2012 University of Cincinnati baja race team brake system

2012 University of Cincinnati SAE Baja

Race Team Brake System

A thesis submitted to the

Faculty of the Mechanical Engineering Technology Program

of the University of Cincinnati

in partial fulfillment of the

requirements for the degree of

Bachelor of Science

in Mechanical Engineering Technology

at the College of Engineering & Applied Science

by

MARK SCHMIDT

Bachelor of Science University of Cincinnati

May 2012

Faculty Advisor: Allen Arthur

Abstract

The following report covers the brake system design of the 2012 University of Cincinnati

Baja SAE car. It covers research into similar products, design of components, budget,

timeline, proof of design and testing. This report is submitted for senior capstone project for

degree in Mechanical Engineering Technology.

Baja Braking System Mark Schmidt

Table of Contents

Introduction ..................................................................................................................................... 1

From the Manager ........................................................................................................................... 1

Problem Statement .......................................................................................................................... 3

Alternatives ..................................................................................................................................... 3

Proposal........................................................................................................................................... 3

Customer Needs .............................................................................................................................. 5

Research and Existing Products ...................................................................................................... 5

Pedal Setup .................................................................................................................................. 5

Master Cylinders ......................................................................................................................... 6

Biasing ......................................................................................................................................... 7

Product Objectives and Features ..................................................................................................... 8

Design ............................................................................................................................................. 9

Pedal Setup .................................................................................................................................. 9

Solidworks ............................................................................................................................... 9

Stress Calculations ................................................................................................................. 10

Finite Element Analysis......................................................................................................... 12

Hydraulics Calculations ............................................................................................................ 14

Purchased Components.......................................................................................................... 16

Fabrication and Assembly............................................................................................................. 16

Proof of Design ............................................................................................................................. 17

Testing Results .............................................................................................................................. 17

Project Management ..................................................................................................................... 18

Schedule .................................................................................................................................... 18

Budget ....................................................................................................................................... 18

Conclusion and Recommendations ............................................................................................... 18

References ..................................................................................................................................... 19

Appendix A- Research .................................................................................................... Appendix A

Appendix B- Part Drawings ............................................................................................ Appendix B

Bill of Material ................................................................................................................ Appendix B


Appendix C- Calculations ................................................................................................ Appendix C

Hydraulics Calculations .............................................................................................. Appendix C

Force Calculations on Pedal ........................................................................................ Appendix C

Appendix D- Schedule ..................................................................................................... Appendix D

Appendix E- Budget ......................................................................................................... Appendix E

List of Figures

Figure 1 2011 Brake Pedal Setup.................................................................................................... 4

Figure 2 2011 Inboard Rear Brakes ................................................................................................ 4

Figure 3 Wilwood Pedal Setup ....................................................................................................... 6

Figure 4 Single Master Cylinder ..................................................................................................... 6

Figure 5 Dual Master Cylinder ....................................................................................................... 7

Figure 6 Balance Bar ...................................................................................................................... 8

Figure 7 Pedal Concept 1 ................................................................................................................ 9

Figure 8 Pedal Concept 2 .............................................................................................................. 10

Figure 9 Loading Conditions ........................................................................................................ 11

Figure 10 Shear Diagram .............................................................................................................. 11

Figure 11 Moment Diagram.......................................................................................................... 11

Figure 12 Pedal Loading Conditions ............................................................................................ 12

Figure 13 Pedal FEA Results ........................................................................................................ 13

Figure 14 Base Loading Conditions ............................................................................................. 13

Figure 15 Base FEA Results ......................................................................................................... 14

Figure 16 Hydraulic Calculations Constants ................................................................................ 15

Figure 17 Hydraulic Calculations Results .................................................................................... 15

Figure 18 Required Machined Parts ............................................................................................. 16

Figure 19 Finished Assembly ....................................................................................................... 17


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Introduction

Every year the Society of American Engineers (SAE) has an intercollegiate competition that puts

colleges against each other in a design and race competition to see who can build the best mini

baja vehicle. The colleges compete against one another in design, build, test, promotion, and a

race event. Colleges and Universities also need to raise the money needed to build the vehicles.

These vehicles all share the same 10 horsepower Briggs and Stratton four cycle motor. It is up to

each college to build off of that motor a vehicle that will endure some of the harshest tests and

courses designed to break anything that attempts them. This competition allows the students to

test what they have learned from the classroom into the real world.

The 2011 SAE Baja Racing team designed and engineered a great car that they took to

competition in the spring of 2011. They had to overcome some major obstacles along the way

but finished strong with a three member team. The competition took a toll on the vehicle and

these issues need to be addressed for the 2012 season. One of the key issues with the 2011

vehicle is weight. The vehicle is about 75-100 pounds too heavy. In order to have a chance at

the competition the cars need to be under 500 lbs. The lighter the car is, the faster it will be and

less stress on the components. Another issue is the inadequacy of the braking system. At the

competition, it took the team four or more tries and many adjustments to pass the brake test.

The following report will cover the braking system of the car. It will focus on making the

braking system more effective, more ergonomic for the driver, as well as making it easily

adjustable. The report will contain calculations for a new pedal setup, and fluids calculations for

the hydraulic braking system. In addition, FEA results will be displayed, and proof of design

showed of the system.

From the Manager

The 2012 team consists of 4 Mechanical Engineering Technology seniors that are determined to

set out and improve on last year's results at the SAE competition. In order to perform this goal

each senior chose one aspect of the old car that they will re-design, re-engineer, and build to

make it a success on the new car. The front suspension and steering of the car needs to be re-

worked to eliminate bump steer. This will be handled by Jeremy Jacobs, who is also managing

the team. A new drive line from the engine to the rear axle as well as lowering the overall center

of gravity is being engineered by Rob Faust. Mike Ratliff will design a new frame that will be

lighter and stronger than last year. Finally, Mark Schmidt will properly design a new brake set

up from the pedal to the wheels, including outboard brakes. The 2012 SAE competition will be a

nice proving ground to ensure these 4 seniors are ready for the real world and real applications.

Not only are these four seniors leading the project, but the overall team has grown to 15

members, including 3 juniors and 2 sophomores who also had projects on the car. The

contribution of everyone on the team and the leadership of the seniors fielded a car that placed


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39th

out of 103 other colleges and universities in the Baja SAE competition on April 18-21st in

Auburn, Al. This was the best finish for any UC team to date. The largest improvement was in

design and maneuverability. The placement finishes are below.

Baja Bearcats Competition Placement

Design 31st

Acceleration 59th

Maneuverability 11th

Suspension 57th

Hill Climb 40th

Endurance Race 37th

Overall 39th


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Problem Statement

The current car is setup with a hydraulic braking system to effectively stop the car. However, this

braking system was proven to be inadequate (especially in the rear wheels) as evidenced by

multiple tries and adjustments to pass the brake test at the previous competition. The system

required too large of a driver input, and too much time to make any adjustments to the system,

such as biasing.

A new braking system from the pedals to the wheels will be designed and implemented to better

perform at the 2012 SAE competition.

Alternatives

1. New easily adjustable pedal setup (top or bottom mount) with single master cylinder, inboard

brakes.

2. New easily adjustable pedal setup (top or bottom mount) with dual master cylinders, inboard

brakes.

3. New easily adjustable pedal setup (top or bottom mount) with single master cylinder,

outboard brakes.

4. New easily adjustable pedal setup (top or bottom mount) with dual master cylinders,

outboard brakes.

Proposal

Looking further into the braking system on the 2011 car, it was seen that there was not enough

mechanical advantage in the system to be effective and ergonomic for a driver during a four hour

endurance race. Mechanical advantage is created two ways in a breaking system. One is through

the pedal in something called the pedal ratio (essentially a force multiplier leverage ratio), and

the other is through the sizing of master cylinders, creating hydraulic pressure.

Another problem with the car was that it took too long, and too many tools to make any sort of

adjustments to the system, especially changing the bias from front to rear. In a race setting, time

is off the essence, and teams need to be able to make fast adjustments. Below is an image

showing the setup of the brake pedal and master cylinders on the 2011 car.


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Figure 1 2011 Brake Pedal Setup

A final problem with the current brake system setup is the inboard brakes in the rear. Because of

the differential setup, the inboard brakes are not very effective during braking. The 2011 team

had the most trouble getting the rear wheels to lock up. Figure 2 shows the current inboard setup

in the rear.

Figure 2 2011 Inboard Rear Brakes

From talking to previous years’ teams, since the differential is an open differential, under

braking, the differential would torque back and forth and would actually be counterproductive

under braking. Having the brakes on the axles also creates more stress on the axles. By moving

brakes to the wheels, it puts the braking power directly to the ground, as well as allowing for axle

redesign in the form of shortening the axles and possibly making them lighter.

In order to solve the problems of the braking system, it is proposed that there is a total revamp of

the system. A new pedal setup will be designed with a larger pedal ratio. This setup will be easily

Bias adjusted by moving

spacers around

Pedal with 5:1 ratio

Brake

s

Differential


5 | P a g e

adjustable, minimizing the time and tools needed. Also, to achieve the correct braking pressures

with minimal driver input, master cylinders will be sized correctly. Finally, the inboard brakes on

the axles of the 2011 car will be moved outboard to the wheels. This will place the braking

forces closer to the wheels, as well as taking space out of the axles, allowing the rear of the car to

be narrower in the future.

Customer Needs

Because this baja vehicle is being designed for an SAE competition, many of the needs are

defined by SAE. The major requirement of the braking system is that all four wheels need to lock

up on pavement from an acceleration run. This test needs to be passed before the car is deemed

safe to drive at the competition.

However, keeping an off-road race setting in mind, there are other requirements that the end

“customer” requires. The customer requires that the system is easily adjusted. Biasing pressure

between front and rear in order to get maximum performance and handling is important.

Especially in a race setting, the customer cannot spend a lot of time searching for tools and

taking time out of a race to adjust the bias in the system. Also, there needs to be minimal driver

input (input force) during braking. This especially applies to the four hour endurance race at the

SAE competition. If the system is designed for a high input force, then the driver can tire very

quickly, and can become a hazard to him/herself or even other drivers/competitors.

Finally, all braking components need to be robust. The braking system is an essential safety

feature of any car, and if parts in the system fail, results can be catastrophic. The customer

requires that every component is strongly built in order to ensure safety and performance.

Research and Existing Products

Pedal Setup

The pedal setup below can be floor mounted or swing mounted, depending on your application

and how much room is available in the vehicle. This specific pedal uses a dual master cylinder

setup (one for front circuit, one for rear), however similar pedals can be purchased that use a

single master cylinder for both circuits. This pedal uses a balance bar for biasing, which can be

easily adapted to be adjusted by the driver on the fly. It has a pedal ratio of 6:1 multiplying driver

input force by a factor of 6. The pedal is shown in Figure 3.


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Figure 3 Wilwood Pedal Setup

As seen, the master cylinders mount out front, which may not fit in the limited space of the baja

car.

Master Cylinders

Braking systems can use a single master cylinder for both front and rear brake circuits, or a dual

master cylinder setup using one for front and one for rear. SAE rules stipulate that front and rear

circuits must be separate from one another, making the dual master cylinder ideal. However a

single master cylinder with a separate fluid reservoir for each circuit may be used. Figure 4

shows a single master cylinder with separate fluid reservoirs.

Figure 4 Single Master Cylinder

Master cylinders mount

here


7 | P a g e

Because of the combined reservoirs, this package is large, and will be harder to fit within the

spatial limitations of the baja car. Figure 5 shows a typical single master cylinder.

Figure 5 Dual Master Cylinder

Compared to the single master cylinder, this is much more compact, especially in the length of it.

Another advantage to using two separate master cylinders is the biasing. Different sized bore

master cylinders can be used since different braking pressures may be required between the front

and rear of the car.

The size of the master cylinders is the second way that mechanical advantage can be achieved in

a braking system. Smaller bore master cylinders produce higher line pressures, creating more

force between the pads and rotors, however there is not as much fluid displacement, requiring

longer pedal travel. Larger bore master cylinders are just the opposite creating lower pressures,

but displacing more fluid. When designing the system, it is about making a tradeoff between

pressures generated and fluid displaced.

Biasing

If a single master cylinder is used to combine front and rear circuits, a proportioning valve can be

used. These valves are installed inline, and can be turned to reduce or increase fluid pressure

within the brake lines. It is very easily adjustable, usually requiring no tools, however because

you have to tap into the hydraulic lines to install it, it has the potential for leaks. Adjusting bias

with a dual master cylinder setup is typically done with something called a balance bar. The

balance bar is built into the pedal itself, and is a totally mechanical way of adjusting bias. Figure

6 shows a balance bar.


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Figure 6 Balance Bar

The swivel bearing is pressed into the pedal, and the black clevises are threaded onto the master

cylinder push rods. These points are fixed. The threaded rod can then be turned to adjust the bias.

Essentially it changes the distance between the pivot thus changing the moment that the driver

applies to the master cylinders. It can be adapted to be driver adjustable using a remote cable

setup.

Biasing is important when designing a braking system. The weight of a car is not evenly

distributed, so not all wheels need the same pressure applied to them. During dynamic braking,

the weight of the car is carried forward by its momentum, generally requiring more force applied

to the front wheels.

These products can be seen in Appendix A where an overview of features will be listed.

Product Objectives and Features

The goals for this braking system are to ultimately fulfill all required SAE rules, and to pass

technical inspection at the competition so that the car is allowed to compete. In order to help the

car brake more effectively, the more specific goals are to make the system more ergonomic by

reducing the input force required by the driver. Also, a major goal is to reduce the time and tools

required to adjust bias in the system. Below is a list of itemized features that the team hopes to

achieve.

Robust system

o This needs to last through testing and the competition, including a 4 hour

endurance race.

Effective

o The system needs to be able to lock up all four wheels on pavement from an

acceleration run.

Attaches to master cylinder

pushrod

Swivel bearing inside pedal


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Ergonomic

o Reduce the required driver input

Easy Adjustability

o Reduce the time and tools required to adjust bias in the system

Design

Pedal Setup

Solidworks

To begin the design process, concept sketches were generated for brake pedal setups. In order to

have a robust design, it was decided upon to go with the pedal setup similar to the Wilwood

pedal shown in Appendix A. A similar concept was generated in Solidworks, shown in the figure

below.

Figure 7 Pedal Concept 1

This pedal setup featured a 6:1 pedal ratio, offering plenty of mechanical advantage leverage to

be ergonomic for the driver. However, after working with the team it was found that this concept

would not fit easily inside the car. By making cardboard cutouts to the dimensions of this

concept and placing it inside the concept frame it was found that in order for the pedal to be in a

comfortable position the master cylinders would be hanging outside the front of the frame. This

is definitely not an ideal scenario. Analyzing the problem, it was seen that the pivot point could

be moved and the master cylinders could be flipped around, and placed inside the car, facing the

driver. Figure 8 shows this design, which is ultimately the design that was decided upon.

Master

Cylinders

6:1 Pedal Ratio


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Figure 8 Pedal Concept 2

This pedal, like the previous has a pedal ratio of 6:1. To get a better idea of sizing inside the

prototype frame, a rapid prototype model was produced. Using this model and the prototype

frame, it was found that there was ample room to place the pedal in the car in a comfortable

position for the driver. To adjust bias, a purchased bias bar from Wilwood will be used. In order

to adjust bias quickly, a remote cable will be setup so that it will be able to be adjusted by the

driver on the fly. The master cylinders will also be purchased from Wilwood. The rest of the

pieces will be fabricated out of 6061-T6 Aluminum so that they are lightweight, keeping the total

weight of the car in mind.

Stress Calculations

In order to analyze the forces that the pedal will experience, a driver input force needed to be

assumed. To find this force, the team placed a scale against a wall and sat in a similar position as

in the car with the driver’s back against another wall. Each team member pressed the scale as

hard as they could. The maximum force that was seen was right around 200 pounds, so this was

the assumed force. Figure 9 below shows the loading conditions.

Master Cylinders

Pedal

Base

Wilwood Balance Bar


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Figure 9 Loading Conditions

Using the 200 lb measured input, the force at the master cylinder was found to be 1200 lbs and

the shearing force at the pin to be 1400 lbs. Figures 10 and 11 show the resulting shear and

moment diagrams.

Figure 10 Shear Diagram

Figure 11 Moment Diagram


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As seen from the figures, the maximum shearing force seen is 1200 lbs, and the maximum

moment is 1980 in lb.

Finite Element Analysis

Knowing the maximum forces finite element analysis (FEA) could be performed in Solidworks

using Cosmos. Figures 12 and 13 show the FEA results for the pedal and figures 14 and 15 for

the base.

Figure 12 Pedal Loading Conditions


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Figure 13 Pedal FEA Results

Figure 14 Base Loading Conditions


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Figure 15 Base FEA Results

The safety factor for the pedal was found to be about 2 and 1.6 for the base. As seen from the

figures, the higher stress concentrations occurred in very small and local areas. Both components

could have been made slightly lighter by removing some material, however displacement was

also considered during the design, so as to not lose any pedal travel from the flexing of

components. When taking material out of the components (which resulted in negligible weight

loss), they became less rigid, and would have taken away from the robustness of the braking

system.

In addition to the FEA, a shear calculation was done on the pivot pin. With a factor of safety of

2, it was found that a standard alloy steel 3/8” shoulder bolt purchased from McMaster Carr

could be used.

Hydraulics Calculations

The second area to achieve mechanical advantage in a braking system is through the hydraulics

and selection of the master cylinders. This is very important to achieve the correct line pressures

in the system. Given the constants listed in Figure 16, hydraulic calculations were able to be

performed, and the results are shown in Figure 17.


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Figure 16 Hydraulic Calculations Constants

Figure 17 Hydraulic Calculations Results

Front Calpier Bore 1.19

Front Caliper Area 1.112

Front Rotor Size 7

Rear Caliper Bore 1.25

Rear Caliper Area 1.227

Rear Rotor Size 8.625

Coefficient of Friction of pads 0.4

Pedal Ratio 6

Driver force input 115

Front Bias 0.7

Rear Bias 0.3

Front Master Cylinder Size 0.625

Rear Master Cylinder Size 0.75

Pedal Travel 3

Required Torque Front Required Torque Rear

in lb in lb

4970.0 764.7

Required Front Circuit Pressure Required Rear Circuit Pressure

psi psi

1595.9 180.6

Front MC Piston Size Rear MC Piston Size

area 0.3026 1.1460

diameter 0.621 1.208

Pressure Generated Std. (Front) Pressure Generated Std. (Rear)

psi psi

1574.3 468.6

Fluid Displaced Front Fluid Displaced Rear

in3 in3

0.1534 0.2209

Caliper Piston Movement (Front) Caliper Piston Movement (Rear)

0.138 0.18


16 | P a g e

From the calculations, it was found to be that the optimal sized master cylinders would be a 5/8”

bore for the front circuit, and a 3/4” bore for the rear. The required driver input would be 115 lbs.

Purchased Components

Items such as the calipers and rotors will be purchased parts. These will be purchased from the

team’s sponsor Polaris so that they will bolt right onto the current locations already provided on

the current Polaris hubs and uprights. Below is a list of all purchased components for the system

1. Front and rear calipers (stock Polaris parts)

2. Front and rear rotors (stock Polaris parts)

3. Front and rear master cylinders (purchased from Wilwood)

4. Balance bar (purchased from Wilwood)

5. Remote bias adjust cable (purchased from Southwest Speed)

Fabrication and Assembly

No special fixtures will be needed to fabricate the pedal assembly. There will be three parts that

will need to be machined. These are illustrated in figure 18.

Figure 18 Required Machined Parts

Only standard milling practices will be required. The middle part and the part on the right will

need to be welded together. Figure 19 shows the finished and assembled pedal assembly.


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Figure 19 Finished Assembly

Proof of Design

In order to prove the design of the braking system the car will undergo testing before the

competition. In order to prove the system is more ergonomic than the previous car, the same

hydraulics calculations will be run using the setup of the 2011 car. Ultimately the required driver

input will be looked at to see if the system is more ergonomic. The team will also compare the

time and amount of tools required to adjust bias on both cars. Finally, the car will need to stop

consistently in the SAE competition stipulated scenario (lock up all four wheels from

acceleration). Testing will be done on the car during March, before the competition.

The ultimate proof of design will be at the Baja SAE competition at the end of April, 2012.

There the car will need to be able to pass the brake test before it is deemed safe to drive. Also the

car will undergo several individual events, as well as a four hour endurance race which is

designed to break the car. If the car and brake system survives the weekend, it is safe to say that

the customer requirements were met.

Testing Results

When the car was assembled and ready for testing, the team drove the car. The brakes were

checked before the car moved, and at slow speeds. In both instances, the brakes performed their

job. It was then determined to test the brakes in a competition technical inspection scenario.

From acceleration the brakes locked up all four wheels on the pavement. The brakes also locked


18 | P a g e

up and effectively stopped the car from a full speed run. Next, the time to adjust the bias was

recorded. To adjust the new system, only a knob needs to be turned, and the system is adjusted;

merely seconds and no tools required. The old car took in excess of five minutes to adjust, and

two wrenches; not ideal in a race/competitive setting. Finally, the driver input required to stop

the vehicles was calculated. With this new setup, a driver input of 115 lbs is required. It was

found that on the 2011 car, the driver needed to input a force in excess of 200 pounds. This is a

42% reduction, and was a major help in making the braking system more effective and

ergonomic.

At the competition, the team passed the brake test on the second try. It was seen that one front

tire would not lock up in the first run, so that line was bled quickly to remove air, and the bias

was adjusted to produce more front pressure. The car passed on the next run; a huge

improvement of the four or more tries in 2011. The car finished every event over the weekend of

the competition, including the four hour endurance race with no major complications, especially

to the braking system. It is safe to say that customer (and team) requirements were met for the

brakes.

Project Management

Schedule

The brake system design did not suffer any major setbacks. There was a delay in installation, due

to waiting on the car to get to a stage where the brakes could be installed. The schedule can be

found in the appendix.

Budget

The brake system was budgeted $1,000. The total amount spent on this project added up to

$1,154.84. The budget was exceeded by about $150. I did not anticipate that brake line fittings

would cost so much. Included in these expenses, however, are spares that were brought to the

competition, such as spare fittings, lines, brake pads, and rotors. The detailed budget can be seen

in the appendix.

Conclusion and Recommendations

It was found that the brakes on the 2011 car were ineffective. They required too large of a driver

input and too much time to adjust bias. The results of this year’s car make this even more

evident. Driver input force was reduced by over 40%, and time to adjust the bias in the system

was reduced to measly seconds compared to minutes and frustration of the 2011 car. A lot was

learned about the engineering process from research and ideation all the way up to testing and

proving the design. Also from doing a group project, a lot about working with a team of

engineers was learned. If you’re not a team player, failure is inevitable. Everybody relies on

somebody else at some point, and the more teamwork goes on, the better your results will be.


19 | P a g e

Some notes and recommendations for next year’s team. I recommend losing weight anywhere

possible on the car. At 555 lbs, the car isn’t the heaviest one out at the competition, but it

certainly is not the lightest. To save on costs and design time, a lot of the components are

purchased parts. Many of these parts are overdesigned for our application, and thus have a lot of

weight that could be lost. Perhaps things such as hubs and uprights can be manufactured in

house, and better designed for our application. Due to the improvements in the braking system

and moving the rear brakes outboard this year, the rear axles can be shortened. Those could use a

total redesign in the shortening, as well as making them lighter, losing rotational weight in the

driveline possibly yielding better acceleration. But most of all have fun. Doing Baja for your

senior design project is a lot of work, and it WILL be hard at times. Keep your eyes on the prize.

Driving that car for the first time during testing and at the competition will make it all worth it in

the end. Seeing something come to life that you literally have blood, sweat, and tears into is the

culmination of your senior year. I wish you all good luck.

References

Ansell, Bill. The Brake Bible. 2008. November 2011

<http://www.pirate4x4.com/tech/billavista/Brakes/>.

Bicknell Racking Products. Brake Balance Bar Set-Up. 2009. January 2012

<http://www.bicknellracingproducts.com/index.php?option=com_content&view=article&id=9:br

ake-balance-bar-set-up&catid=5:brp-dirt-modifieds&Itemid=11>.

Engineering Inspiration. Brake Calculations. 2011. November 2011

<http://www.engineeringinspiration.co.uk/brakecalcs.html>.

Oshiro, Dean. Brake Article. 2011. November 2011

<http://www.deanoshiro.com/brakes/brakearticle.html>.

Stop Tech. Technical Support. November 2011 <http://www.stoptech.com/technical-support>.

Wilwood. November 2011 <http://wilwood.com/>.


Appendix A| P a g e

Appendix A- Research

Pedal setup designed for off-road cars and buggies

Comments:

Uses dual master cylinders

Swing mount or floor mount

Bias adjustability

Driver bias adjustable capable

Simple design

Single, combined master cylinder for race car applications

Comments:

Separate fluid reservoir for front

and rear circuits

Large packaging

9/24/11

http://www.wilwood.com/pe

dals/PedalList.aspx

9/24/11

http://www.wilwood.com/MasterCylinders/Mas

terCylinderList.aspx?minorname=Aluminum%20

Tandem%20Master%20Cylinder

http://www.wilwood.com/pedals/PedalList.aspx


http://www.wilwood.com/MasterCylinders/MasterCylinderList.aspx?minorname=Aluminum%20Tandem%20Master%20Cylinder




Appendix A | P a g e

Master cylinder for race car applications

Comments:

Compact size

Lightweight

Need MC for both front and

rear

Integrated fluid reservoir

Balance Bar to adjust brake bias

Comments:

Mechanical balancing

Robust

Cheap

No tapping into brake lines

Effective

9/24/11

http://www.wilwood.com/MasterCylinders/Maste

rCylinderList.aspx?minorname=Integral%20Reserv

oir%20Compact%20Master%20Cylinder

9/24/11


http://www.wilwood.com/MasterCylinders/MasterCylinderList.aspx?minorname=Integral%20Reservoir%20Compact%20Master%20Cylinder





Appendix B| P a g e

Appendix B- Part Drawings


Appendix B | P a g e







Bill of Material


Appendix C | P a g e

Appendix C- Calculations

Hydraulics Calculations

Mas

s of C

arM

ass o

f Car

+Driv

erHe

ight o

f CG

Whe

elba

seFr

ont T

ire D

iamet

erRe

ar Ti

re D

iamet

er

lblb

inin

inin

548

698

31.05

6521

.525

Velo

city (

mph

)Ve

locit

y (fp

s)Co

effic

ient

of Fr

ictio

nDe

cele

ratio

n Rat

e, (f

t/s2)

Dece

lera

tion R

ate,

(g)

Stop

ping

Dist

ance

(Fee

t)

3044

0.832

.21

112.8

Wei

ght T

rans

fer

Dyna

mic

Fron

t Axle

Wt

Dyna

mic

Rear

Axle

Wt.

lblb

lb

333.4

616.4

81.6



Stopping Distance

Dynamic Weight Transfer (at 1 g deceleration rate)



Using 115 lb driver input force, 6:1 pedal ratio, and 70%/30% front/rear bias forces put into

system:



The closest standard sized master cylinders in the correct style are .625” and .750” in diameter.

Below are the generated pressures for these sizes.



These calculations were performed using weights and heights of the center of gravity of the 2011

car. Less weight would mean that required brake torques as well as circuit pressures would

decrease. Lowering the center of gravity would increase required pressures in the rear, however

decrease in the front. Both generated pressures from a standard size master cylinder would then

exceed the required pressure.



Proof of design Calculations

In order to prove the design the braking system of the 2011 car was put into the same Excel

spreadsheet that was used to design the current system on the 2012 car. Below are the inputs

of the 2011 Car, and the resulting values along with a sample calculation.

Front Calpier Bore 1.188

Front Caliper Area 1.108

Front Rotor Size 7

Rear Caliper Bore 1.375

Rear Caliper Area 1.485

Rear Rotor Size 7.125

Coefficient of Friction of pads 0.4

Pedal Ratio 6

Driver force input 115

Front Bias 0.6

Rear Bias 0.4

Front Master Cylinder Size 0.875

Rear Master Cylinder Size 0.875

Pedal Travel 3



Mas

s of C

arM

ass o

f Car+

Drive

rHe

ight o

f CG

Whe

elbas

eFro

nt Ti

re Dia

meter

Rear

Tire D

iamet

er

lblb

inin

inin

548

698

31.05

6521

.525

Veloc

ity (m

ph)

Veloc

ity (fp

s)Co

effici

ent o

f Fric

tion

Dece

lerati

on Ra

te, (f

t/s2)

Dece

lerati

on Ra

te, (g

)Sto

pping

Dista

nce (

Feet

)

3044

0.832

.21

37.6

Weig

ht Tr

ansfe

rDy

nami

c Fro

nt Ax

le W

tDy

nami

c Rea

r Axle

Wt.

lblb

lb

333.4

616.4

81.6



(Force using 115 lb driver input)

Value does not exceed the needed 1600 psi.

Force using 230 driver input produces 1606.5 psi of circuit pressure, a value meeting the

required line pressure in the front circuit. The 2012 car requires 115 lb input to stop the car—a

50% reduction in the required driver input.

Required Torque Front Required Torque Rear

in lb in lb

4970.0 764.7

Required Front Circuit Pressure Required Rear Circuit Pressure

psi psi

1601.3 180.7

Front MC Piston Size Rear MC Piston Size

area 0.2585 1.5274

diameter 0.574 1.395

Pressure Generated Std. (Front) Pressure Generated Std. (Rear)

psi psi

688.5 459.0

Fluid Displaced Front Fluid Displaced Rear

in3 in3

0.3007 0.3007

Caliper Piston Movement (Front) Caliper Piston Movement (Rear)

0.271 0.202



Force Calculations on Pedal

1.65”

9.9”



Shear Diagram

Moment Diagram



Shear Stress of Shoulder Bolt

Alloy steel shoulder bolt from McMaster Carr has shear strength of 84,000 psi. Using factor

safety of 2, 3/8” shoulder bolt satisfies requirements.


Appendix D | P a g e

Appendix D- Schedule

Week Num

ber1

35

79

112

46

810

122

13

57

911

13

57

9

Build Point

7/4/2011

7/18/2011

8/1/2011

8/15/2011

8/29/2011

9/12/2011

9/26/2011

10/10/2011

10/24/2011

11/7/2011

11/21/2011

12/5/2011

12/19/2011

1/2/2012

1/16/2012

1/30/2012

2/13/2012

2/27/2012

3/12/2012

3/26/2012

4/9/2012

4/23/2012

5/7/2012

5/21/2012

Sponsor Money Due

Frame Design

Suspension Design

Transmission Design

Brake Design

Prototype Frame Work

Frame Construction

Suspension Construction

Transmission Construction

Brake Construction

Purchase Components

Receive Components

Suspension Installation

Transmission Installation

Brake Installation

Component Installation

Testing

Modifications

Body Fabrication

Final Preperations

Competition

Summ

er Quarter / BreakSpring Quarter

Winter Quarter


Appendix E | P a g e

Appendix E- Budget

Company Project Part DescriptionPolaris order $553.60 brakes

Sand Parts $56.79 turning brake cylinder

LPI Racing $61.45 Balance Bar

Kratter (ebay) $39.98 Balance adjuster cable

Wilwood $97.26 Master Cylinders

McMaster Carr2 $19.12 Hardware/Tube Caps

Allstar Performance (amazon) $15.99 3/16" Steel Brake Line

Pep Boys $2.65 Fittings

Summit Racing $199.66 Fittings/Brake Lines

Orielly Auto $7.97 fitting/brake fluid

Pep Boys $2.65 tube nuts

Autozone $3.18 tube nuts

Bridgetown Hardware $27.25 Hardware

Summit Racing $67.29 Banjo Fitting/Spare Lines

expense total $1,154.84

expense grand total $1,154.84

amount left to spend -$154.84

Documents

2012 University of Cincinnati baja race team brake system