2014 UC CEAS battlebot frame and armor

2014 UC CEAS BattleBot Frame and Armor

A Baccalaureate thesis submitted to the

Department of Mechanical and Materials Engineering College of Engineering and Applied Science

University of Cincinnati

in partial fulfillment of the requirements for the degree of

Bachelor of Science

in Mechanical Engineering Technology

by

Nicole Campbell

Thesis Advisor: Dr. Janet Dong

University of Cincinnati

College of Engineering and Applied Science

Mechanical Engineering Technology

2014 UC Battlebot Team

Frame and Armor

Other Team Members and Responsibilities:

Nicolas Manning- Electrical Components and Control

Wes Creed – Weapon Design

Tim Shallenberger – Drive Train Design

2014 UC CEAS BattleBot Frame & Armor Nicole Campbell

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TABLE OF CONTENTS

TABLE OF CONTENTS .......................................................................................................... 1

LIST OF FIGURES .................................................................................................................. 1

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

INTRODUCTION .................................................................................................................... 2

UC SENIOR DESIGN PROJECT ............................................................................................................................. 2 BACKGROUND .................................................................................................................................................... 2 PROBLEM STATEMENT ........................................................................................................................................ 2

RESEARCH .............................................................................................................................. 2

BATTLEBOT IMPROVEMENTS .............................................................................................................................. 2 Team Dynamics ............................................................................................................................................ 2 BattleBot Frame and Armor ........................................................................................................................ 2 Costs ............................................................................................................................................................. 2 Weight ........................................................................................................................................................... 3 Winning Designs .......................................................................................................................................... 3

ARMOR DESIGNS ................................................................................................................................................ 3 The Wedge Design ....................................................................................................................................... 3 The Spinning Design ................................................................................................................................... 3 The Box Design ............................................................................................................................................ 3 The Chosen Design – The Box Design ........................................................................................................ 4

DESIGN .................................................................................................................................... 4

LOADING CONDITIONS ....................................................................................................................................... 4 DESIGN ANALYSIS & FACTOR OF SAFETY ........................................................................................................... 5 DRAWINGS ......................................................................................................................................................... 6

FABRICATION AND ASSEMBLY ........................................................................................ 7

FRAME ................................................................................................................................................................ 7 ARMOR ............................................................................................................................................................... 9

CONCLUSION ......................................................................................................................... 9

FUTURE RECOMMENDATIONS ........................................................................................................................... 10

WORKS CITED ..................................................................................................................... 11

APPENDIX A – SAMPLE CALCULATIONS ....................................................................... 1

LIST OF FIGURES FIGURE 1 – FRAME DESIGN ............................................................................................................................ .4 FIGURE 2 – VON MISES STRESS LOADING ................................................................................................... 5 FIGURE 3 – VON MISES STRESS SCALE ......................................................................................................... 6 FIGURE 4 – FRAME SKELETON (WITH WEAPON) .................. ERROR! BOOKMARK NOT DEFINED. FIGURE 5 – BATTLEBOT .................................................................................................................................. 5 FIGURE 6 – FRAME IN PROGRESS ................................................................................................................... 8 FIGURE 7 – FINISHED FRAME WITH INTERNAL COMPONENTS .............................................................. 6 FIGURE 8 – TOP ARMOR CUT ........................................................................................................................... 7


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ABSTRACT For this project, a combative robot was built to compete against other combative robots in a

competitive arena. A box design Battlebot was built with a 2024 aluminum frame and armor

made of titanium honeycomb. The entire frame and armor set was fabricated and assembled

at the University of Cincinnati machine shop on Victory Parkway.

INTRODUCTION

UC SENIOR DESIGN PROJECT The 2013 BattleBot team of four seniors are designing and building a BattleBot to compete

in the BattleBots IQ National Competition in Miami, Florida, spring 2013. The team is

comprised of:

Nick Manning - Team Manager and Electronics Design

Tim Shallenberger - Drivetrain Design

Wes Creed - Weapon Design

Nicole Campbell - Frame and Armor Design

Dr. Janet Dong - Faculty Advisor

BACKGROUND A BattleBot is a remotely controlled robot that battles other likewise controlled robots in

enclosed arenas. The main purpose of our BattleBot is to disable the competing BattleBots

first while withstanding any blows. Each BattleBot is designed and built to have offensive

and defensive capabilities within the BattleBot rules and guidelines. This year the team has

chosen to compete in the 120 pound weight class (the most challenging weight class in which

to compete when taking into account weights, speeds, costs, and experience). This means the

armor, weapon, drivetrain, and electronics must be designed to the highest standard possible.

PROBLEM STATEMENT This year’s BattleBot is being designed using engineering concepts learned in the Mechanical

Engineering Technology program at UC. The purpose of this report is to discuss the

processes in selection, design, and performance analysis of the frame and armor.

RESEARCH

BATTLEBOT IMPROVEMENTS During an interview with Travis Copas, 2013 UC CEAS BattleBot team member, some

improvements were suggested for the 2014 UC CEAS BattleBot and team. Below is a list of

the items Travis suggested: (2)

Team Dynamics

Adequate time for testing is needed for the BattleBot to be successful

Communicate frequently and effectively

BattleBot Frame and Armor

Do not use aluminum honeycomb; steel is greatly preferred

Eliminate areas where a single hit could disable the weapon

Costs


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Reuse parts from previous year’s BattleBot

Buy frame material in bulk sizes; this will cut down on machining and material costs

Weight

Being able to cut weight in any area is crucial for success

Winning Designs

The BattleBot IQ winner in the collegiate level was a spinning BattleBot that had an

active dampening system built into the armor (shell). Springs were installed to absorb

hits given from the BattleBot and taken from other BattleBots

ARMOR DESIGNS Most BattleBot teams focus on three armor designs. These designs are a wedge, a spinning

BattleBot, and most recently popular a box design. Each one has its advantages and

disadvantages. Below, each design will be shown and discussed.

The Wedge Design

The first (and increasingly popular) design is the wedge. Each side of the BattleBot is sloped.

Offensively, this helps flip BattleBots. Defensively, this helps keep opponents from getting

under their BattleBot. The design features to take into consideration for this type are: center

of gravity, internal size, and armor material. (4) (5)This type of design stresses defensive

capabilities. Therefore, the most significant design feature is the armor material. When

designed well, this type usually does well in competition, but does take on a lot of damage. A

disadvantage to this design is the lower height of the BattleBot which leaves less room for

internal components.

The Spinning Design

The second design is a spinning BattleBot. It is a dome shaped robot with a spinning blade

around the circumference. Offensively, the spinning blades attached to the frame hits

opponents. Defensively, the weapon integrated into the spinning shell helps the BattleBot

from being hit in a vital area. When this starts spinning, the only thing the opponent will hit

when attacking is the blades.

The design features to take into consideration for this type are: center of gravity, internal

size, and weapon material. Since the weapon is used for defense as well, it is considered as a

part of the armor. The most significant design features are the weapon material and the

balancing of the BattleBot. (4) (5) This design has historically done very well in competition;

however it is an expensive design and requires a high level of mechanical accuracy to

function properly.

The Box Design

The third most common design is a box design. This design is simple and very straight

forward. Offensively, the rotating drum damages the armor and weapon of the opposing

robot. Defensively, it is a very strong box which can operate on either side (it is unaffected

by being flipped). This design is common amongst BattleBots that have spinning drums.

There is only one major design feature to take into consideration and that is the armor

material. The heavier the armor material, the harder it is for the BattleBot to maneuver.

Typically, with heavier material comes durability and strength. This design also allows for

increased internal space, and ease of maintenance and cost effectiveness. (8) However, the

disadvantages are vulnerability and weight considerations. (2) (3) Weight limits restrict

teams from using as much material as they want. When choosing this design, teams tend to


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have excess armor, thus unnecessary weight. Even though this design seems to be less

desired, it is also the cheapest design.

The Chosen Design – The Box Design Given the lack of sponsorship and resources available for this competition, the box design

will be the safest design to undertake. This design could easily be made on site at the

University of Cincinnati with little need for outside machining.

DESIGN Frame and armor design is very dependent on the other BattleBot functions. The drivetrain,

weapon, and electronics need to be designed and selected for proper frame fitment, and

weight design. In this design, the width of the frame is dependent on the drivetrain

arrangement, while the length is mainly dependent on the amount of room needed for the

batteries and weapon motor. The figure below shows a cross section of the frame design.

Figure 1 – Frame Design

Because of its simplistic nature, the square design provides less design error, more durability,

and sufficient space for other components.

With the square design, certain characteristics need to be implemented due to their success.

These characteristics are:

Ability to drive inverted

Sufficient protection of vital components

LOADING CONDITIONS Historically, the most vulnerable place for the box design to be hit is at a corner; typically the

corner nearest to weapon. This is also the most common place to be attacked. Research

shows that a force parallel to the ground in this area is a worst case attack. A test in this area

proves if the material and design will withstand an opponent attack. Determined from the


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Sample Calculations in Appendix A the opponent attack force is roughly 13000 lbs. The

variables assumed are:

Opponent weapon is spinning at max velocity (115 ft/s)

Time for weapon to stop after impact is 0.01 s

Opponent weapon weight is 30% of total weight (36 lb)

These assumptions are based on the potential attacking force of our own weapon.

DESIGN ANALYSIS & FACTOR OF SAFETY An analysis of this side piece in SolidWorks SimulationXpress Analysis shows the highest

stress to be around 34,000 psi.

Figure 2 - von Mises Stress Loading


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Figure 3 - von Mises Stress Scale

Note that the yield strength of aluminum is approximately 60,000 psi; well below the

expected stress from the impact.

DRAWINGS The 3D drawing below, in Figure 4, shows the frame and armor without any of the internal

components.

Figure 4 - Frame Skeleton (with weapon)


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Figure 5 – BattleBot

It should be noted that the shown images do not include the protective covering that will

encase the top, bottom, and side plates. Those parts were excluded to show the inner

components and workings without obstruction.

FABRICATION AND ASSEMBLY Fortunately for our team, all of the fabrication and assembly for the frame and armor was

able to be accomplished at the University of Cincinnati machine shop on Victory Parkway.

Also, the entire frame and armor assembly was able to be made from scraped or salvaged

materials from previous Battlebots.

FRAME The Battlebot was constructed using salvaged 2024 aluminum from the Battlebot production

room. All modifications to the pieces were done at the UC machine shop using band saws,

vertical mills, grinders, and a variety of other machines that the University had at our

disposal. Figure 6 shows the frame in progress.


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Figure 6 – Frame in Progress

All measurements, cuts, holes, and taps were made by the Battlebot team at the University of

Cincinnati.

Figure 7 – Finished Frame with Internal Components


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ARMOR The armor (made of titanium honeycomb) proved to be much more difficult to machine than

the aluminum because of the hardness if the material paired with the complexity of the shape.

The honeycomb, also 100% salvaged from previous Battlebots, caught and snagged on every

machine or process we used to cut and grind it and melted several drill bits in the process of

drilling holes for bolts. Fortunately, the UC plasma cutter was able to cut through the

honeycomb with ease which allowed us to make the decorative cut shown in Figure 8. The

cut was made in an effort to cut some weight and provide access to the central power switch

(required by competition rules). We also saw this as an opportunity to represent the

University.

Figure 8 – Top Armor Cut

CONCLUSION Having met all of the criteria required for the competition using only recycled materials, it

can be concluded that this Battlebot is a success. Since the competition takes place after the

finial submission of the report is due, it is not possible to include here the results. However, it

is possible to point out some possible sources of error and make a few recommendations for

future projects.


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FUTURE RECOMMENDATIONS For the next competition, it would be advisable to adopt a smaller frame size. One of the

biggest issues faced was the weight of the robot because the frame was so large. It was also

challenging to fit through doorways during fabrication and assembly. A smaller size would

alleviate both problems.

It would also be wise to look into other materials than honeycomb for armor. While the

honeycomb is very lightweight and accessible, there are an assortment of carbon sprays and

fibers that are relatively inexpensive and perform the task of shielding the body from attacks

just as well (of not, better) than honeycomb. The major complaints about honeycomb include

its difficulty to machine and handle. Its jagged edges caught the clothes and skin of anyone

who attempted to lift or move it.

Lastly, the best way to improve the next design is to seek out potential sponsors as early in

the process as possible. Being fully funded is the best way to start off on track and to ensure

that the design of next year’s team can be feasibly fabricated and its absolute best.


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WORKS CITED 1. Larson, Mark. 2011 UC CEAS Battlebot - Frame and Armor. School of Dynamic

Systems, University of Cincinnati College of Engineering and Applied Science. Cincinnati :

s.n., 2011. p. 1, Baccalaureate Thesis.

2. Copas, Travis. How to build a winning Battlebot. [interv.] Nicole Campbell, Nick

Manning, Wes Creed, Tim Shallenburger. Cincinnati, August 7, 2013

3. Biohazard, Team. Robot Materials. RobotBooks.Com. [Online] Team Biohazard. [Cited:

October 23, 2012.] http://www.robotbooks.com/robot-materials.htm.

4. Battle Robot Building Tips. LoganBot.Com. [Online] August 22, 2002. [Cited: October 23,

2012.] http://www.loganbot.com/bot_tips.html.

5. Ziggy, Team. Team Ziggy. TeamZiggy.Com. [Online] [Cited: September 9, 2012.]

http://www.teamziggy.com/Robots/index.html.

6. Joerger, Mark. The Combat Robot Hall of Fame. Members.Toast.Net. [Online] 2011.

[Cited: October 30, 2012.] http://members.toast.net/joerger/hall_of_fame.html.

7. Industries, M5. Blendo. M5Industries.Com. [Online] [Cited: October 30, 2012.]

http://web.archive.org/web/20071013043744/http://m5industries.com/html/blendoMSHOP.ht

m.

8. Diginati, Team. Codebreaker Intial Construction. Diginati.Com. [Online] January 18,

2000. [Cited: October 30, 2012.] http://www.diginati.com/cb_frame.htm.

Appendix E1

APPENDIX A – SAMPLE CALCULATIONS Assumptions:

Opponent weapon is spinning at max velocity (400 ft/s)

Time for weapon to stop after impact is 0.35 s

Opponent weapon weight is 35% of total weight (42 lb)

Impact Area is 0.25 in2

Weapon Impact (Impulse Theorem)

𝐹 =(𝑚𝑣0 − 𝑚𝑣1)

𝑡

𝑣0 = 0 𝑓𝑡/𝑠

𝑣1 = 115 𝑓𝑡/𝑠

𝑡 = 0.01 𝑠

𝑚 = 𝑤

𝐺

𝑚 = 36 𝑙𝑏

32 𝑓𝑡/𝑠2= 1.125 𝑠𝑙𝑢𝑔

𝐹 =[(1.125 𝑠𝑙𝑢𝑔 × 115 𝑓𝑡/𝑠) − 1.3 𝑠𝑙𝑢𝑔 × 0 𝑓𝑡/𝑠)]

0.01 𝑠≈ 13,000 𝑙𝑏

Armor Stress (Normal Stress Formula)

𝜎 =𝐹

𝐴

𝐴 = 0.5 𝑖𝑛2

𝐹 = 13,000 𝑙𝑏

𝑆. 𝐹. = 3

𝜎 =13,000 𝑙𝑏

0.5 𝑖𝑛2≈ 26,000 𝑝𝑠𝑖

𝜎 = 26,000 𝑝𝑠𝑖 × 3 ≈ 39,000 𝑝𝑠𝑖

2014 UC CEAS battlebot frame and armor

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