The Driver´s Cab (Commercial Vehicle Technology) 3662608472, 9783662608470

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Commercial Vehicle Technology

Michael Hilgers Wilfried Achenbach

The Driver's Cab

Commercial Vehicle Technology Series Editors Michael Hilgers, Weinstadt, Baden-Württemberg, Germany Wilfried Achenbach, HPCC2D-ENG, Daimler Trucks North America LLC, Portland, OR, USA

More information about this series at http://www.springer.com/series/16469

Michael Hilgers · Wilfried Achenbach

The Driver’s Cab

Michael Hilgers Daimler Truck Stuttgart, Germany

Wilfried Achenbach Daimler Truck Portland, OR, USA

Commercial Vehicle Technology ISBN 978-3-662-60846-3 ISBN 978-3-662-60847-0  (eBook) https://doi.org/10.1007/978-3-662-60847-0 © Springer-Verlag GmbH Germany, part of Springer Nature 2021 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer Vieweg imprint is published by the registered company Springer-Verlag GmbH, DE part of Springer Nature. The registered company address is: Heidelberger Platz 3, 14197 Berlin, Germany

Preface

For my children Paul, David and Julia, who derive just as much pleasure from trucks as I do, and for my wife Simone Hilgers-Bach, who indulges us.

I have worked in the commercial vehicle industry for many years. Time and again I am asked, “So you work on the development of trucks?” Or words to that effect. “That’s a young boy’s dream!” Indeed it is! Inspired by this enthusiasm, I have tried to learn as much as I possibly could about the technology of trucks. In the process, I have discovered that you have not really grasped the subject matter until you can explain it convincingly. Or to put it more succinctly, “In order to really learn, you must teach.” Accordingly, as time went on I began to write down as many technical aspects of commercial vehicle technology as I could in my own words. This booklet deals with the driver’s cab. The cab is the part of the commercial vehicle that is probably the most different from other automobiles. It is not only where the driver does their trucking business, it is also where he or she lives and sleeps. The cab is also the part of the truck that features the most regional variations: versions on the Indian subcontinent look different from those in North America. Readers who are studying this subject (students and technicians) will find it to be a good entry point and as a result may discover that commercial vehicle technology is also a fascinating field of work for them. In addition, I am convinced that this booklet will provide added value for technical specialists from related disciplines who would like see the bigger picture and are looking for a compact and easy-to-understand summary of the subjects in question. At this point I would like to thank my superiors and numerous colleagues at the truck division of Daimler AG, who so readily gave me their support while I was working on this series of booklets. My special thanks go to Derek Rotz how helped me with the American content of this booklet. I would like to thank Springer Verlag for their friendly cooperation, which has led to this final result. vii

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Preface

Finally, I have a personal favor to ask. It is important to me that this work should continue to be expanded and refined. Dear reader, I would greatly welcome your help in this regard. Please send any technical comments and suggestions for improvements to the following email address: [email protected]. The more tangible your comments, the easier it will be for me to comprehend them and, where appropriate, integrate them into future editions. If you discover any inconsistencies or even errors in the content or you would like to express your praise, please let me know via the same email address. I wish you much reading pleasure. August 2019

Michael Hilgers Weinstadt-Beutelsbach Stuttgart-Untertürkheim Aachen

Contents

1 The Cab Concept. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Low Mounted Cabs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.2 Material Concepts in the Cab. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2 Functions of the Cab. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1 Driving and Working. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1.1 The Reach Zone. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.1.2 The Driver’s Seat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.1.3 The Steering Wheel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.1.4 Operating Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.1.5 Displays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.1.6 Air-Conditioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.1.7 Working with the Vehicle Parked. . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.2 Living. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.2.1 Stowage Space. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.2.2 Lighting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2.2.3 Entertainment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.2.4 The Passenger Seat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.3 Sleeping and Resting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2.3.1 Comfort . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 2.3.2 Parked HVAC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3 Cab Technology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.1 The Cab Superstructure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.2 Cab Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 3.3 Tilting the Cab. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 3.4 Styling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 3.5 Aerodynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 3.5.1 Soiling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

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Contents

3.6 Visibility Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 3.6.1 Mirrors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 3.6.2 Windows. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 3.6.3 Wipers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 3.6.4 The Lighting System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 3.7 Ingress and Egress. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Comprehension Questions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Abbreviations and Symbols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

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The Cab Concept

The most obvious conceptual question regarding the cab is the difference between the cab-over-engine (also known as cab forward trucks in the US) and the conventional or cab-behind-engine trucks. In the cab-over-engine truck, the driver’s cab is positioned over the engine, and is essentially a cube. In the conventional (cab-behind-engine) design, the engine is covered by a hood and the driver’s cab is built directly behind the engine and its hood. Figure 1.1 shows a classic conventional truck and a cab-over-engine truck. The windshield of a cab-over-engine vehicle is usually very upright, to allow as much usable space as possible inside the cuboid cab. Conventional vehicles are often also designed with a sloping windshield, in order to create a visually smooth, aerodynamically advantageous transition between the hood and the cab. The conventional (cab-behind-engine) vehicle offers a number of advantages. Since the engine is positioned in front of the driver’s area, the cab floor can be flat and the entry can be close to the ground. The engine is easier to access as well. The cab doesn’t need to be tilted to gain access to the engine—Fig. 1.2. A conventional vehicle can be aerodynamically optimized more easily, so its fuel consumption is more favorable [5]. The spatial separation of the engine and driver is generally beneficial, because the driver’s exposure to engine noise is minimized. On the other hand, the engine hood increases the entire vehicle length. In regions where entire vehicle length is limited by law (in Europe, for example) or in operating situations in which the vehicle’s turning radius and space requirement are important (urban distribution haulage), the cab-over-engine vehicle is more suitable than the conventional vehicle. As a result, the conventional vehicle, which was very popular as well (into the 1960s), has now largely disappeared in Europe. Most cab-over-engine trucks are designed with the cab boarding steps in front of the front axle. A variant of this concept places the steps behind the front axle. This makes it more difficult to climb into the cab.

© Springer-Verlag GmbH Germany, part of Springer Nature 2021 M. Hilgers and W. Achenbach, The Driver’s Cab, Commercial Vehicle Technology, https://doi.org/10.1007/978-3-662-60847-0_1

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1  The Cab Concept

Fig. 1.1   a American conventional truck with large living and sleeping space, and b European cab-overengine truck. (Images: Daimler AG)

Fig. 1.2   The American-style conventional cab enables easy access to the engine. (Image: Daimler AG)

Figure 1.3 shows schematic side view of two cabs of a European truck manufacturer. The drawing on the left shows the more uncommon boarding steps behind the front axle. In this case, in order to reach the cab door the driver must climb sideways over the front axle. In the total vehicle design, access behind the axle means that the front axle is positioned farther forward. As a result, the wheelbase is longer; and the axle load distribution is altered. The right half of Fig. 1.3 shows the more common arrangement with the boarding steps located in front of the front axle. In the conventional (cab-behind-engine)

1  The Cab Concept

a

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b

Access BEHIND the front axle

Access IN FRONT OF the front axle

Fig. 1.3   a shows the positioning of the boarding steps to the cab behind the front axle, which is quite unusual for cab-over-engine vehicles. The arrangement with the boarding steps in front of the front axle as shown in b is more common

vehicle, access to the cab is naturally positioned behind the axle—see Figs. 1.1 and 1.2 again. Figure 1.4 shows the dimensions of a cab in a European long-distance haulage truck. The large cabs for long-distance haulage are designed to be about as wide as is permitted (2.5 m) to give the driver as much work and living space as possible despite the length restriction. The designers also try to use height and length to afford the largest possible living space for the driver. The most comfortable cabs have a flat floor (no engine tunnel in the middle of the cab) and enough headroom to allow even tall people to stand and change clothes comfortably in the cab. In other market segments in which the driver does not spend as much time sleeping and living in the cab, the cab designs may be narrower, shorter and have less headroom. Figures 1.5 and 1.6 show a modular cab design with which it is possible to build shorter and lower cabs as well as large, high-roofed and long cabs. Some manufacturers also offer a range of cab widths, so a narrow or wider cab is added depending on space requirement. In short-haul distribution vehicles, a narrower cab has its advantages. The driver can climb in and out of the cab more easily when the boarding steps are designed like stairs. A narrower cab is also lighter and is therefore more suitable for uses in which payload is an important factor.

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1  The Cab Concept

Fig. 1.4   Dimensions of a modern driver’s cab, all dimensions shown in mm. Depicted is a cab with spacious interior and a flat floor (long-distance haulage). Mercedes-Benz Actros 2011. (Image: Daimler AG)

Fig. 1.5   Example of cab configurations for Freightliner Cascadia. (Graphic: Daimler)

1  The Cab Concept

Length

5

Short cab

Midlength cab

Roof height

Long cab Flat roof

Normal roof

Highline roof

Topline roof

Mounting position Low "P"

Medium "G"

High "R"

Special cabs

Low boarding steps

Short crew cabin

Long crew cabin

Fig. 1.6   Example of a cab module kit which allows various cab variants. (Graphic: Scania)

Vehicle manufacturers typically have one common cab platform from which the cabs for long-haul trucks, for building site vehicles and for (heavy) distribution vehicles can be derived (see again Figs. 1.5 and 1.6). For very specific vehicles, special cabs are developed, like the crew cabin (see for example Fig. 1.6) and the low mounted cab in the next section. Many characteristics of the boarding steps are already determined by the basic design of the cab, as is illustrated in Figs. 1.3 and 1.4, and the associated text. In heavy ­long-haul trucks the cab floor is a few steps higher than the road, so the driver and passenger have to climb up into the cab. In order to allow easy access to the cab after this climbing expedition, the door should ideally open to an angle of almost 90°. Space is

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1  The Cab Concept

often limited when parking at rest stops or on ferries, so the doors can’t be fully opened. Therefore, the doors have detent positions, at 60°, for example, so the door is immobilized when it is half open.

1.1 Low Mounted Cabs Particularly in distribution tasks, when the driver is required to climb in and out of the cab repeatedly, low boarding steps are particularly welcome. There are vehicles that have been optimized in this respect. In the case of some special vehicle designs with low access, it makes sense to shift the cab forwards so far that the beginning of the engine is located under the seat area. Then, the floor in the footwell can be flat and low (without an irritating engine compartment), and the boarding steps and footwell in the vehicle are in a very low position. Figure 1.7 shows a design of this kind with a forward-mounted cab. The cab model range illustrated in Fig. 1.6 also makes it possible to configure such a vehicle with optimized low boarding arrangements. The design in Fig. 1.7 is particularly suitable for municipal vehicle applications, in which the occupants have to get into and out of the cab repeatedly. Refuse trucks, for example, are often built on these chassis. Other application-specific product features of this vehicle might be a folding door on the passenger side that makes it easier for passengers to get into and out of the cab during refuse collection operations, the driver’s enormous field of vision increases safety, and the vehicle chassis is designed so that the superstructures can be adapted to perfectly fit. In short-haul operations—particularly for refuse vehicles or similar applications—other, more complicated solutions are also offered in which, for example, the bottom step pivots outwards when the door is opened, to make it easier to get in and out. The advantages of the low-mounted cab for boarding are not only found at the bottom. Since the upper border of the roof is also low, extra space is available at the top, which is convenient for certain applications. Figure 1.8 shows two applications in which the low mounted cab is very helpful. On ladder trucks used by fire departments, the ladder rests on top of the cab while traveling, but the entire vehicle height remains satisfyingly low. The low cab design for airport apron vehicles is most advantageous because it enables a wide range of heights to be reached for transferring items to the aircraft.

1.1 Low Mounted Cabs

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Fig. 1.7   Vehicle design with extra-low boarding arrangement, effective without the need for an engine tunnel. (Photo: Daimler AG)

Fig. 1.8   Examples of applications in which a low upper cab border is advantageous: a Fire service truck with ladder. b Airport apron truck for loading supplies onto aircraft. (Photos: Daimler AG)

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1  The Cab Concept

1.2 Material Concepts in the Cab Besides their geometric size and positioning, cabs also vary with regard to other design considerations. For example, there are cabs in which very different material schemes are implemented. European cabs that are built in very large numbers are made from steel panels, which must usually be welded together. The cab on the right in Fig. 1.1 is a typical example of a steel cab with a spot-welded monocoque construction. In the US, the high volume market also features cabs with shells made from aluminum parts that are joined by riveting, bolting and adhesive bonding. The special cab in Fig. 1.7 is constructed from a welded aluminum frame with plastic cladding panels. For niche applications, cabs made essentially from plastic can be found, thus avoiding the use of expensive pressing tools for sheet metal parts. The cab of the MB Unimog U400 is made from glass fiber-reinforced or carbon fiber-reinforced plastic parts, for example. Metal inserts are incorporated at specific sites in the structure for increased rigidity.

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Functions of the Cab

The cab is first and foremost the driver’s workspace; but especially in long-haul transportation, it must also fulfill additional functions. It is a workplace, living space and sleeping quarters all in one. On some international haulage routes, it is not at all unusual for the driver to live in the cab for two weeks or longer. As a result, the aspect of living is important to the driver, and consequently for the cab as well. At the same time, however, the cab must also satisfy the requirements of a modern place of work. The driver’s workspace must be configured to enable the driver to drive the vehicle safely, economically and quickly for hours on end. Ergonomics and safety considerations have the highest priority in its configuration. Figure 2.1 shows the arrangement of the various functional areas of the three-room accommodation for working, living and sleeping in the cab.

2.1 Driving and Working The most important function of the cab is unquestionably driving, which in this case also means working. All trucks are meant to be driven, but not all trucks must be lived and slept in. The driving function is evaluated in respect of three aspects. Firstly, the safe opera­ bility of the vehicle must be guaranteed. The driver should be able to fully concentrate on the driving task, with as few distractions as possible. This is served by a clear, intuitive configuration of the workspace. Secondly, an optimal workspace and appropriate vehicle technology should ensure that the driver can operate the vehicle efficiently. Drivers must be able to orient themselves in the cab quickly. It should not be possible to make operating errors. And thirdly, the manufacturer would like the driver to enjoy their workspace. Because not only do many drivers involve themselves in the freight forwarders’ purchase decisions, they also tend to take better care of a vehicle they like. © Springer-Verlag GmbH Germany, part of Springer Nature 2021 M. Hilgers and W. Achenbach, The Driver’s Cab, Commercial Vehicle Technology, https://doi.org/10.1007/978-3-662-60847-0_2

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2  Functions of the Cab

Living (stowage space)

Driver's workspace

Living

Sleeping Living (stowage space)

Fig. 2.1   Different areas of the cab are (primarily) designed to cater to the functions of driving, living and sleeping

Figure 2.2 shows the visible changes in the driver’s workspace over the last 50 years; and the changes that are not visible are even more radical. The performance capabilities of the brakes and engine, the quality of the drivetrain, etc, have undergone immense changes, and the driver has been relieved of much of the burden. Even the sheer physical force that must be applied to operate the brake pedal, the clutch pedal and the steering wheel has been reduced considerably over the decades.

2.1.1 The Reach Zone Vehicle manufacturers attempt to configure the cockpit of the vehicle in such a way that the driver can drive as safely and with as little tiring physical effort as possible. Accordingly, the driving tasks are positioned at the center of the driving workspace and auxiliary tasks are arranged separately from them. The displays and operating elements that are used most frequently or are especially important for safe operation are arranged in the driver’s primary field of vision or in their primary reach zone (grab space). The primary reach zone is the area the driver can reach most easily without diverting attention from the traffic situation. Even as they make every effort to find ergonomic solutions, at the same time the various vehicle manufacturers still adhere to certain brand-specific operating philosophies,

2.1  Driving and Working

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Fig. 2.2   Changes in the driver’s workspace over the last 50 years. (Photos: Daimler AG)

which is why all trucks are operated in slightly different ways depending on their make and model.

2.1.2 The Driver’s Seat The driver sits in the driving seat of the truck for hours every (working) day. So the seat is extremely important for the driver’s physical well-being. As a rule, trucks are fitted with suspension seats that isolate the driver from vertical inputs. The vibration behavior of the seat is typically adjustable in suspension seats, so

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2  Functions of the Cab

the driver can adjust the impact absorption from soft (big swing) to hard according to his or her personal preference and depending on the driving conditions. On well-made roads, a suspension seat set to soft drives as comfortably as a sedan. On rough terrain (building sites), stronger damping (less swing) is recommended to minimize the movement of the driver relative to the steering wheel and the operating pedals. Truck seats offer a wide range of adjustment options so that the driver can set up a seat position perfectly suited to their individual needs. Figure 2.3 illustrates a few of these options. The height of the seat is adjustable – (1) in Fig. 2.3. The suspension seat is equipped with a rapid lowering function that lowers the seat to its lowest position to make it easier to climb into and out of the cab. Some truck seats also offer the ability to change the angle of the seat cushion (2). Many are also able to move the seat cushion and thereby changing the size of the seat surface (3). With longitudinal adjustment, the seat can be shifted in the direction of travel to change the distance from the steering wheel and pedals according to the driver’s height (4). The tilt angle of the backrest can usually also be adjusted according to the driver’s wishes (5). Many truck seats are equipped with armrests, which can be folded up and down (6). When folded down, the angle of inclination of the armrest can be adjusted (7). Other functions may be integrated depending on the variant (and price) of the seat, including, for example, a height-adjustable neck support, lumbar support or side contour adjustment. With side contour adjustment, air cushions in the side elements of the backrest are inflated or deflated to vary the contour of the backrest. There are also seats

Fig. 2.3   The driver’s seat: Diagram a shows some of the adjustment options for the driver’s seat. The numbers are explained in the text. Diagram b shows an example of a comfort seat for a long-haul truck. (Photo at right: Grammer AG)

2.1  Driving and Working

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available with a spring system in the longitudinal direction to absorb impacts in the direction of travel. Comfort extras for truck seats include seat temperature control (ventilation) and seat heating. The seatbelt may either be fixed to the cab itself or built into the seat as in Fig. 2.3b). Seats are available with a fabric or leather covering material.

2.1.3 The Steering Wheel The driver is constantly aware of the touch and feel of the steering wheel. It must be held securely and comfortably for long periods. The arrangement and shape of the steering wheel spokes are designed to offer the driver a number of different positions for gripping the steering wheel. After the seat, the steering wheel is the component the driver is in contact with for the longest time, so it must be highly resistant to wear. The steering wheel is also optimized with regard to collision behavior. It undergoes something called the Body Block Test [11] to ensure that in the event of an accident it does not pose a threat to the driver’s safety. A defined test body is forced against the steering wheel at a fixed speed. For steering wheels with an airbag, the results of the Body Block Test are not as particularly significant because the airbag absorbs the impact of the driver with the steering wheel. The steering wheel position is adjustable, so the driver can position the steering wheel to suit themselves depending on height and preferred seat position. The possible adjustment range, called the steering wheel adjustment field, must be able to accommodate short and very tall drivers. Figure 2.4 shows the steering wheel adjustment field of a long-haul truck. The steering wheel adjustment field must allow a comfortable sitting position and good visibility of the main instrument cluster for both the 95% man and the 5% woman.1 Modern trucks typically incorporate steering wheel buttons to operate various vehicle functions. Some of these are associated with essential driving functions such as cruise control and engine brakes or retarder, but they may also control comfort functions such as the volume of the radio. Figure 2.5 shows the cockpit of a long-haul goods truck with the steering wheel and steering wheel buttons.

2.1.4 Operating Elements Besides the steering wheel, which the driver holds constantly, the vehicle is also operated by means of the pedals, and many switches and levers.

1The

95% man describes a person who is taller than 95% percent of the male population. The 5% woman is a woman whose height is such that only 5% of women are shorter than she is.

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2  Functions of the Cab

Fig. 2.4   Steering wheel adjustment field in a heavy goods truck. (Photo: Volvo Trucks, IAA 2012)

For several functions that are activated by a switch or lever, ECE-R 121 [6] explicitly defines how these manual actuating devices are to be positioned and identified. The same regulation also specifies which functions must have indicator lights; the symbols and color to be used for the lights are also prescribed. Regulation ECE-R 121 makes use of the catalog of symbols that are listed in ISO standard 2575 [7]. This includes an extensive compilation of symbols for many different functions.

2.1.4.1 Switches Given the many different functions that operate in a truck, it follows that there are many switches for controlling them. Some manufacturers therefore vary the arrangement of the switches depending on the vehicle’s equipment variant so that the switches can be positioned optimally. Important switches and switches the driver uses often should be placed in ergonomically-favorable positions. Optimum reach zone is limited in the vehicle, so there will always be switches that are not so easy to reach. Logically, switches are organized in functional groups, for example, all switches that control interior light functions are placed close together. There are also switching functions that the driver needs for working outside the vehicle (e.g. for activating a working spotlight). These switches are arranged practically so that they can be operated easily while standing outside the vehicle with the door open.

2.1  Driving and Working

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Fig. 2.5   Steering wheel and cockpit of a heavy-duty truck. Many buttons are built into the steering wheel to enable control of the vehicle functions without taking the hands off the wheel. (Photo: MAN 2013)

As the number of switchable functions is constantly increasing, more and more vehicles currently in development have some switching functions integrated as menus, which are selected using the steering wheel buttons. Multiple switch assignments are also used, so one switch operates different functions according to context. [8] shows one suggestion intended to simplify the multiple assignment of buttons with changing symbols (icons) on the button.

2.1.4.2 Pedals Pedals are used to control the motion of the vehicle. Conventionally, the same two or three pedals are provided as in a passenger car: the brake pedal, the gas pedal, and if necessary a pedal for operating the clutch. As more and more trucks are being built with automated transmissions, fewer and fewer vehicles are being fitted with a clutch pedal. Apart from the main pedals, many vehicles are also equipped with a foot-controlled button for unlocking and locking the steering wheel adjustment field. Some older vehicles (from the 1980s or earlier) also feature a foot control for the engine brake.

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2  Functions of the Cab

2.1.5 Displays In order to reliably control the vehicle, the driver must have up-to-date information about the status of the vehicle, particularly its speed, at all times. The instruments (see, for example, Figs. 2.5 and 2.6) must be clearly readable at all times, including in the dark. Therefore, displays and operating elements are illuminated. In particular, reflection and glare must be prevented both when the cab is brightly lit and at night. The display concept should be designed in such a way that drivers have all the information they need, but at the same time no more than is necessary, to avoid distracting the driver.

2.1.6 Air-Conditioning Air-conditioning during a journey is important, because heat stress while driving is a safety-critical parameter [9]. The driver’s concentration is impaired considerably if the

Fig. 2.6   Cockpit of the Mercedes-Benz Actros 2011. (Photo: Daimler AG 2011)

2.2 Living

17

cab becomes too hot, reaction times are much slower, and the ability to interpret signals diminishes very quickly in high temperatures (over 30° C). Heat has also been shown to be linked to aggressive behavior. Therefore, [9] recommends a temperature window up to 24° C and, for health reasons, not below 19° C in the cab. And air-conditioning in the cab is also important when the vehicle is stationary (see also Sect. 2.3.1): Stationary vehicle air-conditioning enables the driver to establish an agreeable atmosphere while living and sleeping in the cab.

2.1.7 Working with the Vehicle Parked Besides their main job, the driver must often carry out other work tasks as well. These include, for example, loading the vehicle, securing the load and also maintaining the vehicle. Still, there are even more tasks that the driver must do, including paperwork: shipping papers, customs documents, delivery notes and so on. The vehicle manufacturer tries to configure the cab interior so that these work activities can also be performed in comfort. Storage compartments and drawers are often designed to enable the standard DIN A4 documents to fit in there easily. And there are compartments for clipboards and pencil holders.

2.2 Living The driver’s cab is the driver’s house (Cab developer’s adage). The living function is most important in long-distance haulage cabs. The available space in the cab should be sufficient to enable the driver to live in it even for several days at a time (ban on weekend driving in some European countries, for example). In reality, though, the limited space conditions in the cab mean that this is a permanent challenge for drivers.

2.2.1 Stowage Space The driver needs stowage and storage spaces so that they can bring luggage and food in the cab. Figure 2.7 shows the stowage space in a spacious American longhaul truck and stowage compartments above the windshield in a European long-haul trucks (cabs with high roof). Some manufacturers of high-roof vehicles provide additional stowage space below the roof against the rear cab wall. More stowage space is provided under the bed. The lateral stowage spaces under the bed can often be accessed from outside and inside the vehicle—see Fig. 2.8.

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2  Functions of the Cab

Fig. 2.7   Various options for stowage spaces: a stowage space in a Freightliner Cascadia. b Roller doors in the Volvo FH from 2008. c Cover flaps in the Mercedes-Benz Actros 3. (Photo sources: b Volvo Trucks IAA 2008, a and c Daimler AG)

In a special equipment package, long-haul vehicles can be fitted with a refrigerator. As space is very limited in cab-over-engine trucks, the refrigerator must be fitted under the bed – see Fig. 2.9. Other (smaller) stowage spaces are provided in the grab space of the driver’s work position. Storage areas and compartments are usually on the insides of the doors and in the cockpit area. The insides of the doors are logical places to keep drink bottles or things the driver might need outside the vehicle, such as work gloves, high-visibility vests or cleaning materials. It is practical to provide storage compartments for glasses, smoking necessities or documentation within the cockpit area.

2.2 Living

19

Fig. 2.8   Stowage space under the bed. Top: Accessible from inside and outside the vehicle in a cabover-engine truck. Photo: Daimler AG. Bottom: Flap to access sthe stowage space from outside. (Photo: Derek Rotz)

In order to have everything close to hand during sleeping periods or rest breaks, vehicles with bunks have additional storage compartments at the head and foot of the bunk(s).

2.2.2 Lighting Interior lighting enables the driver to find their way around in the cab even in the dark. More sophisticated interior lighting concepts offer a range of settings depending on what the driver is doing at any given time. From very bright lights for reading to cozy, subtle

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2  Functions of the Cab

Fig. 2.9   Example of a refrigerator that slides under the bottom bunk of a European truck. (Photo: MAN AG)

lighting intended to create a pleasant, peaceful atmosphere, various lighting stages are available. Interior light settings also exist that are allowed to be used during driving.

2.2.3 Entertainment The vehicle manufacturers also try to offer reasonable equipment packages to make the driver’s life more pleasant for spending free time in the cab. These include: • the good-old radio, possibly with a CD player and jack for an MP3 player; • infotainment systems2 in which DVDs or Blu-rays can also be played; • storage compartments and sockets for plugging in and connecting consumer electronic devices the driver has brought;

2Infotainment

is a recent coinage made by combining the words information and entertainment.

2.2 Living

21

• folding tables; • adjustable reading lamps; or • special rest corners on the passenger side where the driver can sit as they would in the living room.

2.2.4 The Passenger Seat The passenger side can be fitted variously depending on the task the truck is used for and the customer’s preference. If the vehicle is often driven on long-haul routes by two drivers at a time, a comfortable suspension seat is also fitted on the passenger side. The co-driver is not under physical stress and can relax while their partner is driving. Less expensive solutions also provide for less luxurious seats. Jump seats are also offered: the seat surface can be folded up so that a driver traveling alone has more space, more freedom of movement and standing room on the passenger side during break periods. The rest corner was created with the lone long-haul driver in mind, but if necessary it can also serve as a makeshift passenger seat (Fig. 2.10).

Fig. 2.10   Rest corner on the passenger side as living area for the long-haul driver traveling alone. (Photo: Daimler AG)

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2  Functions of the Cab

2.3 Sleeping and Resting The long-haul driver sleeps in the cab. Therefore, large cabs have comfortable beds built in. Two sleeper positions, one above the other, are offered for when the vehicle is operated with a two-person crew. Figure 2.11 shows a cab with two sleeping positions. When it is not needed, the top bunk can usually be folded upwards to free up more room and create a more agreeable feeling of space. A foot hold or small ladder is provided to reach the top bunk. Even some vehicles that are not used for long-haul assignments have a driver’s lounge so the vehicle can be used for longer routes if necessary, or so that the driver can relax more comfortably during break periods. Besides the bed itself, some vehicles are equipped with additional details intended to make sleep and rest periods as agreeable as possible for the driver. Curtains help to make the cab darker and screen the occupants from the sight of people outside. In the sleeper area, light switches, reading lights, clocks, alarm clocks, etc., can turn the area into a real bedroom. Fig. 2.11   Example of two bunks in a European longdistance truck cab. (Photo: DAF Trucks IAA 2012)

2.3  Sleeping and Resting

23

2.3.1 Comfort The feeling of well-being in the cab is also a safety consideration. If the driver does not sleep well, they feel less rested the following day. Fatigue is one of the biggest contributors of accidents. Drivers can sleep poorly for a number of different reasons: cramped conditions in the sleeping quarters, disturbed sleep in summer because of high temperatures and high noise levels at many rest areas due to traffic and external noise. When rest areas are planned, sleeping drivers can be protected from noise disturbance considerably more effectively by the thoughtout arrangement of parking places and possibly noise barriers. Noise pollution can also originate from the driver’s truck itself, for example, with refrigeration units that (must) switch on periodically at night as well. The sedentary lifestyle that often goes hand-in-hand with the profession as a truck driver undoubtedly does nothing to improve a driver’s sleep quality.

2.3.2 Parked HVAC Parked heating ventilating and air conditioning (HVAC) systems are offered to ensure that the driver feels comfortable when resting in the vehicle. Besides cooling, one welcome side effect is often that the inside air is also dehumidified. Various technical designs are used for air-conditioning in a stationary vehicle.

2.3.2.1 Air Conditioner with Cold Reservoir In the case of a parking air conditioner with cold reservoir, the cold is generated and stored while the vehicle is moving, and consumed when it is parked. While the vehicle is traveling, cold is stored in a cold reservoir designed for this purpose. The driver can flip a switch to begin charging the parking air conditioner. While the vehicle is moving, the system first creates the desired temperature in the cab. Once this is reached, the ­air-conditioning compressor continues running and coolant is directed through a valve into the cold reservoir of the parking air conditioner, where it cools a suitable storage medium. If the interior temperature begins to rise again, the system switches over to cabin cooling. Switching between interior air-conditioning and cooling of the cold reservoir continues until the cold reservoir is fully charged. It can take several hours of driving before the reservoir is charged. The charge time depends on the storage capacity, environmental conditions and the residual cold in the reservoir at the start of the charging process. In cooling mode while the vehicle is parked, air is blown through the cold reservoir by fans. The air is blown past the cold reservoir and cools down. The cooled air flows into the vehicle cab and in high summer creates a pleasant, cool evening atmosphere. Air-conditioning continues until the cold reservoir heats up.

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2  Functions of the Cab

2.3.2.2 Electric Parking Air Conditioner with Coolant Compressor The electrically-operated parking air conditioner with coolant compressor generates cold as and when it is needed. An electric motor powered by the starter battery (Europe) or by additional lead acid batteries, drives the air-conditioning system compressor. The compressor compresses the coolant, which circulates in a closed-process cycle. As it circulates, the coolant is heated up. The coolant is cooled down again (to ambient temperature) by a heat exchanger with the (outside) atmosphere, becoming liquid again (it condenses, which is why the unit is called a condenser). The liquid (pressurized) coolant is metered through a thermal expansion valve, causing the pressure in the coolant to drop. In the evaporator, the coolant evaporates (turns into a gas). In doing so, it absorbs energy (evaporation heat). This cools the evaporator to below the ambient temperature. The cab air is then directed over the outside of the evaporator (by a blower). The cab air cools against the cold sides of the evaporator and the cycle begins again: the coolant is returned to the compressor. The process needs mechanical work (driving power) because the compressor has to be driven; and the cab air has to be actively propelled past the evaporator by a blower. Consequently, the electric air conditioner needs energy, which it draws from the battery when the vehicle is parked. In terms of energy, it is more efficient than the air conditioner with cold reservoir. But the electric air conditioner places a burden on the battery,3 the cold reservoir system does as well, but to a much lesser degree. The parked HVAC can be integrated in the general cab air-conditioning system, or installed as a separate (retrofit) unit that functions independently of the air conditioner/ heater while the vehicle is traveling. Figure 2.12 shows a separate rooftop air conditioning system that is mounted on the vehicle’s roof. 2.3.2.3 The Evaporative Cooler System Another variation of the parking air conditioner is the evaporative cooler system. Here, a suitable medium (a type of wood wool) is wetted with water. This water comes from a water tank that is mounted on the vehicle and must be regularly refilled with fresh water. A blower blows the cab air past the moist medium. The air is cooled by the evaporation of the water (cooling by evaporation). This is not a closed process; the system needs to be replenished regularly with fresh water. The cooling capacity of the system depends on how much water evaporates into the air. If the air humidity is low, a large quantity of water evaporates and the cooling effect works well; but if the air is already so full of moisture that no more water evaporates, no cooling takes place. The evaporated water is then in the cab air, so the evaporation system raises the air humidity. The extra moisture in the air condenses, causing windows to fog up; the increased humidity and condensation can encourage corrosion in the vehicle interior. Wood wool and water-bearing parts have to be maintained regularly for hygiene reasons to prevent fungal and bacterial

3Fortunately,

the electric parking air conditioner drains the battery in summer, when the battery is usually in a healthier condition than in winter.

2.3  Sleeping and Resting

25

Fig. 2.12   Parking air conditioner on the cab roof. In this configuration, the air conditioner is mounted over the opening in the roof hatch. (Photo: Daimler AG)

contamination. The advantage of the evaporative cooler system is that it draws less current than the vaporizer system with closed cooling circuit. Only the blower and a water pump (with low power consumption) have to be operated.

3

Cab Technology

3.1 The Cab Superstructure The bearing structure of the cab is called the frame or, as in building construction, the superstructure. It is typically made from sheet metal or (particularly common in the US) aluminum—see Sect. 1.2. The windshield is clamped or adhesively bonded into the frame with a rubber seal. When the window panes are glued in place, the windshield contributes to the frame’s rigidity. The frame must be able to reflect the enormous variety of cab shapes and sizes (Figs. 1.5 and 1.6). Therefore a modular kit is designed for a variety of structures. Thus, for example, different roof modules can be matched up with the same cab body. Different cab lengths are identical in the front part of the cab as far as the B-pillar (including the door). In some regions, trucks undergo crash tests. The strength of the frame has an important function in protecting occupants in the event of an accident. ECE Regulation R29 [10] contains test procedures and standards for the strength of the cab. Rooftop fixtures Additional components are attached to the roof at certain points. Typical components that are added on the roof are: • the roof spoiler, which is important for the aerodynamic optimization of the vehicle; • the sun visor over the windshield; • various antennas, for receiving radio signals, mobile wireless connection or CB radio communication; • air horns;

© Springer-Verlag GmbH Germany, part of Springer Nature 2021 M. Hilgers and W. Achenbach, The Driver’s Cab, Commercial Vehicle Technology, https://doi.org/10.1007/978-3-662-60847-0_3

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3  Cab Technology

• flashing lights; • chrome U-bars and auxiliary headlamps (as representation accessories); and • in Europe, parked HVAC systems are also fitted on the roof (see Fig. 2.12). Suitable bolt points for these items are provided in the frame.

3.2 Cab Mounting The cab mounting connects the cab to the chassis. A primary function of the cab mounts are to isolate the cab from chassis vibrations while limiting the motions of the cab to prevent contact with other components. The traditional approach has been to use relatively stiff front isolators with softer isolators at the rear. The stiff front isolators limit the motions of the front of the cab relative to the engine and prevent excessive hood flex. The cab is supported by two to four spring elements. There are cabs supported on air springs or steel springs. The elastic mounting causes the cab to lean outwards in bends. This rolling motion is sometimes perceived as unpleasant and creates a somewhat spongy driving feel. In order to lessen this motion, a torsion bar is inserted between the springs at the front. This does not interfere with the purely vertical springing properties of the cab suspension. The torsion bar only functions as a stabilizer when the two spring elements are deflected differently, causing the cab to tilt sideways. In cab-over-engine vehicles, the cab mounting must be designed to allow the cab to tilt forwards. For this, the cab mounting is released at the rear of the cab.

3.3 Tilting the Cab In the case of the cab-over-engine vehicle, it must be possible to tilt the cab to gain access to the engine for repair and maintenance operations. Before the cab is tilted, it must be ensured that there are no loose objects in the cab that will fall in response to the laws of gravity and damage the cab, notably the windshield. No one is permitted to be inside the cab during the tilting operation. For heavy cabs, the cab is typically tilting with the aid of a hydraulic tilting device. This is operated either by a manual pumping action or an electric pump. Figure 3.1 shows an older cab-over-engine model with the cab tilted. The tilting operation affects other parts. The electrical and pneumatic lines between the cab and the chassis must be routed through the pivot point so that the cab can be tilted. The mechanical gearshift must also be taken into account. The equipment that transmits the movement of the gear stick to the gearbox must be designed in such a way that the cab can be tilted. Several technical solutions exist: Fig. 3.1 shows a telescopic linkage. Other common solutions for the mechanical gearshift are transfer by cable pull or hydraulic transfer of the gearshift operation. Again, both of these solutions require the cable pulls or the hydraulic hoses to pass through the cab pivot point. If the vehicle is

3.3  Tilting the Cab

29

Fig. 3.1   Tilting the cab of a cab-over-engine vehicle. Pictured here is a vehicle built in the 1970s. Photo a shows a short cab in the style of the time. Drawing b shows the long cab. In both pictures the telescopic linkage of the manual gearshift is clearly visible. (Photos: Daimler AG)

equipped with an automatic transmission, the intention to shift gears is transmitted via data bus. The design engineering task to transmit the shift command to the transmission is simplified.

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3  Cab Technology

3.4 Styling The external appearance of the vehicle is dictated by the shaping constraints of the shell and the mounted parts such as the radiator grille, bumpers and various decorative features. For practically every customer, the truck is primarily an investment, a utilitarian machine for earning money. Even so, manufacturers in the commercial truck sector as well go to great lengths to bring a good looking product to market. The vehicle’s styling is very important. Its profile, the material from which it is made and the impression of quality it imparts, are all intended to emphasize the vehicle’s characteristics. The styling of the vehicle should reflect its brand identity, and the outer appearance of the vehicle should invoke positive connotations such as reliability, dynamism or safety. The various model ranges offered by a manufacturer should be distinctive, but at the same time they should also speak a uniform brand language to reinforce their brand identity. Figure 3.2 shows the front views of the three model ranges of a European truck manufacturer. The active measures to present a uniform brand styling are clearly evident. Unlike customers in the car market who can freely decide for themselves what color they would like their car to be, the color scheme for trucks is usually determined by other specifications. The color is often determined on the basis of the fleet’s corporate colors or the corporate design of the customer for whom the freight forwarder works most of the time. Therefore, the truck manufacturer offers trucks in practically any color directly from the factory. Trucks take to the roads in a much wider range of colors than cars.

Fig. 3.2   Front view of the three model ranges offered by a truck manufacturer (2014). (Image: DAF AG)

3.5 Aerodynamics

31

3.5 Aerodynamics The shell structure and the exterior determine the aerodynamic quality of the cab. The cab in turn plays a major part in the aerodynamics of the vehicle as a whole. The relationship between the vehicle’s aerodynamics and its fuel consumption is explained thoroughly in [4]. The aerodynamic drag FAero that acts on the vehicle is calculated by:

FAero = 1/2 · ρ · v2 · A · cd

(3.1)

• The coefficient of drag cd is a dimensionless number that describes the aerodynamic efficiency of the body in an airstream. Most modern trucks record values of about 0.5 for cd. • A is the frontal surface area of the vehicle. In modern long-haul trucks, the area is approximately 10 m2, as the vehicle is about 2.55 m wide and 4 m high. The value of about 10 m2 still applies for practical purposes even if the cab is somewhat narrower and less high because the semitrailer or the body of the vehicle typically uses the full legal limits for width and height. • v described the vehicle’s speed. The strength of aerodynamic drag grows exponentially with increasing speed, which is why it is most important for commercial vehicles with a high average speed (above all in long-distance haulage). The power required to overcome the air resistance actually increases by magnitude of 3 (with v3), because power P is given by: P = F · v. • The variable ρ calculated from Eq. 3.1 describes the air density. This changes according to the weather. Changes in the weather are entirely capable of changing the air density by 10% or more. The value cd describes – as mentioned earlier – the aerodynamic efficiency of the cab. Figure 3.3 illustrates the major factors for consideration when designing the streamlined cab shape: • the radius of the cab at the A-pillar, • the shape of the sloping roof versus steep roof leading face, and • the taper. The overall aerodynamic characteristics of the road train are strongly influenced by the body/semitrailer. The body or semitrailer usually takes up the maximum permitted width of 2.55 m, so the vertical rake (Fig. 3.3b) is less beneficial for aerodynamic optimization. The desire for aerodynamic trucks must compete with other requirements such as load capacity and a sufficiently large cab. A large interior space often has a high priority in the design of the cab, so the sweep and taper are somewhat de-emphasized. Besides the major geometric factors, the shape of the cab must also be optimized on a smaller scale. Small edges can cause wind eddies, which together do detract from what

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3  Cab Technology

a

b Contour of the semitrailer

Shape of the roof

Curvature

Inclination of the windshield

c

Sweep

Inclination of the windshield

Corner radius

Taper

Fig. 3.3   Important geometric factors in the base shape of the cab. In this diagram, the differences between the cab shape and a simple cube are slightly exaggerated. The sweep and taper in modern cabs are typically less pronounced than is shown here

was originally an aerodynamically-sound base shape. With the smoke plumes of Fig. 3.4, eddies and adverse airflows can be detected specifically. Low aerodynamic drag is also desirable for other reasons. It also helps to lower the sound level and is welcome as a comfort gain for the driver.

3.5.1 Soiling Another optimization criterion when considering the airflow around the cab is vehicle soiling. A distinction is made between inherent soiling and external soiling. Inherent soiling is caused when the vehicle itself kicks up dirt, which then sticks to the vehicle. Dirt that is kicked up by vehicles traveling ahead or coming towards the truck on the road, or by vehicles in the lane beside the truck (on multi-lane roads) and which then sticks to the truck is called external soiling.

3.5 Aerodynamics

33

Fig. 3.4   Wind tunnel measurement with smoke plume. The smoke plumes render the airflow visible so that eddying and the like can be detected. The total aerodynamic drag is measured over the baseplate the vehicle is standing on. The top picture shows a CoE-prototype with mottled camouflage that is intended to obscure the exact contours of the vehicle. The bottom picture shows an aerodynamically-optimized conventional truck for the American market. (Photos: Daimler AG)

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3  Cab Technology

With regard to soiling, particularly close attention is paid to the areas that impair active safety when they become dirty. These include soiling of the windows and mirrors (vision), and soiling of lights. For reasons of comfort, effort is made to keep certain areas as clean as possible because they are places the driver touches. These notably include the door handles. Soiling can also be reduced by the airflow over the vehicle. The airflow is guided around the cab in such manner that particularly windows and mirrors as well as door handles are exposed to an airstream carrying as little dirt as possible. The soiling properties of a vehicle are examined both in the wind tunnel and in road trials on test circuits as well as on public roads. Of course, soiling is also reduced by taking steps to stir up as little dirt as possible in the first place. Therefore, there is a European directive that prescribes the spray protection systems to be used on heavy commercial vehicles [13].

3.6 Visibility Conditions Good visibility conditions are essential for a low-fatigue, safe journey. Visibility conditions are determined by the shape of the vehicle. Some areas are clearly visible for the driver, others around the truck are difficult or even impossible to see. The mirrors help the driver to see areas without a direct line of sight. Even so, there are still areas around the vehicle that the driver cannot see. These include the area directly behind the vehicle, including the mirror blind spot and obstructed vision areas. For example, the A-pillar and the external mirrors themselves obscure the driver’s view of a small portion of his or her field of vision to the front. The driver’s seat position affects the size of the areas the driver can see clearly and which areas that cannot be seen at all. This is why in complicated situations, many drivers instinctively lean forwards or to one side, to improve their range of vision. Figure 3.5 illustrates the viewing directions that the driver can see while sitting in the driver’s seat. It is obvious that narrow A-pillars and large windows afford good all-round visibility. But because the driver sits so high up, the driver cannot see the surrounding area immediately outside the windows! Extra special caution is required here. Some of the mirrors described next help to alleviate this problem.

3.6.1 Mirrors In order to extend the driver’s viewing range, trucks are fitted with a variety of mirrors. External rear view mirrors – also called main mirrors – make it possible to see along both sides towards the back of the vehicle. They are supplemented by wide-angle external mirrors (convex mirrors), which are designed to allow a wider field of view beside

3.6  Visibility Conditions

35

Fig. 3.5   Schematic representation of the all-round view in a truck

the vehicle. In the vast majority of commercial vehicles, there is no direct line of vision through the backwall of the cab and the body, so an interior rearview mirror is of no use. Interior mirrors are found in vehicles with a window in the cab backwall. On conventional trucks (with hood) additional mirrors are mounted on the hood – the so-called hood mirrors. They supplement the main mirrors and add clarity for blind spots on both sides of the hood, cab and sleeper. A mirror above the passenger door allows the driver to see the blind spot below the passenger door. This mirror also lets the driver look down at the area beside the passenger door. It is called the proximity or ramp mirror in Europe; in the US, the term look-down mirrors. The driver checks the external mirrors and the look-down mirror through the side windows. The area immediately in front of the vehicle is difficult to see because of the high position of the seat. In cab-over-engine trucks, a cross-over mirror enables the driver to see directly in front of the truck. To check the cross-over mirror, which hangs in front of the vehicle, the driver looks through the windshield. The ranges of vision the mirrors must cover at a minimum are defined for Europe in [12] and in [13] for the United States. Figure 3.6 illustrates the various ranges that must be rendered visible by the mirrors in Europe. To ensure that the mirrors satisfy these requirements, the vehicle manufacturer must fit mirrors of appropriate size and with the correct glass curvature. Moreover, the driver is obliged to adjust the mirrors correctly in accordance with his or her height and sitting position before beginning a journey. Figure 3.7 shows the external rearview mirror and the wide angle mirror of a heavy goods truck.

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3  Cab Technology

Proximity mirror

Wide angle external mirror

Forward mirror

Driver's eyelines

Main external rearview mirror

Fig. 3.6   Areas that the external mirrors on a commercial vehicle weighing over 12 t (N3) must render visible in Europe

3.6.2 Windows The driver sees outside the vehicle through the windows. Large window areas allow good all-round vision. But they are also the reason why the interior heats up very quickly in sunlight. This problem can be alleviated with functional glasses. With glass technology, windows can be endowed with a wide variety of functionalities: • Specially coated glasses reduce heating of the interior by sunlight. • Tinted windows make driving more comfortable in very bright sunlight. • Heated windshields are defrosted more quickly. There are several different technologies for this function. The window can be heatable by an invisible metal coating (layer heating) or perfused with almost invisible wires (wire heating). • Acoustically-optimized glasses stop noise from penetrating the glass and reduce traffic sounds as well as wind and engine noise, which are tiring to the driver.

3.6  Visibility Conditions

37

Fig. 3.7   Example of an external rearview mirror and the wide angle mirror of a heavy goods truck. The photo also shows the door control panel with electric mirror adjustment. (Photo: DAF)

3.6.3 Wipers In order to maintain visibility through the windows in rain and road spray, the front windshield is equipped with windshield wipers. Windshield wiper systems for trucks are available with two or three wipers. Several different criteria are applied when developing and evaluating wipers: • The most important of these is how effectively the glass is cleared (the wiping pattern). Wiping performance on a dirty window is also optimized by the development engineers. • The service life of the wiper and any change in the wiping pattern during use is also considered during development. • Of course, the wiping function must be guaranteed equally in both hot and cold weather. • The development engineers even consider the possibility that the wiper blade might freeze to the glass in winter.

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3  Cab Technology

• Everyone knows the unpleasant sounds wipers can make on the glass. Every effort is made to ensure that the driver is not annoyed by these sounds at all. • The wiper blade must be resistant to impact loads. In everyday use, it is inevitable that the wiper blade will strike the windshield as the wiper arms return to their starting position after the windshield has been cleared of moisture, dirt or ice. The blades must also be able to handle aggressive wastewater (containing road salt). • It must be possible to replace and clean them.

3.6.4 The Lighting System The lighting system is responsible for illuminating the surroundings in the dark, so that the driver can see well enough to drive the vehicle in safety. Apart from enabling good vision, of course the lighting system must also ensure that the vehicle is seen clearly by

FRONT

Side

REAR Reverse light

Low beams

High beams

External light functions

Visibility function To see

Front fog lamp

Cornering light (Work light)

Brake light

Daytime running lamp Parking light

Signal function To be seen

Turn signal light (blinker) Clearance lamp

Side marker light

Clearance lamp Rear fog lamp

Special light functions: Emergency vehicle warning light/flashing lights

Miscellaneous

Tracking lamp on the trailer …

Fig. 3.8   Overview of the vehicle’s external light functions

3.7  Ingress and Egress

39

other road users. The various external lighting functions of the vehicle are summarized in Fig. 3.8. The electrical aspects of the lighting system are dealt with in the books on vehicle electrical and electronic systems (e.g. [1, 2] or [3]). And besides their functional duties, the external lights, particularly the headlamps, constitute a distinctive element of the vehicle styling.

3.7 Ingress and Egress Many characteristics of the ingress and egress system are already predetermined as a function of the basic cab concept, as may be seen in Figs. 1.4 and 1.3 and the associated text earlier in this book. There are vehicles that have been optimized to afford low, convenient boarding – Sect. 1.1. Also convenient, but more complicated are some extremely exotic entry variants such as in Fig. 3.9. A set of electric folding steps allows the driver to climb up with little effort despite the awkward placement of the steps behind the front axle on cab-over-engine vehicles (see Fig. 1.3).

Fig. 3.9   Electrically extending stepset for a cab-over-engine vehicle for production in the US. (Photos: Michael Hilgers)

Comprehension Questions

The comprehension questions serve to test how much the reader has learned. The answers to these questions can be found in the sections to which the respective question refers. If it is difficult to answer the questions, it is recommended that you read the relevant sections again. A.1 Functions of the driver's cab What functions must a truck driver's cab fulfill? A.2 Cab-over-engine vehicle What is a cab-over-engine vehicle; what is a conventional (cab-behind-engine) vehicle? A.3 Modules What is a cab module? A.4 Tilting the cab (a) Why must the cab be mounted so that it can be tilted? (b) What structural factors must be consider if a cab is mounted so that it can be tilted? (c) What cab design does not need a tiltable cab? A.5 Aerodynamic drag (a) What variables determine aerodynamic drag? (b) Why is aerodynamic drag more important for long-haul freight transportation than in other applications such as building sites or distribution haulage (2 reasons)? (c) What geometric specifications for the cab determine aerodynamic drag?

© Springer-Verlag GmbH Germany, part of Springer Nature 2021 M. Hilgers and W. Achenbach, The Driver’s Cab, Commercial Vehicle Technology, https://doi.org/10.1007/978-3-662-60847-0

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Fig. A1   Schematic cab representation from above

A.6 The cab shape What parameters are shown in Fig. A1? A.7 Windshield wipers What criteria are considered when evaluating the wiper system?

Comprehension Questions

Abbreviations and Symbols

The following is a list of the abbreviations used in this booklet. The letters assigned to the physical variables is in conformity with with standard usage in the engineering and natural sciences. The same letter can have different meanings depending on the context. For example, lower case c is a very busy letter. Some abbreviations and symbols have been subscripted to avoid confusion and improve the readability of formulas, etc.

Lowercase Latin letters a acceleration b length, often width c coefficient, proportionality constant cd coefficient of aerodynamic drag cT aerodynamic drag in oblique airstream da abbreviation for deka = 10, used particularly often in the expression of force daN (deka-Newton), because 1 daN = 10 N corresponds approximately to the weight force of one kilogram on earth g gravitational acceleration (g = 9.81m/s2) g gram, unit of mass h measure of length, often height h hour, unit of time hp horsepower, unit of power (not an SI unit)—1 hp = 735.5 W k kilo  = 103 = multiplication factor of 1000 kg kilogram, unit of mass km kilometer, unit of length—1 km = 1000 m km/h kilometers per hour—unit of speed;—100 km/h = 27.78 m/s kW kilowatt, unit of power—1 kW = 1000 Watt

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Abbreviations and Symbols

kWh kilowatt-hour—unit of energy l length l liter, unit of volume—1 l = 10−3 m3 m mass m meter, unit of length m milli  = 10−3 = a thousandth part mm millimeter, unit of length—1 mm = 10−3 m r length, often radius s second, unit of time s route (linear measurement) t time t ton, unit of mass—1 t = 1000 kg v speed x typically denotes one of the three spatial coordinate axes y typically denotes one of the three spatial coordinate axes z typically denotes one of the three spatial coordinate axes

Uppercase Latin letters A area, particularly frontal face area C Celsius, unit of temperature DIN Deutsches Institut für Normung (German institute for standardization) E energy ECE Economic Commission for Europe of the United Nations F force FG weight force M torque M mega  = 106 = Million MMI man-machine interface N newton, unit of force NVH stands for noise, vibration and harshness. A summarizing term for vibration phenomena that are audible as sound or perceivable as vibration. OEM original equipment manufacturer P power SI stands for international system of units T temperature (in kelvin or °C) V Volt, unit of electrical tension/electrical potential W mechanical work or mechanical energy W Watt, unit of power

Abbreviations and Symbols

Lowercase Greek letters α angle β angle γ angle δ angle µ stands for micro = 10−6 = a millionth part ρ density φ angle

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References

General reference works  1. Wallentowitz, H., Reif, K. (eds.): Handbuch Kraftfahrzeugelektronik. ATZ/MTZ Specialist publication. Vieweg Verlag, Wiesbaden (2006)  2. Trautmann, T.: Grundlagen der Fahrzeugmechatronik. ATZ/MTZ Specialist publication. Vieweg-Teubner, Wiesbaden (2009)   3. Hilgers, M.: Electrical Systems and Mechatronics. Commercial Vehicle Technology. Berlin/ Heidelberg/New York: Springer (2021)  4. Hilgers, M.: Fuel Consumption and Consumption Optimization. Commercial Vehicle Technology. Berlin/Heidelberg/New York: Springer (2021)

Technical articles  5. Hjelm, L., Bergqvist, B.: European Truck Aerodynamics – A Comparison Between Conventional and CoE Truck Aerodynamics and a Look into Future Trends and Possibilities. In: Browand, F., McCallen, R., Ross, J. (eds.) The Aerodynamics of heavy vehicles II: Trucks, buses and trains. Lecture Notes in Applied and Computational Mechanics, pp. 469–479. Springer, Heidelberg (2009)   6. ECE Regulation No. 121 of the United Nations Economic Commission for Europe (UN/ECE) – Uniform provisions concerning the approval of vehicles with regard to the location and identification of hand controls, tell-tales and indicators   7. ISO 2575: Road vehicles – Symbols for controls, indicators and tell-tales (2010)  8. Küchler, W., Schaare, R.: Technologien für eine neuartige HMI-Gestaltung. ATZelektronik 04(2010), 34 (2010)   9. Taxis-Reischl, B.: Wärmebelastung und Fahrverhalten. ATZ Automobiltechnische Zeitschrift 9(1999), 679 (1999) 10. ECE Regulation No. 29 of the United Nations Economic Commission for Europe (UN/ECE) – Uniform provisions concerning the approval of vehicles with regard to the protection of the occupants of the cab of a commercial vehicle

© Springer-Verlag GmbH Germany, part of Springer Nature 2021 M. Hilgers and W. Achenbach, The Driver’s Cab, Commercial Vehicle Technology, https://doi.org/10.1007/978-3-662-60847-0

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References

11. ECE Regulation No.12, Uniform provisions concerning the approval of vehicles with regard to the protection of the driver against the steering mechanism in the event of impact. Web pages of the German Federal Ministry for Transport, Building and Urban Development. A to Z → ECE Regulations. http://www.bmvbs.de/Verkehr/Strasse/KfZ-technischeVorschriften-,1446.1032708/ECE-Regelungen.htm 12. Council Directive 2003/97/EC on the approximation of the laws of the Member States relating to the type-approval of devices for indirect vision and of vehicles equipped with these devices, amending Directive 70/156/EEC and repealing Directive 71/127/EEC 13. FMVSS FEDERAL MOTOR VEHICLE SAFETY STANDARDS – Standard No. 111; Rear visibility 14. Council Directive 91/226/EEC on the approximation of the laws of the Member States relating to the spray-suppression systems of certain categories of motor vehicles and their trailers

Index

A A-pillar, 34 Aerodynamics, 31 Air-conditioning, 16 Airbag, 13 Appearance, 30 Application of force, 10

B Bed, 22 Blind spot, 34 Boarding low, 6 Boarding steps, 3

C Cab mounting, 28 Cab-over-engine vehicle, 1 Chassis, 28 Coefficient of drag cd, 31 Cold reservoir, 23 Color, 30 Conventional vehicle, 1 Crash test, 27 Cross-over mirror, 35

D Dehumidification, 23 Display, 16 Door opening angle, 6 Driver’s cab module, 3 Driving light, 20

E Engine noise, 1 Enjoying the workspace, 9 Entire vehicle length, 1 Entry, 39 Evaporative cooler system, 24 External light function, 38 External soiling, 32

F Fatigue, 23 Field of vision, 34 Field of vision, primary, 10 Floor, flat, 3 Frame, 27 Front face, 31

G Gearshift by cable pull, 28 Grab space, 10

H Heat stress, 16

I Inherent soiling, 32 Interior lighting, 19

J Jump seat, 21

© Springer-Verlag GmbH Germany, part of Springer Nature 2021 M. Hilgers and W. Achenbach, The Driver’s Cab, Commercial Vehicle Technology, https://doi.org/10.1007/978-3-662-60847-0

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M Main mirror, 34 Material concepts, 8 Menu, 15 Mirror, 34

N Noise disturbance, 23

O Operability, 9 Operating elements, 13 Operation, efficient, 9

P Parking air conditioner, 23 Paperwork, 17 Pedal, 13 Pivot point, 28

R Rapid lowering, 12 Rolling motion, 28 Rooftop air conditioning system, 24

Index S Shell, 27 Sleeper position, 22 Sleeping quarters, 9 Soiling, 32 Steel cab, 8 Steering wheel, 13 Steering wheel adjustment field, 13 Steering wheel button, 13 Stepset, 39 Storage compartment, 19 Stowage space, 17 Styling, 30 Suspension seat, 12 Switch, 13

T Tilting operation, 28 Torsion spring, 28 Two-man crew, 22

V Visibility conditions, 34

W Water tank, 24 Wide angle external mirror, 34 Wind eddies, 31 Wind tunnel, 33 Window, 36 Window area, 36 Windshield, heatable, 36 Wiper, 37 Workplace, 9