity. Manufacturing and assembly processes introduce variations in the nominal values of these parameters resulting in a scatter of vehicle level NVH simulation responses. An example of a high frequency NVH concern will be studied and modified to arrive at robust design guidance when faced with uncertainty. The validity of a “deterministic digital prototype” simulation model and its relevant role as a “trend predictor” rather than “absolute predictor” tool in guiding the design is also discussed.

Development and Experimental Evaluation of a Vehicle Structural-Acoustic Trimmed-Body Model

A structural-acoustic finite-element model of an automobile trimmed-body is developed and experimentally evaluated for predicting body vibration and interior noise for frequencies up to 200 Hz. The structural-acoustic model is developed by coupling finite element models of trimmed-body structure and the passenger-compartment acoustic cavity. Frequency-response-function measurements of the structural vibration and interior acoustic response for shaker excitation of a trimmed body are used to assess the accuracy of the structural-acoustic model.

Active Noise Control and Sound Quality Design in Motor Vehicles

Interior noise in motor vehicles is essentially influenced by the engine which may contribute via both, structural and acoustic transmission paths. This engine related interior noise components may be controlled deliberately by active control measures without changing any source or transfer paths characteristics. Besides attenuating dominant noise components, the approach may equally be used to optimise interior sounds with respect to sound quality. Based on general considerations how active noise and vibration control measures may effect subjective criteria, the paper gives examples how different, sometimes extremely contrasting noise characteristics may be realised in a given car.

Safety Related Testing and Results of Polycarbonate and Tempered Glass Non-Windshield Glazing Applications

This paper presents results from a series of tests that address safety related issues concerning vehicle glazing. These issues include occupant containment, head impact injury, neck injuries, fracture modes, and laceration. Component-level and full vehicle crash tests of standard and polycarbonate non-windshield glazing were conducted. The tests were conducted as part of a study to demonstrate that there is no decrease in the safety benefits offered by polycarbonate glazing when compared to current glazing. Readers of this paper will gain a broader understanding of the tests that are typically conducted for glazing evaluation from a safety perspective, as well as gain insight into the meaning of the results.

Package Tray Optimization Using Experimental and Analytical Techniques

The area in the neighborhood of the package tray can be a significant path for road noise and exhaust noise. Air extraction routes and loudspeakers add to the difficulty of effective system design. A variety of designs were prototyped and their transmission loss measured in a standard SAE J1400 sound transmission loss suite. The performance of the various designs was compared to an untrimmed piece of sheet metal with embedded air extraction holes. The addition of trim added from 1 dB to 14 dB to the transmission loss. Statistical energy analysis (SEA) models of a variety of package tray systems will also be shown. Both of these techniques can provide design guidance at an early stage of vehicle program development.

THE WINDOWBAG: AN INNOVATION IN SIDE IMPACT PROTECTION

A new additional airbag system will provide enhanced protection in side impact collisions. The so - called Window Bag will be installed in some Mercedes cars beginning with the E-Class Sedan for the MY99 and in the new S - Class.

Dispelling the Misconceptions about Side Impact Protection

Those responsible for designing cars to meet the European Side Impact Test Procedure are tending to find it more difficult than they originally expected. The conventional wisdom has been that strengthening the car and providing padding should improve protection. However, many are finding that attempts to meet the test requirements, by reducing door intrusion or intrusion velocity, are proving ineffective. Extensive research carried out at TRL has helped to explain why strengthening the car side is ineffective. It has also given an insight into the side impact injury process and provided design guidelines which can be used to ensure that cars meet the test requirements. The difficulties experienced by car designers may explain why alternative test procedures have been suggested and proposals have been made which would reduce the severity and effectiveness of the full scale test procedure. This paper reports on the extensive research carried out by TRL, explains why the conventional wisdom was flawed, details the design guidelines and provides reasons why the beneficial use of quasi-static and component testing of doors is likely to be limited.

The Application of the Simulation Techniques to Reduce the Noise and Vibration in Vehicle Development

An overview of the analytical noise and vibration simulations performed to support the design and development of the passenger car was presented. Analytical models of the structural vehicle and acoustic cavity were developed, and several simulations related to the NVH were performed in the prototype development stage. All of the simulations were performed to minimize development time as well as to optimize the cost, weight, and performance of the NVH and the maximum frequency of these analyses is 200 Hz. The modal analysis and design sensitivity analysis of the body-in-white was performed to minimize the mass while maintaining the body stiffness by using the concept model and detailed model. Most of the subsystems such as engine mount, steering, suspension and exhaust pipe system were analyzed respectively and in the combined system for the design studies of the idle shake and high-speed wheel shake analysis. Structure-borne noise due to both road-induced vibration and engine vibration were considered. Most of the analysis was performed before prototype vehicles were tested to make the design implementation. The vehicle design cycle was reduced and the noise and vibration quality was improved by application of these simulations.

CUPOLA Environmental Control System

The Cupola Environmental Control System (ECS) has the task to ensure the required Cupola internal environment using passive and active control means, in response to the relevant applicable Cupola requirements. The ECS is subdivided into a Thermal Control Subsystem (TCS) and an Environmental & Life Control Subsystem (ECLS). The particular characteristics of Cupola design requires a non standard way to control the internal environment conditions: TCS controls the Cupola primary structures through an High Temperature water Loop (HTL) avoiding shell heaters necessity in the cold cases and representing also an heat sink for the windows assy in the hot cases; ECLS design realizes the air distribution inside the cabin volume using the gap existing between the primary and secondary structure without dedicated ducts. The major ECS functions are: to control the primary and secondary structure temperatures, to homogenize the structural walls temperature using the HTL, to prevent the condensate formation inside the Cupola, to control the Cupola Internal Pressure, to guarantee a fire protection inside Cupola, to define an air distribution concept, to support a safe, habitable, shirtsleeve environment inside the Cupola. The paper describes also the extensive analysis campaign planned to support the Cupola TCS and ECLS design and verification phases.

Subcompact Sport Vehicle Development

Considering that the sport cars versions are normally derived from medium car segment, the big challenge in this program was to transform one subcompact in a real sport car. With the focus at the consumer that looks for performance and enjoys sporty driving in conjunction with project financials and competition data the preliminary content was established together with all involved areas, Marketing, Finance, Manufacturing and Quality. Based on the items that indicate high performance, the items considered mandatory or desired by the customer and items detected by Quality research including internal indicators and external indicators, ICCD (Intensified Customer Concern Definition) and TGW (Things Going Wrong), the content was developed in three main directions towards Customer Satisfaction, I) Characterize the vehicle as a high performance car, a pure sport car with outstanding performance for power train, suspensions and brakes mainly. II) Identify the items considered mandatory by the customer for a sport car, for example. Alloy wheels, low profile tires, spoiler and rocker panel cladding, etc. III) Incorporate Quality and Durability improvements at modified or new systems. As part of the actions included at content the project objectives were established for Performance, Fuel Economy, Noise/Vibration/Harshness, Brakes, etc. These atributes was considered strategic for this product, a real sport car. With content preliminarily defined and the project strategy defined the development started with a timing plan defined with progressive phases until Job#1. The development phases consist in the verification and confirmation of product attributes with attribute and confirmation prototypes with durability and certification tests, resulting at engineering signoff and subsequent phases at production, with the 1st production prove out, and first field evaluation units and consequent production acceleration curve and the start of production.

Comparison of Performance between Several Vehicle Windshield Defrosting and Demisting Mechanisms

The safety and comfort aspects of passenger cars are significant sales argument and have become a topic of rising importance during the development process of a new car. The objective of this study is to compare the performance of several current model vehicles, highlight the drawbacks of current defrosting/demisting systems and point the way to improved passive mechanisms. The investigation is experimental. The experiments are carried out using full-scale current vehicle models. The results show that the current designs of the defroster nozzle give maximum airflow rates in the vicinity of the lower part of the windshield, which decrease gradually towards the upper parts of the windshield. This hinders and limits the vision of the driver, particularly at the top of the windshield, which can be uncomfortable and indeed dangerous.

Development and Application of an Integrated Dew Point and Glass Temperature Sensor

With the optimization of HVAC system controls for comfort, air quality and energy efficiency the potential for fogging the glass has increased. To maintain occupant safety, a method to predict when such fogging conditions exist is necessary to be able to execute proactive control corrections to prevent fogging. Windshield fog conditions are predicated on windshield surface temperature, cabin relative humidity and the reference temperature of the humidity sensor. This has driven a joint development project between Delphi Automotive Systems divisions to develop an Integrated Dew Point and Glass Temperature (IDGT) sensor. This sensor is a combination of three elements: a glass temperature sensor, a relative humidity sensor, and a humidity reference temperature sensor. Using this sensor package, the cabin dew point is calculated from the relative humidity and humidity reference temperature for comparison with the windshield glass temperature. When the windshield glass temperature drops to or is below the cabin dew point temperature, fog will form on the windshield. Utilizing this information, a proactive automatic climate control system implements corrections before the occurrence of fogging. This paper discusses the following issues concerning this new technology: Sensor design and development. A comparison between the existing technologies and the new sensor design. Vehicle / system integration of the sensor.

Integration of Fluid Flow Modelling in the Vehicles Renault Development Process

This paper presents some of Renault's knowhow in modelling aerodynamic flows obtained in an operational environment on development configurations. The methodologies, developed from Navier Stokes equations averaged for turbulence, are used indeed to size openings and body elements, determine positions and optimize the geometry of the various air inlets and outlets, reduce pressure losses in the cab ventilation circuits, improve exchanger efficiency, optimize the underhood architecture devise encapsulation solutions, model windscreen de-icing, reduce aerodynamic noise and improve the understanding of certain physical processes associated with fouling.

Conditions for Incipient Windshield Fogging and Anti-Fog Strategy for Automatic Climate Control

This paper describes a strategy, suitable for use in a climate control ATC (Automatic Temperature Controller) for predicting the onset or existence of fog (or misting) conditions and automatically taking action to avoid or reduce such conditions. Two variables currently measured by the ATC, cabin air temperature and ambient (outside) temperature are combined with cabin air relative humidity information provided by an additional sensor to allow the calculation of a degree of likelihood of windshield/window fogging. As fogging conditions are approached, a staged alteration of climate control strategy can relieve or even avoid altogether windshield fogging.

42V Design Process

Demands for new features, increasing electrical loads, and improved fuel-economy are driving development of 42V PowerNets in automobiles. Shorter design cycles, increased complexity and a focus on quality are making robust design processes a strategic advantage for competitive manufacturers. Hardware prototypes are both time-consuming and inadequate for the task of verifying performance over a broad range of operating modes, environmental conditions and part-to-part variations. This paper outlines the use of an advanced design-flow, from idea to manufacturing, for vehicle power systems. It starts with the analysis of different topologies down to the subsystem modeling of a power window system. Finally it integrates everything to a Digital Mock-Up (DMU) and analysis of the entire system. Dynamic interactions among the various supplies, converters and loads are examined. System stability and performance are assessed under normal and extreme operating conditions.

Automotive Glazing: Issues and Trends

Key current issues and future trends in automotive glazing were identified through extensive interviews of global OEM and supplier engineers. Although the performance of tempered glass has significantly improved, application of laminated glass to side and rear windows is expected to increase globally. Plastic, most notably polycarbonate (PC), glazing is also under development although the material technology has not reached a level for mass application. Incorporating multiple features and functions into glazing is another important technology development area. Needs and acceptance as to new materials and technologies vary by the automaker and the geographic market.

Use of PVB in Laminated Side Glass for Passenger Vehicle Interior Noise Reduction

Polyvinyl butyral (PVB) is used in laminated side glass on several new vehicles. One of the major benefits of PVB-laminated side glass is the reduction of interior noise. To quantify this benefit, Solutia commissioned NVH testing of an S80® passenger car from Volvo with factory-equipped laminate side glass, comparing that with factory-equipped tempered glass. The noise source was a tractor-trailer truck traveling side-by-side with the vehicle. Significant noise reduction was noted (-2-6 dB in the 2k - 6k Hz range). The dampening characteristics of the PVB laminate interlayer reduced wind noise and greatly reduced traffic noise entering the cabin. A secondary benefit is that the NVH reduction was achieved while lowering the weight of the side glass by 11%. In this paper, results of the S80 vehicle testing will be reviewed and comparisons to conventional tempered glass shown. Also discussed will be OEMs, including Audi and Peugeot, which are marketing this benefit to customers.

Comfort and Durability of Cabin of Commercial Vehicle

With the opening up of the economy and globalization in India, provision of reliable infrastructure has become a priority area in order to facilitate faster economic growth. The backbone for the economic growth is transportation. In transportation, the commercial vehicle industry plays a lion's role and hence demands urgent attention. One of the neglected areas in the commercial vehicles is its cabin. Driving commercial vehicle in India, is hard and hazardous work lasting for long hours in distant and unknown places of varying environmental conditions. In India, most often, the driver of a commercial vehicle is an employee unlike in developed countries where he is a owner driver. Further, most of the commercial vehicles supplied in India today are drive-away chassis and with the engine in the driver's compartment unlike the built-in cabins abroad. The design of the cab and the compartment of the driver and its comfort which is essential for safe driving, an area left to the whims and fancies of body builders, calls for immediate attention for improvement. This paper details many of the parameters required to be looked into such as space, ergonomic design, noise, vibration, heat, safety features, materials used in the cabin, durability, etc. This paper also compares quantitatively the above parameters between the Indian scenario and advanced design/developed countries, as well as mandatory requirements imposed by Occupational Safety and Health Act (OSHA), Bureau of Motor Carrier Safety (BMCS), Federal Highway Administration, US Department of Transportation, etc. It also suggests recommendations for the improvement of the cab as a work place. This paper also presents a case study on a detailed exercise carried out in characterisation and improvement of the vibration levels and methodology of carrying out vibration durability and structural integrity of the cab design for commercial vehicles.

Automotive Engineering International 2000-09-01

Improving lightweight vehicle dynamics Bosch engineers used numerical simulation to evaluate vehicle concepts using variable semi-active components, tire specifications, and suspension spring rates. Dr. Reitzle's prescription for Jaguar His vision for the brand is to "use top-level technology and do so in a very emotional way." Dual-voltage power networks Lear Automotive EEDS has developed an innovative electrical and electronic architecture to handle future high-power requirements in vehicles. New door closure concepts Bosch and Temic engineers are developing technologies for passive entry, vehicle immobilization, and remote control. TwinCAN: one module for two nodes The ability to use one module to control two CAN nodes provides benefits including reduced hardware and software requirements, improved functionality, and lower CPU load, according to Infineon researchers. Java for telematics Motorola engineers believe the Java framework will allow the secure deployment of infotainment services to the automobile. Car computing device analysis Unique solutions are required to match computer devices to human needs for a safer, more comfortable driving environment. Electricity builds for Convergence 2000 The automotive and electronics worlds are meshing to an ever-greater extent. Convergence 2000 provides a forum in which engineers and related professionals who populate those worlds come together to explore just how "wired" the vehicle can become.

Aerospace Engineering 2000-01-01

Simulation solves C5 cargo door problem Dynamic analysis software allows engineers to solve fatigue-related problems without prototypes. UAV development Although unmanned aerial vehicles (UAVs) have been employed successfully by the U.S. military to date, many development and operational challenges remain for these to become viable alternatives for manned aircraft. Aircraft engine testing: the test tig developer Engineers at Belcan's Advanced Engineering & Technology Division share their insights and experiences on the development of aircraft gas turbine test rigs and stands. This is the first installment of a three-part series on aircraft engine testing. Looking back at factory automation The ability to improve quality while substantially reducing the cost of production and span times is becoming a necessity to complete in today's aerospace industry. Matt Borland, Director of Production Integration on the C-17, Airlift, and Tanker programs, talked about the value that automation presented to the C-17 assembly program.

Structure Borne Sound Transmission Through a Motor Vehicle

Sound transmission at joints in a motor vehicle is studied using Statistical Energy Analysis. It is shown that transmission at edges of windows can be modelled successfully as transmission past an elastic interlayer. Coupling from the car body to the doors is modelled as transmission across a pin. Corner cross and tee joints between panels are also studied. Measurements were carried out on a motor vehicle using an impulsive noise source and results for acceleration level differences and damping are presented. The measured results are compared with results obtained using a Statistical Energy Analysis model for sound transmission, where only bending wave transmission is considered. Large acceleration level differences are measured and predicted results show good agreement. The results show that Statistical Energy Analysis techniques can be used to study structure borne sound transmission in motor vehicles.

A Multiplexing Communication IC for Automotive Body-Electronic Control

In the field of automotive body electronic control such as control of door locks, power windows, and wipers, there is a growing need of multiplexing communication to reduce the amount of wire harnesses. To meet this need, we developed a multiplexing communication protocol particularly suited to the body electronic control. Based on the developed protocol, we designed a communication control IC and a simple driver/receiver circuit with a few discrete components. The bus access method of the communication is the CSMA/CD with nondestructive bit arbitration, and its bit rate is 5 kbps. Its transmission media is a single wire. The communication IC has a multiplexing control block and a serial I/O block for an interface with a host CPU. It was fabricated using CMOS technology and has a chip of 2.6mm x 3.0mm in size that contains about 5,000 transistors. The driver/receiver circuit consists of one transistor, one capacitor and several resistors. Therefore, the cost of the circuit is quite low. This paper gives a detailed description of the design specification and features of the communication control IC and the driver/receiver circuit.

The Design Considerations of an Anechoic Chamber

There are a number of factors that dictate the size, type, and resultant over all cost of a controlled acoustical environment in which measurements can be made accurately and reliably. The type of acoustical environment is generally specified in the appropriate SAE, ISO, ANSI or ASTM standards. The purpose of this paper is to concentrate upon the design considerations of a properly engineered anechoic chamber. Anechoic is defined as “free from echoes or reverberations”. An ideal chamber would contain no reflections of sound from its walls, ceiling, or floor and an acoustical free-field condition would exist. Probably the best testing environment is outside with no boundaries to cause reflections. However, temperature, pressure, humidity, and wind can significantly and unpredictably disturb the uniform radiation of sound waves. In an ideal free-field environment, the inverse square law would function perfectly. This means the sound pressure level from a sound source would decrease six decibels for each doubling of distance from the source. For anechoic chambers to function as required to meet the various standards, a number of acoustical, mechanical, electrical, and aerodynamic considerations apply. This paper is intended to briefly address these considerations which include some, or all, of the following: Test object size Anechoic treatment selection Cut-off frequency Test object noise levels Parent room noise levels Vibration isolation Ventilation system requirements Structural requirements Physical access requirements Lighting and electrical requirements Visual requirements Housekeeping requirements RF shielding requirements

Fast Determination of Vehicle Sound Level per ISO 5130

Noise from vehicles is a major contributor to community noise. While at high speed often the pavement-tire interaction may be the predominant source, engine noise may also be significant, especially at low speeds. In some European countries most trucks, autos, and motorcycles must be tested at regular intervals per ISO 5130 (1982) “Acoustics- measurement of noise emitted by stationary vehicles- Survey method.” The standard requires a measure of the maximum emitted exhaust Fast, A-weighted sound level between a given engine RPM and an idle condition. In the past, the RPM has required a significant time to measure since it requires connecting a transducer somewhere in the engine compartment. This paper discusses an instrument that extracts the engine RPM from the acoustic signal at the exhaust, based on different engine types. This eliminates the need for a direct connection and considerably speeds vehicle tests.

Practical Applications of SEA CAE Analysis in Vehicle Sound Package Development

Vehicle sound package serves two basic functions: general acoustic insulation and local problem treatment. The former is often done at the up-front phase of the vehicle development process, and the latter at the downstream phase when representative prototype hardware becomes available and specific noise problems are identified. This paper examines the goals and key tasks of practical SEA CAE applications in the two phases of the sound package development process. Topics on CAE model requirement, typical analysis applications, and ways to improve the effectiveness of SEA applications to compliment hardware testing are discussed.

Wind Noise and Aerodynamic Drag Optimization of Outside Rear View Mirrors

Automotive outside rear view mirror shape has become an important consideration in achieving wind noise and aerodynamic performance objectives. This paper describes a two step process used to develop a mirror shape which meets both wind noise and aerodynamic objectives. First, basic understanding of door mounted verses sail mounted mirrors and shape parameters was obtained by evaluating selected shapes and studying their physical measurements relative to their measured responses. Relationships between the wind noise and drag responses revealed performance range limitations for sail mounted mirrors. Second, a central composite experimental design was utilized to more closely investigate door mounted mirror shape parameters to determine optimal mirror performance potential. The resulting empirical models developed were used to determine the best overall solution.

Development of Door Beam ERW Tubing Made of 1470N/mm2 Cold Rolled High Strength Steel Sheet

To develop ultra high strength ERW tubing for the door beams of passenger cars using cold rolled steel sheet, an FEM analysis was performed using a tubing deformation model which simulated door beam testing. In the elastic and plastic FEM analysis, the effects of the yield strength and tensile strength of the steel sheet on tubing properties were investigated. The results showed that the tubing peak load in three-point bending increases with an increase in tensile strength. An increase in yield strength enhances the endurance load in the early stages of deflection while it slightly accelerates buckling. The analysis resulted in the production of TS 1470N/mm2 grade cold rolled sheet to be manufactured into ERW tubing. A 0.22%C-0.4%Si-2.4%Mn-0.03%Nb cold rolled steel with a thickness of 2mm was processed in a continuous annealing line which employed water quenching. An ultra high tensile strength along with a relatively high yield ratio was obtained by the introduction of large amounts of tempered martensite into the microstructure. ERW tubing made from cold rolled sheet with a tensile strength of 1470N/mm2 and a yield ratio of 0.82 showed, in actual door beam testing, as high a peak load and absorbed energy as conventional induction heated and quenched ERW tubing made from hot rolled steel. These results show the potential for a more economical manufacturing process.

Clean Digital Data Acquisition With Anti-Aliasing Filters

When acquiring low-data-rate signals such as temperature, engineers sometimes forget that low-data-rate sampling does not guarantee an uncontaminated recording. Regardless of the sample rate employed in digital data acquisition, signals entering the sampler above half the sampling frequency will be reflected and added into the band below to distort and corrupt the signal of interest.

A New Optimization Approach in the Field of Structural-Acoustics

It is shown in how far modal correction techniques can contribute to reduce the CPU effort in the scope of numerical structural-acoustic investigations. Due to this technique a quasi-online interactive acoustic optimization of a basic system configuration can be achieved. In this context special focus is pointed on structural optimization aspects. Finally, the limits of validity as to the accuracy of the results obtained by the modal correction approach in the case of larger modifications are determined.

Improving Vehicle Windshield Defrosting and Demisting

This paper examines the prevailing fluid flow and heat transfer on the windshield of a full–scale vehicle and examines ways of promoting efficient de–icing and demisting. It establishes that present methods of defrosting and demisting windshields are inefficient; since the first area cleared is below the driver's eye level and even this result only occurs some considerable time after the blower has been switched on. The complexity of the windshield topography and the defroster nozzle geometry yield inadequate flow mixing, poor momentum interchange and consequently dead flow zones in critical visibility areas. This study explores ways of improving the defrosting and demisting process through passive means and using the existing air handling system of the vehicle. The results presented are from numerical simulations validated by experiment.

Acoustical Selection of Class 8 Truck Floormats

Class 8 truck manufacturers use a wide variety of materials for cab floor construction. These include traditional steel and aluminum plate as well as aluminum honey-comb and balsa wood core composites. Each of these materials has unique transmission loss properties. The acoustical performance of the floor system, (cab floor, decoupler, and barrier) depends not only on the acoustical performance of the decoupler and barrier, but also on the cab floor material. This paper outlines an experimental technique for selecting an acoustical floormat system utilizing vehicle and laboratory tests that takes these factors into account.

Squeak and Rattle - State of the Art and Beyond

Modern trends in noise control engineering have subjected the automobile to the “drained swamp” syndrome. Squeaks and rattles (S&R) have surfaced as major concerns. Customers increasingly perceive S&R as direct indicators of vehicle build quality and durability. The high profile nature of S&R has led manufacturers to formulate numerous specifications for assemblies and components. Even so, a large majority of buzz, squeak and rattle (BSR) issues are identified very late in the production cycle, some often after the vehicle is launched. Traditionally, the “find-and-fix” approach is widely adopted, leading to extensive BSR warranty bills. The “design-right-the-first-time” approach must replace the “find-and-fix” approach. Due to the vast breadth and depth of S&R issues, a comprehensive summary of the present state of the art is essential. This paper includes a literature survey of the current state of the art of S&R, and discusses the methods available to further advance it. Dedicated and focused attempts to advance the state of the art require the formulation of an integrated design strategy that attacks S&R during the earliest stages of design and development, leading to substantial savings in fix and warranty bills.

Enhanced Series of Mid-Size Agricultural Tractors

The J I Case Company recently introduced a new series of Maxxum tractors (Figure 1). The product line now offers 60, 67, 75, and 84 PTO kW versions. The all new 84 kW version features a new fuel delivery system providing both greater power and reduced exhaust emissions. The powertrain also features increased capacity components required for the reliability of the increased power, 84 kW model. The new series incorporates numerous customer requested improvements of the 5100 Series, including increased comfort, convenience, and visibility features such as swivel seat, in-cab remote coupler flow controls, fender mounted hitch controls and all glass doors.

Upper Extremity Injuries Related to Air Bag Deployments

From our crash investigations of air bag equipped passenger cars, a subset of upper extremity injuries are presented that are related to air bag deployments. Minor hand, wrist or forearm injuries-contusions, abrasions, and sprains are not uncommonly reported. Infrequently, hand fractures have been sustained and, in isolated cases, fractures of the forearm bones or of the thumb and/or adjacent hand. The close proximity of the forearm or hand to the air bag module door is related to most of the fractures identified. Steering wheel air bag deployments can fling the hand-forearm into the instrument panel, rearview mirror or windshield as indicated by contact scuffs or tissue debris or the star burst (spider web) pattern of windshield breakage in front of the steering wheel.

A Methodology for Evaluating Barriers and Aids to Vehicle Ingress/Egress

A methodology for evaluating aids and barriers to vehicle Ingress/Egress (I/E) was developed to assess subject performance with prototype features designed to improve I/E. The measures used included Perceived User Difficulty, Total Time to perform a task, and Observed Body Movements identified during video analysis of the I/E tasks. The observed movements included foot/door interference, movement discontinuity, trunk rocking, and upper extremity usage. Pilot testing of this methodology showed that subjective and objective user preference and performance data could be measured and that this information provided a more complete understanding of the problems associated with specific prototype solutions.

Current and Future Trends of Cabin Trining Simulation

Currently, the airline industry is demanding increased performance from its training staff and training systems. And today, optimal training performance depends on new technology. This challenge has led to the creation of systems that offer a broader range of cabin training solutions. One new system is the IntelliDoor™. This new system is an intelligent door training program that integrates the latest touchscreen computer technology with multi-media interaction and proven instructional methods. The result is a product that delivers consistent, precise, self-paced training without the need for constant instructor supervision.

High Precision in Car Body Manufacturing

Flexible car body production, including prototyping, is one answer to the market targets where customers ask for an increasing number of models / variants and shorter lead time. The in-house interests of car builders are, besides investment and manpower flexibility, also improved product quality. Quality in body in white is mainly related to geometry (= high precision), to make sure that the final assembly shops will have the right conditions to keep customers satisfied (flush in doors, hood, fenders etc.). The consequences are that both the product and the process equipment have to be in a stable condition to guarantee low spread in the complete car-body. CAD technology is one of the keys to reach this goal, where: Off-line tooling Off-line programming Flow simulation Measurement strategy, off-line / in-line are the main powerful tools to reduce lead time as well as costs. In the realisation phase of the new flexible body shop, in VTK / Gothenburg Sweden, new methods were used for the interaction with all process-suppliers. The co-operation at early stages was highlighted under the aspect of simultaneous engineering. The bottleneck was to find an overall measurement strategy that could be used in all phases of the project, including maintenance during later production. Geometry-wise the targets, for the complete car body, were focused on completely new demands in body-in-white history, with dimensions defined as: ≤ 0.2 mm spread in stamped parts, ≤ 0.5 mm spread in pre assembled parts, ≤ 0.7 mm spread in complete car bodies, for functional values. To reach these values, a metrological concept was developed with a Norwegian company, before the start of the project, and later implemented in our work routines as a standard tool. Process equipment from the main suppliers for the new flexible body shop was controlled geometrically by Volvo-teams with transportable Metronor systems during the three phases: Equipment assembly at suppliers site, Installation on site, Maintenance in production, using the same method of measurement. The result out of this project was that car no. 1 already showed customer quality, even if control-fixtures were not used in the flexible body shop.

Sound Quality in Cars: New Ideas, New Tools

In recent years, car manufacturers have been shifting their efforts towards improving quality of interior noise, rather than simply reducing noise levels. One of the most important issues, which is today widely accepted, is that noise contains information. Slamming noise should warn us that doors are safely closed, control panel pushbutton “clicks” inform us about the correct turning on of devices, etc.. One of the acoustic researchers' task is therefore to modify the original noise to emphasize quality of information and to reduce annoying components. For these reasons, it is very important to affect noise timbre, by investigating the relationships between mechanical and acoustical parameters. In this paper we describe a workstation (which we have called N.O.T.E.: Noise Optimizator for Thermal Engine) for intake and exhaust system noise synthesis, that integrates an acoustical simulation code with a synthesizer. By means of this flexible system, it is possible to lay out the engine acoustical model, starting from physical laws and using a few general purpose predefined blocks (such as noise sources, resonators, filters, etc.) in a CAD environment. The most important feature of the sound synthesis workstation is the possibility of changing all parameters in real time, making it feasible to “play” every kind of engine noise, before building any prototype.

Glass Drop Design for Automobile Windows - Design of Glass Contour, Shape, Drop Motion, and Motion Guidance Systems

This paper presents a new computerized approach for designing the automobile window glass contour, the glass drop motion, and the regulator systems. The three-dimensional geometrical relationship of the glass contour, the drop path, and its guidance system have been studied. Methods for barrel and helical drops are presented for optimizing the glass profile and drop path trajectories. Criteria for perfecting the glass contour are developed for shaping the profile of the vehicle clay model. Methods for correcting the glass contour and shape are presented. Examples are provided to illustrate how to improve the design. This approach integrates the development works of glass contour, drop motion and regulator systems. Through this design approach the window glass can fit and move perfectly in the door assembly.

J1850 Compliant Chip Set

The J1850 Automotive Multiplexing System is opening up new opportunities for automotive designers. Multiplexing not only reduces wiring, weight and cost; but is also adding features by sharing information among modules. For example a door module could communicate that the car is being unlocked and who is unlocking it. The body controller can use this information and tell smart seats and mirrors to adjust themselves to that driver's preferences; tell the radio to turn to a particular station and start the engine. The number of modules that are being multiplexed are increasing in both number and function. Everything from sophisticated engine controllers to simple actuator/sensor nodes are being multiplexed. The challenge with Multiplexing a large number of modules is how to make an integrated circuit that fits all their diverse needs. A complex module, like an engine controller, requires the integrated circuit to be sophisticated enough to handle all the message buffering and filtering functions. Whereas a very cost sensitive, low end module does not require the same performance. How does an IC meet the conflicting needs of an increasing number of modules? Harris Semiconductor found an answer by taking a building block approach. Harris implemented the J1850 analog and digital functions into separate integrated circuits. Doing this not only developed a flexible solution but one optimized to a degree not possible using a single integrated circuit. This article will explain how the three Harris J1850 integrated circuits (HIP7010, HIP7020 and the HIP7030) make up a flexible and cost effective solution for the J1850 Variable Pulse Width Modulation (VPW) Standard.

Designing Mobile Air–conditioning Systems to Provide Occupant Comfort

The designer of mobile air–conditioning systems must consider the total vehicle in order to provide occupant comfort. An effective refrigerant circuit is only one portion of the vehicle “Comfort System” and without the system's ability to deliver adequate cooling it will not meet the consumer's expectations. A significant considered is the design of the vehicle's body, including the panel outlets and the extent of window glazing surfaces. The location of the panel outlets to provide the occupant's adequate and controllable system airflow for changing weather conditions is a major factor in achieving comfort. Window glazing locations and areas have a major effect on increasing the air–conditioning thermal load by allowing direct solar radiation into the vehicle. Unfortunately, the styling of the vehicle dictates these areas and these constraints very often result in the customer having an air–conditioning system that provides an unsatisfactory level of performance. This paper provides an overview of some areas that are not always given adequate consideration during development of a new vehicle and its air–conditioning system.

Geometries of Simple Hinges Hidden by Flush Contoured Surface Doors

Doors are very important parts of transportation products as exemplified by the large number of them. In addition to doors for occupants to enter and exit there are doors for access to engine, cargo, luggage, air flow, fuel fill, etc. For transportation products, doors are usually designed to be flush with surrounding surfaces -- and most of them have hidden hinges . There are only a few mechanical alternatives to provide for the opening of doors and the use of simple pivoting hinges is predominant. There are two kinds of simple pivot hidden hinges -- in swinging and outswinging. These are named according to the initial motion of the edge of door with respect to its adjacent surface. Inswinging hinges are most prevalent for occupant entry/exit doors since they are required for most rear doors and they provide more pleasing cut line shapes for current surfaces, usually at lower cost. The door cut lines for hidden hinges which studio designers initially style on proposed products frequently cannot be achieved due to the inherent limitations. While achievable cut lines can be developed using trial -and- error methods, quicker and more reliable results together with a true understanding of the problems requires an analysis which identifies causes and simplifies their visualization. Such an analysis has led to a system for establishing the limits of surfaces and cut lines which has been named the “Volume-in- Space” method. It was developed originally for automotive occupant doors but is also applicable to other transportation items such as doors for luggage, engine, air flow, fuel, etc. as well as other pivoted parts such as convertible tops and aerodynamic suspension arms -- and even non- transportation hinged applications such as cabinets and machinery housings. As the top end view of a hinge center line for automotive occupant doors is observed, there are four basic limits to the volume in which the edge of the door must be contained. These limits are (1) the Swing-By Limit, determined by the requirement of the door swinging clear as it passes by the adjacent panel (or door) at initial movement, (2) the Molding Clearance Limit, determined by the requirement that any randomly located molding on the vehicle surface must not be contacted when the door is fully opened, (3) the Swung Limit, determined by the requirement that the door and the body parts must not contact each other when the door is swung fully opened, and (4)) the Inner Limit, determined by the most inward exterior surface possible with respect to the hinge on the door or other hardware in the door. By examining the parameters which affect each limit, projections can be made regarding ways of increasing the size of the limiting “Volume- in-Space”. Additional discussion is included on advantages for occupant entry/exit which have been gained in some products by orientating the hinge centerline at angles up to 4° from vertical. There are also opportunities for improving the door openings for both body structure and occupant entry/exit.

Advanced Materials and the Pivoting Door Reverser

HUREL-DUBOIS patented a new concept of thrust reverser in 1981 known as “the door forward reverser”. It gives numerous advantages over the conventional cascade reverser, and in particular is inherently lighter. The extensive use of advanced materials has allowed a highly competitive weight to be achieved. This paper describes the work currently under way for the pivoting door reverser for the ROLLS-ROYCE Trent engine and covers: Thrust Reverser door structure predominantly in composite. Acoustic treatment with composite sandwich. IFS design with carbon bismaleimide material This reverser will be used on MD11 and Airbus A330 aircraft.

Innovations in Design and Functionality of Acoustical Insualtion

In response to the demands of today's automotive market, advancements have been made where acoustical insulation does much more than just reduce noise. Insulators are now being manufactured to precise tolerances allowing for improved value added features, while also reducing part count and simplifying assembly. In addition, methods have been developed to reduce part weight and provide a product that is fully recyclable while maintaining superior acoustical performance.

Investigation into the Noise Associated with Airbag Deployment: Part II - Injury Risk Study Using a Mathematical Model of the Human Ear

Airbag deployments are associated with loud noise of short duration, called impulse noise. Research performed in the late 1960's and early 1970's established several criteria for assessment of the risk of impulse noise-induced hearing loss for military weapons and general exposures. These criteria were modified for airbag noise in the early 1970's, but field accident statistics and experimental results with human volunteers exposed to airbags do not seem to agree with the criteria. More recent research on impulse noise from weapons firing, in particular that of Price & Kalb of the US Army Research Laboratory, has led to development of a mathematical model of the ear. This model incorporates transfer functions which alter the incident sound pressure through various parts of the ear. It also calculates a function, called the “hazard”, that is a measure of mechanical fatigue of the hair cells in the inner ear. The repeatability of the model was examined in the present study by comparing its predictive behavior for airbag noise impulses generated by nominally identical airbag systems. Calculations of potential “hazard” made by the model were also examined for reasonableness based on mechanical and biomechanical considerations. A large number of airbag noise pulses were examined using the model. The results provide some counter-intuitive insights into the mechanism of noise-induced hearing loss from deployment of airbag systems. They also indicate that, based upon testing of feline subjects (which are believed to be a good indicator of the risk to the more susceptible segment of the human population), there could be a risk of temporary and possibly permanent threshold shifts in approximately sixty seven percent of the 1990-1995 model year vehicles from 19 manufacturers which were tested and assessed using the human ear model. A statistical estimate of the risk for the human population has yet to be quantified, but work is in progress to do so. Work is also underway to develop a pre-production airbag component test for deployment noise that component suppliers can incorporate into the design and development process. Once injury risk curves and test protocols are established, it is recommended that the ARL Human Ear Model be utilized by the automotive community as the assessment method of choice.

An Innovative Light Weight Instrument Panel Reinforcement Structure

A light weight, cost effective IP reinforcement structure with a high degree of resistance to steering wheel vibration and with a safe and efficient crash energy management has been developed by Alcoa Automotive Structures (AAS). It also demonstrates other desirable attributes like modularity for world-car platform applications and improved dimensional consistency. The design was analyzed using finite element methods (FEM) for vibration and crash performance and prototype assemblies have been tested. Results demonstrate conformance to vibration and crash response expectations. The concept demonstrates viability and benefits of Alcoa's multiple material and product form solution for IP structures. This paper describes the design and shows some of the analysis and test results

Anti-Trap Function for Electrical Power Windows

Today electrically driven windows are a standard feature in many automobiles. Further technical enhancements like express up/down or remote controlled central closing are important features for increased comfort and ease of operation. Some of these new functions cannot be implemented without inherent safety precautions to avoid the risk of being trapped and severely injured by automatically moving window panes. A sophisticated technical approach is described which solves this problem using state of the art electronics and modern software design combined to yield high cost efficiency. This patented concept is based on motor current detection. Theoretical explanations and practical results illustrate that it is superior to other approaches. Examples are shown of high volume applications currently in production.

Practical Noise and Vibration Optimization of HVAC Systems

Next to air temperature, humidity, and air quality, it is sound emission that exerts a significant impact on the driver's and passenger's comfort. Major progress in vehicle acoustics has motivated vehicle manufacturers and systems suppliers to evaluate HVAC systems no longer by their air conditioning performance alone. Sound emissions and sound quality have become additional important criteria for the development of new HVAC systems. In the initial conception phase, where systems and packaging considerations are made, acoustic optimization must begin with preliminary system studies and feasibility studies. In this phase acoustics should be based on fairly general systems specifications which describe the desired degree of acoustic comfort. In the subsequent design phase follows the specification of the acoustic goals and the optimization of the HVAC unit. Detailed analysis and optimization of air flow and blower are the common targets for improvement at this time. Finally, component optimization starts with including the detailed design process and the mounting of possible noisy components. The paper further outlines four pillars, on which good acoustics of an HVAC system is based, focusing on the subsystem ‘air flow’. These are reduction of pressure drop, flow optimization, sound proofing and sound deadening, and at least the insulation of structure borne sound.

Psychoacoustic Considerations in Vehicle Ergonomic Design

In order to experience harmony among the various perceptual cues experienced by an automobile customer, the acoustic environment must be considered. Acoustic events generated by automotive systems can have a dramatic effect on a customer's impression of vehicle quality and reliability. Additionally, certain vehicle segments are partially defined by the vehicle's sound characteristic. For example, luxury segments are defined by quiet and smooth powertrain sound, whereas some sports car segments are defined by loud and rough powertrain sound. This paper is a discussion of the impact automotive acoustic events can have on the customer. Addressed will be the methods typically used in both data collection and subsequent jury evaluations. Two case studies will be discussed. Finally, there will be a brief discussion on the future role of psychoacoustics in the vehicle environment. Exploring the relationships between acoustic, visual and haptic stimuli is an area which has been largely unexplored. Additionally, auditory warnings and displays may become increasingly important in advanced safety and navigational systems and can be positively influenced by psychoacoustic principles and methods.

International Space Station Temperature and Humidity Control Subassembly Hardware, Control and Performance Description

The temperature and humidity of the air within the habitable areas of the International Space Station are controlled by a set of hardware and software collectively referred to as the Temperature and Humidity Control (THC) subassembly. This subassembly 1) controls the temperature of the cabin air based on a crew selected temperature, 2) maintains humidity within defined limits, and 3) generates a ventilation air flow which circulates through the cabin. This paper provides descriptions of the components of the THC subassembly, their performance ranges, and the control approach of the hardware. In addition, the solutions of the design challenges of maintaining a maximum case radiated noise level of NC 45, controlling the cabin air temperature to within ±2°F of a setpoint temperature, and providing a means of controlling microbial growth on the heat exchanger surfaces are described.

Laminated Sidelights and Asymmetrical Windshields for Cars

This paper deals with new concepts for automotive glazing applications, with reference to weight reduction, improved security, and enhanced robustness: Laminated sidelights and asymmetrical windshields are considered. Main advantages are reviewed. Best designs are proposed considering the main functionalities of both products, particularly the mechanical properties required for automotive glazing.

Evaluating the Intrusion Resistance of Installed Motor Vehicle Glazing

Intrusion resistant glazing increases the time and effort required to gain unauthorized entry to a motor vehicle. This paper presents the results from a series of tests designed to measure the performance of laminated intrusion resistant glazings as installed. These tests were conducted as part of a study to evaluate the performance of different polyvinyl butyral (PVB) interlayer thicknesses and adhesions for penetration resistance. Readers of this paper should gain a broad understanding of the performance of these glazings and their level of resistance.

Interior Noise Analysis Based on Acoustic Excitation Tests at Low-Frequency Range

An experimental analysis is performed on structure-borne sound in the low-frequency range under 50 Hz by applying an acoustic excitation test to a fully trimmed vehicle. This analysis makes use of the structural-acoustic reciprocity technique in which the vibration distribution of the car body is measured while the vehicle is being acoustically excited by a loudspeaker placed at the position of a passenger's ear. This paper explains why the concept of reciprocity should be applied to the study of low-frequency structure-borne sound, and discusses the causes of road noise, a typical problem in structure-borne sound associated with passenger cars.

Experimental Evaluation of Wind Noise Sources: A Case Study

Several of the authors have recently developed procedures to efficiently evaluate experimentally the relative contributions of various wind noise paths and sources. These procedures are described and, as a case study, results are provided for the noise in the interior of a production automobile subjected to wind tunnel airflow. The present measurements and analysis indicate that for the tested vehicle significant contributions to interior noise are provided by underbody and wheel well flows, radiation from the roof and seal aspiration. A significant tone associated with vortex shedding from the radio antenna was also noted.

Empirical Noise Model for Power Train Noise in a Passenger Vehicle

Power train noise reaches the interior through structureborne paths and through airborne transmission of engine casing noise. To determine transfer functions from vibration to interior noise a shaker was attached at the engine attachment points, with the engine removed. A simple engine noise simulator, with loudspeaker cones on its faces, was placed in the engine compartment to measure airborne transfer functions to interior noise. Empirical noise estimates, based on the incoherent sum of contributions for individual source terms times the appropriate transfer function, compared remarkably well with measured levels obtained from dynomometer tests. Airborne transmission dominates above 1.5kHz. At lower frequencies engine casing radiation and vibration contributions are comparable.

Analysis of Vehicle Pillar Cavity Foam Block Effect on Interior Noise Using SEA

Closed cell foam has been used for filling vehicle pillar cavities at select locations to block road noise transmitted through pillars. In the past, most pillar foam implementations in vehicle programs were driven by subjective improvements in interior sound. In this study road test results are used to correlate a detailed CAE (Computer-Aided Engineering) model based on the statistical energy analysis method. Noise reduction characteristics of pillar with a number of foam block fillings were then studied using the CAE model. The CAE models provided means to model and understand the mechanism of noise energy flow through pillar cavities. A number of insightful conclusions were obtained as result of the study.

Perceptual Transfer Function for Automotive Sound Systems

Measurement of acoustic frequency response is extended to include aspects of speech and music perception in rooms. An apparatus is described that combines established and new techniques in a computer based measuring system. The resulting objective plot has a better correlation with subjective assessment than previous methods. The flexibility of the measurement platform encourages future development.

All Olefinic Interiors-What Will It Take To Happen?

TPO is getting wider acceptance for automotive applications. An exterior application like a fascia is a very good example. Interiors are still a challenge due to many reasons including overall system cost. For interior applications, “all-olefin” means it mainly consists of three materials: TPO skin, cross-linked olefinic-based foam and PP substrate. The driving force for TPO in Europe is mainly recyclability while in the USA, it is long-term durability. This paper describes the key limitations of the current TPO systems which are: poor grain retention of TPO skin, shrinkage in-consistency of the skin, high cost of priming (or other treatments) and painting of the skin, lower process window of the semi-crystalline TPO material during thermoforming or In-mold lamination / Low pressure molding, high cost of the foam, low tear strength of the foam for deep draw ratio etc. The paper shows the different ways of manufacturing the all olefinic parts which are: thermoforming over PP substrate, different Low pressure molding with in-mold lamination techniques, expanded PP foam process, slush molding etc. The limitations for each process and suggestions to overcome the disadvantages will be discussed to make all olefinic TPO interior parts viable and cost effective. The possibility of reducing the overall system cost will also be discussed such as: general information on formulation development to reduce the skin thickness for thermoforming, how to improve the properties of foam to reduce the thickness without affecting the formability and resiliency, value added recyclability of the skin/foam offal from production, and improving the paint efficiency etc.

Frequency Domain Considerations in Vehicle Design for Optimal Structural Feel

A vehicle perceived to be solid and vibration free is said to have good “structural feel”. Specification for vehicle design to achieve a good stuctural feel depends heavily on the management of resonant modes existing in the low frequency domain. These resonances include vehicle rigid body, chassis subsystem, body flexure and large component modes. A process to specify the placement of resonant modes in the low frequency domain is discussed. This process allocates blocks within the frequency domain for classes of resonant modes stated above. Segregation of these blocks of resonant modes in the frequency domain limits modal interaction, thereby minimizing sympathetic vibration. Additionally, known areas of human body sensitivity within this low frequency domain are stated. Lastly, known vibration inputs are identified. This process is cognizant of these inputs and avoids overlapping with the vehicle resonant modes to provide further insurance of minimal modal interaction.

The Strategy of Accelerated Reliability Testing Development for Car Components

This paper analyzes the reasons why current accelerated reliability testing (ART) results for passenger cars often cannot give accurate information for sufficient reliability, fatigue, and durability evaluation and prediction in the field. Why does accelerated testing (AT) give often minimum benefits for companies that use it? The basic principles of strategy that can help to eliminate these reasons will be described. In order to execute this strategy the following will be shown: the full hierarchy of the car and its components in a connection and interaction with each other; how accelerated environmental testing can be improved if a simultaneous combination of basic environmental factors (temperature, humidity, pollution, radiation, etc.) will be used; how each of these factors can be simulated more accurately in the laboratory; how one can improve accelerated corrosion testing of the car components if one takes into account that it is a combination of chemical, mechanical, motion, etc. influences; how one can improve vibration testing if one takes into account that the car's vibration is complicated and acts simultaneously with the rotation of the wheels; etc.

The Effects of Outlet Geometry on Automotive Demister Performance

The established method of clearing a misted car windshield or of maintaining a clear view under misting conditions is through the application of an air supply via jet outlets in the instrument panel. The ability of such arrangements to perform adequately is a function of the prevailing environmental conditions, the vehicle speed, the condition of the demist air source and the geometry and arrangement of the jet outlets. This paper presents experimental data obtained in a purpose built environmental chamber designed to accommodate simple rectangular jets impinging on a misted glass surface. The facility consists of three conditioned air sources applied to a test chamber designed to represent the external, internal and demist air flows. Mist conditions on the glass surface are determined using a novel technique employing a CCD camera acquiring grey scale images which are digitally analysed to generate mist detection, grading and clearing contour data. The test facility and mist analysis techniques are described. Transient jet performance is investigated in a parametric study that addresses the effects of jet aspect ratio, offset, impingement angle and mean volume flow rate on clearing performance. Results are presented in terms of parameters derived from the images recorded during the clearing process. These parameters include rate of clearing terms, breakthrough time and location of clearing centre relative to geometric impingement point. Steady state performance is presented for a number of representative geometries by examining the size of the clear area for a range of interior humidity levels.

The Importance of Sealing Pass-Through Locations Via the Front of Dash Barrier Assembly

An improvement in a vehicle's front of dash barrier assembly's acoustical performance has in the past been addressed by both adding individual absorbers and increasing the overall weight of the dash sound barrier assembly. Depending upon the target market of the vehicle, adding mass may not be an option for improved acoustical performance. Understanding the value of an increase in vehicle mass and / or cost for a specific level of improved acoustical performance continues to plague both Original Equipment Manufacturer (OEM) Engineers and Purchasing representatives. This paper examines the importance of properly sealing the front of dash pass-through areas and offers recommendations which can improve the overall vehicle acoustical performance without the addition of cost and mass to the vehicle. It also examines how the acoustical performance of an engineering change can be determined and relates this performance to a Value Statement in an effort to assist the engineering community in judging the overall value of this engineering change.

The Next Step in Acoustical Part Weight Reduction

Weight reduction with maintained part performance is a continuing trend throughout the automotive industry. Acoustical insulation parts (carpet underlay and dash insulators) are no exception. Several years ago, ICI Polyurethanes led the industry in establishing a molded density standard of 48 kg/m3. Although this is the current production standard, the technology drive is toward even lower weights. Recent technological demonstrations show that molded densities of 35-38 kg/m3 are achievable. In addition to removing weight, acoustical performance can be maintained with no deficiencies in physical characteristics.

Acoustical Advantages of a New Polypropylene Absorbing Material

Sound absorption is one way to control noise in automotive passenger compartments. Fibrous or porous materials absorb sound in a cavity by dissipating energy associated with a propagating sound wave. The objective of this study was to evaluate the acoustic performance of a cotton fiber absorbing material in comparison to a new polypropylene fibrous material, called ECOSORB ®. The acoustical evaluation was done using measurements of material properties along with sound pressure level from road testing of a fully-assembled vehicle. The new polypropylene fibrous material showed significant advantages over the cotton fiber materials in material properties testing and also in-vehicle measurements. In addition to the performance benefits, the polypropylene absorber provided weight savings over the cotton fiber material.

Assessing the Performance of Electrically Heated Windshield

The safety and comfort aspects of passenger vehicles are significant sales argument and have become a topic of rising importance during the development process of a new vehicle. The objective of this study is to compare the performance of several current model vehicles, highlight the drawbacks of current defrosting/demisting systems and point the way to improved passive mechanisms. The investigation is experimental. The work presented is an experimental and numeric investigation of the clear-up pattern of a current vehicle fitted with an electrically heated windshield. Nottingham FDL climatic wind tunnel is used to perform the experimental tests. The clear up pattern developed utilising the vehicle defroster system is digitally captured and compared to the clear up pattern developed utilising the electrical heated windshield. Moreover, the clear up pattern developed using the vehicle defroster system is used to validate a computational model. The aim is to build a confidence on the relatively new developed numerical tools for phase change simulation. The design features of electrically heated windshields and the associated gadgets are briefly discussed. With the predicted shift to use 42V powernet, the market will require more vehicles to be installed with electrically heated windshields. The main benefit to the vehicle customer is the convenience of reducing the clear up times.

Safety Performance of a Chemically Strengthened Windshield

Safety performance of an experimental windshield with a thin, chemically tempered inner pane is compared with the standard windshield and other experimental windshields. The chemically tempered windshield has a penetration velocity of 35 mph compared with 26 mph penetration velocity for the standard windshield and has lower peak head accelerations than other types used in the experiments. The windshield tested produces a bulge on impact, which decelerates the head over a long distance with low accelerations. The bulge or pocket is lined with particles that are less lacerative than the standard annealed glass.

A Vibro-Acoustic Test System for Simulation of Saturn V Dynamic Launch Environment on Major Space Vehicle Structures

A description of the largest Acoustic and Vibration Test Facilities in existence for the simulation of major launch vehicle dynamic environment is given and the operational characteristics of both are discussed. Sinusoidal and random excitation techniques are described and unique vibration control methods presented. A comparison of the effects of vibration and acoustic excitation on major space vehicle structures is made.

Causes of Significant Injuries in Nonfatal Traffic Accidents

The Vehicular Trauma Research Group of the UCLA School of Medicine is currently conducting intensive studies of selected traffic accidents. Data is presented from an analysis of the first 150 traffic accidents studied. The role of vehicular design, mechanical failure and the performance of the new 1966 windshield in injury causation are discussed and illustrative examples are presented. The importance of detailed studies of traffic accidents is stressed as a method of yielding information not readily available by other methods of study. This approach is mandatory to evaluate new and pending vehicular design modifications and may be the only method of detecting and assessing the role of mechanical failure in traffic accident causation.

Ejection - The Leading Cause of Death in Automobile Accidents *

From on-scene investigations of 139 fatal automobile accidents during four years, it was found that of 177 persons killed, 48, or 27%, died by ejection, which is thus the leading cause of death. As would be expected, most (two-thirds) were ejected through opened doors; others were ejected through windshields, open convertible roofs, or door windows. From the investigations it is postulated that 80% of the ejection deaths would have been prevented had the ejectees worn seat belts.

Passenger Protection from Front-End Impacts

Scientific methodology and engineering techniques were applied to a series of thirteen automobile collision experiments involving the front-end impact exposures of full-size passenger vehicles rear ending identical sedans. The purpose was to evaluate the relative protective merits of seat designs, steering columns, windshields, restraints and general interior surface design with respect to the many variables common to front-end impacts. The front-end collisions reported in this paper provide additional design data for protection of motorists from collision-injuries for the wide range of exposure speeds from 10 through 55 mph.

Automotive Piston-Engine Noise And Its Reduction - A Literature Survey

This paper reviews the sources of externally radiated automotive piston engine and vehicle noise and describes them in detail. The effects of various design and operational characters on intensity and character of noise, noise measurement, and analysis and identifications procedures are given extensive examination. A summary of current research on the reduction of engine noise is presented.

Basic Facts about Noise as Related to Aviation

NOISE has two aspects: (1) subjectively, it is any unwanted sound; (2) objectively, it is characterized by many variables. The subjective view is important in determining the response of people to aircraft noise and in establishing engineering design objectives for noise control. The engineering of noise control deals with the objective aspect in three parts: 1. The noise source — characterized by its total noise power output and the distribution of this power with respect to frequency and space. 2. The path — propagation in structures, through the air, and over terrain as influenced by properties of materials, geometry, meteorological conditions, and topography. 3. The received noise — its sound level, frequency spectrum, time pattern, and other variables as required to correlate with the subjective response of man in the aircraft, on the line or in the community.

Safety Glass Breakage by Motorists During Collisions

Five intersection-type collision experiments were conducted at 40 mph to provide data on several categories of collision performance. This paper presents the interactions of passenger heads with car windshields and side-glass. Instrumentation included 60 channels of force and acceleration data, supported by the photographic coverage of 40 cameras. Tri-axial accelerometers, mounted in anthropometric dummy heads and chests, and strain gauges bonded to windshields facilitated data collection on the relative collision performances of different types of safety glass.

Accidental Motorist Ejection and Door Latching Systems

A general dissertation on the factors relating to accidental door opening, including: nomenclature, classification of the various types of loading of significance; description of five known causes of accidental door opening not associated with door latch strength; supporting evidence from full-scale collision research; photographic display of 1964 model door latches; review of the factors relating to the evaluation of door latch installation and three suggested test configurations to cover the most significant causes of accidental door opening.

A Review of ACIR Findings

During a period of ten years, ACIR has amassed a large accident sample, drawn from a total of 28 states. Statistical analysis has aimed at (1) identification of leading injury sources and (2) statistical evaluation of car safety features. Studies show that ejection, the steering wheel, instrument panel, and the windshield are the four categories most often associated with car occupant injuries. Countermeasures include seat belts, safety door latches, recessed-hub steering wheels, and instrument panel padding. Studies have shown partial-to-substantial countermeasure effectiveness for seat belts, safety door latches, and instrument panel padding. Analysis of other safety devices is under way.

Modern Concepts in Rapid Transit and the Use of Rubber Tires for Transit Vehicles

A resurgence of interest in rapid transit has resulted in a multiplicity of systems being proposed. Among these have been proposals to use guided rubber tired vehicles. The history and current status of development of a number of these systems is presented. The development of a new supported, dual track rubber tired system is described together with a review of operation and design considerations. Rolling resistance and acoustical factors are discussed and costs of several types of systems are compared. While rubber-tired systems are more costly than those having conventional steel wheels, special consideration of grades and community acceptance may justify their use.

Tooling for Multiple Lead Applications of Electrical Discharge Machining

Multiple lead enables electrical discharge machining to compete as a production method with conventional machining methods, provided proper tooling is used. In this paper, the electrical discharge power supply, the machine, the work and electrode holding fixtures, the electrodes, and the dielectric are all considered as tools. Each has its individual function in obtaining an efficient EDM cut which is essential for multiple-lead operation. The power supply must be capable of producing discharges that are compatible with the electrodes and workpieces being used. Machines must furnish the servo function and auxiliary cycling equipment. Work and electrode holding fixtures must hold precision relationship between electrodes and workpieces as well as eliminate electrode vibration and direct dielectric flow. The electrodes must be suitable to the application, and because they are expendable, must be economically produced. The dielectric must be suitable to the application and must be adequately filtered and directed.

General Approach to the FLUTTER PROBLEM

AGENERAL approach to the flutter problem is outlined, which can be used to investigate any mode of flutter of any structure provided the air-forces are known. The method can be used to investigate the possibility of flutter on such structures as airplane wings, tail surfaces, and bomb doors, aircraft propeller blades, vehicular bridges, buildings, and so on. With a well-known solution for the air-forces for two-dimensional flow over an airfoil with an aileron, equations have been derived which can be used to determine the flutter speed for the wing or tail surfaces of any conventional airplane. The use of still-air vibration tests in obtaining the structural friction of structures, and in checking a part of the flutter computations experimentally is indicated. Finally, to suggest the possibilities in the use of this method, a standardized procedure for its general application to aircraft flutter problems is outlined briefly.

Heating, Ventilating, and Cooling of Passenger Cars

MANY question whether a complete job of air-conditioning passenger cars for all weather conditions can be done at a price which most car buyers care to pay and with assurance that dependable and acceptable results can be guaranteed, Mr. Chase reports in prefacing this paper, a comparative study of existing heating, ventilating, and cooling systems. Some 1939 and many more 1940 car models, he believes, yield greatly improved results in heating the entire car and ventilating it well with all windows closed, but, he points out, the design of such systems is still in a state of flux. Mr. Chase divides all currently available systems into four classifications for convenient discussion: (1) heating by recirculation only, ventilation incidental; (2) heating in which part of the air is recirculated and part taken from outside and can be heated before delivery; (3) heating in which all air passing through heater is taken from outside; (4) systems which include means for heating, cooling by refrigeration, and at least incidental circulation. The author describes and compares current systems in each of the classifications and comments on the problems, advantages and disadvantages involved in each of the designs. He includes also structural considerations, mentioning that, except for compressors, valves, and a few other somewhat special parts, most of the components of all these systems are produced largely from sheet metal or are die-cast in zinc alloy.

DEFICIENCIES of CONVERTED PASSENGER AIRPLANES for CARGO TRANSPORT and OPERATING REQUIREMENTS

SHORTCOMINGS of the converted passenger plane are at least 10 in number, says Mr. Froesch, classifying them as follows: (1) floor slope and irregularity of floor at door causing concentration of load at that point; (2) floors too weak, requiring reinforcing; (3) doors too narrow for entrance of bulky loads; (4) no anchorage for load fasteners; (5) no provisions for cargo handler station; (6) hard to distribute load so as to give a satisfactory center-of-gravity location; (7) lavatory in the wrong place; (8) insufficient fire extinguisher protection; (9) door sill heights too variable; (10) circular or oval fuselage shape, which cannot be used effectively. A big problem is to get the rate down to the point where repeat business will follow. Eventually this might mean a 10 to 12¢ per mile rate under proper designing, Mr. Froesch declares. But, he says, size and capacity of the cargo plane cannot be predicted until a thorough analysis of the air express and freight market has been made. A density-volume ratio of 8 to 9 lb per cu ft can be used, Mr. Froesch says, as a design criterion in figuring size of compartment. He points out heating and ventilation aspects of the cargo compartment and explains desirability of having a small compartment for protection of valuables close to the cockpit. The airplane should also be designed so that preventive maintenance and service methods can be best applied.

Passenger-Car Road Noise

THE authors introduce their paper by outlining the various sources of noise existing in the motor car, together with some of the suppression means. Noise measurement, test methods, and the mechanism of the transmission of forces generated by the contact between the tire and the road to the body and frame are discussed. The authors state that, since these forces produce motion and deflection of the body, they are responsible for the road noise, and conclude that the proper approach to a method for suppressing road noise is through the structural design of the vehicle. They suggest, in the main, the localizing of stress to stress members, the raising of the resonant frequencies of the structure, the detuning of the suspension system, the body, and the frame, together with some isolation at selected points.

What Motor Cars Can Be

FUTURE motor-car development, Mr. Stout contends, will follow the functional art of bus and airplane development rather than motor-car precedents. The interior instead of the exterior, he believes, is the basic thing to be studied, pointing out that passenger room has been growing less and less. The car of the future, therefore, he predicts, will have an interior that extends out the full width of the car with no running boards, will have totally enclosed wheels, will have a unit frame and body, the engine in the rear, and either double or sliding doors. The effect of rear-engine construction on ride, bounce control, braking, and traction on muddy and icy roads is explained. New body materials, such as plastics, are looked for on future cars to insulate them from the radiant heat of the sun, especially for roofs. Mr. Stout sees light-weight air-cooled engines in future cars, weighing not over 3½ lb per hp. The possibilities of rubber springs are discussed.

WOOD FOR AUTOMOBILE BODIES 1

Shortage of the most desirable kinds of wood for automobile-body purposes has necessitated the substitution of second-choice woods having the essential required properties and the buying of stock for body parts in cut-up dimensions that conform in size with those now produced in the cutting-room. An investigation by the United States Forest Products Laboratory as to the species, kinds, grades, sizes and amounts used by the automotive industry shows that maple and elm comprise over one-half the total amount used and that ash and gum constitute one-half of the remainder. Although the quantity of ash used has not decreased, the increase in the production of medium and low-priced cars in the last few years bas caused a proportional increase in the demand for maple and elm. Classifying cars for purposes of analysis into four groups, small, medium, medium-large and large, the investigators found that the woods most used in small cars are hard and soft maple, elm, birch, beech, oak, gum and pine; that maple, elm and birch are used extensively in bodies of the medium and medium-large classes; and that ash predominates in the large cars, with hard maple as an alternative choice. Fifty-one per cent of the running-boards are made of pine, and 17 per cent are made of sound wormy oak. Oak, ash and elm are used for top-bows in the proportion of 92, 7 and 1. The grade of lumber used in bodies is very high, 40 per cent being firsts and seconds, and 49 per cent No. 1 common and selects. The problem of eliminating light or brash ash is important and, while there are no visual means by which tough and brash ash can be separated, the factors that afford a fairly reliable criterion of strength and toughness are density, rate of growth, proportion of summerwood and the original position of the wood in the tree. Seasoned ash that has good weight and is sound will have strength. Unseasoned ash, on the other hand, cannot be judged by weight. Little or no uniformity in size of corresponding parts was found among the various makes of body, although the majority fall within very narrow limits. Charts have been prepared showing the range and grouping of the sizes of several of the main body parts, such as the body and door pillars of closed bodies, the main side sills, the side roof-rails, the front and rear roof-rails and the rear belt-rails. The stock used in the larger bodies is of very high quality; in open bodies a few small defects are allowed; in smaller and lighter bodies the requirements are not so severe, a mixture of woods is used, and some defects, such as small sound knots, are allowed; in soft maple, elm and gum, considerable amounts of stain and dote are admitted. When the requirements are not exacting it would be possible to utilize sound low-grades; the use of clear stock where sound stock is sufficient introduces unwarranted expense and wastes material that might serve higher purposes. As the waste in cutting ranges from 20 to 50 per cent, it is evident that careful work at the saws may result in considerable saving. Other ways in which saving may be effected are the gluing-up of stock to get required sizes and a more general use of ready-cut small-dimension stock. As automobile builders are much interested in finding woods that may be substituted for those now in use, a table is given showing the specific gravity, strength, stiffness, shock-resisting ability and hardness of the principal species as compared with those of forest-grown white ash; and the advantages and disadvantages of first and second-growth timber, and such woods as ash, hard and soft maple, rock and white elm, birch, red and sap gum, oak and the softwoods are discussed.

GLIMPSES OF BALLOON-TIRE PROGRESS

The balloon tire has run the gauntlet of skepticism and credulity and has received scientific and popular approval from engineers and car-owners. The reasons for its acceptance are satisfactory appearance, practicability and transportation comfort. Tire and rim sizes, masquerading for years under wrong dimensional markings, have caused immeasurable inconvenience. This condition resulted from poor standards or entire lack of standards supervision. A committee with backbone is needed to fix and to maintain standards. Rapid balloon-tire tread-wear depends on tread profile, pressure and movement. Increased inflation-pressure and a scientifically designed tread will reduce the rapidity of this wear. Tread-contact areas and pressures are pictured to explain the advantages of a properly designed tread, and to demonstrate that the casing carries an appreciable part of the tire load. Tread configuration should assure traction, flexibility, easy steering, and good wear and should be not too rugged. Tread surface should be largely non-skid for best all-year and all-highway service. The public is confused by diverse balloon-tire inflation-pressure tables offered by tire and vehicle makers. One standard table can and should be adopted for all balloon tires. Increasing the number of plies in a balloon tire increases the ease of entry of a puncturing object into the tread, but decreases the probability of complete penetration and actual deflation from puncture. Gradual loss of air from tires is due chiefly to diffusion through the tube rubber. The rate depends on daily mileage, road conditions and tube quality and thickness. Average diffusion amounts to from 1 to 5 lb. per week. Volume of noise in closed cars is no greater with balloon tires than with high-pressure tires, as indicated by audiometer measurements. Different cars show important differences in noise volume, due principally to differences in engines. Balloon tires are not a fundamental cause of shimmying. Improper balance between front-end units appears to offer the chief cause. There is no common remedy. More original and thorough research by experts in their particular fields is urged so that America will lead in the refinement as well as in the production of tires and automobiles.

PYROXYLIN ENAMEL OVERCOMES FINISH FAILURES

Public demand for more durability in automobile finishes has led to new developments in finishing materials and methods through cooperation of finishing materials manufacturers and automobile builders. By experimentation it has been found that certain cellulose nitrate materials, when applied over suitable under-coats, dry quickly in the air by evaporation of the solvents and leave a film that is hard and tough. Its durability is many times greater than that of the most durable finishing-varnish and, as it has been discovered that sufficient luster can be produced by rubbing and polishing the unprotected cellulose-nitrate surface, one of the large automobile production plants adopted, in July, 1923, as its standard method of finishing, the use of such a finishing coat over primer and surfacer coats, obtaining the luster by polishing the cellulose-nitrate top-coat. A number of companies have now adopted this process. Certain finishing-material companies, having discovered how to increase the quantity of cellulose-nitrate in solution without increasing the viscosity, made possible its use for automobile finishing. The change from a varnish to a pyroxylin finishing-system seems simple but a cellulose-nitrate finishing-material is complex. A large number of gums and oils can be used to obtain the desired properties but considerable study is required to determine the kinds and the quantities to use. The softeners and the stabilizers may be part of the solvents but they have their own duties to perform. The solvents hold the cellulose nitrate in solution and their evaporation permits the film to be deposited and harden. The nature of the solvents greatly influences the character of the film. Not all pyroxylin materials have great durability. This is obtained only by using the proper basic materials, combined in the right proportion and applied in the correct way. The fundamental cause of the failure of finishes is the contraction of the top material while the underlying material is still moist. During exposure to rain or other dampness out of doors, the entire film absorbs moisture, swells and softens. When the sun comes out, the outer surface dries and contracts and, if the material is not sufficiently elastic to withstand the stresses, cracks develop. Durability can be increased by reducing the severity of these factors. By nature, the pyroxylin film is much less absorbent than the varnish film and the particles of pigment shade the materials beneath so that only the extreme outer surface is exposed to the sunlight. In time, the moisture and sunlight do, however, cause a type of failure known as “chalking.” This effect is of such microscopic depth that it can be removed easily by washing with a mild abrasive or by polishing, thereby exposing a fresh surface, and in the case of a good cellulose-nitrate finish the washing or polishing can be repeated many times before any serious wearing away of the surface occurs. By mild polishing every few weeks, together with ordinary cleaning of the car, the finish can be kept with an appearance as good as it had on the showroom floor. The author describes the fundamental operations in finishing an automobile body with paints and varnishes, explaining the purposes of the different coatings and the filling and rubbing, and classifies the successive coatings in all finishing systems as (a) primer, (b) surfacer, (c) color and rubbing, and (d) finishing. To determine the cause of the rapid failure of finishes, test panels were exposed to the weather during different periods of the year and it was found that the length of life of varnishes depends greatly upon the season, varying with the amount of sunlight and heat, being shortest in summer and longest in winter. These tests also showed that the primer and surfacer coats were very durable but that the color and rubbing varnishes were of low durability, failing in from 1 to 5 weeks when unprotected by finishing varnish. The real reason for the short life of the ordinary automobile-finish was discovered to be the failure of the color and rubbing varnishes, which crack and take the finishing varnish with them. However, the finishing varnish is itself partially responsible for the failure of the color and the rubbing coats, because its film is easily scratched by grit and cleaning or by other mechanical injury, and failure of the underlying coat starts at these unprotected spots. The life of a varnish surface is shortened by regular polishing even if it is washed regularly only with water. A polish that is as nearly harmless as any is made of linseed oil mixed with enough turpentine to prevent the application of too heavy a film of oil. The life of ordinary production varnish-finishes can be doubled or quadrupled by the use of color and rubbing varnishes of high durability but they require a long time for air-drying and forced drying is likely to injure the color.

HEADLIGHTS

Two points are cited as illustrating the difficulty of enforcing the present regulations, namely, (a) the variation in the angle of the headlight beam caused by the compression of the springs when the loading of the car is changed from no load to full load and (b) the variation of the tilting of the beam caused by the pitching of the car on an ordinary road, the effect being similar to that produced by flashes of lightning in a pitch-dark night. Denial is made of the author's alleged advocacy of diffused lighting and comparison is made of the distribution-curves obtained with frosted bulbs and those obtained with fairly good lamps conforming to the Society's specifications. Attention is called to three points in this comparison: (a) the light from the frosted bulb along the horizontal is only about 50 per cent of that available with a lamp conforming to the Society's specification, (b) the foot-candle illumination measured perpendicularly to the beam at various points on the surface of a level road is much less with the frosted bulb than with the lamp of the Society's specification, how much harm a bright illumination immediately in front of the car interferes with acuity of vision is a subject for additional research and (c) the light from the frosted bulb does not change appreciably for any angle through which the chassis is likely to move as a result of road shocks; consequently, when the frosted bulb is used, road shocks and spring vibration do not affect the eyes of an approaching driver. Sharp cut-off above the horizontal is considered in-advisable. The possibilities of non-symmetrical lighting, the author believes, are worth considering, and the results of some experiments are detailed. He expresses a preference for the use of two diffused lights as regular equipment and of a third lamp, adjusted according to the Society's specifications, so that the maximum candlepower would be horizontal. Reference is made to the test target in use by the Royal Automobile Club and to the results of tests made with it, but this method is said to be objectionable as a basis of specifications because it is tedious and the results depend largely upon the condition of the observer's eyes. Although measurements of all the imaginable functions of the human eye have apparently been made, such tests should be repeated under automobile-lighting conditions, for factors that previously may have been neglected in tests frequently become important when the conditions are changed. As the normal eye requires nearly 1 sec. to adjust itself to radically changed conditions of illumination, this period is dangerously long when a car is running at high speed.

Automobile Bodies, from the Abstract Customer's Viewpoint

CONSTRUCTIVE criticism of automobile bodies as now built is given herein, based on experience gained in driving five-passenger sedan cars of many makes a total distance of nearly 10,000,000 miles in one year in tests at the General Motors Proving Ground. The fault finding, although humorously exaggerated, will be valuable if taken seriously, as it gives to all body designers and builders the benefit of testing experience that few companies are in a position to gain at first hand. The author treats his subject from the viewpoint of the abstract customer; that is, the automobile-purchasing public as a whole and as represened by the imaginary average man, who is assumed to have average stature and body structure and to drive all the different makes of car. Thus he is assumed to change from one to another make frequently, instead of becoming used to only one or two cars. Factors that influence the initial and the repeated purchase of a car are given in the order of their importance, and the index by which the customer measures the merit of the car is said to be the maximum satisfaction he has experienced with each individual characteristic in all the other cars he has driven. In other words, the best in all cars is his basis of comparison of the individual car and body, and he can be completely satisfied only if one car is as good in every respect as the best that has been found in any car for that particular feature. Standardization of fundamental dimensions based on the measurements of the average figure of all drivers is indicated as a need of primary importance. Strictures are laid on various bodies because of interference with vision in front and through the rear window, because of squeaks and rattles and many other details that, because they are constantly evident to eye or ear, are more annoying than faults of the chassis. No attempt is made, however, to set up specifications for a body that will give complete satisfaction to various classes of user.

DAMPING IN SUSPENSIONS

THE various types of damping present in vehicle suspensions and their effect on the ride are discussed by Mr. O'Connor, who compares the characteristics of the various types of damping with the mathematically adaptable viscous damping. The ideal damper and the present-day practical approach are considered. The discussion is maintained on a nonmathematical plane throughout, as the author believes that the mathematics of vibration theory is ably covered in numerous texts on the subject.