PROJECT MANAGEMENT AND DESIGN II MAE 435. March 3 rd, Editors. Authors. Project Advisors. Dr. Sebastian Bawab. Dr.

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1 PROJECT MANAGEMENT AND DESIGN II MAE 435 March 3 rd, 2015 Editors Elliott Clowdis Michael Perkins Authors Robert Burns Keith Camp Tyler Craven Ricardo Enriquez Justin Frericks-Leclair Charles Hodgkins Mark Klepeisz Kyle Lowe Johnathan Meador Brandon Napier Joseph Peterson Trevor Ramey Project Advisors Dr. Sebastian Bawab Dr. Colin Britcher Mr. Nathan Leutke

2 CONTENTS 1 ABSTRACT INTRODUCTION DRIVETRAIN INTRODUCTION COMPLETE METHODS PROPOSED METHODS DRIVER CONTROLS INTRODUCTION COMPLETED METHODS PROPOSED METHODS SUSPENSION INTRODUCTION COMPLETED METHODS PROPOSED METHODS.10 6 BRAKES INTRODUCTION COMPLETED METHODS PROPOSED METHODS INTAKE INTRODUCTION COMPLETED METHODS PROPOSED METHODS

3 8 AERODYNAMICS INTRODUCTION COMPLETED METHODS PROPOSED METHODS.17 9 RESULTS DISCUSSION

4 LIST OF FIGURES Figure 1: Suspension Calculator...10 Figure 2: Push Rod Suspension Example...11 Figure 3: Upright and Brake Assembly...13 Figure 4: Intake Manifold Assembly...15 Figure 5: Flow Analysis of Nosecone...16 LIST OF EQUATIONS Equation 1: Gear Ratio Calculator...6 Equation 2: Intake Runner Calculation...14 APPENDICES Appendix 1: Gantt Chart...20 Appendix 2: Budgeted Hours and Progression...21 Appendix 3: Budget

5 1 Abstract The 2015 Formula SAE (Society of Automotive Engineers) competition requires students to fabricate and test an open-wheeled racecar of their own design. The overall goal for the Old Dominion University Formula SAE team is to place higher than 37th at the 2015 competition. This objective will be achieved through various improvements to the 2015 car. A new seat position will allow better visibility and proper viewing angle of the MoTeC instrument cluster. The intake manifold will have runner length and plenum dimensions determined using a program written in MATLAB (MathWorks, Natick, MA). Aerodynamics will incorporate a rear active diffuser and body panels to minimize drag. Both front and rear suspension will utilize a push-rod system, as opposed to last year s rear pull-rod system. This will alleviate the binding at the rocker arms and allow the suspension to utilize more of its travel. The differential carrier has been improved to better handle the forces applied during operation. The gear ratio in the differential has been adjusted to allow for full use of the 6-speed transmission. To improve braking, all four wheels will each have their own rotor and caliper combination. Also, a proportioning valve will be incorporated for adjustment of front to rear braking bias

6 2 Introduction In 2014 the Old Dominion University s (ODU) Formula SAE team placed thirty-seventh out of one hundred and nine competing teams. For the 2015 entry, ODU has decided to focus on fine-tuning the design of last year s car. While the 2014 car performed well there are several areas that will be redesigned for the 2015 car. At the 2014 Formula SAE competition, there were significant problems with vehicle handling. For the 2014 car the frame was redesigned; however, the suspension was carried over from the 2013 car. These designs did not perform well together and caused a significant portion of the poor driving characteristics experienced such as under steer, bump steer and excessive wheel travel. This car also cornered poorly and had uneven braking bias towards the front. The goal of the Formula SAE team is to have ODU place higher than last year. To accomplish this goal our major concern is to improve vehicle-handling characteristics. This will be done through a redesign of the suspension and braking systems. Additionally, design changes will be made in the areas of drivetrain, driver controls, intake, and aerodynamics to achieve improved performance. 3 Drivetrain 3.1 Introduction The drivetrain has several components including the tripods, axles, and rear end gear. It is crucial for each piece to be properly installed and cut or placed in its designated location for optimal performance. The tripod is a joint that has an inner spline, which consists of teeth on the - 5 -

7 inside used to connect to an axle shaft [1]. The tripod is known as the constant velocity (CV) joint due to the dynamic movement analysis applied to it during constant velocity [1,2]. The Formula SAE car s axle assembly is also vital due to the component covering multiple areas of performance of the car. A complete axle assembly works with the differential and stub axles to make the wheels rotate. Building a reliable and efficient axle assembly can fail due to small miscellaneous tasks that can be overlooked during design and fabrication. One issue is cutting the axles to proper lengths, and if the task is not performed perfectly it can initiate failure. Another main product for maintaining the axle assembly is having the differential brackets secured to withstand enough force without bending or failing. Applying finite element analysis (FEA) to the brackets gives data to design the differential mounts to maintain rigidity from the appropriate forces [3]. An important component to the drivetrain of the car is the gear differential. In the design of a differential for a Formula SAE car, it is important to calculate the gear ratios because they affect the handling and power transfer to the tires. The differential allows the right and left axles to spin at different rates and torques which are determined by gear ratios [4]. 3.2 Completed Methods A spreadsheet calculator was completed to configure the gear ratios and mile-per-hour (mph) of each gear at each revolution-per-minute (rpm) that the engine will produce in that given gear. The equation to calculate that is the following: rpm (( ) (60min))/(5280 feet) overall gear ratio Equation 1-6 -

8 With that equation you can find the mph of each gear at each rpm when given a specific set number of front and rear sprocket sizes. These calculations show what size sprockets should be used for competition and will calculate the more suitable gear ratio for each event. 3.3 Proposed Methods Utilizing the differential carrier to maintain the loads necessary during testing and competition, purchasing the correct parts for installation of the axle assembly and sprockets, and calculating the correct gear ratio for all of the events at competition is vital for performance. The differential carrier undergoes several loads when testing and if not machined correctly or installed correctly will lead to deflection and possibly failure. Last year there were several issues dealing with the differential carrier and those issues have been addressed appropriately for testing and competition. Using SolidWorks Simulation (Dassault Syste mes S.A., Waltham, MA) to calculate the FEA on the differential carrier showed that it should not fail during loading under vigorous testing. The parts for completing the build of the car have been purchased and not all have been delivered to the Engineering department as of yet. The axles, tripods, c-clips, rod fillers, plastic rod ends, rubber covers, and springs have been delivered, and when the differential and grease is delivered the drivetrain fabrication will start. Lastly, the gear ratio has been calculated and will be higher compared to last years 3.25:1 gear ratio. We have calculated with the engine gear to be a thirteen tooth sprocket and the differential sprocket to be a fifty-five tooth sprocket to give us an overall 4.23:1 gear ratio. It - 7 -

9 gives the drivers more options for shifting and to use more of the gearbox compared to previous years. When in the past the highest gear used at competition was third gear, now it is possible to reach fifth or sixth gear out of the gearbox. 4 Driver Controls 4.1 Introduction As the cockpit is the place the driver interacts with the vehicle, proper design is of utmost importance. A properly designed cockpit can increase driver performance through a lessening of fatigue and discomfort [5]. The cockpit design is also vital to the driver s survival in the event of a crash, so safety must always remain a priority during the design process [6]. For the purposes of this project, driver controls is expanded to include the seat, shifter, steering wheel, harness, steering rack, and dash. 4.2 Completed Methods All major parts needed to complete the driver controls have been selected, ordered, and received, including a different steering rack and seat. A cross-member has been designed and fabricated to accommodate the new rack and its different mounting. The pedal design was revised to allow removal of the brake pedal once installed, and the shifter design was revised to allow the correct shifting motion (forward to downshift, backward to upshift). The dash design was also revised so that the MoTeC can be viewed by the driver at a 20 angle, to ensure screen visibility

10 4.3 Proposed Methods A driver position study will be completed. This will involve a mocked up cockpit area and the current list of competition drivers to ensure comfort and increase driver performance [7]. In doing so the dash design will be finalized and able to be fabricated. Remaining parts will be fabricated, installed, and tested. 5 Suspension 5.1 Introduction The suspension of a high performance vehicle is arguably one of the most crucial systems to the vehicles overall performance. A motors power can only matter if it can be properly transferred to the ground through the tires. The suspension maintains contact between the tires and the ground, which assures both stability and control over the vehicle [8]. One of the most crucial moments that tire contact comes into play is when cornering. Camber gain in the front suspension allows the wheels to keep grip through a corner, and keeps the vehicle under control. Tire contact is also effected by weight transfer and body roll about the roll center. The suspension type allows the roll center to be adjusted through the design geometry of the components involved [8]. 5.2 Completed Methods A sketch was created in SolidWorks to determine the control arm geometry needed to achieve a specific roll center with a given ride height. A calculator created by the 2013 team was - 9 -

11 then used to determine the static camber and camber gain associated with this geometry. Figure 1: Suspension Calculator Proper control arms were then designed using SolidWorks, and were fabricated by the team. Frame mounts for the control arms have been machined and the front mounts have been bolted to the frame. A design has been developed for the front push-rod suspension and the rockers have been designed in SolidWorks. 5.3 Proposed Methods The mounts for the rear control arms will be finished and welded to the frame. The control arms will then be fitted with threaded bungs and hiem joints and be mounted to the frame. Gussets will be welded over the joints of the control arms to add to their structural integrity. The finished uprights will be mounted as well to double check the geometry of the control arms

12 The rear suspension will be a push rod system as opposed to the pull rod used in last years car. The pull rod did not allow for proper travel, which resulted in binding at the rocker arms upon rebound. A push rod will allow for greater travel in both jounce and rebound. This system will also allow for the rockers to be mounted higher, which will allow the rod itself to be close to perpendicular to the control arm. This will ensure that the motion ratio is as close to one as is possible, which utilizes the shock to a fuller extent. Figure 2: Push Rod Suspension Example With the suspension system completely assembled, proper testing can be performed to ensure all components function correctly and in tandem. Minor adjustments will be made to the shocks to create the desired range of motion for the wheels. 6 Brakes 6.1 Introduction The brakes are one of the most important systems on a car, they enable a car to safely reduce speed and maintain control. According to FSAE rules, all four wheels must undergo braking force while pressure is applied to the brake pedal. In previous years, the Old Dominion

13 University car had a disc brake on each front wheel and one disc brake on the right rear axle acting as a rear common brake using the differential to apply brake force to both rear wheels without separate disc brakes. While this system works, the rear brakes have less braking force available than the front; and when the brakes are applied the force is uneven between the rear wheels due to mechanical losses between the right and left axles through the differential. To improve this year s car, the team has decided to utilize a four wheel disc brake system. Another part of the FSAE rulebook regarding brakes is requiring two completely separate hydraulic systems. The method used by the University s former teams has been to run two brake master cylinders, one to control the front brakes and the other to control the rear brake. This year a similar system is being used, but in an effort to improve upon the old design and account for increased rear braking force there will be a brake proportioning valve in the cockpit. The valve will allow for adjusting the difference in braking force between the front and rear brakes. At full open, the front/rear brake bias will be 50%-50%. As the valve is turned, it will slowly reduce the amount of pressure on the rear brakes; with adjustment, the brake bias can be set to 60%-40%, or any other combination desired. 6.2 Completed Methods The Formula car is going to have four wheel disc brakes in an effort to increase the braking abilities of the vehicle. Changing from single rear disc to dual rear discs will provide an even braking distribution from left to right, thus giving the driver more control when applying the brakes. However, there are some design challenges that had to be overcome when adding individual rear brakes. The biggest challenge is creating a lightweight, high strength, and compact mounting setup for the rear calipers and discs outboard of each wheel. The caliper mounting brackets are going to be made of.250 plate aluminum to maintain

14 minimal space requirements; after designing the brackets in SolidWorks, finite element analysis was done, showing that the plate design is viable. The rear brake disc carrier is a much more complex design. The wheel centers do not have the holes to allow brake discs to mount directly to the wheel. The brake disc carrier applies braking force using the spline on the rear spindle; by integrating the outboard upright bearing spacer into the disc carrier, there was enough spline area to sufficiently apply braking force to the wheel. 6.3 Proposed Methods Figure 3: Upright and Brake Assembly In order to achieve desirable front to rear braking bias, experimentation needs to be applied. Multiple trials of accelerating and braking will be performed. Starting at the full open position on the brake proportioning valve (50%-50% front-rear bias), the car will accelerate to 35mph then the driver will apply full brakes. In theory, the rear brakes will lock first since the force of friction on the tires will be less than the front wheels due to weight shifting forward. Over the trials the team will begin to make adjustments to the proportioning valve; at some point (presumably near F60%-R40% bias) the front and rear wheels will lock up at almost the exact

15 same time. This means that both the front and rear brakes have hit their respective limits simultaneously; meaning both wheels are applying the maximum braking force available. 7 Intake 7.1 Introduction When tuning a naturally aspirated engine, the intake and exhaust are critical for maximizing power and determining when peak power will occur. The major components of the intake are the runners and the plenum. Adjusting runner length changes when peak toque occurs in the engine's operating range. The plenum supplies each runner with fresh air and joins them all to the throttle body. 7.2 Completed Methods Intake runner lengths were tuned using the Helmholtz resonance theory [9,10]. A simple model was established with the combustion chambers and intake runners serving as the resonators. A program was written in MATLAB using the following equation in order to solve for intake runner length at a desired engine revolutions per minute (RPM) [10]. A(R 1) RPM = 81c LV(R + 1) c = local speed of sound (ft/s) A = cross-sectional area of intake runner (in 2 ) L = runner length (in) V = cylinder dieplacement (in 3 ) R = compression ratio (dimensionless) Equation

16 The results were calculated across an RPM range of 8,000 to 12,000 in increments of 250. The GSXR-600 engine was selected for the car and has a compression ratio of 12.5:1. 12,000 RPM was chosen as the desired peak, which required intake runner length to be set to 7.65 inches for a in. inner diameter runner. No reliable methods for calculating a desired plenum volume could be found; thus the plenum was designed to be large in support the air requirements of the engine and provide little restriction to the runners. The calculated volume of the plenum was 2044 cm 3, making it roughly 3.41 times as large as the engine displacement. The intake manifold, Figure 4, was designed in Autodesk Inventor Pro (Autodesk Inc., San Rafael, CA). 7.3 Proposed Methods Figure 4: Intake Manifold Assembly Transient flow analysis will be performed on the intake manifold using Simulation CFD (Autodesk Inc., San Rafael, CA) or SolidWorks. This will enable any unfavorable flow characteristics to be detected, so the design may be altered. Further flow analysis will be performed pairing the intake manifold to an intake pipe incorporating a venturi nozzle and the

17 throttle body. Rubber isolator mounts will be designed for the intake after the plenum has been manufactured. 8 Aerodynamics 8.1 Introduction The ODU FSAE car will feature a wingless, rear active diffuser set up with side pods. The goal is to minimize drag while staying within FSAE regulations. 8.2 Completed Methods A full SolidWorks model of the diffuser, nose cone, and side pods have been created. This will allow to theoretically determine the coefficient of drag on the car. 17 oz biaxial fabric with a polyester resin to act as the binder have been chosen as the material to fabricate body. The biaxial fabric will limit the amount of layers the team will have to apply while still maintaining FSAE strength requirements. Figure 5: Flow Analysis of Nosecone

18 8.3 Proposed Methods Determine theoretical coefficient of drag using Solid Works or another form of Computational Fluid Dynamics (CFD) software. Determine actual coefficient of drag via wind tunnel testing if time and facilities are available. Create both positive plugs and negative molds to fabricate the body. 9 Results A differential mount has been designed to better handle the forces exerted while racing. Gear ratio for the differential has been calculated to be 4.23:1. All cockpit components have been designed and integrate well with each other. Shifting has been corrected to the traditional motion (forward to downshift, backward to upshift). The design of the control arms produced front suspension with proper static camber and camber gain. Rear suspension will be a push-rod system. The rear brakes will incorporate a disk at each wheel to better control braking, as well as a proportional controller. The caliper mounting brackets are.250 thick aluminum plates. Intake runner lengths were calculated to be 7.65 and a inner diameter runner. The plenum has a volume of 2044 cm3. Diffuser, nose cone, and side pods have been designed and are made from biaxial fabric with polyester resin. 10 Discussion The purpose of our project is to design and fabricate a Formula SAE car that can exceed the performance of last year s car at the Formula SAE competition in May, With focus on optimizing the suspension, drivetrain, and intake outperforming the team can be accomplished

19 Most of the team s results came from online research, and computational analysis of each major component of the car. Creating a more efficient rear suspension system would help with control of the car. With a better suspension design the car has smoother weight transfer and can handle in corners better. Researching suspension geometries and designing them for computational testing helps the team determine which suspension design is best. The results from testing will help finalize the rear suspension and start fabrication. The drivetrain is important for the endurance portion of competition. The gear ratio needed to be adjusted from last year s so that the car was capable of shifting through all gears during endurance competition. Using research and discussion a better gear ratio can be selected for this year s car. To achieve more engine power the intake was redesigned. Adjusting runner lengths can change when peak torque is achieved. Also restructuring the plenum from last year s car can optimize the amount of air that goes through the runners and helps create more efficient combustion in the engine. The overall design of the intake system determines engine power, so optimal design is key. Design of driver controls such as seat, shifter, steering wheel, harness, steering rack, and dash all need to be designed and fabricated efficiently to ensure driver safety and comfort during competition. Researching the driver controls component of the previous Formula SAE cars will help the team modify this year s car such as the seat and steering rack for better overall driving experience

20 The future work to be performed is completing fabrication of the car. The intake, suspension, drivetrain, suspension, and electrical work are being fabricated right now. After the car is fully fabricated the car will be tested up until competition

21 References [1] S. Zeller, MLR: Drivetrain Study Guide, Melior Inc., pp 43-44, [2] Chang, D.G.; Song, D.Z.; Yang, F.Q., "Simulation Analysis of Twin Tripod Sliding Universal Joints," Intelligent Human-Machine Systems and Cybernetics, IHMSC '09. International Conference on, vol.2, no., pp.448, 450, Aug [3] K. Durand, "Design of a chain driven limited slip differential and rear driveline package for Formula SAE applications," Massachusetts Institute of Technology, [4] T. Scelfo, "Lightweight Torsen style limited slip differential and rear driveline package for Formula SAE," Massachusetts Institute of Technology, [5] F. J. Sanchez-Alejo, M. A. Alvarez, N. F. Holgado, and J. M. Lopez, "Defining the ergonomic parameters of the driver's seat in a competition single-seater," International Journal of Vehicle Design, vol. 55, pp , [6] H. Davies and B. Gugliotta, "Investigating the injury risk in frontal impacts of Formula Student cars: a computer-aided engineering analysis," Proceedings of the Institution of Mechanical Engineers, Part D: Journal of automobile engineering, vol. 226, pp , [7] E. Mariotti and B. Jawad, "Formula SAE Race Car Cockpit Design And Ergonomics Study for the Cockpit," SAE Technical Paper, [8] D. Bastow, G. Howard, and J. Whitehead, Car Suspension and Handling, 4th ed. Warrendale, PA: SAE International, [9] S. Potul, R. Nachnolkar, and S. Bhave, "Analysis of Change in Intake Manifold Length And Development Of Variable Intake System" International Journal of Scientific & Technology Research, Vol. 3, No. 5. May 2014 [10] D. Moster, "Intake Manifold Design for an Air Restricted Engine," M.S. thesis, Dept. Mech. Eng., Univ. of Cincinnati, Cincinnati, Ohio,

22 Appendices Appendix A: Gantt Chart

23 Cumulative Avg Hours Worked Appendix B: Budgeted Hours and Progression 700 Work Hours (Spring 2015) Theoretical Average Hours Avg Hours Worked /27/20141/16/2015 2/5/2015 2/25/2015 3/17/2015 4/6/2015 4/26/2015 5/16/2015 Week

24 Appendix C: Budget

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