An engineering drawing refers to a type of technical drawing that defines entirely and the requirements for engineered items. As such, it is drafted following the layout standard conventions, appearance size, nomenclature, etc. consequently, all geometric features regarding the product or component are captured accurately. Notably, the drawing covers the electrical and mechanical design of the car (Luzadder, 1992, 14).
First of all, engineering drawing starts with sketching. Sketching gives the pictorial view of the desired final product. For instance, the side view, the top view, and the front view are included. Similarly, a 3D sketch is also possible and will provide a better view of the final project.
After that, get the proportions right. It is evident that making a drawing is time-consuming. It starts with a poor drawing but gets better later. After that, choose the formal layout. A sketch then followed by The Orthographic Projection (Dieter and Schmidt, 2013, 108). In both the first angle projection and third angle projection, details about the front elevation, the plan, and the end elevation should be developed.
Finally, final design with detailed drawing containing all the components is drafted. Thorough revision should be done to ascertain that all drawing problems are solved. That gives the accurate details used in the final design of the project.
Five key aspects and elements that need to be present if an engineering drawing is to be used as a basis for manufacture.
Firstly, drawing sheet sizes are identified. The drawing paper is available in rolls of different widths and trimmed standard sizes. Most of which are printed with the borders and the title block. Similarly, there exist five standard sizes that are frequently used. Drawing sheets can be employed either with longer sides placed vertically or horizontally. Therefore, the original drawing has to be done on the smallest sheet as it permits the required resolution and clarity.
The drawing sheet layout is an important aspect as it facilitates the reading of the drawing. Moreover, the plan should be clear and neat in its appearance to permit easy location of essential references. Borders are also specified in all the sheet sizes and are required to be 20mm for size A0 and A1 and a width of 20mm for other sheet sizes (Dieter and Schmidt, 2013, 108). Also, there exists drawing sheets that have features such as the title block, the center marks, frame and other optional features.
After that, engineering drawings should have dimensions. A detail drawing should provide the complete description of the part as well as the description of the furnish size. Such information is provided given concerning the location of holes, type of material or the distance between surfaces. On a drawing, they are illustrated by use of lines, figures, symbols, and notes. Furthermore, dimensions are classified into the functional dimension, non-functional dimension, and auxiliary dimension.
Information on a drawing is fundamental. Thus, all information has to be numbered. As such, many numbering systems exist. Various digits of the numbers indicate different details such as the nature of the part or the machine model number. For instance, companies use numbers such as K2-70524 or 70524 without a prefix (Luzadder, 1992, 14). Moreover, specifications regarding the material, general notes, finish, and tolerances are located near the title block. Finally, all drawings are made to a particular scale which is indicated near the title block. However, if different levels are applied, they should be stated on own designs.
A design specification refers to detailed documentation that provides information about a project that is to be executed to set the criteria with which developers or engineers will need to follow to ensure successful completion of the set target for the project. In most scenarios, a design specification plays a significant role where a structure or a given product is to be designed as per specific needs or requirements. Design specifications should have all the necessary drawings, dimensions, ergonomic, aesthetic, environmental, cost and maintenance factors that will be required. It should also contain the safety, quality, description, and documentation. Design specification gives specific details of how a design on a project should be undertaken thus enabling work to be done efficiently and more (Dym et al., 2009).
Uncertainty results in inaccuracy and complexity in the specification, this may lead to any loop hole in the specification eliminating competition and allowing a bidder to take advantage of the purchaser. Moreover, it results in the inability to understand the specification by both the bidder and the buyer. It further results to the inflexibility of the specification which later defeats the competitive bid process.
Similarly, it leads to lack of legibility and concise in a specification and causes additional specification which tends to be expensive. It also becomes unfair to bidders that thus inhibits the ability for competitive bidding by several bidders.
When a bidder is considering a newly manufactured product, the most crucial step is conveying the impression to some team developers, so the idea is converted into some engineering drawings portraying plans to be used for manufacture. In case the idea is not communicated properly and efficiently, repetitions may occur in the design and analysis stage of conception.
Thus, the development processes are bettered if design aims are defined. The importance of the objectives is rated; as a result, a plan written. One of the methods that are used to deliver the design objectives is the use many design parameters and then evaluate the meaning of each part. The process of noting down the parameters forces a person to identify the goals which give the designers and engineers vital information concerning their relative importance. Therefore, the finished product impression can vary based all the input design aspects.
For example, if we consider creating a coat hanger, we note that the relevant parameters to be considered include the strength, the cost, aesthetics, the capability to clutch pants, rust, and the inability to crease pants. Thus, on a scale of 0 to 4, a customer may produce for the ranking of a hanger based on a scale of 0 to 4 (Dym et al., 2009).
After the designers have got a distinct understanding regarding the design goals and have written an engineering drawing specification, many tools can be applied to commence the entire design process. Thus, design sessions can be helpful in generating product design ideas. Similarly, drawing hand-sketches is a perfect way to begin communicating the real physical concepts. Eventually, models of parts are produced by the computer program 3D, models which can be further affected by photo-realistic interpretations (Bucciarelli, 1988,162).
Besides, a careful understanding of the materials and engineering manufacturing processes is vital to a profound design. Moreover, the selection of the materials and manufacturing processes has to match the design requirements making some methods being suited to high volume and others high volume production.
Before the detailed design can start, the first step of looking at the design objectives has taken place. Thus, a list bearing the design parameters and the rating based on their application and importance is rendered helpful during the first communication.
In the early days, the design of automotive constituted a carriage without a horse. As such, the first cart was manufactured without much consideration to the center of mass, aerodynamics and other safety features in modern vehicles. Since then, design engineers have made several changes that have improved performance regarding the carriage capacity, the speed, and efficiency. Notably, the improvements have been attributed to by enhancement in technology. Thus, improving the ability of engineers to design cheaper, faster, comfortable and more efficient electric carts for the consumers. However, there exist some factors that affect the performance of electric cars’ as follows.
Firstly, engine efficiency is directly proportional to the effectiveness of the vehicle. Individual metals used in current engines can be understood through a materials science approach. For example, when pistons are made of light materials, we can analyze the parts regarding the momentum(P). P equals mass times velocity. With reduced weight, the impulse force that is required to modify the momentum is reduced. Hence, a lighter material requires less force and the energy wasted in manufacturing the engine can be applied in driving the engine.
Secondly, reducing the friction in moving parts of the engine is another way of improving the efficiency. All these are done by use of synthetic oil with less viscosity, special coated cylinders and cylinder walls based on chemistry point of view. As a result, energy loss in the form of friction is minimized thus better efficiency.
Thirdly, when thinking of vehicle performance, speed becomes inevitable. Often, the question becomes, what factors affect the speed of the car and how can we mitigate the barriers that limit speed? Drag force and horsepower are the underlying factors which influence the speed of a cart. Therefore, a cart can be made faster by building a superior engine. However, the drag force is proportional to the square of velocity. As a result, the faster the automobile is traveling, the higher the opposing forces.
After that, Horse power measures the amount of force an engine can apply to a cart over a specified amount of time. It refers to a measurement of power in Watts. Instantaneous Power is measured using the equation P=FV in case of motion in a straight line. Additionally, F=MA, so that P=MAV. Hence, to get the answer in horsepower, the solution is divided by 746 since one horsepower equals to 746watts (Roberts et al., 2014, 337). This explains why an engine can be rated for a given power. Some might think that if an engine from a heavy vehicle and placed in a light weight vehicle, the car might generate more horsepower. However, because A=F/M the acceleration of the car will increase with a decrease in mass, resulting in a constant horsepower.
Finally, the handling capacity is a consideration in design. The best design is that which the engine is placed close to the center of the car. With this configuration, the engine becomes the center of mass for the car. If you have a car in which the center of mass is at the back or the front side, the forces acting on the point will break the tires grip on the road. Which is as a result of force having to overcome the friction of only two tires instead of four. For example, a car negotiating a corner has many forces acting on it. For instance, friction acting on the tires cause centripetal force which makes the car to move in a circle. Contrary, the momentum of the car moves in a direction such as to oppose friction force. The sum of all the forces should be equal, or the tires would slide. Moreover, if the center of mass is in the center, the momentum will oppose the friction over the four tires. Similarly, if the center of mass acts on the back tires, the momentum force will have to overcome the friction on the rear tires. Hence, a car with the engine at the center is more stable and safe.
The Testing strategies to optimize the speed, the carrying capacity and efficiency of an electrically powered cart
The legislation and emissions performance. There exists metrics for measuring the internal combustion engine efficiency. For example, the “New Europe Drive Cycle (NEDC)” (Bielaczyc et al., 2011). NEDC which is a 1200s long cycle is used to test all engines and simulate a range of scenarios as shown in figure 1 below. In the European union, the figures for fuel consumption for new cars are quantified based on the NEDC. Hence, the method used to boost cold-start efficiency should be useful. Thus, fuel consumption is reduced through NEDC test.
Fig 1. Speed- time curve for the NEDC
The steady state performance of the internal combustion has improved noticeably over time. A trend that can be attributed to a series of developments that include the use of advanced lubricants, rail fuel injection, sophisticated engine control means and the use of catalytic converters on most vehicles. However, the cold-start performance of vehicle engines remains challenging (Dohner, 1980, 21) .
Engine fuel consumption is related linearly to the ambient temperature as shown for a Euro 1 compliant S.I. engine. Over the drive cycle, the use of fuel increased by 18% as a result of the decrease in room temperature from 31 °C to −2 °C (Iodice and Senatore, 2016, 1). Moreover, a similar trend for the other variants of engines (a 1400 cc 4-cylinder S.I. engine, a 1200 cc 3-cylinder S.I. engine and a 1800 cc S.I. engine) were recorded with a 3.3 l S.I. engine (Bielaczyc et al., 2011).
Such notes eased cart designers since NEDC test is needed to be carried out at a temperature ranging between 20 °C and 30 °C. Also, the consumption of gasoline engine fuel averagely dropped by 10% over the period of the NEDC. Consequently, whereas the vehicle might have performance credentials that are acceptable once warm, the low-quality cold-start performance could result in failure of the vehicle in emission tests. These behaviors can lead to high fuel consumption. Therefore, improving fuel consumption during the cold-start and warm-up phases is rendered critical since consumer driving behaviors repeatedly include short distance trips and as a result of the engine never reaches its required working temperature. It is estimated that up to 80% of trips made in the United States of America is less than 15 km as opposed to the average European vehicle journey that is approximately 10 km (Roberts et al., 2014, 337). Later on, it was concluded that a third of automobile journeys are completed before the engine is fully warm.
References
Luzadder, W.J., 1992. Introduction to Engineering Drawing: The Foundations of Engineering Design and Computer Aided Drafting. Prentice Hall PTR.
Dieter, G.E. and Schmidt, L.C., 2013. Engineering design (Vol. 3). New York: McGraw-Hill.
Dym, C.L., Little, P., Orwin, E.J. and Spjut, E., 2009. Engineering design: A project-based introduction. John Wiley and sons.
Jones, J.C. and Ertas, A., 1996. The engineering design process. Wiley.
Bucciarelli, L.L., 1988. An ethnographic perspective on engineering design. Design studies, 9(3), pp.159-168.
Roberts, A., Brooks, R. and Shipway, P., 2014. Internal combustion engine cold-start efficiency: A review of the problem, causes and potential solutions. Energy Conversion and Management, 82, pp.327-350.
Iodice, P. and Senatore, A., 2016. A numerical-experimental approach to assess emission performance of new generation engines during the cold transient. International Journal of Automotive & Mechanical Engineering, 13(3).
Bielaczyc, P., Szczotka, A. and Woodburn, J., 2011. The effect of a low ambient temperature on the cold-start emissions and fuel consumption of passenger cars. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 225(9), pp.1253-1264.
Dohner, D.J., 1980. A mathematical engine model for development of dynamic engine control (No. 800054). SAE Technical Paper.
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