SUNY POLY Mechanical Engineering Technology Capstone ...curtisjacksonsportfolio.weebly.com/uploads/5/6/9/9/56999845/capst… · Figure 2.4 PADT machine used to remove soluble support

SUNY POLY

Mechanical Engineering Technology

Capstone Experience, MTC 420

Designing a BAJA Frame

Devinne Jalowiec and Curtis Jackson

7/14/2015

Dr. Tadros

Table of Contents:

Introduction ....................................................................................................3

Equipment ......................................................................................................3

Theory ............................................................................................................7

Procedure .......................................................................................................8

Analysis and Results ......................................................................................8

Discussion ......................................................................................................10

Teamwork ......................................................................................................10

Conclusion .....................................................................................................12

References ......................................................................................................12

Appendix A – Material Calculations .............................................................13

Appendix B – Frame Requirements ...............................................................19

Appendix C – Frame Design..........................................................................25

Appendix D – Rapid Prototyping ..................................................................28

Designing a Baja Frame

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Introduction:

The intended goal is to design the frame for a Baja vehicle complying with standards put in place

by Baja Society of Automotive Engineering. The main points of the project will be design of the

frame, choice of material, a finite element analysis of the stresses present on the frame, and a

scaled 3D model.

The design of the frame must include proper clearances for driver fitment and appropriate

location for drivetrain. From the driver’s helmet to the frame of the baja vehicle there must be at

least six inches of clearance, and from the driver’s shoulders, torso, hips, thighs, knees, arms,

elbows, and hands they must have at least three inches of clearance. All while minimizing the

weight of the vehicle, but retaining maximum strength.

A comparison between standard 1020 DOM and 4130 chromoly with appropriate wall thickness

comparative to the specifications put into place by Baja will be completed to choose the most

appropriate material for usage.

The finite element analysis will be completed using symmetry since the vehicle will be

symmetric about the center plane. There will be four separate analyses based on a head-on

collision, rear-impact, side-impact, and a roll-over. The loads applied to the finite element

analysis will be derived from the average speed of the Baja vehicle just before the collision

occurs.

The model will be designed using weldments in Solidworks. In order to use weldments, the

sketch of the outline of the frame of the baja vehicle will first be created. Structural elements

will then be applied to the sketch. A scaled down model will be created using a rapid

prototyping machine.

Equipment:

For this project, we used Microsoft Excel. Microsoft can be reached twenty-four hours a day,

seven days a week at 1-877-696-7786.

Excel was very important in this project because it provided us with a way to organize all the

necessary data. Also, Excel is able to connect data in separate cells using equations.

The main page of Excel can be seen on the following page in Figure 2.1. From this page, one

can find the tools necessary to change the font, text size, font, color, and background color.

Excel is mainly used to create tables and graphs.

Once a template is created in Excel, it can be used for many different tasks. A template may be

difficult to create for some tasks, but once created the template can be used over and over again.

The benefits provided by Excel are almost endless, as one can organize any source of data using

multiple sheets, workbooks, or single one single sheet. Excel was used to material calculations,


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a log for time spent working on the project, and a table to divide the necessary tasks into smaller

time periods.

Figure 2.1 – Excel main page

Also for this experiment, Solidworks was used for all the necessary modeling done to create the

frame of the baja vehicle. Solidworks can be reached at the following address:

Dassault Systèmes SolidWorks Corporation

175 Wyman Street

Waltham, MA 02451

They can also be reached by phone at 1-800-693-9000 in the United States and Canada.

Solidworks is also very important for this project because it allows us to accurately model the

frame of the baja vehicle.

The main screen of Solidworks can be seen on the following page in Figure 2.2. From the main

screen one is able to select a plane, create a new plane, or draw a 3D sketch. Once a plane is

selected the sketching tools become available. The sketching tools include: line, circle, spline,

rectangle, arc, ellipse, slot, polygon, and fillet/chamfer. Once the sketch is complete, one can

then extrude, revolve, or loft the sketch in order to create a 3D model.

For the project at hand, we used many different planes. To do so one needs to click on “Plane”

under “Reference Geometry” which is located under the “Features” tab. Planes other than the


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front, right, and top planes were needed because the frame of the baja vehicle needed to be

designed at many different angles.

Figure 2.2 Solidworks main screen

The main frame of the baja vehicle was first sketched using a total of 16 planes. Then

“Structural Elements” were used which can be found under the “Weldments” tab. The purpose

of using structural elements, is that it allows the user to add a profile to an entire sketch. For

example, the entire frame of the baja vehicle was sketch then the profile of a pipe was added to

see the correct joints and dimensions of the finished product. Structural elements are a quick

way to add much necessary detail to a model in a matter of seconds rather than minutes.

In order to create a scaled 3 dimensional model of the baja vehicle frame, a Dimension Elite

rapid prototyping machine produced by Stratasys was used. Stratasys can be reached through

their website at www.stratasys.com. An image of the rapid prototyping machine used can be

seen below in Figure 2.3 on the following page.

This machine made it possible to see how the finished product would turn out. With such a short

time frame it would have been impossible to design and construct the actual baja vehicle frame.

The Dimension Elite rapid prototyping machine not only made a scaled model possible, but it

also created the model in as little as thirteen hours and fifteen minutes.

Rapid prototyping is just a relative term. It means that using a rapid prototyping machine will

take less time to create the product at hand than conventional manufacturing methods. By no

means would thirteen hours to 3D print the baja vehicle frame be considered rapid; however,


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when compared to how long it would take us to produce it using conventional manufacturing

methods one can see how it would seem rapid by comparison.

Figure 2.3 – Dimension Elite rapid prototyping machine

An advantage to using this machine over a similar couterpart is that the dimension elite uses

soluble support technology. This soluble support is used to create a base for the model to begin

building off of when printed. Also, if the model being printed needs support material when

being constructed to withhold its integrity, these support materials will also be constructed of the

soluble support technology. Supports can then be dissolved using a water-based solution.

A specialty machine made by Phoenix Analysis & Design Technologies (PADT) was used to

remove all soluble support material present on the model and can be seen in Figure 2.4. PADT

can be reached at their headquarters at the following address:

7755 S. Research Dr.

Suite 110

Tempe, AZ 85284

They can also be reached by phone at 1-800-293-PADT. This device uses a proprietary fluid

which will dissolve the special support material but not the model material. The part is fully

submerged in to the heated fluid (up to 70º C) it then acts similar to an ultrasonic cleaner, and

gently pushes the fluid around the part.


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Figure 2.4 PADT machine used to remove soluble support material

Initally, we planned on completing a finite element analysis on the baja car as though it had

encountered a head on collision, rear impact, roll over and side impact using Autodesk

Simulation Mechanical 2013. Autodesk can be reached at the following address:

Autodesk, Inc.

111 McInnis Parkway

San Rafael, CA 94903

USA

Or by phone at 415-507-5000. Autodesk would be used to apply forces to our model and find

the stress present in the baja vehicle frame. However, when the frame was uploaded into

Solidworks as a 3D element the meshing of the model into separate elements took over twelve

hours and then crashed the computer. We attempted to import the frame as a solid model, a wire

frame, and then we attempted to re-draw the entire frame in Autodesk. This was again

unsuccessful when we ran the analysis on the model once forces were added. It was decided that

rather than waste useful time, we would calculate hand calculations for all of the impact

situations at hand.

Theory:

For the successful creation of a baja frame the frame must meet a very specific criteria of rules

set into place by SAE. In order to meet this the proper material must be selected according to the

strength of the steel. SAE uses 1018 DOM (drawn over mandrel) steel with an outer diameter of

one inch and a wall thickness of .120 inches as the minimum standard. Required will be the

comparison of the steels bending strength, and the cross comparison of the steels weight per foot

to find both the lightest, and strongest material to be used for a frames design.

All of the calculations done in this comparison can be found in Appendix A.


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Procedure:

1 – Complete material calculations so that the material of the frame is as strong as or stronger

than 1018 steel with an outer diameter of one inch and a wall thickness of 0.120 of an inch. For

a detailed material calculation see Appendix A.

2 – Design the frame of the baja vehicle being sure to abide by all frame requirements put in

place by baja SAE. For the specific requirements see Appendix B. A step-by-step process of the

frame design can be seen in Appendix C.

3 – Use the rapid prototyping machine in order to create a 3 dimensional scaled model of the baja

vehicle frame. See Appendix D for photos and a description of the process of 3D printing.

4 – Calculate the forces present on the baja vehicle frame in the event of:

- Head-on collision

- Rear-impact

- Side-impact

- Roll-over

These calculations can be seen in Appendix E.

5 – Complete hand calculations to determine the stress present on the baja vehicle frame in each

of these situations, and compare the stress to the maximum yield strength of the material.

Analysis and Results:

Initially, it was planned that after frame design we were going to complete a finite element

analysis for the baja vehicle frame simulating a head on collision, rear impact, side impact, and a

roll over. These simulations are very important when designing a baja frame for competition

because roll overs and other collisions are much more common than one would think. With the

results from these simulations the driver of the baja vehicle can rest assured that the frame will

protect him/her in the event of an accident. Autodesk Simulation Mechanical was going to be

used to complete the finite element analysis; however, we ran into multiple issues with the

completion of the analysis.

The analysis was unsuccessful. When the model was imported into the program from

Solidworks we generated a 3D mesh, and the mesh would not complete it simply repeated the

meshing process multiple times before simply erasing the entire model from the viewing screen.

The 3D mesh breaks the model up into individual elements and creates nodes where forces and


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boundary conditions may be placed. Therefore, the mesh is necessary in order to add any

boundary conditions or load.

Thinking the problem may have been caused by a problem in the frame design with Solidworks,

we went step-by-step through our entire design looking for sources of error. We made a few

minimal changes and attempted to mesh our model again using Autodesk Simulation

Mechanical. However, we again encountered the same error and decided to try another resource

to deal with the problem at hand.

We then attempted to use the simulation portion of Solidworks to complete a finite element

analysis. During a Solidworks class, one of our professors made it known that the simulating

technology of Solidworks is not accurate and is nowhere near up to par with that of other

programs. However, with the lack of success from Autodesk Simulation Mechanical we wanted

to try another program. We were able to add a load to the model and view the analysis of the

baja vehicle frame model with that load applied. The only downfall was that the load that we

had applied to the model would do nearly zero damage to the frame, and there was a great

amount of displacement present. Although, this analysis was again unsuccessful we were

pleased to see that we were able to complete a finite element analysis after the many hours spent

designing the frame. In Figure 5.1 below one can see the model in Solidworks after a nominal

load was applied.

Figure 5.1 Finite Element Analysis in Solidworks


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Discussion:

We intended on calculating the forces acting on the baja vehicle frame, as well as, completing

multiple finite element analyses of these forces. With this class only being eight weeks in the

summer, rather than a full sixteen week course during the spring or fall semester we knew that

we would be pressed for time. The design of the baja frame is what we both shared a genuine

interest in, and that is why we had chosen this project. In the end we see that we had bitten of

more than we could handle in such a short amount of time. Even with meeting two to three times

a week and working on our own during the week we were not able to complete everything we set

out to do. The design of the frame took much more time than anticipated with the strict

regulations put in place by baja SAE. It was important for us to design a frame that follows each

and every standard so we know in our future careers we will be able to design parts and

assemblies within the specifications put in place by not only the customer, but safety

requirements for the task at hand.

The biggest problem we encountered was attempting to transfer our model from Solidworks into

Autodesk Simulation Mechanical. Only one of us had taken a finite element analysis course, but

even with all notes and labs at our disposal we were not able to find an example that mirrored

what we were facing. It would have been more beneficial to have taken multiple finite element

analysis courses where more complex models where examined.

Teamwork:

Teamwork was very important for this project. The majority of the actual design of the baja

vehicle frame was done as a group so we would each have equal understanding of the process

and requirements put in place by baja SAE. Each member of the team worked approximately the

same amount of time on the project, as well as meeting between two to three times per week. At

these meetings, we discussed how the project was coming along, what needed to be next, and if

there were any problems that were encountered. The time spent on the designing the baja

vehicle frame by each person can be seen below in Table 7.1.


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Date Start Time

End Time

Time Elapsed Name Description

6/2/2015 16:45 17:30 0:45 Curtis Create project proposal

6/2/2015 16:45 17:30 0:45 Devinne Create project proposal

6/8/2015 16:45 18:45 2:00 Devinne Introduction and Material Calculations

6/8/2015 16:45 18:45 2:00 Curtis Introduction and Material Calculations

6/8/2015 20:00 21:00 1:00 Devinne Equipment and Frame design

6/8/2015 20:00 21:00 1:00 Curtis Equipment and Frame design

6/9/2015 16:30 18:00 1:30 Devinne Frame Design

6/9/2015 16:30 18:00 1:30 Curtis Frame Design




6/16/2015 16:00 18:30 2:30 Devinne Equipment and Material Calculations

6/22/2015 20:00 22:45 2:45 Devinne Presentation for 6/22/2015





7/7/2015 18:00 20:00 2:00 Devinne Equiptment and Procedure

7/7/2015 20:45 21:30 0:45 Devinne Material Calculations, Outlining, and

References

7/8/2015 20:15 22:15 2:00 Devinne Edit Paper

7/8/2015 9:00 14:00 5:00 Curtis Paper and Presentation 7/14/15

7/9/2015 9:30 11:30 2:00 Curtis Paper and Presentation 7/14/15

7/11/2015 20:00 22:00 2:00 Devinne FEA

7/12/2015 16:15 19:30 3:15 Devinne FEA, hand calculations

7/12/2015 16:15 19:00 2:45 Curtis FEA

7/12/2015 20:30 21:30 1:00 Devinne FEA

7/13/2015 18:00 23:45 5:45 Devinne FEA, paper

7/13/2015 18:30 23:30 5:00 Curtis FEA, Paper, Presentation 7/14/15

7/14/2015 9:00 13:30 4:30 Curtis Presentation 7/14/15, Paper

7/14/2015 15:00 16:00 1:00 Curtis Presentation 7/14/15

7/14/2015 15:00 16:00 1:00 Devinne Presentation 7/14/15

Total Time 68Hrs

25 Min

Table 7.1 All hours spent on Capstone Experience by each team member


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Conclusion:

One of the goals for this project was to perform a finite element analysis; however, we were

unable to complete, due to reasons stated prior regarding the time span for this project, and our

miss calculation of how much time each segment would require. The design of the frame has

been a success we have been able to prove the worth of using 4130 steel over the current steel of

choice 1020 DOM. Through using the more capable material and a well thought through design

we have been able to design an overall much lighter frame then all previous years with a weight

savings of 18% from last year.

The greatest challenge for this project has been tackling the shortened time frame of eight weeks

compared to a standard of 16. If this project where to continue there will be time to go back and

look at the analysis again, and correct the issues between the modeled part and the appropriate

analysis program.

References:

Contact Us at SOLIDWORKS. (n.d.). Retrieved June 9, 2015, from

http://www.solidworks.com/sw/contact.htm

"Dimension Elite." About 3D Printer. N.p., n.d. Web. 07 July 2015.

<http://www.stratasys.com/~/link.aspx?_id=D66B9A2BC1CE4B2CA126E5FCDEA54D

BD&_z=z>.

"DOM Tubing (Drawn Over Mandrel)." DOM Tubing. N.p., n.d. Web. 07 July 2015.

<http://www.twmetals.com/1026-dom-tubing.html>.

"Locate Offices." <i>Autodesk</i>. N.p., n.d. Web. 13 July 2015.

<http://usa.autodesk.com/adsk/servlet/index?siteID=123112&id=304753>.

"SAE Collegiate Design Series." Rules & Documents. N.p., n.d. Web. 08 July 2015.

<http://students.sae.org/cds/bajasae/rules/>.

Sales and support. (n.d.). Retrieved June 9, 2015, from

http://www.microsoftstore.com/store/msusa/en_US/DisplayHelpContactUsPage/

"Seamless 4130 Alloy Steel Tubing." 4130 Tubing Supplier. N.p., n.d. Web. 07 July 2015.

<http://www.twmetals.com/4130-tubing.html>.

http://www.solidworks.com/sw/contact.htm

http://www.microsoftstore.com/store/msusa/en_US/DisplayHelpContactUsPage/


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Appendix A- Material Calculations:

Material calculations were need in order to choose the most appropriate material for the frame of

the baja vehicle. Baja SAE specifications state that the frame of the baja vehicle must be as

strong if not stronger than 1018 steel with an outer diameter of one inch and a wall thickness of

0.120 of an inch. The comparison consisted of two different materials 1020 DOM and 4130

Steel. For each of the materials, a material calculation was computed for the following sizes:

- Outer diameter of one inch and a wall thickness of 0.065 of an inch


- Outer diameter of one and a quarter inches and a wall thickness of 0.065 of an inch

The material calculations of 1018 steel were computed to compare to the other material

situations, and can be seen below in Table 10.1.

Table 10.1 Material standard required by Baja SAE

It was important to remember when completing the material calculations to keep all units

consistent, in this circumstance it was decided to use metric units. The switch from inches to

millimeters is the only conversion factor needed, and it can be seen below.

1 inch = 25.4 millimeters

Sample calculations shown below are based off of the material standard required by Baja SAE.

The following equation was used to calculate the inner diameter of the pipe.

1018 Steel ( 1", 0.120 wall)

Outer Diameter= 25.4 mm

Wall Thickness= 3.048 mm

Inner Diameter= 19.304 mm

Modulus of Elasticity= 205,000 MPa

Yield Strength= 370 MPa

Distance to Extreme Fiber= 12.7 mm

Weight per foot = 1.13 lbs

Area Moment of Inertia = (π (Do4-Di

4))/64

13,615 mm4

Bending Strength= (Sy*I)/c

396,665 N-mm

Bending Stiffness= E*I

2,791,126 MPa-mm4


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Equation 1: 𝐼𝑛𝑛𝑒𝑟 𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟 = 𝑂𝑢𝑡𝑒𝑟 𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟 − (2 ∗ 𝑊𝑎𝑙𝑙 𝑇ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠)

𝐼𝑛𝑛𝑒𝑟 𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟 = 25.4𝑚𝑚 − (2 ∗ 3.048𝑚𝑚)

𝐼𝑛𝑛𝑒𝑟 𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟 = 19.304𝑚𝑚

Equation two below was used to calculate the area moment of inertia.

Equation 2: 𝐴𝑟𝑒𝑎 𝑀𝑜𝑚𝑒𝑛𝑡 𝑜𝑓 𝐼𝑛𝑒𝑟𝑡𝑖𝑎 = 𝜋(𝐷𝑜

4−𝐷𝑖4)

64

𝐴𝑟𝑒𝑎 𝑀𝑜𝑚𝑒𝑛𝑡 𝑜𝑓 𝐼𝑛𝑒𝑟𝑡𝑖𝑎 = 𝜋(25.4𝑚𝑚4−19.304𝑚𝑚4)

64

𝐴𝑟𝑒𝑎 𝑀𝑜𝑚𝑒𝑛𝑡 𝑜𝑓 𝐼𝑛𝑒𝑟𝑡𝑖𝑎 = 13,614 𝑚𝑚4

The following equations were used to calculate the bending strength of the material. The

variable “c” in Equation 4 below must first be calculated and its calculation can be seen below in

Equation 3.

Equation 3: 𝑐 = 𝑂𝑢𝑡𝑒𝑟 𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟

2

𝑐 = 25.4𝑚𝑚

2

𝑐 = 12.7 𝑚𝑚

Equation 4: 𝐵𝑒𝑛𝑑𝑖𝑛𝑔 𝑆𝑡𝑟𝑒𝑛𝑔𝑡ℎ = 𝑆𝑦∗𝐼

𝑐

𝐵𝑒𝑛𝑑𝑖𝑛𝑔 𝑆𝑡𝑟𝑒𝑛𝑔𝑡ℎ = 370𝑀𝑃𝑎∗13,614𝑚𝑚4

12.7𝑚𝑚

𝐵𝑒𝑛𝑑𝑖𝑛𝑔 𝑆𝑡𝑟𝑒𝑛𝑔𝑡ℎ = 396,665 𝑁 − 𝑚𝑚

Lastly, the bending stiffness of the materials can be calculated as shown below in Equation 5.

Equation 5: 𝐵𝑒𝑛𝑑𝑖𝑛𝑔 𝑆𝑡𝑖𝑓𝑓𝑛𝑒𝑠𝑠 = 𝐸 ∗ 𝐼

𝐵𝑒𝑛𝑑𝑖𝑛𝑔 𝑆𝑡𝑖𝑓𝑓𝑛𝑒𝑠𝑠 = 205𝐺𝑃𝑎 ∗ 13,614𝑚𝑚4

𝐵𝑒𝑛𝑑𝑖𝑛𝑔 𝑆𝑡𝑖𝑓𝑓𝑛𝑒𝑠𝑠 = 2,791,126 𝑀𝑃𝑎 − 𝑚𝑚4

The material calculations for 1020 DOM (drawn over mandrel) with an:




These material calculations can be seen in Tables 10.2, 10.3, and 10.4 respectively.


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1020 DOM ( 1", 0.065 wall)

Diameter= 25.4 mm





c= 12.7 Mm

Weight per foot = 0.65 Lbs


4))/64

8,726 mm4


355,241 N-mm


1,788,919 MPa-mm4

Table 10.2 Material Calculations for 1020 DOM outer diameter of one inch and a wall

thickness of 0.065 of an inch

1020 DOM ( 1", 0.120 wall)

Diameter= 25.4 Mm

Wall Thickness= 3.048 Mm

Inner Diameter= 19.304 Mm



c= 12.7 Mm

Weight per foot = 1.13 Lbs


4))/64

13,615 mm4


554,258 N-mm


2,791,126 MPa-mm4

Table 10.3 Material Calculations for 1020 DOM outer diameter of one inch and a wall



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Table 10.4 Material Calculations for 1020 DOM outer diameter of one and a quarter inches and a

wall thickness of 0.065 of an inch

The material calculations for 4130 steel with an:




These material calculations can be seen in Tables 10.5, 10.6, and 10.7 respectively.

1020 DOM ( 1.25", 0.065 wall)

Diameter= 31.75 Mm

Wall Thickness= 1.651 Mm

Inner Diameter= 28.448 Mm



c= 15.875 Mm



4))/64

17,732 mm4


577,490 N-mm


3,635,145 MPa-mm4


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4130 Steel ( 1", 0.065 wall)

Diameter= 25.4 mm





c= 12.7 mm



4))/64

8,726 mm4


412,272 N-mm


1,788,919 MPa-mm4

Table 10.5 Material Calculations for 4130 steel outer diameter of one inch and a wall


4130 Steel ( 1", 0.120 wall)

Diameter= 25.4 mm





c= 12.7 mm



4))/64

13,615 mm4


643,240 N-mm


2,791,126 MPa-mm4

Table 10.6 Material Calculations for 4130 steel outer diameter of one inch and a wall



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4130 Steel ( 1.25", 0.065 wall)

Diameter= 31.75 mm





c= 15.875 mm



4))/64

17,732 mm4


670,201 N-mm


3,635,145 MPa-mm4

Table 10.7 Material Calculations for 4130 steel outer diameter of one and a quarter

inches and a wall thickness of 0.065 of an inch

Based on the material calculations of 1018 steel, 1020 DOM, and 4130 Steel shown on

the previous pages, the material chosen for the construction of the frame of the baja

vehicle was 4130 steel with an outer diameter of one inch and a wall thickness of 0.065

of an inch. This decision is based almost entirely on the bending strength of the material

and the weight per foot of material.


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Appendix B – Frame Requirements:

Rules are given from SAE (found at http://students.sae.org/cds/bajasae/rules/ ) and are very

detailed and specific, in order to keep the competition both fair for all teams as well as safe for

the driver and others on the track, as accidents and roll overs do happen and these vehicles must

be capable of handling the abuse which they are dealt.

Lateral Space:

o A minimum spacing is required for the drivers fit in the roll cage

6 inches or 152mm from the drivers helmet

3 inches of 76mm for the drivers shoulders, torso, hips, thighs, knees,

arms, elbow, and hands.

These are for all competition drivers and must be measured when wearing

all of the approved equipment.

Roll cage Elements

o The roll cage is broken into Primary, and secondary members.

o Primary members include members are shown in Figure 11.1

Rear Roll Hoop (RRH)

Roll Hoop Overhead Members (RHO)

Front Bracing Members (FBM)

Lateral Cross Member (LC)

Front Lateral Cross Member (FLC)

Lower Frame Side Members (LFS)

o Secondary members include

Lateral Diagonal Bracing (LBD)

Side Impact Member (SIM)

Fore/Aft Bracing (FAB)

Under Seat Member (USM)

All Other Required Cross Members

Any tube that is used to mount the safety belts

o Secondary members must be steel and have a minimum wall thickness of .035in

or .89mm, and a minimum outside Diameter of 1.0in or 25.4mm.

o Roll cage members that are not straight must not be longer than 28in or 711mm

between supports. Small bend radii (<6in or 152mm) at a supported end of a

member are expected and are not considered to make a member not straight.

o The angle between two ends of a not-straight tube must not exceed 30º.


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Figure 11.1 Roll Cage Elements

Lateral Cross member

o Cannot be less than 8in or 203.5mm long

o Cannot have a bend; however it can be part of a larger bent tube between bends.

Rear Roll Hoop (RRH) Shown in Figure 11.2

o The RRH is a structural Panel behind the drivers back, and defines the back side

of the roll cage.

o The driver and seat must be entirely forward of this panel.

o The RRH may be inclined up to 20º from vertical.

o The minimum width of the RRH, measured at a point 27in or 686mm from the

seats bottom is 29in or 739mm.

o The vertical members of the RRH may be straight of bent and defined as

beginning and ending where they intersect the top and bottom horizontal planes.

o The vertical members must be continuous tubes

o The vertical members must be joined by LC members at the top and bottom.

o The LC members must be continuous tubes.


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Figure 11.2 Rear Roll Hoop (RRH)

Rear Roll Hoop Lateral Diagonal Bracing (LDB) Shown in Figure 11.3

o The RRH must be diagonally braced.

o Diagonal brace(s) must extend from one RRH vertical member to the other.

o The top and bottom intersections of the LDB members and the RRH vertical

members must be no more that 5in or 127mm form the RRH top and bottom

horizontal planes.

o The angle between the LDB members and the RRH vertical members must be

greater than or equal to 20º

Figure 11.3 Rear Roll Hop Lateral Diagonal Bracing (LDB)


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Roll hoop Overhead Members (RHO)

o The forward ends of the RHO members define points CR and CL (Figure 11.4)

o Points CR and CL must be 12in or 305mm forward of a point in the vehicles

elevation view, defined by the intersection of the RHO members and a vertical

line rising from the after end of the seat bottom.

o This point on the seat is defined by the seat bottom intersection with a 4in or

101mm radius circle which touches the seat bottom and the seat back.

o The top edge of the template is exactly horizontal with respect to gravity.

Lower Frame Side Members (LFS)

o The two lower frame side members define the lower right and left edges of the

roll cage.

o These members are joined to the bottom of the RRH and extend generally

forward, at least as far as a point forward of every driver’s heels when seated in a

driving position

o The forward ends of the LFS members are joined by an LC, the front lateral cross

(FLC)

o The intersection of the LFS members and the FLC defines the points AFR and

AFL

Figure 11.4 Lateral cross members

Side Impact Members (SIM)

o The two side impact members define a horizontal mid-plane within the roll cage.

o These members are joined to the RRH and extend generally forward, at least as

far as a point forward of every driver’s toes, when seated in a driving position


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o The forward ends of the SIM members are joined by an LC.

o The intersection of the SIM members and this LC defines the points SFR and SFL.

o The SIM members must be between 8in or 203mm and 14in or 356mm above the

inside seat bottom.

Under seat members (USM)

o The two LFS members must be joined by the Under Seat members.

o The USM must pass directly below the driver where the template in RC3

intersects the seat bottom.

o The USM must be positioned to prevent the driver passing throught the plane of

the LFS in the event of a seat failure.

Front Bracing Members (FBM)

o Front bracing members must join the Rho, the SIM and the LFS.

o The upper front bracing members (FBMUP) must join points C on the RHO to the

SIM at or behind points SF.

o The lower Front Bracing members (FBMLOW) must join points AF to points SF.

o The FBM must be continuous tubes.

o The angle between the FBMUP and the vertical must be less than or equal to 45

degrees.

o If a Front FAB is used there is no angle requirement between FBM and vertical.

Figure 11.5 Bracing

Fore/Aft Bracing (FAB)

o The RRH must be restrained from rotation and bending in the elevation plane by a

system of triangulated bracing.


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o Bracing must either

Rear bracing- directly restrain both points B from longitudinal in the event

of failure of the joints at points C.

Front bracing- restrain both points C from longitudinal and vertical

displacement, thus supporting points B through the RHO members.

o Members used in the FAB system must not exceed 40in or 1016mm in

unsupported length.

o Triangulation angles must be at least 20º

Front Bracing

o The Front systems of FAB must connect the FBMUP members to the SIM

members (on the same sides).

o The intersection with the FBM up members must be within 5in or 127mm

measured as a straight-line distance from centerline to centerline of points C.

o The intersection with the SIM members must be vertically supported by further

members connecting the SIM members to the LFS members.


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Appendix C – Frame Design:

The frame was designed as three segments utilizing the material which best fit each one.

Primary members can be seen below in Figure 12.1

o These members are all using 4130 steel with an outer diameter of 1inch and a wall

thickness of 0.065 of an inch.

Figure 12.1 Primary members of the baja vehicle frame

Secondary members

o These members are highlighted in green in Figure 12.2, and are all made using

4130 steel with an outer diameter of 1inch and a wall thickness of 0.065 of an

inch.


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Figure 12.2 Primary members in red and secondary members in green

Tertiary members

o These members are made using either 4130 with an outer diameter of 1 inch and a

wall thickness of 0.065 of an inch (highlighted Dark grey) or 4130 with an outer

diameter of 1 inch and a wall thickness of 0.035 of an inch (highlighted light

grey). Both can be seen below in Figure 12.3.

o The reason behind choosing two separate material sizes for these members are

due to what they are used for.

o The Dark grey members are there to support the drivetrain mounts, as well as the

driver in the event of a rear impact collision.

o The light grey members are simply added features to either add a minimal safety

aspect, or help to pass another set of ruling for safety.


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Figure 12.3 Finished Baja vehicle frame including primary, secondary, and tertiary members.


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Appendix D – Rapid Prototyping:

Rapid prototyping works by extruding a heated malleable plastic on to a tray and layering in a

support material to help achieve the desired part. The printer we used to prototype models of our

frame for us was a Dimension Elite. This printer utilized abs plastic as the model material, and a

special soluble support material to make cleaning the part a simple and easy process.

Figure 13.1 shows the inside of the printer used, you can see the extruder and heater element in

the upper right-hand corner and the printing base is the black tray on the bottom.

Figure 13.1 Inside of the Dimension Elite rapid prototyping machine

The printer lays down a couple of layers of just support material. This allows the part to snap off

the tray easily and a level printing surface of the part. The creation of the support material can

be seen in Figure 13.2.


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Figure 13.2 Creation of support material

As the rapid prototyping machine continues to print, the base tray lowers itself to allow the part

to gain height. In Figure 13.3, one can see how the base tray lowers by noting the difference in

dimension from the base tray to the extruder compared to Figure 13.2.

Figure 13.3 Base tray lowers as the material creating the part builds up in height


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The first completed part can be seen in Figure 13.4.

Figure 13.4 First completed 3D model of the baja vehicle frame

Upon close inspection some issues with the printed layers in the model appeared. This was due

to improper support of those segments. We decided to try another print with a different support

system in hopes to eliminate the bad layers. This method was indeed successful, however it did

use more support material then the previous attempt as can be seen in Figure 13.5.

Figure 13.5 Second completed 3D model of the baja vehicle frame


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In order to remove the support material a specialty machine made by PADT was used and can be

seen in Figure 13.6. This device uses a proprietary fluid which will dissolve the special support

material but not the model material. The part is fully submerged in to the heated fluid (up to 70º

C) it then acts similar to an ultrasonic cleaner, and gently pushes the fluid around the part.

Figure 13.6 PADT machine used to remove soluble support material

The model being placed in the bath of heated fluid and the model submerged in the heated fluid

are shown in Figures 13.7 and 13.8 respectively.

Figure 13.7 Model being placed in the bath of heated fluid


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Figure 13.8 Model submerged in the heated fluid to remove the soluble material

After the part has been submerged for an extended period of time, depending upon the amount of

support material, size of the part, and quantity in the wash, the soluble material is completely

dissolved and only the model remains. Both models with all soluble support material removed

can be seen in Figure 13.9.

Figure 13.9 Finished models of the baja vehicle frame with all support material removed