Design and manufacture of the body for a fuel-saving prototype car aimed at aerodynamic purposes. The purpose of this project is to establish the design and manufacture of the bodywork for fuel efficient vehicles that cater for aerodynamic purposes.
Project Background
Problem Statement
Objectives and Scope ofWork
Place the vacuum connection on top of the infusion net on the opposite side of the mold to the resin delivery coil. Remove the duct tape from the edge of the mold (quick, sharp strokes are most effective). The Catia software is used to design the vehicle based on the desired characteristic of the vehicle.
The resin flow is random as it depends on the porosity of the layers. Precautions on the sharp edge of the resin part when removing the fiberglass product. The previous design used aluminum alloy for the frame of the car while the body panel is made of fiberglass.
From observation, there is no problem with the weight of the vehicle's chassis. The bending elongation of the car frame depends on the translational displacement from the FEA analysis. The surface finish of the fiberglass product depends on the mold surface.
During infusion, the resin feeds into the vacuum bag through the layers of the fiberglass.
PAC-Car 11
Aerodynarnics
Types of chassis
Although, the backbone chassis frame is the simplest chassis, it is disadvantageous due to the bending effect of the load on the vehicle. Therefore, a strong material is used as the backbone of the vehicle which includes additional weight for the vehicle.
Wind Tunnel Test
Vacuum Resin Infusion
Fabrication Method
Fortis Saxonia
- Moulding
- Preparation
- Layout Fiber Glass
- Infusion
- De-moulding
Some sketches or initial drafts of the vehicle are made based on the study of the project. The physical limitation and safety factor are determined for the vehicle design limitation and specification. From the design, finite element analysis is performed to ensure that the design meets all specifications.
From this analysis, we can determine an alternative solution and design change to optimize the car's performance. At this stage, computer simulation and modeling are important to determine the stress analysis of the vehicle body. All vehicle components will be assembled together into one complete UTP vehicle with the best fuel consumption.
Fabrication
- Preparation
- Layout Fiber Glass
- Infusion
- Demoulding
Next, mold release wax is applied to the surface of the mold to facilitate the process of deformation of the fiberglass. However, this process must be repeated several times to obtain multiple layers of fiberglass. The function of this layer is to allow the resin to flow through the shell layer and then into the fiberglass layer.
The resin tube connector is placed in the center of the resin coil tube to channel the resin flow to the fiber optic. The vacuum pump is turned on to evacuate the air from the fiberglass layers. The infusion is controlled to ensure that the resin passes through the entire fiberglass layers.
Gantt Chart
Final Year Project 1
Final Year Project 2
This section will be discussed from the analysis of the previous design and a design concept for the new prototype of the car to finalizing the vehicle. The first part of this section is to analyze the previous design and the main failure factor of the previous design. The next section will discuss the design concept, which includes the morphology map and some design sketches for the prototype vehicles.
After that, wind tunnel test analysis comes into play to discuss the best aerodynamic shape for the prototype car. Then finite stress analysis is used to verify the best design that can reduce the skew problem of the previous design. After stress analysis, bend test and visible test are performed to optimize the new chassis to meet the requirements.
Analysis of Previous Design
Weight Factor
The weight includes not only the weight of the body frame, but also the weight of the driver, the engine and many other components to complete the vehicle. The volume or size and the material used to make the vehicle has a lot to do with the weight factor we want to discuss. The larger the size of the vehicle will make the higher the weight of the car.
In addition, the body panel for the previous design 2 is lighter, but the body panel has low stiffness. For this reason, we should find a solution to overcome the problem of low rigidity and high weight of the case.
Engine Compartment
Ventilation System
Design Concept
- Design Constraint
- Morphology Chart
- Chassis Design Concept
- Body Panel Design concept
Aerodynamic principles had to be considered early in the design process, as the body shape design and the resulting aerodynamics are based on the vehicle topology [[6]]. As mentioned in the literature review section, a vehicle's aerodynamic properties depend on its drag coefficient and its frontal area. These prototypes are made of soft wood because soft wood is easy to shape into desired design.
Aerodynamic Test
Experiment 1: Drag Force Wind Tunnel
From the graph above, aircraft prototype 1 and aircraft prototype 2 have an increased drag force value. In the same way, as the speed of the air stream increases, the drag force acting on the car increases, resulting in an opposite direction of the force acting on the body. Therefore, the next step is to determine the coefficient of drag force, Cv, to determine which one is better in terms of aerodynamic performance.
The calculation for this experiment is to obtain the value of the drag coefficient, Cv. From the calculation, prototype 2 has lower value of drag coefficient, Co compared to prototype I because the frontal surface of prototype 2 is smaller than prototype I. By the way, both prototypes have very small value of drag coefficient , which proves that the teardrop shape is a very aerodynamic shape.
Experiment 2: Smoke test-Wind Tunnel
Stress Analysis
- Ergonomic Measurement
- Types of Chassis Selection
- Finite Element Analysis
- Chassis Design Selection
Based on the concept design, the car's frame design takes into account the strength and robustness of the car chassis. At the same time, the size of the previous design is obtained as a reference for designing the frame. The backbone chassis needs a strong material, such as stainless steel, to support the entire body of the car.
Therefore, for this project, Catia V 5 software is used to make the finite element analysis of the stress to analyze the body's maximum stress location and make the comparison between the designs. The displacement option in Catia V5 allows us to see the translational displacement of the model based on the loads applied to the model. So the next car must have a rib to increase the rigidity of the body frame.
Chassis Fabrication Modification
The von Mises stress is the maximum stress response after a load is applied to the specimen. In this case, design 1 has the lowest von Mises stress value which is about 7.97x06 Nm2•. Additionally, the lower von Mises stress value is a good sign that the design has good stress distribution throughout the body frame.
Since the aluminum material has a yield strength of 9.5 x 107 N.m2, the entire structure is well below the maximum yield strength. This design has high stiffness and is very light, as the honeycomb gives the material added properties of strength and low weight. The previous second team has a similarity to the design for the new chassis, which is the FEA 3 design from the previous stress analysis.
Bending Test
Based on the original displacement of location A, B, and C, the displacements show that the landing gear is tilted slightly upwards, giving additional strength to the landing gear itself. This result showed that the chassis has high strength and can withstand the rigidity and firmness of the vehicle body. The objective of the visibility test is to verify that the design meets the requirements for measuring visibility safety.
The criteria for driver visibility are front view and 90 degrees for both left and right [11]. PETG plastic or also known as polyethylene terephthalate is a thermoplastic polymer resin from the polyester family and is used in plastic bottles, food and other liquid containers [26]. To maintain the shape of the PETG, an aluminum frame is made according to the design of the window.
Body Panel Fabrication Result
- Body Panel Design Finalize
- Female Mould Fabrication
- Engine compartment separation
- Body Panel Stiffness
- Finishing Appearance
In addition, the surface of the female mold must be smooth to obtain a better surface finish. Previous designs have attached the engine bay or rear body panel to the front body. For the new body panel, we used a lot of foam to create a layer of frames to increase the stiffness of the body panel.
Finishing is the last step in the production of the body, intended to make the vehicle look better. However, we have some issues with body panel spraying expertise and resources or sponsorship for the finishing of the product. After much consideration, we decided to use a full decal finish for the entire body panel.
Weight of the Vehicle
Total Weight of New Prototype Car
This decision is made because we can solve the problem of the appearance of voids, since the sticker creates a protective layer on the case.
Resin infusion versus Conventional Technique
Conclusion
Recommendation
August 12, 2010 http://www.jtc-ergobuddy.com/English!Ergonomics.asp. http://www.thefreedictionary.com/aerodynamics [3]. http://www.shell.com/home/content/ecomarathonl. Swiss Federal Institute of Technology Zurich PAC-Car II world record. http://www.esoro.ch!english/contentlkernk/nhanst/paccar/Olpaccar.htm [6]. Center of Gravity, September 10, 2010. http://dictionary.reference.com/browse/center+of+gravitv [15]. http://www.technica.net/NF/NF2/efibreinorganiche.htm [16].
Finite Element Analysis, 31 Oct. 2010. http://www.sv.vt.edu/classes/MSE2094 NoteBook/97ClassProj/num/widaslhi story.html. http://en.wikipedia.org/wikiNon Mises yield criterion. http://www.tvgavac.co.uk/process/resin-infusion.html. http://www.carbomnods.co.uk/Downloads/carbon-mods-guide-to-resin-infusion.pdf.
Drag Equation
