PROJECT OF AN ELEVATING AND TILTING END OF LIFE VEHICLE PLATFORM

Transcription

1 PROJECT OF AN ELEVATING AND TILTING END OF LIFE VEHICLE PLATFORM João Velho Cabral Harding Read Abstract - This report presents the work developed in a project of a lifting and tilting End of Life Vehicle (ELV) platform with the objective of making it an economic and simple alternative to the concurrent one. The scope of this project was market, patents registry and legislation research, generation and selection of concepts of alternative platforms and structural dimensioning. Market and patents registry research have not produced results that would influence the platform design, something that could be justified by the youth of the market in question. Of all the nine alternative concepts of platforms generated, one was selected with the help of selection tools based on criteria that are important to the company that proposed this project. For the structural dimensioning it was applied the norm EN 1493:1998 [1] along with Regulamento de Estruturas de Aço (REA) [2]. It was also used gathered information by the institution NHTSA [3]. The objectives of simplicity and economy were reached with the adopted alternative platform, chosen among the proposed concepts, because the result was a simpler and more efficient platform then the one of the competing company. One of the less accomplished demands is the weight that is greater than expected although it shouldn t be a limiting factor and it could be improved in future projects. 1 Introduction 1.1 Motivation The evolution of European environmental legislation in the area of residue management has been posing technological challenges to the operators of recycling systems. These operators have been confronted with the obligation of separating and proper routing for recycling of new products and materials. These operations are normally performed by the use of intensive handwork. This fact opens the door for the development of innovative technological solutions that will integrate a new market. The company Ambop Environmental Solutions was created with the objective of seizing this market. One of the concurrent products is a platform, manufactured by the company LSD (Fig.1.1 and 1.2) that allows an operator to elevate or tilt an End of Life Vehicle (ELV) in order to achieve an easier access to the bottom of a vehicle. Figure 1.1: LSD company platform.

2 Figure 1.2: LSD company platform, tilted close to 90º [4]. This will allow an easier de-pollution of the vehicle according to the European Directive 2000/53/CE [5], namely the removal of the vehicle catalyst and easier removal of used parts. For example the removal of the catalyst with a metal cutting tool can be difficult (due to its weight) if the vehicle is in an elevated position (Fig. 1.3). By tilting the vehicle this operation becomes easier (Fig. 1.2). descends into the roof of the vehicle so that it won t move when it s tilted. The locking and elevation of the vehicle movements are actuated by the same hydraulic cylinders. Between the elevation and tilting of the vehicle, it has to be removed from the platform in order to mount the locking crossbar and to connect the crossbar to the actuating hydraulic cylinders. This is considered to be a disadvantage because it reduces the efficiency of the intended vehicle operations. Another disadvantage is the need to a fixed fastened installation to the ground of the platform. 1.2 Objective The objectives of this work are to propose an economic alternative and more efficient configuration of the elevating and tilting ELV platform of the company LSD and the respective structural dimensioning. 1.3 Project specifications Figura 1.3: Catalyst removal. This platform can elevate or tilt vehicles up to 2000 kg, has a total weight of 800 kg, can elevate a vehicle up to 2000 mm, can tilt a vehicle up to 90º and the overall dimensions of the needed space to function are 2995 mm 1200 mm 4235 mm. The platform has three main movements: vehicle elevation, vehicle tilting and vehicle locking. To lock the vehicle in place, a crossbar Project requirements In order to eliminate the need for removal of the vehicle of the platform, mounting of the crossbar and manually connecting the hydraulic cylinders to the crossbar between elevation and tilting of the vehicle, the two movements (elevation and locking) have to be independent. The original platform requires a fixed fastened installation to the ground so another project requirement is the elimination of the necessity for a fixed installation. In order to maintain a simple manufacturing it s required that all the movements are actuated by a hydraulic system.

3 The platform must be able to function outdoors with maximum wind speeds defined by the European norm EN 1493:1998 [1]. A reasonable number of vehicles were being left out by the load capacity limit of 2000 kg (see point 2.3), so the load capacity for this project is P = 2500 kg. In order to accommodate higher operators, the elevation capacity will be increased to 2100 mm. The original platform has a tilting capacity of 90º, value to be maintained in this projects platform. The original platform allows a permissible ground inclination of 5º, value to be maintained in this projects platform Project constrains The main project constrains are the accomplishment of the European norm EN 1493:1998 [1] and of REA [2]. 2 Legislation, Market and Patents 2.1 European Machinery Directive An important directive to this project is the European Machinery Directive 2006/42/CE [6]. The European Machinery Directive regulates machine safety establishing a set of market regulating rules having has addressees the respective manufacturers and traders, privileging the prevention in the conception of such equipments. Such rules establish the maximum demands that should be respected in legislations and administrative practices (for example, technique norms) of State members and function has a guarantee of free goods circulation in the internal European market. One of the simpler ways to oblige the European Machinery Directive is to fulfil the European norm EN 1493:1998 [1] EN 1493:1998 This norm specifies an approximate load of two times the specified load capacity and it also specifies how it has to be distributed. The norm indicates a yield stress safety factor of 1,33 but it does not specify a maximum value to beam deflection, so this value was taken from REA [2]. Also specified are emergency stop and catching devices and hydraulic system safety measurements and speeds. Platform stability calculations safety factor is specified to a minimum of 1, Regulamento de Estruturas de Aço (REA) The norm EN 1493:1998 [1] does not specify a maximum value to beam deflection, so this value was taken from REA [2]. The considered maximum allowable beam deflection is L/200, with L being the span of the beam in question. 2.3 Directive 2000/53/CE Another directive relevant to this project is the Directive 2000/53/CE [5] regarding ELV, which led to the birth of the market responsible for the development of this project. This directive specifies all the depollution procedures of ELV and one of these procedures is the catalyst removal. This directive covers vehicle categories M1 and N1 and three wheel vehicles. M1 are passenger motor vehicles up to eight seats

4 plus the driver, and N1 are vehicles to carry merchandise with maximum loaded weight of 3500 kg, according to Annex II of the Directive 2001/116/CE [7]. Most of these vehicles weight is under 2500 kg unloaded. 2.4 Market and Patents The only platform similar to the one in this project is the platform manufactured by the company LSD that inspired this project. No other platforms of this kind were found. The patents registry search performed hasn t produced any result capable of influencing this project. 3 Concept generation and selection With the problem identified, project specifications defined, normative and actual market framing defined, it s time to conceive and select the alternative concept to be developed. It is understood that a concept is a concrete idea of the general shapes and lines of equipment, destined to perform well identified tasks that in this particular case cannot be performed by a human being. Nine concepts were generated and designed in 3D modelling software (Autodesk Inventor ). In all generated concepts there are three independent movements: vehicle elevation, vehicle tilting and vehicle locking that should be actuated before vehicle tilting. There s no need to actuate the vehicle locking before vehicle elevation. To select a concept, several criteria were defined in order to differentiate the several generated concepts. These criteria are the ones considered to be the most important to the company Ambop and that were possible to quantify in this stage of the project. These criteria were necessary functioning space, actuating system complexity, number of components to be manufactured, manufacturing process, need for a ditch and operation difficulty. The necessary functioning space is the amount of space that each concept needs to perform all the possible movements. Actuating system complexity is evaluated in three levels. The exclusive use of hydraulic actuators or the use of hydraulic actuators and gears or the use of hydraulic actuators, gears and transmission chains. Manufacturing process is evaluated in two levels. Welding and fastening of normalized components or welding and fastening of normalized components and metal casting of some components. A ditch to install the platform is considered to be needed when the distance between the lower point of the vehicle, when it s tilted to 90º, and the ground is superior to 400 mm. Operation difficulty is a qualitative measurement of the accessibility to the bottom of the vehicle and ease of the operator movement in front (vehicle tilted) and under the vehicle (Fig. 3.1). Figure 3.1: Concept 4 in elevated position.

5 It was asked to the company Ambop to attribute weights to each criterion. The results were: necessary functioning space 5%, actuating system complexity 15%, number of components to be manufactured 25%, manufacturing process 20%, need for a ditch 10% and operation difficulty 25%. Using various methods of Concept Scoring tools, each concept was evaluated under each criterion that was affected by the respective weight. These tools do not substitute the designers experience and sensibility and therefore the Concept Scoring tools results don t dispense a critic review. The chosen concept for development in this project is presented at Figure 3.2. In Figure 3.2 with nº 1 is presented the support, with nº 2 is presented the crossbar, with nº 3 is presented the column and with nº 4 is presented the base that will be bigger in order to support the entire platform so it does not need to be fastened to the ground. indicated the locking hydraulic cylinder connecting the support and the crossbar and with the nº 7 are indicated the tilting hydraulic cylinders connecting the column and the base. Figure 3.3: Concept 1 tilted to 90º. Figure 3.4: Concept 1 in elevated position. 4 Structural Dimensioning Figure 3.2: Concept 1. In Figure 3.3 the vehicle is in the tilted position at 90º. In Figure 3.4 with the nº 5 is indicated the elevation hydraulic cylinder connecting the column and the support, with the nº 6 is With the objective of respecting the project specifications, normalized elements were chosen to compose the platform and the chosen construction material was a structural steel FeE 355 according to the norm EN 10025:1990. This steel has a yield strength of 355 MPa for a thickness inferior to 40 mm. To select the adequate normalized elements, each component was analysed on a commercial numeric simulation program, based on the Finite Element Theory, called Ansys.

6 The static analysis is applied to a structure composed by steel beams, a ductile material that imposes the use of a structural, beam type finite element. Considering all solicitations the chosen finite element type must be three-dimensional. The chosen finite element type is Beam4 of Ansys, an element of the Euler-Bernoulli Beam Theory, beam type, tree-dimensional, linear and elastic. It s important to refer that all centres of gravity were determined using a three dimensional CAD modelling software named Autodesk Inventor. Since REA [2] does not specify the load distribution, EN 1493:1998 [1] load distribution was used (Fig. 4.1). So there are two main loading modes: EN 1493:1998 [1] mode using a load of approximately two times the pretended load capacity (see point 1.3.1) and imposed load distribution (Fig. 4.1) to verify a yield strength safety factor of 1,33 and REA [2] mode using a load correspondent to the pretended load capacity and EN 1493:1998 [1] load distribution (Fig. 4.1) to verify a deflection of L/ Loading modes All loads are applied in the most unfavourable possible way. For the structural dimensioning, two criteria were used, yield strength and deflection. EN 1493:1998 [1] indicates a yield strength security factor of 1,33 but imposes a load of approximately two times the pretended load capacity (see point 1.3.1) and also imposes the load distribution (Fig. 4.1). REA [2] indicates a maximum deflection of L/200 but does not indicate how the load of the vehicle should be applied to the platform. To avoid over dimensioning the two criteria weren t overlapped. To verify REA [2] the support was loaded with only the load capacity pretended (see point 1.3.1) instead of the approximated value of two times of the pretended load capacity imposed by EN 1493:1998 [1]. The yield strength security safety factor obtained, by using REA [2] verification loading, is more realistic than the one obtained by using EN 1493:1998 [1] verification loading, helping in preventing over dimensioning. Figure 4.1: Vehicle load according EN 1493:1998 [1] With the introduction of the project requirement of α = 5º of permissible ground inclination (see point 1.3.1), all gravitic forces are decomposed in three components according to the referential aligned with the platform as shown in Figure 4.2. Figure 4.2: Gravitic forces decomposition.

7 4.2 Normalized elements All components to be analysed are presented in Figure 4.3, along with the indication of the normalised elements (Table 1) that compose each component of the platform. the maximum load that the crossbar it s subjected to, is known. An extreme but possible situation is the one represented in Figure 4.4, since the vehicle can be badly damaged. Figure 4.4: Locked and tilted vehicle. Figure 4.3: Concept 1 components. Element Number Section Description Section Type #1 Rectangular 120*60*12 #2 H HEB 120 #3 Square 160*14 #4 H HEM 140 #5 H HEM 200 #6 Square 200*14 Using gathered information by the institution NHTSA [3], the maximum distance r can be determined for the vehicles witch this platform is intended (see point 2.3), by the use of SSF (Static Stability Factor). The result is F T = N. The obtained yield strength safety factor is 2,05 (Fig. 4.5). To verify REA [2], L/200 = 5 mm and the obtained maximum deflection is 4,6 mm. Table 1: Normalized elements in concept 1. H shaped beams (#2, #4 and #5) respect dimensional norm DIN and hollow square (#3 and #6) and rectangular shaped beams (#1) respect dimensional norm EN Crossbar The norm EN 1493:1998 [1] does not predict the use of a crossbar to lock a vehicle in place, and so the force needed to lock the vehicle in place must be determined so that Figure 4.5: Crossbar Von Mises stress. The crossbar weight will be approximately 40 kg. 4.4 Support, right side The interaction between the crossbar and the right side of the support (Fig. 4.3) resulted in constrains applied to the analysis of the

8 crossbar in Ansys. As a result, reactions are obtained and applied to the analysis of the right side of the support in Ansys. Using the EN 1493:1998 [1] load mode (see point 4.1), a safety yield strength factor of 1,43 is obtained which corresponds to a maximum Von Mises stress of 249 MPa (Fig. 4.6). Figure 4.7: Von Mises stress with EN 1493:1998 [1] load mode for the left side of the support. Figure 4.6: Von Mises stress with EN 1493:1998 [1] load mode for the right side of the support. Using the REA [2] load mode (see point 4.1), a safety yield strength factor of 1,9 is obtained which corresponds to a maximum Von Mises stress of 188 MPa. Maximum deflection is 7,5 mm witch respects the REA [2] limit of L/200 = 10,75 mm. 4.5 Support, left side The left side is practically identical to the right side of the support with the exception of the inexistence of the beam that guides the crossbar (Fig. 4.3), so the crossbar reactions aren t applied to the left side of the support. Using the EN 1493:1998 [1] load mode (see point 4.1), a safety yield strength factor of 1,43 is obtained which corresponds to a maximum Von Mises stress of 249 MPa (Fig. 4.7). Using the REA [2] load mode (see point 4.1), a safety yield strength factor of 2,98 is obtained which corresponds to a maximum Von Mises stress of 119 MPa. Maximum deflection is 7,44 mm witch respects the REA [2] limit of L/200 = 10,75 mm. The supports weight will be approximately 580 kg. 4.6 Column Loading on the column results from the load specified for the vehicle by the load modes defined in point 4.1, adding the effect of the support and crossbar weights. Constrains are applied in Ansys to simulate the interaction with the base (Fig. 4.3). Using the EN 1493:1998 [1] load mode (see point 4.1), a safety yield strength factor of 1,67 is obtained which corresponds to a maximum Von Mises stress of 212 MPa (Fig. 4.8).

9 Using the REA [2] load mode, a safety yield strength factor of 3,09 is obtained which corresponds to a maximum Von Mises stress of 115 MPa. Maximum deflection is 8,6 mm witch respects the REA [2] limit of L/200 = 9,15 mm. The bases weight will be approximately 920 kg. Figure 4.8: Von Mises stress with EN 1493:1998 [1] load mode for the column. Using the REA [2] load mode, a safety yield strength factor of 3,6 is obtained which corresponds to a maximum Von Mises stress of 98,5 MPa. Maximum deflection is 11,1 mm witch respects the REA [2] limit of L/200 = 14,75 mm. The columns weight will be approximately 275 kg. 4.7 Base Loading on the base results from the loads applied to the column with the added effect of the weight of the column. Using the EN 1493:1998 [1] load mode, a safety yield strength factor of 1,44 is obtained which corresponds to a maximum Von Mises stress of 247 MPa (Fig. 4.9). Figure 4.9: Von Mises stress with EN 1493:1998 [1] load mode for the base. 4.8 Stability Stability calculations must be performed to ensure that the platform remains in place in the most unfavourable situations. It was concluded that the most unfavourable situation is when the vehicle is elevated with a ground inclination of 5º. Norm EN 1493:1998 [1] specifies that the minimum safety stability factor is 1,3. So M S 1,3.M T. M S is a stabilizing moment and M T is a tilting moment. Calculations revealed that lateral stability safety factor is 1,8 and longitudinal stability safety factor is 2,64 (Fig. 4.3). 5 Conclusions and Future Developments 5.1 Conclusions The performed patents registry and market research haven t produced any result capable of influencing this project. The main probable reason for this fact may be the youth of the market in question. Selection between the generated concepts can be complicated due to the number of variables involved. Tools like Concept Scoring perform a valuable service in choosing the concept that best meets the companys demands. It s important to note that these tools are not a substitute to a

10 designer experience and sensibility and therefore do not dispense a critic interpretation of the results. The crossbar (Fig. 4.3) is composed by a hollow rectangular beam. This component weights approximately 40 kg. The support (Fig. 4.3) is composed by square hollow and H shaped beams. Hollow beams are used in elements subjected to torsion while H beams are used in elements not subjected to torsion. This component weights approximately 580 kg that compared to the total weight of the concurrent platform (880 kg) can be seen as too heavy. This difference can be justified by the increased load capacity, greatly increased length of the beams that support the vehicle (Fig. 1.2) and design nature of the support. The column (Fig. 4.3) is composed by an H shaped beam despite being subjected to torsion, in order to guide the support. This component weights approximately 275 kg. The base (Fig. 4.3) is composed by square hollow beams. This component weights approximately 920 kg which is superior to the total weight of the concurrent platform (880 kg). The most unfavourable situation is when the vehicle is elevated. In this position, the column is kept in the vertical position by the tilting hydraulic cylinders (see number 7 in Fig.3.4), passing the effort to the back of the base. In order to accomplish the necessary rigidity, the connection between the right side and the left side of the base have to be reinforced so it can resist the high torsion effort that this connection is subjected to (Fig. 4.9). Given the obtained weight for the base there are two possible ways for its reduction: the elimination of the necessity for a fastened fixed installation of the platform is reconsidered or a mechanical stop can be added to the base (in front of the column) so that the column is kept in the vertical position by the stop and not by the tiling hydraulic cylinders. This will remove the effort from the back of the base, greatly reducing efforts to the base. It s important to refer that the use of the hydraulic cylinders to keep the column, the support and the vehicle in the vertical position, may not be the most correct choice because the hydraulic cylinders may not be capable of withstanding the forces involved. REA [2] loading mode (see point 4.1) revealed yield strength safety factors of around 3 that seem to be adequate when human lives are at risk. The comparison of the platforms weights is only valid, if the same kind of base is considered, because a base for a fastened fixed installation of the platform is significantly lighter than a base for a platform that doesn t require a fastened fixed installation. Considering the increased load capacity of about 25%, an acceptable weight is 1100 kg (original platform weight of 880 kg affected by 25% of increased load capacity). The combined weight of the column, support and crossbar is 895 kg, 205 kg under the limit of 1100 kg, more than enough for a base for a fastened fixed installation of the platform, considering what can be seen in Figures 1.1 and 1.2. The introduction of the requirement of permissible ground inclination of α = 5º as increased stress in the support by approximately 10% and in the column by approximately 20%.

11 5.2 Future Developments The base should be the target of future developments in order to reduce its weight and to eliminate the use of the hydraulic cylinders to keep the column, the support and the vehicle in the vertical position. Norm EN 1493:1998 [1] indicates that if the loading cycles are superior to 22000, the structure has to be able to resist to fatigue phenomena s. Welded joints and hydraulic system dimensioning are necessary. It s also very important to analyze the stresses involved on the fixation points of the hydraulic cylinders and in the interaction between components (Fig. 4.3). Bearings have to be selected to these interactions. Finally an economic study can be elaborated to estimate the costs involved on the manufacturing process of the projected platform. 6 References [1] EN 1493:1998. European Norm referent to vehicle lifts. Cen European Committee for Standardization. [2] Regulamento de Segurança e Acções para Estruturas de Edifícios e Pontes e Regulamento de Estruturas de Aço para Edifícios (April 1998). 2ªEdition, Rei dos Livros Publisher. [3] NHTSA (National Highway Traffic Safety Administration), Accessed at 12 September [4] LSD Recycling Technology. Accessed at 5 October [5] Directive 2000/53/CE of the European Parliament and of the Council of 18 September European Directive relative to end-of life vehicles. Official Journal of the European Union of 21 October [6] Directive 2006/42/CE of the European Parliament and of the Council of 17 May European Directive relative to machinery. Official Journal of the European Union of 9 June [7] Directive 2001/116/CEE of the European Parliament and of the Council of 20 December European Directive to adapt progress Council Directive 70/156/EEC on the approximation of the laws of the Member States relating to the type-approval of motor vehicles and their trailers. Official Journal of the European Union of 21 January [8] Read, J. (2007). Project of an Elevating and Tilting End of Life Vehicle Platform. Master Theses in Mechanical Engineering. Instituto Superior Técnico Universidade Técnica de Lisboa.