Design of A Modular Scania LowEntry Instep Anna Gharibi & Anton Svensson Master’s Thesis in the Master Degree Programme Industrial Design Engineering CHALMERS UNIVERSITY OF TECHNOLOGY Gothenburg, Sweden, 2011 Department of Product and Production Development Division Design & Human factors i Abstract This master’s thesis concerns a new instep for the LowEntry truck segment of Scania. The current instep has major ergonomic, safety and aesthetic issues. The solution is manufactured by an ex- ternal supplier and therefore it does not have a coherent design that matches the Scania brand. Considering the problems, studies about the truck segment, the existing solutions within Scania and on the market were conducted. A user analysis was conducted and information was gathered about the standards and regulations of the truck business. The set requirements acquired from the study have been used as a basis for the design proposals in the next phase. Different design concepts were proposed, on steps, step wells and finally on a new instep. The last phase has been the development of the potential solutions, choosing the best set, design- ing it in details and progressing to a complete and tested prototype. The report is written in English. Keywords LowEntry, Modular, Instep, Ergonomic, Design, Development, Scania CV AB. ii iii Acknowledgements This master’s thesis has been a great and valuable experience. The project has given us the oppor- tunity to work with experienced people from various departments within Scania. We would like to thank the special vehicles department for their continuous support throughout the project. We wish to acknowledge our supervisors at the Scania special vehicles department, Andreas Bys- tröm and Håkan Schildt for their continuous support and encouragement during the thesis work. A special thanks to Andreas Byström for his willingness to help and guidance throughout the entire thesis work. I (Anna Gharibi) would also like to thank Ulrike Rahe, my supervisor and examinator, together with the Design and Human Factors department at Chalmers University of Technology for their support and educational contribution. Anna Gharibi Anton Svensson iv v Notation M Moment F Force σ Stress τ Sheer stress α Step Gradient angle Indices t Tensile Strength s Yield Strength Abbreviations QFD Quality Function Development APS Air process system LSV Laxå Special vehicles STD Scania Specific Standard PP Painting with powder paint FEM Finite Element Method STC Scania Technical Centre vi vii Table of Contents 1. Introduction 1 1.1. Project background 1 1.2. Objectives 1 1.3. Method 2 1.4. Delimitations 2 1.5. Background of Scania 3 Pre-Studies 2. Theory 6 2.1. Scania cab program 6 2.2. LowEntry 7 2.3. LowEntry background 8 2.4. Product analysis 9 2.5. Ergonomic guidelines 13 2.6. Standards 13 2.7. Single instep 13 3. Exterior design elements 15 3.1. Exterior element break down 15 3.2. Scania modular instep VS. LowEntry instep 16 4. Competitor analysis 19 4.1. Volvo 19 4.2. Dennis Eagle 20 4.3. MAN 20 4.4. Mercedes-Benz 21 4.5. BMC 23 4.6. Summary 23 5. User Analysis 27 5.1. User scenarios 27 5.2. Conclusions 29 6. Setting requirements 31 viii 6.1. Requirements 31 6.2. Quality Function Deployment 32 Concept Design 7. Concept generation 34 7.1. Step concepts 34 7.2. Step concept test analysis 37 7.3. The morphological chart 39 7.4. Concept selection 40 8. Concept improvement 43 8.1. Step concept X “Combined” 43 8.2. Instep concept 1 “add-on 90°” 44 8.3. Instep concept 2 ”Add-on 45°” 45 8.4. Instep concept 3”Add-on 30°” 47 8.5. Concept scoring 49 Development 9. Concept development 54 9.1. New circumstances 54 9.2. Form exploration 55 9.3. Step well plate 50° 60 9.4. Rear cover 61 9.5. Steps 61 9.6. Brackets 63 9.7. Assemble 67 10. Prototype 69 10.1. Simplification 69 10.2. Assemble 70 10.3. Functionality test 71 10.4. Improvement 71 11. Further development 75 ix 11.1. Step well plate 75 11.2. Steps 77 11.3. Brackets 78 11.4. Further requirements 81 11.5. Assemble 81 11.6. Courtesy light 82 11.7. Standard components selection 82 11.8. Material selection 84 11.9. Design calculations 86 11.10. Surface treatment 86 12. Cost analysis 89 12.1. Cost analysis conclusion 89 13. Risk assessment 91 14. ECO-audit 93 14.1. ECO product definition 93 14.2. Energy and carbon footprint summary 94 15. Final solution 99 Closing Analysis 16. Discussion 104 16.1. Result 104 16.2. Conclusion 105 16.3. Recommendation 105 17. References 107 Supporting Documents Methods descriptions 112 x Appendix 1 Ergonomic guidelines 115 Appendix 2 Instep Standards 116 Appendix 3 User Analysis 119 Appendix 4 QFD-chart 128 Appendix 5 Step concept test 129 Appendix 6 “Future concepts” 134 Appendix 7 “Add-on 45°” 136 Appendix 8 Design calculations 138 Appendix 10 Media appendix 159 1 1. Introduction The purpose of this chapter is to give the reader a background and the objectives for this master’s thesis. This section also includes a brief description of the methods used to carry out the thesis along with a background introducing Scania. 1.1. Project background LowEntry is a member of the Scania trucks family suited for applications requiring a low-entry boarding step. Recently the chassis of the model has been revised and created new opportunities for adapting the instep. 1.2. Objectives Design a modular instep that can be used for LowEntry cabs with one or two insteps, depending on the height of the vehicle. The instep shall be designed to be safe, ergonomic and robust and give a high-quality impression. Since the instep is an exterior part of the cab’s design, it is impor- tant that the design is integrated into the truck’s exterior shape. 1.2.1. Clarifying objectives To get a clear view of the projects’ goals and desired result, the objectives are broken down with the “Objective tree” method. (1) Modular Use both as single and double instep Fit both driver and co-driver side Safe Minimize risk of injuries Ergonomic Prevent abnormal and dangerous use Robust and quality impression Long life time Resistant to external stresses Integrated with the cab exterior Follow the design line of the cab Look like a product of Scania 2 1.2.1.1. Assignment directives from Scania CV AB • Study demands, standards and desires on instep for similar vehicles and compile a specification of requirements • Obtain information and knowledge about insteps within Scania • Study different solutions and evaluate different options • Choose an option for detailed study • Discuss options with ergonomics and styling departments within Scania as well as with Laxå Special Vehicles • Provide drawings for the proposed solution • Production adaption; tools, costs, inputs from suppliers • Contacts with suppliers and customers is possible • Visits to Laxå Special Vehicles • Legislative demands, investigate legal requirements • Generate CAD material • Prototype modeling • Cost analysis: parts and tools costs • Presentation: written report and oral presentation • If possible: cover the instep e.g. prolonging the door 1.3. Method The project is divided in three main phases; Pre-study, Concept design and Development. The Pre-study phase is aimed at analysing the existing design’s function and exterior expressions. The concept design phase is aimed at generating many design solutions to find the best possible con- cepts. In the developing phase the concepts are developed to a complete design proposal. The phases are carried out with the guidance from Ulrich and Eppingers´s Product Design and Development, (2) Nigel Cross´s Engineering Design Methods (1) and Fredy Olsson´s Princip- konstruktion (3) and Primärkonstruktion (4). 1.4. Delimitations • A time limit of 20 weeks for the master’s thesis. • The LowEntry truck is a modification of a regular Scania truck, with several Scania standard parts. Due to the low sales volume of LowEntry trucks, major changes are difficult to make. • Major changes that require investments in new production tools are hard to imple- ment because of the high cost per unit. • Limited drawing documentation is available. • The existing 3D models have been modeled in the CAD software CATIA V4. • The conversion to the currently in use version CATIA V5 is not editable, which makes it time-consuming to modify the existing parts. • Due to that the LowEntry is an adaptation made by Laxå Special vehicles; there are a lot of accurate 3D models missing. 3 1.5. Background of Scania Scania was founded in 1891 and is now one of the world’s leading manufacturers of heavy trucks and buses as well as industrial and marine engines. Unlike the other competitors Scania focuses only on the heavy transport segment. (5) “Scania’s objective is to deliver optimised heavy trucks and buses, engines and services, provide the best total operating economy for our customers, and thereby be the leading company in our industry. The foundation is our core values, our focus on methods and the dedicated people of Scania.” (5) The Scania’s identity and strategy are reflected in their brand values: “Pride” and “Trust” and their core values: “Customer first”, “Respect for the individual” and “Quality”. Scania communicates its philosophy as focusing on methods rather than results. “Results will come as a consequence of doing the right things right. In order to be successful it is essential to continuously work with improvements.” (5) Scania´s modular system gives the possibility of having a minimum number of parts and allows for many variations. This system provides a high degree of customization while keeping down the cost of product development and production as well as providing a global accessibility to parts and services. So tailoring each vehicle to specific transport needs and providing a better overall operating economy is the way Scania fulfills its core values. (6) 4 5 Pre-Studies 6 2. Theory The theory chapter aims to give an understanding of LowEntry and analyse the existing instep solution to declare possible areas of improvement and to distinguish limitations and regulations. 2.1. Scania cab program The existing Scania trucks are the 5th generation of cabs, with three different standard truck se- ries; the P-, G- and R-series. The current total sales rate for Scania trucks is approximately 75.000 trucks a year. The series offers a range of different cab versions, short, day and sleeper. The sleep- er cab version is available in different heights; Low, Normal, Highline and the R-series exclusive Topline height. See the different cab models in figure 2-1. (7) Figure 2-1 Scania Cab program (8) P-Series The P-series are compact, lightweight, manoeuvrable and fuel-efficient trucks suited for applica- tions such as regional and local distribution, short-range transportation and hectic construction sites. (7) G-Series The G- series offer more power, space and comfort compared to the P- series. The trucks are de- veloped for national long-haulage, distribution and all types of construction applications. (7) R-Series The R-series are Scania’s premium trucks. They are designed to meet the highest and toughest demands in the world regarding long-haulage and construction applications. (7) 7 2.2. LowEntry The Scania LowEntry cab is part of the special vehicle program, and is suited for applications re- quiring a LowEntry step; where the crew frequently need to ingress and egress the cab through- out the workday. The main difference between a LowEntry and a regular truck is the lower height from the ground to the cab floor. In figure 2-2 a LowEntry cab is compared with a P-series cab. Figure 2-2 LowEntry compared with a regular P-series truck The Scania LowEntry truck is a modification of the P-series, using the modular program from R and T-series, where the T-series are out of production. The cab front is taken from the P-series, the cab floor is from the R-series and the door is from the T-series. The cab is mounted 550 mm ahead of the front axle and the floor is lowered 450 mm compared to the R-Series. The configura- tion enables a LowEntry design with a wide instep. The truck has a kneeling function, which ac- tivates when the truck door opens if the parking brake is applied. This allows the cab to go lower. This process combined with a cab floor designed for cross-cab movement and the 90º opening door offers up to a four man crew an easy boarding from both sides of the truck. (9) The LowEntry truck is intended for an urban and rural environment characterized by a hectic work schedule where there is a need for frequent, quick and convenient access to the cab. Ex- amples of the suitable fields are refuse collectors, recycling transporters, multi-drop distribution and airside markets. The annual current sales rate is approximately 50 LowEntry trucks a year. 2.2.1. Overview of the LowEntry This subsection illustrates an overview of the LowEntry cab in driving and kneeling position. Figure 2-3 Illustrated LowEntry overviews (8) 8 Specifications: • Kneeling function • Double steps entry • Total height from the ground to the cab floor 1010 mm* • Total height from the ground to the cab floor kneeled 885 mm* • The lower step’s height from the ground 327 mm* • The lower step’s height from the ground after kneeling 200 mm* • Instep width 810 mm • 90º opening door • Overall cab width 2486 mm * Can vary depending on tire size and chassis height. The LowEntry truck is available in Normal and Low chassis heights, with a difference of 58 mm. 2.3. LowEntry background Scania has been manufacturing the LowEntry cabs for three sequent truck generations. The prin- ciple of moving the cab forward, ahead of the front axle and lowering it down has been the same. The first Scania LowEntry cab arose during the 1980’s. The truck was named the Low-Liner and was based on Scania’s 3rd cab generation. The cab had a single instep. See figure 2-4. Figure 2-4 Scania Low-Liner (8) The second LowEntry cab was based on the 4th generation of the Scania trucks launched in the mid-1990’s. Similar to the current LowEntry model, the cab was higher than the earlier model. Therefore a double instep was necessary for accessing the cab. See figure 2-5. Figure 2-5 Scania LowEntry 4th generation cab (8) 9 2.4. Product analysis This section aims to clarify and define the instep’s functions, relationship between parts and in order to give a general understanding of the existing instep. 2.4.1. Function The instep’s main function is to assist the driver to enter and exit the cab in a safe, quick and con- venient way. Figure 2-6 Process for an instep 2.4.2. Scania modular instep The LowEntry instep is based on the standard Scania instep that is part of the Scania´s modular system. The modular system allows Scania to minimize the number of unique parts. All Scania truck series use the same design concept, except LowEntry since the cab is placed differently. See figure 2-7. Figure 2-7 Standard modular insteps (8) Regular truck instep specifications: • The steps are symmetrical, fits both left and right side • The design has anti-slip texture • The steps let dirt through the structure • The steps are mounted directly on the step well • The step well is integrated with the surrounding environment using plastic covers 2.4.3. LowEntry instep The current instep’s main parts are the step well, the steps and a support frame. See figure 2-8. (3) 10 Figure 2-8 Instep overviews (10) 2.4.3.1. The step well The LowEntry step well is a modification of the standard Scania step well. The step well has been cut into two mounting brackets that are separated, extended and offset from each other in longi- tude direction with a sheet metal to fit the existing standard assembly points. Since the standard brackets are designed for different height and placement, they do not fit the LowEntry trucks. The adjustment results in a step well with non-symmetric edges, bumps and holes. See figure 2-9 and 2-10 The general dimension of the house is 1065 x 520 mm, the thickness of the sheet metal is 1.5 mm and the mounting-brackets are 1.75 mm thick. The parts are irregular for the left and right side of the truck, the left side needs cuts for the nozzle with the level indicator for the anti-freeze liquid. The right side step well has cuts for the engine and the compartment heater plugs. See figure 2-9 and 2-10. Figure 2-9 Cut standard brackets The step well’s functions are to: • Mount the steps to the cab • Connect bumper with the wheelhouse and mudguards • Mount internal brackets • Cover internal parts like radiator, heaters, controllers, cabling, etc. 11 The internal standard parts that the step well is mounted on are shaped after the bump on the cut standard mounting brackets. See figure 2-8. The internal parts limit the depth of the instep. Figure 2-10 Step wells with left and right cuts (10) 2.4.3.2. The steps and support frame The current steps are made of 2 mm thick sheet metal that is folded around a steel frame. The frame supports the steps and is mounted on the step well. See figure 2-11. The reason a frame is used to support the steps is the asymmetrical placement of the cut standard brackets. This causes the bumps and the screw holes’ position out of place which makes it difficult to mount the steps directly on the step well in a good way. • The lower step is 965 mm wide with a maximum depth of 250 mm • The upper step is 920 mm wide with a maximum depth of 200 mm • The distance between the steps are 318 mm. • Step gradient angle α 81° • The steps are asymmetric, which means that each cab needs four unique steps, two for the right side and two for the left side of the cab. • The edges have no anti-slip protection • Texture of the topside doesn’t give a good foothold Figure 2-11 Support frame without and with steps 12 Figure 2-12 Existing insteps 2.4.3.3. The cab floor In the regular Scania truck, the gap between the cab floor and the instep is covered with a plastic cover which follows the line from the bumper all the way to the mudguard. The solution is not applicable in the LowEntry trucks due to the lower cab placement. The plastic cover would clash with the cab floor because of the cab movement while driving. Therefore the current LowEntry instep has an elastic rubber sheet mounted from the cab to cover the gap and hide the inner parts. See figure 2-12. 2.4.3.4. The washer fluid container The washer fluid container is located in front of the left side of the truck, where the container’s pipe neck continues above the step well edge. The pipe does not perfectly fit the LowEntry instep; because the LowEntry instep has a shorter step well compared to the regular Scania trucks. See figure 2-12. 2.4.3.5. The mudguard lock The wheel-house mudguards are connected to the step well with a spring lock fixed on the outer side of the rear cut standard bracket. The purpose of the step frame is to avoid the spring lock. See figure 2-12. 2.4.3.6. Pipe guiding rail The Pipe guiding rail is a unique LowEntry part. The rail is mounted on the driver side step well and the part’s function is to support and guide the cables due to the 550 mm cab extension. See figure 2-13. Figure 2-13 Pipe guiding rail 13 2.4.4. Manufacturing and costs The existing LowEntry instep is designed by Laxå Special Vehicles AB. The company has devel- oped and manufactured special vehicles for Scania since the 1960’s. Most of the standard Scania parts on the LowEntry chassis are assembled on the Scania´s pro- duction line in Södertälje and then delivered to Laxå Special Vehicles. Their production of the LowEntry includes: • Modification of the cab • Modification of the chassis • Docking the cab to the chassis Laxå Special Vehicles AB is a part of Scania’s production system for the LowEntry and Crew-cab trucks. (11) The manufacturing costs for a single complete existing instep is approximately 3000 SEK includ- ing the steps, frames and step well for each side of the cab. 2.5. Ergonomic guidelines Transport-related activities involving manual handling on and off trucks are a major contributor to workplace injuries. Egression and ingression is often associated with poor steps, handholds and slipping risk. It is important that getting in and out of the cab is carried out in an easy and safe way. There are a number of factors that are necessary for ease of ingress and egress in trucks. They are also required for avoiding potential accidents. These factors are presented in appendix A1. 2.6. Standards There are standards and legislations for how a truck instep should be designed. It is important that the design fulfills the necessary standards and legislations. The LowEntry truck has a broad range of applications, and needs to fulfill a range of different standards. A summary of the gen- eral access, refuse collectors and rescue service vehicles standards are available in appendix A2. 2.7. Single instep One of the project’s objectives is to design a modular instep that can be used as both a single and double instep. It is difficult to have a single instep on the existing LowEntry truck because of the height of the cab floor. The cab floor height from the ground in driving position is approximately 1010 mm and 885 mm in kneeling position. According to the European Directive 70/387/EEC available in appendix A2 the maximum distance allowed between steps for a truck instep is 400 mm, which results in a step placement as in figure 2-14. 14 Figure 2-14 Single Step heights in driving and kneeling position (8) According to the Swedish standard SS-EN 1501-1 available in appendix A2, the maximum al- lowed height to the first step from the ground in driving position for a regular truck is 600 mm (550 mm for fire fighter truck). For a refuse collector the maximum approved height to the first step from the ground is 450 mm (no specification on driving position). To be able to design an approved single instep the truck needs to be lowered at least 10 mm (60 mm for fire fighters) in driving position and 35 mm kneeling position. A good single instep de- sign requires the truck to be lowered so the cab floor height in kneeling position is maximum 800 mm. The engine´s location and its size set restrictions on lowering the cab height in driving position and the minimum clearance between the ground and the bumper limits the kneeling height. 15 3. Exterior design elements Products can be designed to carry explicit and implicit references (or simply called as explicit and implicit design cues) (12) Explicit visual references are embedded in the design features that designers implement with the intention to be immediately perceived and recognised. (13) The exterior of the current Scania trucks was analysed with an element break down to find strong design cues that are present in the truck design. The analysis identified the most important design elements used by Scania. The LowEntry’s front is taken from the P-Series cab. There are minor changes in the chassis, the doors and the instep (lower part) but the explicit design identity of Scania remains the same. Figure 3-1 Scania P- Series truck (8) 3.1. Exterior element break down The explicit design cues of the Scania exterior were listed to be used in order to integrate the new instep with the rest of the truck. Some design elements are more applicable to designing an instep while there are some others that are explicit but less relevant to this project. In this part the focus is on the relevant design elements and some less related ones are briefly mentioned. See figure 3-2. 16 Figure 3-2 Scania exterior element (8) 3.2. Scania modular instep VS. LowEntry instep A comparison between the regular modular instep and the LowEntry instep has been carried out. The comparison shows that despite that there is a design thought behind the regular insteps in order to make them connected visually with the rest of the truck, the LowEntry insteps follow 17 none of the directions and it is totally different. See figure 3-3. Figure 3-3 Comparison of the regular and LowEntry instep (8) 18 19 4. Competitor analysis This chapter’s aim is to get a general understanding of possible solutions for a new instep and find additional requirements. See the requirements from other manufacturers’ point of view reflected on their design solutions. Therefore a market analysis on five LowEntry truck manufac- tures is carried out. The analysis focused on the latest solutions in the market for each brand. 4.1. Volvo Volvo is a Swedish supplier of commercial transport solutions providing products such as trucks, buses, construction equipment, engines and drive systems for boats and industrial applications as well as aircraft engine components. (14) 4.1.1. FE low-entry cab (LEC) Volvo FE Low Entry Cab (LEC) launched in 2010, is aimed at the waste collection and recycling sector in both urban and rural environments. It is especially designed for the UK and the Irish market. The Volvo LEC is built on the standard FE truck chassis, mounted 600 mm ahead of the front axle and lowered 200mm. (15) “LEC” Specifications: • Four men crew cab • Overall cab width of 2300 mm • Flat floor • Single step entry • The lower step’s height from the ground 550 mm at the both sides • Available with air suspension (with the option of kneeling function) • The first instep’s height after kneeling function, 440 mm • 90º opening door Figure 4-1 Volvo LEC (15) 20 4.2. Dennis Eagle Dennis Eagle is a manufacturer of refuse collection trucks based in the UK. The company focuses on the complete recycling solutions. (16) 4.2.1. Olympus The Olympus low-entry cab is based on the Pheonix2 body, an earlier low-entry cab from Dennis Eagle. (17) “Olympus” specifications: • Four to six men crew cab • Overall cab width of 2500 mm • The cab floor’s height from the ground 790 mm • Single step entry • The first step’s height from the ground 435 mm Figure 4-2 Dennis Eagle Olympus (17) 4.3. MAN MAN is a German supplier of commercial vehicles, diesel engines, turbo machinery and related services in Europe. (18) 4.3.1. TGA low-entry The MAN TGA low-entry was produced from 2005 to 2008. The cab was bought from Dennis Eagle in the UK. (19) “TGA” specifications: • Four men crew cab • The entry width of 750 mm on the co-driver’s side • The cab floor’s height from the ground 700 mm • Pivoting door used on buses at the co-driver’s side 21 • The first step’s height from the ground 345 mm • Air suspension function Figure 4-3 TGA low-entry (19) 4.4. Mercedes-Benz Mercedes-Benz is a German manufacturer of automobiles, buses, coaches and trucks. 4.4.1. Econic II The second Mercedes-Benz’s low-entry truck (Econic I/1998) introduced in 2006 is a municipal, collection and distribution vehicle. The cab is available with a low and high roof. (20) Econic II specifications: • Four men crew cab • Overall cab width of 2032 mm • Entry width of 620 mm • Flat cab floor • The cab floor’s height from the ground 795 mm • Folding door at the co-driver side • The first step’s height from the ground 450 mm • The standing height in the cab 1930 mm in high cab • Air suspension with kneeling function Figure 4-4 Mercedes Econic (20) 22 Figure 4-5 Air Suspension (20) 4.4.2. Renault Renault is a French automaker producing cars, vans, buses, tractors, trucks and in the past auto rail vehicles. 4.4.3. Access Renault Trucks new low-entry cab named “Access” added to Renault’s distribution range in 2010. The truck is mainly designed for refuse collection. The cab is mounted on a Dennis Eagle Elite2 chassis at the Dennis Eagle manufacturing site badged with the Renault brand, initially launched for the French market. (21) “Access” specifications: • Three men crew cab • Flat cab floor • Single step entry • The first step’s height from the ground 435 mm • The standing height in the cab 2000 mm Figure 4-6 Renault Access (21) 4.4.4. Puncher The “Puncher” model was a common project from both Renault Trucks and PVI (Ponticelli Ve- hicles Industrials). When launched (2004), the Puncher introduced the highest payload capacity on the existing refuse market, while also having a very low access. The “Puncher” low-entry cab is especially suited to household refuse collection, street cleaning and urban delivery in European cities. The series is out of production since 2007. (22) (23) 23 Figure 4-7 Puncher (23) 4.5. BMC BMC is one of the largest commercial vehicle manufacturers in Turkey. It was founded 1964 by Ergün Özakat in partnership with the British Motor Corporation in Izmir. BMC’s product range consists of light commercial vehicles, heavy commercial vehicles, buses and coaches. (24) 4.5.1. BMC Professional 628 low-entry cab truck The BMC Professional 628 Low entry truck is designed to ease the access of the cab by emphasiz- ing the step height and door opening. (24) BMC Low Entry specifications: • Four men cab • Overall cab width of 1850mm • Flat cab floor • Low frame • Single step entry • The cab floor’s height from the ground ~800mm Figure 4-8 BMC Professional 628 (24) 4.6. Summary According to the analysis, providing a low access and an easy ingress/egress without obstacles are the most manoeuvrable features in new low-entry trucks. By combining some of the elements from buses and trucks, especially for refuse collectors results in an easy and fast access. 24 Figure 4-9 Competitor Comparison 4.6.1. Kneeling function Kneeling function lowers the cab with air suspension. Since Scania LowEntry trucks are mount- ed on a truck chassis, the kneeling function is needed to lower the cab down as much as possible for a lower access. While it’s an added value to Econic II to become even lower. 4.6.2. Bus chassis Lower level of bus chassis offers easy and convenient access in and out. The disadvantage in com- parison with the truck chassis is less driving comfort. 4.6.3. Folding doors Positioned low, bus doors provide a convenient and easy way in and out. One of the disadvan- tages of folding doors is the higher noise level in the cab. 4.6.4. Single instep It provides lower access, easy and safe ingress and egress. Scania LowEntry trucks are the highest from the ground and the only one with double steps. 4.6.5. Flat floors Flat floor allows the cab-crew to get in and out on both sides - a very practical feature when cars or walls restrict access to the vehicle. Scania has a flat floor with a bump in between and that’s because of the engine tunnel. 25 4.6.6. Floor height from the ground Lower floor height provides ease of entry and exit. Scania LowEntry trucks are the highest from the ground in the market. 4.6.7. Lower step from the ground Lower floor height provides ease of entry and exit. Scania has the lowest first step level only be- cause it has double steps entry. 4.6.8. Upper step to the floor An evenly distributed distance from the ground/upper step to the floor eases the cab access. 26 27 5. User Analysis The user analysis aims to clarify the users’ needs and recognise their behaviour as well as identi- fying the opportunities to satisfy the users’ requirements. (2) (1) To be able to clarify the needs and behaviours, three visits has been carried out at different refuse collector companies and at one storage distributor, where observations, recordings, interviews and user tests of the existing LowEntry instep have been done. The outcome is presented in dif- ferent user scenarios based on the visits. See appendix A3 with correlated media files in appendix A10 for more details. 5.1. User scenarios A user scenario includes a well-defined hypothetical user and storyline about the user, using the product. The purpose of the scenarios is to present a feeling about how and in what environment the product is used, and reveal the opportunity for improvement. (1) 5.1.1. Fredrik the refuse collector Fredrik is 42 years old and has been working in a refuse collector company for more than 5 years. He drives a Scania LowEntry truck with a sweeper and fraction for collecting household wastes. The refuse collection field characteristics are very hectic; Fredrik has to collect all the households in his district during one workday. Customers follow a schedule for when the bins should be placed at the road for the refuse collector to pick them up. His daily collecting tour has about 300 collection stops. It means that Fredrik has to step in and out of the cab more than 300 times during a working day and he has started to get problems with his knees because of the repetitive strain that the continuous ingress and egress causes in the knees. Fredrik needs to hurry to be able to finish his daily round, and then get home. But the truck’s instep doesn’t fit his needs very well. The steps are placed like a ladder; he can’t see the lower step. In addition the steps are very slippery. Despite being very cautious, he has fallen several times from the instep and hurt his shinbone. Due to him avoiding a fall and putting strain on the knees, he never jumps or skips any steps. Instead he uses both steps and climbs in and out carefully, gripping the door handle and the steering wheel. Especially in winter when the steps and his shoes collect snow and mud and it gets even more slippery. Fredrik needs a better positioned instep in which he can step in and out instead of climbing. He wants non-slippery steps for safe access. He wants the steps not to collect dirt and water or snow. 28 Figure 5-1 Fredrik the refuse collector 5.1.2. Mark the storage distributor Mark is 28 and has been working as storage distributor in IKEA for 2 years. He drives a Scania LowEntry truck with a kneeling function and distributes containers to different warehouses in- side the storage area. He usually works together with another colleague. They divide the driving task between them during the day, but both exit the truck for the delivery and loading process. They have a tight schedule of delivering 4 to 5 containers every hour. Each load and delivery re- quires 5 to 6 exits and entries in order to be able to connect and disconnect the container on the truck. During an 8 hour work day, they ingress and egress at least 200 times. Mark always approaches the cab entrance from the back of the truck, he opens the door and the cab kneels. He grabs the door handle and reaches for the steering wheel and lift himself up using both steps, long before the cab has fully kneeled. If the truck is already in kneeling position, he sometimes uses only the upper step because he feels the lower step is placed too low. But the up- per step is too high to always be used as a single entry step. In order to be fast, Mark needs to step in and out instead of climbing the stairs. But the lower step is hard to reach in a fast pace. Most of the times he just touches the steps’ edges with his foot paw. Because of the steps position and the slippery steps, there is a risk of falling. Mark has slipped on the steps several times and feels unsecure exiting the cab, so he often jumps off from the upper step. He is aware that the frequent jumps put a lot of strain on his knees and in the long term he will get problems with his knees, like his elder colleagues. Mark needs an instep with a stair feeling, easy to reach without gripping the door and steering wheel with a good anti-slip texture. 29 Figure 5-2 Mark the storage distributor 5.2. Conclusions The user analysis displays that the user desires an instep with a stair feeling, which enables the user to walk in and out of the cab instead of climbing. The defied areas of improvement are: • The steps are slippery • The steps collect water, dirt and snow • The lower step is hidden under the upper step and hard to reach • The kneeling function is too slow • The steps are not robust enough 30 31 6. Setting requirements The purpose of setting the requirements is to make an accurate specification of the performance required for the design solution that consists of both demands (D) and wishes (W). The specifica- tion defines the required performance, and not the required product. The requirements for the instep are developed together with Scania’s Special Vehicles department. 6.1. Requirements General function • Assist the user’s entry and exit of the cab (D) Safety • Anti-slip function (D) • Safety labels/notations (W) • Fulfill ergonomic guidelines (W) Design • Modular, adjusted for different range of use (D) • Fit on the truck (D) • Adjustable instep heights (W) • Use the existing step well (W) • Use standard parts (W) • Single instep (W) • Hide instep by the door (W) • Convey the Scania identity (D) Technical • Carry static load of 1800 N (D) • Temperature range (-30) – (+80)°C (D) • Last 75000 design load cycles (D) • No visible corrosion for the first 3 years (D) • No visible corrosion for the first 5 years (W) Standards and legislations • Fulfill the standard for general insteps (D) • Fulfill the standard for refuse collectors (D) • Fulfill the standard for fire and rescue service vehicles (D) • Fulfill the general standards regarding truck measurements (D) • Fulfill general Scania standards (D) 32 Costs • Price of the final product should be proportional with the existing solution (D) Manufacturing • Possible to assemble by Laxå Special Vehicles AB (D) • Possible to be sourced by Scania CV AB (D) Environment • Recyclable (D) • Designed for disassemble (W) • Environmental friendly materials and surface treatment (W) 6.2. Quality Function Deployment The aim of the Quality Function Deployment (QFD) method is to set and weigh the engineering characteristics of the product against the customer demands and to clarify the relationship be- tween them. The customer demands in the QFD are the project objectives. The QFD chart shows that the step placement, distance between the steps and the shape of the steps are the main engineering criteria for an ergonomic instep design. See appendix A4. 33 Concept Design 34 7. Concept generation To find a solution which meets the set requirements, demands and wishes, four weeks of concept design is carried out. The aim has been to generate as many ideas as possible in order to find the feasible concepts according to the limitations and develop them further to come across the best solution. (2) The approach has been to find basic principal solutions that are essential for the instep. Then make different variations of the principles to explore different shapes, connections and integra- tion. The concept generation are separated in step concept and step well concepts, which later are combined with a morphological chart for further development. Pencil and paper are the main tools used for the design phase. To be able to determine the con- cepts’ functionality, simple wooden prototypes are made and tested in an instep model rig. Based on the test results and consultation with advisors at the special vehicles, the ergonomics and styling departments the concepts are screened and the concepts with the most potential are further developed. 7.1. Step concepts The generated step shapes are categorized into 6 main concept principles. See figure 7-1. Each concept group consists of several shape and form variations of the same basic principle. The con- cepts’ sketches are presented in table 7-1, a part of a developed morphological chart section. Figure 7-1 Step concepts 35 7.1.1. Concept 1 “Positive wave” The aim with this principle is to have an instep with a stair feeling that allows the user to walk in and out of the cab with good comfort and good visibility of the steps. The idea is based on the us- ers’ tendency to approach the truck from the back side so offering a stair from the side. The Step is intended to be a single part step in different levels, resulting in a double step as well. 7.1.2. Concept 2 “Negative wave” The design principle behind concept 2 is similar to concept 1. The only difference is the reverse angle. The “Wave” has a gradient towards the rear of the instep, allowing for a wider upper step. 7.1.3. Concept 3 “Wedge” The concept principle is that the steps are shaped like a Wedge. The purpose is to get a comfort- able stair feeling for both ingress and egress of the cab. 7.1.4. Concept 4 “Inverted wedge” The Inverted Wedge is the same principle as the Wedge. The difference is that the upper step is inverted for more shin clearance while getting out. 7.1.5. Concept 5 “Double step” Concept 5 is a regular double step solution similar to the existing solution but with different depth of the steps to obtain a better “walk-in-and-out” feeling. 7.1.6. Concept 6 “Double wave” The principle behind the concept 6 is to have the possibility of both single and double steps in the same design. The concepts are supposed to be used as both single, double or a combination of steps depending on the user’s length. 7.1.7. Concept X “Mix” Concept X is consisting of random concepts with irregular shapes that are not practical or func- tional. More sketches are available in the media appendix A10. 36 Table 7-1 Morphological chart steps 37 7.2. Step concept test analysis The test analysis aims to evaluate the ergonomics of the principal concepts and determine the best height placement of the steps. The principle shapes of the steps are manufactured in wood and tested at different heights in an instep model rig at the Scania´s model workshop. The different concepts are tested with 7 participants, including 3 vehicle ergonomists from Scania R&D. The test includes both kneeling and driving position. The summary of the tests are avail- able in appendix 5 and the video recordings of the test are available in the media appendix A10. 7.2.1. Single instep test A test with a single instep demonstrates that a single instep is a bad ergonomic solution with the current cab floor height of 885 mm in kneeling position. The height obliges the user to put a lot of extra strain on knees and hips. The test concludes that the floor height for a good ergonomic single instep is maximum 800 mm. 7.2.2. Step test conclusions The tests conclude that “The Inverted Wedge” and “The double step” concepts are the safest and most ergonomic step concepts. According to the test, an equal spaced distance between the steps from 300 to 340 mm and a maximum step gradient α of 75°offers good ergonomic when entering and exiting from the cab. See figure 7-2, 7-3 and table 7-2. Figure 7-2 Step gradient α (25) Table 7-2 Step placement 38 Figure 7-3 Step heights (8) 7.2.3. Step well concepts The generated step well designs are categorized in 3 main concepts principles. Each concept group consists of several shape and form variations of the same basic principle. See table 7-3. The main design idea is to cover the asymmetrical uneven instep brackets as well as the non- effective ingress and egress area of the steps. Early concept sketches are available in the media appendix A10. 7.2.4. Delimitation Very early in the design phase, limitations were revealed that not many changes are possible in order to refine the design. These limitations affected and limited the idea generation process. Some of the limitations are listed below: • Scania’s modular system restricts use of new parts • Some of the standard parts are altered in Laxå Special Vehicles in order to fit the LowEntry • Lack of resources restricts possible solutions 7.2.5. Concept 1 “Remake” The “Remake” principle is a complete new step well that is more integrated with the exterior design of the LowEntry truck. The design concepts focus on following the design lines from the side view of the cab. The remake concept requires altering of the internal standard Scania parts to fit the new step. 7.2.6. Concept 2 “Instep add-on” The “instep add-on” concepts are based on the existing cut standard bracket. The brackets are in- tended to mount a bent sheet metal that offer a smooth and clean surface for the whole step well. That allows for an easy mount of the steps directly on the step well wall in a clean way. 7.2.7. Concept 3 “Edge covers” The “Edge covers” principle is based on the existing instep. The steps are mounted with a frame. The frame and the bracket edges are covered in different variations. 39 Table 7-3 Morphological chart step wells 7.3. The morphological chart The Morphological chart lists the possible features and functions that are essential for a complete instep. The chart displays a large number of possible design combinations. (1) The intention of this chart is to combine the variations of the step and the step well concepts pre- sented in previous sections with features to be able to generate complete concepts proposals. 40 Table 7-4 Morphological Chart Features 7.4. Concept selection The concepts are screened with a two-stage concept selections method. The two stages are con- cept screening followed by concept scoring. Each stage is supported by a decision matrix which is used to rate, rank and select the best concept(s). The concept screening is a quick and approxi- mate evaluation that aims to introduce a few viable alternatives. The concept scoring is a more detailed analysis and evaluation of these relative few concepts. Highly scored concepts will be developed further. (2 pp. 124-129) Both stages follow a six-step process: • Prepare the selection matrix • Rate the concept • Rank the concept • Combine and improve the concepts • Select one or more concepts • Reflect on the result and the process 7.4.1. Concept screening Concept screening is based on a method called the Pugh concept selection. The aim of this stage is to narrow down the concept quickly and to improve them before the final selection. The pro- cess is done systematically through the six-step mentioned above. (2 pp. 130-133) The selection matrix criteria are based on the main relevant objectives set of Scania for the mas- ter’s thesis, where each criterion is given an equal weight at this stage. The screening process 41 focuses on the step and the step well concepts, which are screened separately. See table 7-6 and 7-7. The design concepts are benchmarked relatively against a reference, in this case the existing LowEntry instep design. The relative grading system is presented in Table 7-5. Table 7-5 Relative screening grading 7.4.2. Step selection The step concept selection is based on the concept test and evaluations made with responsible advisors at the special vehicles department at Scania that made it obvious to identify the more promising concepts. See table 7-6. Table 7-6 Step Concept Screening The concepts principle “Inverted Wedge” and the “Double Step” are selected to be improved further. The ergonomic design was the main criteria when choosing the concepts to be further developed. 7.4.3. Step well selection The step well concept selection is carried out as well together with responsible advisors at special vehicles department. 42 Table 7-7 Step well Concept Screening The concept “instep add-on” is selected to be improved further because the concept provides a clean surface, which makes the mounting of the steps easy and without any expensive invest- ments in tools. The new instep design faces a lot of limitations especially regarding investment costs because of the low sales volume of the LowEntry truck. (~50 vs. 75,000 trucks) Encountering these restrictions, the possible solutions have been narrowed down to a few op- tions which can be adapted to the existing parts. On the other hand Scania would like to have some suggestions regardless of the limitation that could be used for future application where the single step entry is feasible. Brief concepts description is available in appendix A6. 43 8. Concept improvement The selected concepts are improved to get a resolution that will better differentiate the competing concepts. The concepts are drawn in CATIA V5 in order to inspect the form in interaction with the surrounding parts. This method helps to examine the general shape on a basic level. The section includes a description of an improved step concept together with 3 compatible step well concepts. All of them are labelled under the “instep add-on” category. 8.1. Step concept X “Combined” Based on the conclusions from the test, a new step concept is generated. The advantages from the “Positive Wave” and the “Inverted Wedge” are combined in order to develop a solution which has the required strength points. The concept utilizes the “Wave” concepts stair feeling with a longitude offset of the upper step relative to the lower step. The step has an angle that allows an ergonomic “attack angle” entering the cab and the step clearance gotten from the “Inverted Wedge” concept, comfortable for exiting the cab. See the basic shape in figure 8-1. The tests summaries are available in appendix A5 and in the media appendix A10. Figure 8-1 Concept X “Combined” The steps are intended to be of an open waved texture similar to the regular Scania steps. The symmetric texture provides a modular solution where the steps can be flipped and used both on the driver and co-driver side. See figure 8-2 Figure 8-2 Step texture 44 8.2. Instep concept 1 “add-on 90°” The concept consists of a variety of the “add-on” step well and the “Double step” concept. The add-on concept is going to be fully done in sheet metal with the help of folding and bending techniques in order to avoid tooling costs. 8.2.1. Step well The “add-on 90°” offers a smooth and clean surface that covers the asymmetric standard brack- ets. The design has a wide instep and the covered parts do not affect the functionality of the in- step, since they are not the effective parts used in ingress and egress the truck. See figure 8-3. The step well is supposed to be mounted with brackets on the edges of the cut standard brackets. Figure 8-3 “Add-on 90°” Side view The concept is a sheet metal bent at 90º both in the front and rear bracket. The sheet metal fol- lows the bumper and the wheel house. See figure 8-4. Figure 8-4 “add-on 90°” ISO view 45 8.2.2. Steps The suggested step for this step well is bent 90º with a stair like “Double step” at its maximum width in the lower step parallel to minimum depth at the upper one, which provides an ergo- nomic stair feeling both entering and exiting. Figure 8-5 illustrates a top view of the basic shape of the steps. Figure 8-5 Steps - “add-on 90°” Top view The lower step exceeds outside the wheelhouse, which gives a slight attack angle for the foot en- tering the cab. See figure 8-6 Figure 8-6 “add-on 90°” attack angle 8.2.2.1. Disadvantages • Wide areas of plane sheet metal without any function. • The required depth of the step well doesn’t fit the Air Process System cooling coil mounted on the wheelhouse bracket that is connected to the chassis. 8.3. Instep concept 2 ”Add-on 45°” This concept consists of a variant of the “add-on” step well and the “Combined” step concept. The “add-on 45°” offers a smooth and clean surface suitable for placing the steps. 46 8.3.1. Step well Figure 8-7 Instep “add-on 45°” ISO view The step well Add-on 45° concept is a sheet metal bent 45º in the front and the rear bracket. The straight surface makes it easy to mount the steps directly on the step well. The symmetric angles form a wide and welcoming instep. See figure 8-7 and 8-8. The step well is supposed to be mounted with brackets on the edges of the cut standard brackets. Figure 8-8 Instep “add-on 45°” Side view 8.3.2. Steps The suggested step for this concept is the combined “Wave” and “Inverted Wedge” step concept with 45º angle on sides. See figure 8-9. 47 Figure 8-9 Attack angle “add-on 45” The wedge angle allows a good step gradient for exiting the cab. From the top view the step shape represents a variation of the eagle beak shape used often in the truck’s exterior. The 45° angle on the step well plate allows for a deep step that results in a good step gradient. See figure 8-10. Figure 8-10 Steps -“add-on 45” Top view 8.3.2.1. Disadvantages The angle in the front interferes with the nozzle neck of the washer fluid container. 8.4. Instep concept 3”Add-on 30°” The concept is similar variant of the “add-on 45º” concept with the “Combined” step concept. The “add-on 30°” offers a smooth and clean surface in the same way as the “add-on 45” concept. 8.4.1. Step well The step well Add-on 30° concept is a sheet metal bent at 30º in the rear and 45º in the front. The angles grant a wide and welcoming instep. See figure 8-11 and 8-12. 48 Figure 8-11 Instep “add-on 30°” ISO view Figure 8-12 Instep “add-on 30°” Side view 8.4.2. Steps The combined “Wave” and “Inverted Wedge” step concept offers a stair feeling with a good shin clearance with 30 º angles on the sides. See figure 8-13. Figure 8-13 Attack angle “add-on 30” 49 The wedge angle allows a good step gradient for exiting the cab and the offset upper step offers a good stair feeling entering the cab. The step shape represents a variation of the eagle beak shape from the top view. The design thought for the 30º angle in the rear is to amplify an ergonomic walk angle suited to place the user foot approaching the cab from the rear. See figure 8-14. Figure 8-14 Steps -“add-on 30” Top view 8.4.2.1. Disadvantages • The 30º angle steals step depth. • The angle results in a large gap between the standard bracket and the Step well. • The angle in the front can cause problems when integrating the nozzle neck of the washer fluid container. 8.5. Concept scoring The concept scoring is a more detailed evaluation that aims to identify the best concept. The in- creased resolution of the concept due to a more detailed design will better differentiate the com- peting concepts. In this stage the selection matrix criteria are more detailed compared to the screening matrix in table 7-8 and 7-9. The criteria are set based on the clarified objectives and the specification of the requirements set in the previous chapters. The concept scoring rating system is a weighing system, with 100 percentage points allocated among the selection criteria in the matrix. A new reference system is used as a benchmark for all the criteria as in the previous stage. See table 8-1. Since the reference will be of average perfor- mance relative to all criteria, it will result in a “scale compression” from 5 to 3 levels for some of the criteria. Different references are points for various criteria among all the concepts. The refer- ence points are designated by a bold font value in the scoring matrix shown in Table 8-2. The concepts are ranked from the sum of the weighted scores. Table 8-1 Relative scoring grading 50 8.5.1. Instep scoring The Concept scoring is prepared and carried out together with the responsible advisors at the special vehicles and market department to obtain different aspects on the improved concepts. Table 8-2 Relative scoring grading Concept 2 achieves the highest score from the evaluation and is ranked as number one. 8.5.2. Reflection According to Ulrich and Eppinger it is essential to supplement the evaluation, done in the con- cept scoring with a discussion to ensure that the selected concept is the one with greatest poten- tial for success (2 p. 137). The concept scoring reflection is done with the responsible advisors and concerned managers at the market department. The concepts are reviewed, and it could conclude that the selected con- cept has the most potential. Because of the good ergonomic and integrated design regarding the delimitations discussed below. 51 8.5.2.1. Delimitations • The standard instep is part of the Scania’s modular system. The cut standard brackets are shaped after standard internal parts that connect the instep to the chassis. Redesign of the step well to suit the LowEntry requires changes of several internal standard parts as well. This is not an option with the current sales rates. • Since the tooling cost is very high and the LowEntry is a minor share of the company’s market, using details that require investment in tools cannot be a reasonable option. • The distance between the cab floor and the instep is different in the regular trucks. Therefore the similar integration covering solution on the top is hard to implement. Be- cause of the cab movement, there needs to be a minimum tolerance of 50 mm between the cab floor and the step well. • Lowering the cab more is difficult because of the existing engine size and the cab can- not kneel more because of the required clearance between the bumper and the ground. 52 53 Development 54 9. Concept development This section aims to describe the development phase of the selected design concept “add-on 45º with the “combined” step concept. In this phase with the help of the 3D software AliasStudio and CATIA V5, shape explorations in details are carried out. The aim is to adapt the design practically to the interacting parts and to evaluate the connection with the exterior of the truck in relation to the new instep design. 9.1. New circumstances The initial conditions for the step well are changed in this phase. The main changes are: • The Air Process System (APS) located on the wheelhouse mounting bracket • A new bumper design. 9.1.1. Air process system The development of the “Add-on 45º” concept faced problems with the Air Process System (APS). The standard APS is located on the Wheel house bracket that is assembled to the chassis on the main production line in Södertälje. Laxå Special Vehicles rebuilds the Air Process Sys- tem to fit the unique design of the LowEntry truck. This results in the “add-on 45º” concept that clashes with the new APS configuration. Scania special vehicles department were not aware of the rebuild Laxå Special Vehicle did to the APS since it wasn’t available in any CAD models or drawings. The discovery of this forced the development to restart and adapt to the newly discov- ered problem. The development of the original “Add-on 45º” concept is briefly presented in Ap- pendix A7. 9.1.2. Horn The horn is originally placed on the wheelhouse mounting bracket, but the new rebuild of the APS requires the horn to be placed on the step well plate. 9.1.3. Bumper The LowEntry truck will have an upgraded front that includes a new bumper called the Pro- truded bumper. It is a wider steel bumper with different connection types compared to the old bumper with plastic covers. See figure 9-1 and 9-2. 55 Figure 9-1 The Protruded bumper Figure 9-2 Bumper width comparison 9.2. Form exploration In the following subsections a form exploration on the selected concept has been carried out. The examination has been performed with the aid of AliasStudio and CATIA V5. The purpose for using the CAD software is to do quick form variations, in combination with the interacting parts. This method helps to narrow down the possible solutions to the most feasible result. 9.2.1. 50º angle The step well angles are modified from 45º to 50º in order to leave space for the LowEntry unique Air Process System (APS). The alteration also provides more space for the top cover both for accessing the lock and the placement of the pipe, as it gets 5º wider. 56 Figure 9-3 Tilted 45º Figure 9-4 Straight 50º 9.2.2. Tilting angle The 45º step well had a tilting angle on the sides in order to fit the bumper’s shape and the cut standard brackets which are curved after the bumper and the wheel-house. The front surface was tilted 2º and the rear part was tilted 3º inwards. With changing the old bumper and emerging the Protruded bumper which is wider, the tilted angles were fixed to the straight angle surfaces. Figure 9-5 Tilted angle after the existing bumper 57 9.2.3. Integration In order to integrate the new step well with the rest of the truck, especially the nearby involved parts like the bumper, headlight, headlight seal and the wheel-house. Since the top integration also has to be considered together with the top cover some limitations ascended e.g. the posi- tion of the washer fluid pipe, the complexity of the casted plastic shapes of the seal, possible placement of the steps and lack of resources narrowed down the alternatives. The solution was to follow some lines from the front all the way to the rear of the instep with a chamfer from the headlight seal all the way to the wheel-house. Figure 9-6 Following lines 9.2.4. Wheelhouse lock cut The assemble order requires the wheel-house cover to be positioned in place after the placement of the instep. The wheelhouse is disassembled due to services, repair and maintenance which set a requirement for the lock to be accessible. The lock is required to be reachable with an opening clearance of minimum 35 mm in 160º opening angle. A cut has been made with the required proportions parallel to the mudguards. See figure 9-6. Figure 9-7 Lock position 58 9.2.5. Top cover As figure 9-7 illustrates the new design causes a hole between the cut standard brackets and the step well plate. This is the space that is required to be covered. Figure 9-8 Top hole rear The cover solutions are intended to be made in sheet metal as the rest of the instep. The reason for this choice is: • The high tooling costs for plastic parts • The plastic cover does not fit the aesthetic expression of the rest instep 9.2.5.1. Front top cover The washer fluid container on the driver side should be accessible from the top to be opened and filled up easily. Therefore a cut out is necessary in order to open up space for accessing the pipe. A number of solutions on the front cover where generated. See the discarded front top cover designs due to cost and manufacturing complexity in figure 9-9. Figure 9-9 Discard front Top cover designs 59 The selected top cover solution is the sheet metal, bent to follow the headlight seal chamfer with a cut gives space to the pipe neck. See figure 9-10. Figure 9-10 Selected Top cover front 9.2.5.2. Rear cover The spring lock at the rear cut standard bracket is required to be reached by hand and the rear cover should be east to remove by the user. Therefore the connections should be simple and reachable from the top which means that the cover can’t be connected to the standard bracket. On the other hand the rear part has a very limited space, thus the design has to provide maxi- mum space with no sharp edges. Therefore each millimeter is important. Some design solutions were discarded due to complexity. See figure 9-11. The selected solution is a sheet metal part, bent down in 2 edges and screwed to the step well plate top surface. Figure 9-11 Rear top cover concepts 60 9.3. Step well plate 50° The step well plate is a 2.5 mm thick sheet metal where the design shape is cut-out with a water or laser cutter. See figure 9-12. Figure 9-12 Unfolded view The sheet is bending with 50º angles creating the structure for the step well. Bending sheet metal is not a precise manufacturing method, there is always a spring back resulting in a wide tolerance range to the hole patterns. Due to the wide tolerances, the mounting holes are oval. See figure 9-12 and 9-13 Figure 9-13 Step well plate The front top cover is part of the step well plate, folded to cover the front hole. Figure 9-14 Top cover- Front • Thickness: 2.5 mm • Weight: 12 Kg 61 9.3.1. Engine heater and reflector cut The engine heater plug cut on the co-driver’s side of the truck is positioned below the upper step to be less visible providing a cleaner surface. The reflector light located on the step well plate is placed in accordance to the Commercial ve- hicle regulations for lightning installation. 9.3.2. Liquid level indicator The liquid level indicator cut is removed due to the gap between the outer surface and the con- tainer. The gap between the container and the step well surface makes it hard to see throughout the container especially when the container’s material is not transparent enough to see through. On the other hand an automatic indicator on the control panel is supposed to inform the user inside the cab when there is a need for refilling the container. 9.4. Rear cover The rear cover is 1.5 mm thick sheet metal, folded down 90º to reinforce the cover structure. It’s to be screwed on the rear part to be easily removable. The cover for the co-driver side is a mirror image of the driver-side cover. Figure 9-15 Top cover- Rear • Thickness: 1.5 mm • Weight: 0.2 Kg 9.5. Steps The steps are open waved casted steps similar to the standard Scania steps. The open waved design let water, dirt and snow through the step surface. The anti-slip textures function is well established on the regular Scania trucks. See figure 9-16 Figure 9-16 Step texture 62 9.5.1. 50º steps The steps are placed in an equal distance of 320 mm between the steps and the cab floor with an overlap of 90 mm and offer a step gradient angle α of 74.3º. The existing instep offers a step gra- dient angle α of 81º. The maximum standard required angle is 85º. See figure 9-17 and 9-18. Figure 8-17 50º Step overlap The lower step height from the ground is approximately 370 mm in driving position and 245 mm in kneeling position. See figure 9-18. Figure 8-18 Step placements driving level The 50º steps’ pattern sizes are changed from 40 to 45 mm squares compared to the 45° steps. This is done to minimize weight and to keep consistency with the standard Scania steps. 9.5.1.1. 50º upper step The upper step maximum depth is 170 mm and the minimum depth is 120 mm. The step’s length is 650 mm. The upper step fulfils the European directives regarding the minimum foothold of 150 mm in depth at 300 mm in step width. 63 Figure 9- 19 50º Upper step overall dimension • Thickness: 30 mm • Weight: 2.0 Kg 9.5.1.2. 50º lower step The lower step’s maximum depth is 260 mm and the minimum depth is 205 mm. The step’s length is 780 mm. The lower step’s outer edge has a tolerance to the maximum vehicle width of 10 mm. The maximum vehicle width is 2550 mm. Figure 9-20 50º Lower step overall dimension • Thickness: 30 mm • Weight: 3.2 Kg 9.6. Brackets The step well plate is mounted to the cut standard brackets with 6 connector brackets. See figure 9-21. 64 Figure 9-21 Brackets overview The initial idea for the connector brackets was to weld them to the step well plate and then screw it to the cut standard bracket to avoid screws on the step well plate surface. But that would re- quire the plate to be screwed from the inside of the step well. This is not possible due to the as- semble order. See the section 9.7 Assemble. 9.6.1. Cut standard brackets The standard step well is cut in two parts and is offset 550 mm in longitude direction and 37 mm in horizontal direction. See figure 9-22. The purpose for keeping the cut standard bracket principle is that they are shaped after the inner brackets. Therefore they have the required connection points to the standard parts, and fulfill necessary functions. Figure 9-22 Cut standard brackets 65 The standard brackets are the base brackets which the instep-brackets are mounted on to carry the step well plate with the steps. The front standard bracket is mounted to the bumper bracket and also connects the bumper and the washer fluid container. The rear standard bracket mounts to the wheelhouse bracket and also acts as support for the mudguard which is connected to the bracket with the spring lock. • Thickness 1.75 mm • Weight: Front: 1.7 Kg, Rear: 1.6 Kg 9.6.2. Front instep-bracket The front instep bracket is a 3mm thick V-profile bracket with an inside angle of 130º. The bracket’s flange on the standard bracket is spot welded and screwed to the cut standard bracket. The instep bracket’s function is to mount the step well plate to the truck. Figure 9–23 Front and rear view of the front instep bracket The bracket has 6 weld nuts that the step well plate is screwed to. The hole on the upper edge of the bracket flange is where the upper step screw head is positioned. See figure 9-23. • Thickness: 3 mm • Weight: 1.5 Kg 9.6.3. Rear instep-bracket The Rear instep-bracket is also a 3 mm thick V-profile bracket with an inside angle of 130º. The fillet on the flange against the standard bracket is there to give more space to be able to access the spring lock connection from the top. See figure 9-24. 66 Figure 9–24 Front and rear view of the rear instep-bracket The flange against the standard bracket is spot welded to the standard bracket and screwed to the bracket together with the wheelhouse mounting bracket. The step well plate has 6 weld nuts on the outer flange which the step well plate is screwed to. • Thickness: 3 mm • Weight: 1.7 Kg 9.6.4. Bracket 1 and 2 Bracket 1 and 2 are L-profile minor support brackets mounted on the side of the cut standard brackets. Their function is to support the outer edges of the step well plate. The brackets are the same size except for the positioning of the holes since the holes’ pattern on the standard bracket mounted flange differs with 5mm. Figure 9–25 Support brackets 1 & 2 • Thickness: 2 mm • Weight: 4x 0.06 Kg 67 For the side support it was not possible to have one continuous bracket similar to the front and rear instep brackets because the cut standard brackets surface is not flat. The rear bracket is curved after the wheelhouse, and the front has a slight curve on the inside. 9.7. Assemble The assemble line is served with preassembled articles that are assembled to the truck chas- sis. The assemble process has to be carried out towards the work plane since all the connection points have to be reachable with the tool from the side of the cab. The step well plate and the steps are preassembled separately. The cut standard brackets with the connector brackets are first mounted to the truck chassis. In the last phase is the preassembled step well plate with the steps assembled to the standard brackets. See figure 9-26. Figure 9-26 Assemble order The instep is a robust design that has to withstand many loads, resulting in a total design weight of 24 kg. 68 69 10. Prototype The purpose of prototyping is to evaluate the design’s function and manufacturability. The prototype for the 50º design presented in previous chapter is manufactured by Scania´s pro- totype workshop “Mekaniska STC”. The design and technical drawings are prepared in CATIA V5. See figure 10-1. All the prototype drawings are available in the media appendix A10. Figure 10-1 Prototype model 10.1. Simplification Because of the cost limitations, and to be able to manufacture the prototype in the Mekaniska STC the steps are simplified. The prototype steps are built on the same principle as the existing steps with a frame that is covered by a folded sheet metal plate. The prototype steps have an outer steel frame bent like the new step shape. This is supported with three support bars that are welded to the frame. Three distances are welded on the frame to sup- port the frame against the step well plate. Above the frame the sheet metal plates are bent around the frame edges. See figure 10-1 and 10-2 70 Figure 10-2 Prototype Step Structure 10.2. Assemble The prototype is assembled and tested on the special vehicles’ laboratory truck “Lägst”. An overview of the result of the prototype can be seen in figure 10-3. Figure 10-3 Prototype Overview The assemble process was carried out in the prototype workshop at Scania by the authors. The parts were preassembled and assembled according to the designed order. In the assemble process no major problem were faced. All the parts were fitted well. See figure 10-4 Figure 10-4 Assembly process 71 10.3. Functionality test The functionality and appearance of the prototype confirm and provide a feeling that the instep has good strength and robust design. The prototype is tested by the refuse collectors at SRV-återvinning in Tumba, Botkyrka. The conclusion of the test is that the shape and placement of the steps offer a significant ergonomic improvement compared to the existing instep design. The concept allows the user to walk in and out of the cab with great comfort, especially in driving level. This is important because of the slow and not always used kneeling function. See figure 10-5. With the open-waved casted steps and the anti-slip texture the design will be ergonomic and safe with good visibility of the step edges during egress from the cab. Figure 10-5 Function test 10.4. Improvement Some minor details were discovered that should be changed in order to improve the function or appearance of the concept. 10.4.1. Step well plate After assembling the instep a gap between the step well plate and the headlight seal in the front and the mudguard in the rear were observed. See figure 10-6 72 Figure 10-6 Step well plate gap The clearance between the rear step well plate’s wall and the cut standard bracket were consider- ably large, especially in the upper part of the rear step well plate curvature. See figure 10-7 Figure 10-7 The rear gap 10.4.2. Top cover The cut for the washer fluid container seemed to be tight. A larger cut can provide an easier ac- cess to the container. See figure 10-8 Figure 10-8 Washer fluid container clearance 73 Based on the prototype the chamfers did not properly follow the headlight seal chamfer. The chamfer is positioned high in comparison to the seal. See figure 10-9 Figure 10-9 Chamfer continuity One fastening screw hole can be removed because it was revealed that 3 screws can hold the cover tight enough. See figure 10-10 Figure 10-10 Rear cover screws 10.4.3. Mudguard lock The step well plates rear cover edge clashes on the inside with the opening angle for the spring lock. This leads to that the spring lock cannot be fully opened, causing difficulties when closing and opening it. See figure 10-11. Figure 10-11 Mudguard lock 74 75 11. Further development The further development section is aimed at optimising the design by decreasing the part num- bers and weight. This optimisation was done in parallel to and after the prototype manufacturing and test process. Detail drawings of the developed concept are available in appendix A9. 11.1. Step well plate • The side sections of the step well plate are moved forward in order to minimise the gap between the step wells and head light seal and the mudguard. • The rear outer edge of the step well plate is extended from the top reducing all the way down to fill the gap and creates a cleaner surface. • The chamfer in the rear part was also extended in longitude, parallel to the cut stan- dard bracket’s curvature to fill the gap. • The chamfer is lowered in order to follow the headlight seal line more precisely. • In order to give more space for the users hand to screw the washer fluid container’s cover, an oval cut is made instead of a circular one. • The thickness of the step well plate is reduced from 2.5 mm to 2 mm to minimize weight. The weight is reduced from 12 Kg to 9 Kg. Figure 11-1 Unfolded view driver side 11.1.1. Co-driver side The co-driver side is a mirror image of the driver side without the cut for the washer fluid con- tainer. See figure 11-2 and 11-3 76 Figure 11-2 Unfolded view co-driver side Figure 11-3 Step well plate co-driver side 11.1.2. Pipe guiding rail The pipe guiding rail is lowered 60 mm from the former position. The reason to change the posi- tion of the guiding rail is that in the new position the screw heads are hidden by the upper step, resulting in a cleaner surface. See figure 11-4 11.1.3. Horn bracket The horn bracket mounted to the plain side of the driver side step well plate close to the APS configuration. See figure 11-4 Figure 11-4 Pipe guiding rail and horn position 77 11.2. Steps The pattern shapes and the anti-slip texture on the steps are optimized for the best visual appear- ance and function. The symmetrical pattern of the steps allows them to be flipped around and used as modular steps on both the driver and co-driver side. See figure 11-5. Figure 11-5 Modular step driver and co-driver side The steps are screwed to the step well plate, where the screw holes on the steps are untapped, to prevent the screw from loosening due to vibration from the truck. The mounting holes are de- signed according to the STD3863. 11.2.1. Upper step Figure 11-6 Upper step • Thickness: 36 mm • Weight: 2 Kg 11.2.2. Lower step Figure 11-7 Lower step • Thickness: 36 mm • Weight: 3.2 Kg 11.2.3. 3D-print of the steps 3D printed prototypes of the steps are manufactured to be able to get a real feeling of the shape and size of the actual steps. They are painted with metallic colour similar to the real steps to look as real as possible. In figure 11-8 and 11-9 are the steps mounted on the LowEntry truck “Lägst”. 78 Figure 11-8 3D-print of steps ISO view The open-waved casted steps offer good visibility of the lower step edge. See figure 11-9. Figure 11-9 3D-print of steps top view 11.3. Brackets The further development of the brackets focuses on minimizing the number of unique parts ac- cording to Scania´s modular system principle. 79 11.3.1. Cut standard bracket The 2 cuts of the standard bracket are adapted to the new modular instep-bracket. Unnecessary treatments of the cut standard brackets and the useless holes for the old steps are removed. See figure 11-10 and 11-11 Figure 11-10 New cut standard brackets Figure 11-11 Cut standard brackets driver and co-driver side • Thickness 1.75 mm • Weight: Front: 1.7 Kg, Rear: 1.6 Kg 11.3.2. Instep-bracket The two instep brackets are modified to be one modular bracket. The symmetric shape allows the bracket to be used on the front and rear standard bracket, both driver and co-driver side of the truck. See figure 11-12 80 Figure 11-12 Front and rear view of the modular instep-bracket • Thickness: 2.5 mm • Weight: 1.5 Kg 11.3.3. Side bracket The supporting L profile-brackets named, 1 and 2 are reduced to one single modular bracket that fits on all four positions on both driver and co-driver sides. The different positioning of the holes in the standard cut brackets are compensated with bigger holes. See figure 11-13 The brackets are also extended out after the step well plate extension described in section 11.1 in order to fit the interacting parts. Figure 11-13 Side bracket • Thickness: 2 mm • Weight: 4x 0.06 Kg 11.3.4. Rear cover After extending the rear step well plate’s edge towards the cut standard bracket, the rear cover is changed after the extended plate. The cover’s flange on the right side is also removed. This makes it easier to manufacture and therefore cheaper to produce. Three screws fasten the rear cover instead of four. Figure 11-14 Rear cover 81 11.4. Further requirements To take the presented concept further some requirements should be included. The requirements were introduced late in the development process therefore due to the lack of time they are re- maining to be considered. • The side mark lamp required with mudguard extension. • The new front placement of the cab tilting device’s positioning. 11.5. Assemble The preassembled brackets are mounted to the bumper bracket and the wheelhouse bracket. Then the steps together with the step well plate are assembled to the brackets followed by the pipe guiding bracket and the horn bracket assembled to the step well plate back. The rear cover is assembled last; after the mudguard is assembled to the rear cut standard bracket. See figure 11- 15. An animation of the assembling is available in the media appendix A10. Figure 11-15 Final Assemble order The instep’s total design weight in the concept design is 22 kg which is acceptable, compared to the existing solution design weight of 19 kg. 82 11.6. Courtesy light To avoid accidents when entering and exiting the cab in darkness, a suggestion is to have an auto- matic courtesy light that will light up the steps and ground when the door is opened by the user. The selected suitable courtesy light lamp for the LowEntry instep is a LED-light from Braslux. Originally the lamp is used to light up the rear registration plate of the trucks in the Brazil mar- ket. The lamp is a 24 volt with a socket approved to be used outside. This LED light is placed beneath the lower step, where it will light up the ground around the truck entrance visible through the open waved casted steps. See figure 11-16 Figure 11- 16 Courtesy light suggestion The registration plate LED lamp is available in the Scania drawing archive. (2025980) 11.7. Standard components selection This section aims to select the appropriate standard screws, washers and nuts for the concept based on the Scania´s Guide 010 for available fasteners in production with associated STD. The selection criteria are an annual demand above 10000 units, and used in similar designs. M8 threads are used in the existing step wells and the standard connecting weld nuts on the wheelhouse and bumper brackets. In table 11-1 the selected screws are presented. Self-tap screws are used together with the untapped weld nuts and steps to not loosen due to the truck vibration. 83 Table 11-1 Screw Selection The selected M8 nuts in table 11-2 are untapped weld nuts and self-lock nuts, to be able to resist the truck vibration. Table 11-2 Nut Selection Suitable washers in table 11-3 are selected after the screw diameter. Table 11-3 Washer selection 84 11.8. Material selection The aim is to select the most suitable material for the instep based on material properties, en- vironmental issues and cost. The material selections are carried out with Granta CES Selector, where the material yield strength is compared to density, price and CO2 footprint. The diagram in figure 11-17, 11-18 and 11-19 illustrates available materials with a minimum yield strength limit of 100 MPa plot against density, price and CO2 footprint. 11.8.1. Selection criteria 11.8.1.1. Properties criteria The chosen material would have to be able to withstand the forces applied by the user and at the same time be as light as possible. This would suggest that the material would have to have rela- tively high mechanical properties as yield strength and young’s modulus with a low density. See figure 11-17. Figure 11-17 Yield strength vs. Density (26) 11.8.1.2. Cost criteria Cost is a major factor for the material selection regarding the final price. It is important to choose a material which would withstand the required forces while being relatively cheap. In figure 11- 18, the yield strength is set against the price per kg. Figure 11-18 Yield strength vs. price (26) 85 11.8.1.3. Environment criteria The selected material should have a minimum effect on the environment. In figure 11-19 the Yield strength is set against the CO2 footprint at production. Figure 11-19 Yield strength vs. CO2 footprint, production (26) 11.8.2. Selected material The selected material is optimized based on the three diagrams; Carbon steel is selected as a material for the step well and the brackets. Cast alumina-alloy selected for the steps. The quality class of both materials are selected based on the related STD. 11.8.2.1. Carbon steel Carbon steel is a metal that is strong, tough, easily formed - and cheap. Carbon steels are alloys of iron with carbon and often a little manganese, nickel, and silicon. (26) The specific material is selected according to the STD755. The selected cold-rolled sheet is nor- mally used for thicknesses up to 3 mm. Brackets and structural compartments for the cab are typical uses for the cold-rolled sheet. Mechanical properties SS-EN 10268 HC260LA Tensile strength: 350-430 MPa Yield Strength: 260-330 MPa SS-EN 10130 DC03 Tensile strength: 270-410 MPa Yield Strength: 180-230 MPa 11.8.2.2. Cast Al-alloys Aluminium, the first of the “light alloys” (with magnesium and titanium), is the third most abun- dant metal in the earth’s crust (after iron and silicon) but extracting it costs much energy. (26) Almost all aluminium alloys for casting contain 5 - 22% silicon (Si) - the silicon makes the alloys more fluid so that they fill the mold and take up fine detail, even in thin sections. Due to the low sales volume of the LowEntry truck sand casted steps are recommended. Casting in sand moulds (or plaster moulds) is the only method which is suitable for small batches, e.g. prototypes, but using automatic moulding equipment, it can also be used for large batches. The 86 method gives relatively slow solidification and as a consequence the mechanical properties are normally somewhat lower than when casting in permanent forms. Precise selection of cast-aluminium suitable for sand casting is selected according to STD4279. The selected cast-aluminium is appropriate for sand casting and permanent mould casting. Mechanical properties Scania Aluminum 42100 EN AC-42100 Tensile strength: 230 MPa Yield Strength: 190 MPa 11.9. Design calculations The strength calculations are carried out as a reasonable estimation of the concept dimensioning. Due to the complex design the dimensioning process is hard to carry out with handbook meth- ods. The design is estimated by experience and supporting FEM simulations. The strength is also tested on the prototype as well as some minor estimation calculations. Spot welding design cal- culations and bolt connection estimation are available in appendix A8. 11.9.1. Finite Element Method Finite Element Method is an approximate numerical method in order to solve differential equa- tions. Depending on the problem the results will always differ from the actual fallouts. The FEM simulations are carried out with CATIA V5´s Generative Structure Analysis feature. Due to the complexity of the design the FEM simulation are used as an estimation of the overall stresses and visualise the behaviour of the design. In appendix A8, under the section “FEM simulations” the results are presented with comments for each simulation. The results are not fully reliable due to the assumption of the boundary con- dition and accuracy of the element size and meshing. The conclusions of the FEM simulations are that none of the stresses applied to the instep con- cept are critical. The stresses are well below the materials yield strength limit. This is necessary so that the instep can withstand the minimum Scania standard of 75000 load cycles. The simula- tions are supported with the robust feeling the prototype gives. 11.10. Surface treatment The qualities of the surface treatment are set after the Surface treatment standard STD4111. The Scania’s standard states that the products should have surface treatment which provides an attractive appearance and corrosion protection with satisfactory durability. The quality of the surface treatment is dependent on the visibility of the product. See table 11-4. Powder painting is the selected surface treatment method. 87 Table 11- 4 Requirement levels 11.10.1. Step well and top cover The step well is a major visible part of the cab. STD411 requirement states that after three to five years there should not be any visible corrosion on the cab body. The step well should be coloured with the standard sub-grey chassis colour. To fulfill corrosion requirement a “very good” B3 surface finish is selected for the front of the step well plate and “Good” C3 for the rear side of the plate. The top cover will also have B3 surface finish, all accord- ing to the table 11-4. Step well Front: STD4111-B3-PP-1346692 Step well Rear: STD4111-C3-PP-1346692 Cover: STD4111-B3-PP-1346692 88 11.10.2. Steps The selected treatments for the steps are the same as for the regular Scania steps. It is a “Good” C2 finish for visible parts of the step and a D2 for non-visible parts. The colour is a standard step grey found on Scania’s regular insteps. Visible: STD4111-C2-PP-1386297 Non visible: STD4111-D2-PP-1386297 11.10.3. Brackets The brackets are non-visible because of the step well plate and will be treated with a C3 quality and a sub grey colour. According to the table 11-4 STD4111-C3-PP-1346692 89 12. Cost analysis The cost analysis has been carried out together with the Purchasing department at Scania. The analysis is an estimation of the maximum price on the required tool investments and part costs. The cost and annual demands for the parts are based on the current sales volume of the LowEn- try trucks. Table 12-1 Cost analysis 12.1. Cost analysis conclusion The cost for the complete instep design (April 2011) is about 5570 SEK for both sides of the truck, a total cost reduction of approximately 430 SEK compared to the existing solution. The steps are the main cost due to required investment of new production tools. To be able to reduce the cost further requires an increase in total sales volumes of the LowEntry truck. 90 91 13. Risk assessment In this chapter the hazards associated with the use of the instep are documented. A hazard is a situation where the people, the property or the environment can get harmed. (27) The risk caused by the hazard and the measures are introduced to reduce the risk is presented in table 13-1. This is done to minimize injury and harm to the user. Table 13-1 Hazards to user 92 93 14. ECO-audit The purpose of the ECO-Audit section is to evaluate the concept’s main environmental impact in a life cycle perspective (material, manufacture, transport, use and end of life) with focus on energy use and carbon footprint compared to the existing instep solution. See figure 14-1. The ECO-audit has been carried out with Granta CES Selector ECO database. Figure 14-1 Life Cycle principle (26) Surface treatment is not included in the analysis because of the complexity. 14.1. ECO product definition The primary data for each life cycle phase is set by the ECO product definition. The ECO product definition is split into three main sections; material, manufacturing and end of life, use and transport. 14.1.1. Material, manufacture and end of life The product definition estimation shows that the rolling and casting are the primary manufac- turing process with focus on energy use. The production energy of steel is comparatively low per unit weight, about half of polymers/per unit volume. Carbon steels are easy to recycle, and the energy consumption to do so is small. Aluminium ore is abundant. It takes a lot of energy to extract aluminium, but it is easily recycled at low energy cost. (26) In table 14-1 and 14-2 the material, manufacturing and end of life are stated for the two instep designs. 94 Table 14-1 Material, manufacture and end of life new instep design. Table 14-2 Material, manufacture and end of life existing instep design To be able to recycle the casted steps it is required that the parts material composition is marked according to STD3871. 14.1.1.1. Transport The transportation of the product is estimated based on the location of Scania´s suppliers and the main market for the LowEntry truck. • 1000 Km with truck • 1500 Km with sea freight. 14.1.1.2. Use The product life span of an average refuse collector is approximately 10 years, with an average use of 52000 km per year. (28) 14.2. Energy and carbon footprint summary The main environmental impact of the design is caused by the process of material production. The recycling of the product contributes to an end of life savings corresponding to the replace- ment of virgin materials. 95 14.2.1. New LowEntry Design Figure 14-2 Energy use summary new design (26) Figure 14-3 Carbon footprint summary new design (26) Table 14-3 Energy and Carbon Summary new design (26) The total estimated energy required for the product’s life cycle is 78 MJ, and the carbon emission is approximately 8 Kg. (26) 96 14.2.2. Existing design Figure 14-4 Energy use summary existing design (26) Figure 14-5 Energy use summary existing design (26) Table 14-4 Energy and Carbon Summary new design (26) The total estimated energy required for the product’s life cycle is 226 MJ, and the carbon emis- sion is approximately 16 Kg. (26) 14.2.3. Eco conclusion The ECO-audit illustrate that the new instep design requires more energy to produce the mate- rial compared to the existing design due to that the aluminium casting process requires a lot of energy. In the further life-cycle stages the two designs are similar in energy usage. The new in- 97 step design has a higher potential environmental impact saving with the end of life recycling due to the potential energy savings of producing new aluminium from recycled material compared to creating aluminium from virgin minerals. The new instep design has a minor potential environment saving effect compared to the existing solution. There are no sophisticated test-machines to measure embodied energies or carbon footprints. International standards, detailed in ISO 14040, lay out procedures, but these are vague and not easily applied. The differences in the process routes by which materials are made in different production facilities, the difficulty in setting system boundaries and the procedural problems in assessing energy, CO2 and the other eco-attributes all contribute to the imprecision. The impre- cision derivation is approximately 20 %. (26) 98 99 15. Final solution In this chapter are photo realistic images of the final design in detail and integrated on the truck with the protruded bumper presented. The images are done with Autodesk 3d Max. Figure 15-1 Detailed view driver side Figure 15-2 Detailed view co-driver side 100 Figure 15-3 ISO-view with protruded bumper 101 Figure 15-4 Front view instep 102 103 Closing Analysis 104 16. Discussion The approach to the whole project was based on the presented objectives; a modular, safe, er- gonomic, robust integrated and preferably single step instep. As the project went on new input emerged to the surface in the project which caused many revisions and start overs. Scania’s modular system has made the Scania products highly modularized. This has brought many advantages like minimizing the unique parts and cost as well as fast and easy service. On the other hand since, in the modular system, parts are designed and shaped after each other, changes to the parts are not easily possible without changing the related parts. Soon in the design phase many barriers were revealed which influenced the final design notably. Perhaps other solutions could have been sought and considered to a larger extent if the current circumstances could be changed or if more resources were available. The solution is designed for the current truck with the current tightly interactive parts with low sale numbers and very limited resources. The result could be highly different if there were areas of freedom. 16.1. Result This thesis has resulted in a double step instep which is: Modular The concept has less unique parts compared to the existing LowEntry instep (12 parts on both side compared to 22 parts) which helps in lowering the price, ease of manufacturing and as- semble. The design fit both driver and co-driver side. The steps, the brackets and the step well plates are highly modularized. The step well plate and the rear cover are different parts on the driver and co-driver side but they are mirrored and shaped after the same principal. Safe Safety has been a major issue in the current instep for LowEntry. The new steps have anti-slip- pery pattern and texture as the regular Scania step which provides a safe foothold on the steps, which let dirt and snow through. Ergonomic Based on the prototype test the minimum comfortable width for the upper step and the maxi- mum width for the lower step with the 74.3º step gradient angle provide a good visibility over the steps and a good shinbone clearance and consequently an easier ingress and egress. Robust and Quality Impression Based on the calculations and the prototype test the concept’s design is very robust and can with- stand the design load well. This gives a long life and durable quality to the concept. 105 More integrated with the cab exterior The concept follows the design of the exterior to some possible extent. Clean large surfaces with smooth broken angle and continuity all around were considered in the new design. As men- tioned, limited available resources have narrowed down the material selection and the properties of the material limited the form giving process. The casted aluminum steps based on the Scania standard step’s principals also help the product to look more like a Scania product. In the end a result close to completion is presented which fulfills the requirements to possible extent in the given time and possible frame. 16.2. Conclusion Product development is a long process. The limited time has directed this project to some ex- tent. The time that was spent on doing very basic researches and gathering information from the company and the co-workers, structuring the information, finding a working solution which is feasible within Scania and Laxå Special Vehicles has left too little time for truly creative work and innovative solutions. Although the focus has been on realistic solutions a lot of interesting ideas arised in the beginning of the concept design phase and soon discarded by the limitations. Some of the ideas were not documented. Scania LowEntry trucks are manufactured in low volumes and the advertisement on the segment has been underprivileged. During the pre-study the fact had revealed that dealers even in Sweden were unaware of this Scania product. In order to make a successful segment out of LowEntry, engineering, design and human factors disciplines as well as financial investments should work hand to hand. It might require the LowEntry trucks become a standard order in Scania instead of special order. The current solution on the instep is done by Laxå Special Vehicles without considering Scania’s exterior design standards in design and development. This lack of integration damaged the co- herency of the product family. 16.3. Recommendation Document all information about LowEntry e.g. requirements, different parts and CAD files at Scania. It speeds up related projects to a large extent. Manufacture the parts as Scania parts inside Scania to be able to keep track of them, reduce the cost and maintain the coherency. Spread more information about LowEntry inside and outside the company. 106 107 17. References 1. Cross, Nigel. Engineering Design Methods 4th