2006 formula sae chassis design

8/8/2019 2006 Formula Sae Chassis Design

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MECH 460 Final Design Report2006 Formula SAE Chassis Design

Queen's UniversityDepartment of Mechanical Engineering

Advisor:

Dr. Diak

Design Team:

Michael Hynes

Asle Olsen

Pravin Advani

Rami Laitila

Submitted:

December 5 2005


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For the 2006 season the Formula S.A.E. team is looking to change some components ofthe car to better its performance. A redesign of the chassis will be done to better suit an

ergonomic driving position and to better the suspension. Also, the safety during sideimpact will be investigated.

To determine the most comfortable driving position fort the 95th percentile male, a

mock-up chassis was built in which various parameters such as steering column height,

angle of backrest, position of pedals, and dash distance could be adjusted. With thepersonal preferences from each team member, averages were found that would suit

everybody, and adjustable pedals were used to accommodate the differences in height of

the team members. Also a computer model of the 95thpercentile male was used during

the 3D modeling of the car, to make sure anyone up to that size would fit properly.

It was found that every driver would fit in a cockpit with a length of 54 inches, while theshortest drivers needed a cockpit with a length of 50 inches. By allowing adjustments of

the backrest by up to 2.75 inches and the pedals by up to 2 inches, all drivers will fit

comfortably in the cockpit. The cockpit was also made wider, by 6.3 inches in the frontand 2.126 inches in the back, to accommodate for wider drivers and to make it more

spacious for everyone in general.

To further improve the chassis, its overall shape was adjusted to improve the integration

with the suspension. The chassis profile was changed to allow for longer lower A-arms,

which improves cornering. In order to allow for longer lower A-arms, the walls of thechassis are now at a 40-degree angle for some distance, before going vertical at the

desired width, while the old design had the walls going up at an 81-degree angle. Thisdesign allows for the lower A-arms to be much longer than the upper A-arms, asspecified by the suspension team.

After some research an appropriate method of testing the monocoque for side impact was

found. The selected test is based on the ASTM D 3763-02 (see Appendix C), which hasbeen modified for thicker sample sizes than that of the original test. This test will be

performed at the local Novelis site as soon as a date is agreed upon. It will be performed

at 20m/s, at least five times, to assure that the results are correct.

With high-rate impact research and testing, improvements in an ergonomic driving

position, and improvements in the integration of the suspension, the overall result will bean increase in reliability and drivability of the car.

Abstract


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ABSTRACT........................................................................................................................... 2

TABLE OF CONTENTS ......................................................................................................... 3

1. INTRODUCTION ......................................................................................................... 4

1.1 Background ........................................................................................................... 4

1.2 Objectives.............................................................................................................. 4

2. PERFORMANCE CRITERIA ........................................................................................ 6

2.1 Ergonomics .............................................................................................................. 6

2.2 Suspension Integration............................................................................................. 6

2.3 Impact Equivalency.................................................................................................. 6

3. ANALYSIS .................................................................................................................. 8

3.1 QFD Analysis........................................................................................................... 8

3.1.1 Design............................................................................................................... 8

3.1.2 Test Methods.................................................................................................... 8

3.2 Methods.................................................................................................................. 10

3.2.1 Ergonomic Influence ...................................................................................... 10

3.2.2 Suspension Influence...................................................................................... 11

4. FINAL DESIGN ......................................................................................................... 13

5. FUTURE WORK ....................................................................................................... 15

6. CONCLUSIONS ......................................................................................................... 16

7. REFERENCES ........................................................................................................... 17

8. APPENDICES ............................................................................................................ 18

Appendix A: Ergonomic mockup rig........................................................................... 18

Appendix B: Ergonomic Data...................................................................................... 19Appendix C: ASTM D 3763-02................................................................................... 20

Appendix D: Test rig for ASTM D 3763-02 test......................................................... 30

Appendix E: Comparison of old and new chassis........................................................ 31

Table of Contents


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1.1 Background

Since 1993, Queens University has participated in the Formula SAE competition.

This is a competition for students to use their knowledge to design, build and race a small

formula style racecar. Each year teams from all around the world assemble in Pontiac,Michigan, bringing their cars to be evaluated in many areas important to the success of a

car. Judges evaluate the cars based on design, cost, manufacturability, dependability,safety and performance.

Over the years in which Queens has participated there has been a steady improvement inthe design of the chassis. Material selection in particular has had a great impact on the

cars performance. Originally a steel tube space frame was built with aluminum body

panels, weighing 85 lbs. This was reduced to 47 lbs with the use of an aluminum-balsa

wood composite monocoque, and even further reduced to 35 lbs last year using thecurrent carbon-aluminum honeycomb monocoque.

1.2 Objectives

The objective of this project is to design the chassis for Queens 2006 Formula

SAE car. Last years carbon-aluminum honeycomb monocoque will be used as a baselinefor this years design, focusing on making adjustments to driver comfort, sub-system

integration, performance, and driver safety with respect to crashworthiness. .

1.2.1 Ergonomics

In order to achieve the ergonomic goals of this project, chassisdimensional changes will be investigated in order to adjust the driving position,

and provide more space in tight areas pointed out by drivers last year.Furthermore, it will now be easier for larger drivers to comply with FSAE

evacuation regulations, which state that a driver should be able to exit the car,

from a fully strapped in driving condition, in under five seconds.

1.2.2 Suspension Geometry

Significant changes to the suspension geometry have called forcorresponding changes to the shape of the chassis. Working closely with the

suspension team has allowed the chassis to be designed such that it optimizes the

integration of the new suspension system.

1.2.3 Impact Equivalency

To achieve the desired level of driver safety, the crashworthiness of the

carbon-aluminum honeycomb composite must be fully explored. A relevanttesting procedure, and corresponding apparatus, must show that the carbon

composite used in the chassis is fully equivalent to the FSAE baseline design of a

steel tube frame. Another goal is to implement the testing procedure as standard

1. Introduction


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protocol for the team in future years, as SAE regulations require equivalency testresults each time a chassis differs from the steel tubing design.


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2.1 Ergonomics

Ergonomic concerns are based upon drivers observations from previous years.From these concerns it was determined that the chassis width, length, and the driverposition are to be modified.

FSAE safety regulations require that a driver should be able to exit the car, from a fullystrapped in driving condition, in under five seconds. The car should be able to

accommodate the teams largest member in this regard. Because of the tight confines of

last years cockpit, it has been decided that the chassis will be made slightly wider. This

will create more space for drivers shoulders, which have been concerns for some of thelarger drivers to date.

Furthermore it was felt the drivers position was too reclined. It is believed thataddressing this concern will make it easier for drivers to evacuate the vehicle. In addition,

drivers response will also be improved by bringing the driving position closer to the

steering wheel, which was also a concern with the previous chassis. This change willalso necessitate making a taller roll hoop to meet FSAE regulations, and refining the

position of the driving pedals.

2.2 Suspension Integration

In an effort to increase the turning performance of the car, the suspension teamhas lowered the vehicles roll point. This is the longitudinal axis about which the car

leans in a turn. By lowering this axis, the suspension team is confident in theircapabilities to improve camber gain in static cornering, thus increasing the grip achievedin turns.

In order for the chassis to facilitate the suspension integration, it must be built such thatthe lower control arms are significantly longer than the upper control arms. By designing

the chassis to fit the desired suspension geometry a better overall performance is

achieved.

2.3 Impact Equivalency

The baseline FSAE regulations call for three tubes to be used as side impactbeams for each side of the car: One upper bar which is to be 300-350 mm above the

ground, one lower bar, and one diagonal bar which connects the two previous. These bars

are required to be at least as strong as 1% carbon tubing having an outer dimension of25.4 mm and a wall thickness of 1.60 mm. A schematic is shown in Figure 1 below.

2. Performance Criteria


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3.1 QFD Analysis

Considering the SAE judging criteria - design, cost, manufacturability,dependability, safety and performance- two different designs, and five different testswere ranked in a Quality Function Deployment (QFD) chart. This allows the design

parameters to be ranked as an analytical process, and effectively outlines the most

appropriate design solution. Each factor was weighted and assigned a ranking out of nine

for each design solution, and then the sum of the products was normalized to produce ascore out of nine.

3.1.1 Design

Design 1:

Steel Tube

This design uses steel tubing to reinforce the sides of the carbon composite monocoque inthe event of impact.

QFD Score: 4.3

This design ended up scoring lowest of the two considered, mainly due to its high weight,and the difficulties integrating it with the current carbon composite monocoque.

Design 2:

Carbon Composite

This design either just use the monocoque as is, or adds an extra layer of carbon

composite to the sides to increase safety. This is dependant on the test results that are

going to be performed on the existing monocoque material.

QFD Score: 8.1

The carbon composite design was by far the better of the two, as it is lighter, stronger,and easier to integrate with the monocoque and is aesthetically pleasing. Based on the

result in the QFD this is the design that was chosen. Whether or not the sides will need

reinforcing will be evident after testing the properties of the material.

3.1.2 Test Methods

Test 1:

Static Test

This tests the strength of the material, through bending the material until it breaks.

QFD Score: 6.6The static test ended up scoring second highest, due to its low cost and low time

consumption. However, due to its low relevancy to high velocity impacts it is not the

ideal test to perform.

3. Analysis


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Test 2:

Drop Test

In this test an object of known mass is dropped from a known height, on to the testspecimens. The results are measured and compared to decide if the carbon composite is

strong enough, or if it needs to be reinforced.

QFD Score: 6.9

This test scored highest of all the tests, due to its ease of construction, high velocity

impact relevance, and its low cost.

Test 3:

Impact Sled

In this test an impact sled is driven into the side of the car. This means that a whole car

has to be made and tested, instead of just a small sample of the material.

QFD Score: 4.6

Although this test is a very good way to see how the car actually performs in a side

impact, it ended up scoring fairly low. This is due to the fact that a whole car would have

to be constructed, which would be both expensive, time consuming and hard to do.

Test 4:

Theoretical

This involves constructing the car in a computer program, including the materialproperties, and then simulating a side impact.

QFD Score: 5.7Due to its low cost and its high relevancy to high velocity impacts, this test scored fairly

high. However, due to its significant time consumption and the difficulty involved in

making a virtual model of the car, it is not the preferred test.

Test 5:TMAC (Test Machine for Automotive Crashworthiness)The TMAC crushes the test specimen at a predetermined velocity and force, similar to a

drop test. However, in this case the velocity and force is constant throughout the test.

QFD Score: 4.6

Although this is a very good test, it is not feasible to perform, due to its high cost and low

availability.

After deciding on the drop test, a way of performing it was needed. Novelis wascontacted and agreed to the use of one of their machines for this test. In principle it is the


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same as a drop test, but instead of simply dropping an object onto the test specimen, apiston is driven into the specimen at a known velocity. The piston also has sensors

attached to it that will record data, such as the velocity and force.

3.2 Methods

3.2.1 Ergonomic Influence

To find the best ergonomic seating position a mock up rig was

constructed. This rig was made to be fully adjustable so that members of the team

could find their comfortable seating position. The measurement data from each

driver was compiled and is shown in appendix B!. The most importantdimensions for modeling the car can be seen below in Table 1 and Figure 2.

Table 1: Pertinent Ergonomic Data

Axis 1: centered atrear roll hoop

Axis 2: centered atfront roll hoop

DriverA B C D

Chris 32.50 54.00 -32.50 21.50

Dallas 29.75 51.00 -29.75 21.25

Mike 31.50 51.00 -31.50 19.50

Ereth 30.00 50.00 -30.00 20.00

Christie 30.50 51.00 -30.50 20.50

Ethan 31.00 51.00 -31.00 20.00

John 30.50 50.00 -30.50 19.50

Bruce 31.00 51.00 -31.00 20.00

Max 32.50 54.00 -29.75 21.50

Min 29.75 50.00 -32.50 19.50

S.D. 0.88 1.25 0.88 0.75

Range 2.75 4.00 2.75 2.00

Mean 30.84 51.13 -30.84 20.28

As can be seen, dimension D for all drivers is very close with a standard deviation

of 0.75 inches and a range of 2.0 inches. The range of values of D can be

compensated by an adjustable pedal system, which will be incorporated into thefinal assembly of the car. The distances A and C will be compensated by

different seat foam thickness for various driver heights. The car was then

modeled for the largest drivers seating position and can still be adjusted for

smaller drivers.


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Figure 2: Ergonomic dimensioning with 95

thpercentile male

The 3D model was assembled with a 95th percentile male to ensure that any parts

added to a given point could be moved to avoid interfering with the driver.

3.2.2 Suspension InfluenceUntil recently, Queens chassis and suspension designs existed separately.

Suspension mounting points were based primarily on available room on the

chassis. However, this year the two teams approached this problem by workingclosely with each other to determine what needed to change in order to attain a

favorable suspension system.

One of the main concerns was optimizing the outside front tires surface contact

during turning. Lengthening the lower A-arm solved this problem. In doing so

the system becomes less symmetrical and the overall result is shown in Figure 3

below.

Figure 3: Desired suspension set up under 0o

and 10o

body roll respectively


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Also the Roll center of the front suspension was placed lower than the rear to

assure more force is transferred to the front outside tire during turning. The

chassis shape was iterated many times until the mounting points could be placedin both reinforced and plausible positions.


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After all design influences were taken into account, a final chassis design was decidedupon. This resulted in a whole new profile for the Queens formula car shown in Figure

4 below.

Figure 4: Transformation of Queens formula car profile

With the chassis and suspension design working together, the overall output was a much

more suitable integration between the two. The chassis was designed around the

suspension and not the other way around.

Progress was also made to improve the overall ergonomics of the car. The seating

position was adjusted to be most comfortable. This new seating position resulted in a

shorter, wider chassis, which is shown with a model 95th

percentile male in Figure 5below.

Figure 5: 2006 car assembly with 95th

percentile male

4. Final Design


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Early next semester the material testing will be performed at Novelis. The rig to be usedhas already been constructed, and all that is needed is for Novelis to come up with a date

to perform the test. The test data will be analyzed as soon as the test is completed, andany modifications the chassis may require will be dealt with at as such.

The chassis will be constructed in early January. The carbon fiber and the aluminum

honeycomb have not been delivered to date, but they are expected to arrive within twoweeks. As soon as they are delivered the construction of the chassis itself can start. After

the chassis has been constructed the other components will be added. If the other parts do

not fit, minor modifications may be needed at this point. However, this is not very likely,

as everything has been modeled accurately in Solid Edge to make sure a good fit isaccomplished on the first try.

5. Future Work


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The 2006 chassis was designed to fit the suspension and ergonomics and not the otherway around. The two designs being done together made it easy to assemble the car in

Solid Edge and verify all the relevant parts.


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The final design of the chassis has successfully addressed the following concerns. Driver

ergonomics and drivability were improved through an ergonomic survey of the team.

Also, the integration of the suspension was improved by working closely with thesuspension team such that the chassis profile accommodates the new suspension design.

Through the ergonomic survey of the team a comfortable driving position was

determined which would suit all of the drivers. Different sized drivers, up to a 95th

percentile male, were accommodated by incorporating some adjustability in the backrest

and foot pedals. This provided everybody with the ideal driving position, improving the

comfort and drivability of the car. This also allowed for the chassis to be shortened by 4inches.

Suspension mounting points, which improve cornering, were determined by working

alongside the suspension team. The profile of the chassis was then adjusted in order toaccommodate the new suspension design. As a result the new suspension integration will

improve the cars handling and drivability.

The design of the test procedure, and apparatus were finalized to investigate

crashworthiness. The testing, yet to be performed, will hope to confirm the carbon

composite crashworthiness as compared to the standard regulation steel framed chassis.

In conclusion, the design revisions incorporated into the 2006 chassis successfully

improve the ergonomics and cornering ability of the car. In addition, testing methods to

prove the crashworthiness of the Carbon Aluminum composite were successfully

designed.

6. Conclusions


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1. ASTM D 3763-02, "Standard Test Method for High Speed Puncture Properties ofPlastics Using Load and Displacement Sensors" ASTM International

2 SAE International, 2006 Formula SAE Ruleshttp://www.sae.org/students/fsaerules.pdf

7. References


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Appendix A: Ergonomic mockup rig

8. Appendices

2006 formula sae chassis design

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