Difference between revisions of "Boom Construction Competition"

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<h2>OBJECTIVES</h2>
=Objective=


<p>The experimental objective of this lab is to design and construct a boom, following
The experimental objective of this lab is to design and assemble a boom. This is a competition lab, and the booms will be judged by a design ratio that uses boom weight, boom length, weight held, and anchor time. The highest design ratio wins the competition.
the specifications provided. Your boom will be entered in a competition against
the other students' booms in your section. You will learn how booms are used and what
factors engineers consider when designing them.</p>


<h2>OVERVIEW</h2>
=Overview=


<p>A <b><i>boom</i></b> is
A <b>boom</b> is used to lift and move heavy objects, often objects that are much heavier than the boom itself. Distributing the load being lifted over the length of the boom is the main problem in boom design. The design must consider the maximum load the boom will be required to lift, how high the load will be lifted, and whether the boom will be moved or remain stationary while loaded.  
used to help lift and move heavy objects; objects much heavier than the boom
itself. Distributing the weight of the object (the load) being lifted over the
length of the boom is the main problem in boom design. The engineer must
consider the maximum load the boom will be required to lift, how high the load
will need to be lifted, and whether the boom will be moved around while loaded or
not.</p>


<p>Examples of booms that you may not have thought of are certain types of bridges.
== Examples of Booms ==
A cantilever bridge is actually two booms extending from a common base. One type of
cantilever bridge is a cable-stayed bridge, with a concept of one shown in Figure 1.</p>


[[Image:Lab_boom_13.png|frame|center|Figure 1: A cable-stayed (cantilever) bridge]]
Certain types of bridges use booms. A cantilever bridge uses two booms extending from a common base. One type of cantilever bridge is a cable-stayed bridge (Figure 1).


<p>The Queensboro Bridge is an example of a double cantilever bridge, and is shown in
[[Image:Lab_boom_13.png|650px|thumb|center|Figure 1: A Cable-Stayed (Cantilever) Bridge]]
Figure 2. If youlook carefully at the figure, you'll see two bases, and the two
booms extending from each base, with the cantilevers placed end to end.</p>


[[Image:lab_boom_10.jpg|frame|center|Figure 2: Queensboro Bridge (double cantilever)]]
The Ed Koch Queensboro Bridge is a double cantilever bridge (Figure 2). It has two bases with two booms extending from each base and the cantilevers placed end to end.


<p>The Grand Bridge over Newtown Creek is an example of a swing bridge, also known as
[[Image:lab_boom_10.jpg|frame|center|Figure 2: Ed Koch Queensboro Bridge (Double Cantilever)]]
a rotating bridge, and is shown in Figure 3. In this case, the bridge is two booms
mounted on a base that rotates.</p>


[[Image:lab_boom_11.jpg|frame|center|Figure 3: Grand Bridge (swing bridge)]]
The Grand Bridge over Newtown Creek is a swing bridge, also known as a rotating bridge (Figure 3). This bridge has two booms mounted on a base that rotates.


<p>Finally, Figure 4 shows a bascule bridge, more commonly known as a drawbridge, where
[[Image:lab_boom_11.jpg|650px|thumb|center|Figure 3: Grand Bridge (Swing Bridge)]]
it's clear that the bridge is a big very flat boom.</p>


[[Image:lab_boom_12.jpg|frame|center|Figure 4: A typical buscule bridge]]
Figure 4 shows a bascule bridge, more commonly known as a drawbridge, where it is clear that the bridge uses a big, very flat boom.


<p>Note that not all bridges are booms. For example, suspension bridges, where the deck
[[Image:lab_boom_12.jpg|650px|thumb|center|Figure 4: Bascule Bridge]]
is supported by steel cables, are not booms. Examples of suspension bridges are the
Brooklyn Bridge, Manhattan Bridge, Verrazano-Narrows Bridge, and George Washington Bridge.</p>


<p>Cranes are the most common example of booms in action. The crane pictured
Not all bridges are booms. Suspension bridges use a deck that is supported by steel cables, not booms. Examples of suspension bridges are the Brooklyn Bridge, Manhattan Bridge, Verrazano-Narrows Bridge, and the George Washington Bridge.
in Figure 5 is a tower crane. These cranes are a
fixture on construction sites across the country and around the world. A tower
crane can lift a staggering 40,000 pound load of construction material and
machinery. It is attached to the ground by anchor bolts driven through a
400,000-pound concrete pad poured a few weeks before the crane is erected.<sup>1</sup></p>


[[Image:lab_boom_6.jpg|frame|center|Figure 5: A tower crane (from www.howstuffworks.com)]]
Cranes are the most common example of booms. The crane pictured in Figure 5 is a tower crane. These cranes are a fixture on construction sites around the world. A tower crane can lift a 40,000 lb load. It is attached to the ground by anchor bolts driven through a 400,000 lb concrete pad poured a few weeks before the crane is erected (Howstuffworks.com, 2003).


<p><b>FYI:</b>
[[Image:Tower Crane.jpg|650px|thumb|center|Figure 5: A Tower Crane (Jennings, 2015)]]
<ul>
 
<li>A Dead Load is a stationary load</li>
== Stress and Strain ==
<li>A Live Load is a moving or mobile load</li>
 
<li>A Cyclic Load is a load that changes periodically</li>
The design of a boom must consider the properties of the materials used to build the boom. The mechanical properties and deformation of solids are explained by stress and strain. When an external force is applied to a material, it changes shape (e.g. changes length and cross-section perpendicular to the length). Understanding how deformation will affect materials is a critical consideration in boom design.
</ul>


When you work on the design for your boom, you must take into account the properties
According to Serway and Beichner in “Physics for Scientists and Engineers,” <b>stress</b> is the external force acting on an object per unit cross sectional area. <b>Strain</b> is the measure of deformation resulting from an applied stress (Figure 6).
of the materials you will use. To discuss the mechanical properties and
deformation of solids, we must first understand stress and strain. When an
external force is applied to a piece of material, it changes shape (e.g.,
changes length and cross section perpendicular to the length). Understanding how such deformations will
affect materials is critical information for an engineer.</p>


<p>There are three basic types of stresses; tensile (pulling or stretching), compressive
[[Image:lab_boom_1.jpg|frame|center|Figure 6: Material Under Tension]]
(squeezing or squashing) and shear (bending or cleaving). If a rod of material is put under tensile
stress, its length increases slightly in the direction of the applied force and
its cross-section perpendicular to the force decreases.  If the rod is placed under compressive
stress, its length in the direction of the force will decrease and its cross-section
perpendicular to the force will increase.
If the rod is place under shear stress it will bend in the direction of
the applied force and its length and cross-section will be distorted, see
Figure 6.</p>


[[Image:Lab_boom_7.gif|frame|center|Figure 6: Rods of Material being stressed.]]
The expression (1) for tensile stress shows the relationship between an applied force and the cross-sectional area.


<p>According to Serway and Beichner in <i>Physics for Scientists and Engineers,<sup>2</sup></i>
<center><math>\sigma = \frac{F}{A}\,</math></center>
<b><i>stress </i></b>is
<p style="text-align:right">(1)</p>
the external force acting on an object per unit cross sectional area. <b><i>Strain </i></b>is the measure of
deformation resulting from an applied <b><i>stress</i></b>.
</p>


[[Image:lab_boom_1.jpg|frame|center|Figure 7: A piece of material under tension.]]
In (1), &sigma; is the stress, F is the applied force, and A is the cross-sectional area of the object perpendicular to the force. The resulting strain (2) is calculated by dividing the change in length of the object by the original length.


<p>The expression for tensile stress is:</p>
<center><math>\varepsilon = \frac{\Delta L}{L_{\text{0}}}\,</math></center>
<p style="text-align:right">(2)</p>


<math>\sigma = \frac{F}{A}\,</math>
In (2), &Delta;L is the change in length and L<sub>0</sub> is the object's original length.


<p>where <i>s</i> is the stress, <i>F</i><i> </i>is the applied force and <i>A </i>is
There are three basic types of stresses; <b>tensile</b> (pulling or stretching), <b>compressive</b> (squeezing or squashing), and <b>shear</b> (bending or cleaving). Consider a straight metal beam. If a <b>tensile stress</b> is applied to both ends, its length will increase in both directions of the force, while its cross-sectional area perpendicular to the force applied will decrease. Under <b>compressive stress</b>, the opposite will occur. If the beam is subjected to <b>shear stress</b>, it will bend towards the direction of the applied force, and both the length and cross-sectional area of the beam will become distorted. Figure 7 depicts a graphic representation of the three common forms of stress.
the cross-sectional area of the object perpendicular to the force. The expression for the
resulting strain <i>e</i> is:</p>


<math>\varepsilon = \frac{\Delta L}{L_{\text{0}}}\,</math>
[[Image:Lab_boom_7.gif|frame|center|Figure 7: Example of Cylindrical Material Under Three Common Modes of Stress]]


<p>where <math>\Delta L\,</math>is the change in length and <i>L</i><i><sub>0</sub></i><i> </i>is
Strain is proportional to stress for material dependent values of strain. If the material is known, it is possible to derive strain from measured stress, and vice-versa, up to a certain level of stress. This proportionality constant is referred to as the <b>elastic modulus</b>, or Young’s modulus.  The moduli of different materials is an important factor to consider when designing or building any form of structure that will be under stresses.
the object's original length.</p>


<p>Strain is proportional to stress for small values of strain, and the proportionality
== Stress-Strain Curve ==
constant depends on the material being deformed and on the type of
deformation.  The proportionality
constant is called an elastic modulus.
The moduli for different materials vary
considerably and the various moduli for a particular
material may also vary significantly, e.g., concrete is very strong in
compression but less so in tension; wood breaks quite easily when bent, and
because of its natural grain is anisotropic (properties depend on direction in
the material).</p>


[[Image:lab_boom_2.jpg|frame|center|Figure 8: Stress-Strain relation for a piece of material under tension]]
A <b>stress-strain</b> graphically shows the relationship between the stress and strain of a material under load. Figure 8 shows the stress-strain curve of a common metallic building material. In the <b>elastic region</b>, the material will regain its original shape once the stress is removed. The elastic region in Figure 8 is fairly linear. The slope of this linear portion of the stress-strain curve is the elastic modulus.


<p>Figure 8 shows the effects of tensile stress on a typical rod of material. In the
[[Image:lab_boom_2.jpg|frame|center|Figure 8: Stress-Strain Curve of a Material Under Tension]]
elastic region, the material will regain its original shape once the stress (or
load) is removed.  In the plastic region,
the material loses its elasticity and is permanently deformed.</p>


<p>The <b><i>elastic limit</i></b> for
The <b>elastic limit</b> for a material is the maximum strain it can sustain before it becomes permanently deformed (i.e. if the stress is decreased, the object no longer returns to its original size and shape). In the <b>plastic region</b>, the material loses its elasticity and is permanently deformed. A linear approximation with the elastic modulus is no longer accurate.  
a material is the maximum strain it can sustain before it becomes permanently
deformed (i.e. if you decrease the stress, the object no longer relaxes back to
its original size and shape). If you
increase the stress past the elastic limit, the material will plastically
deform and for sufficiently large stress ultimately fail. The ultimate tensile strength<b><i> </i></b>is
the maximum amount of stress a material can undergo. The fracture stress<b><i> </i></b>is
the point at which the material breaks under tension.  Fracture
stress<b><i> </i></b>is lower than the ultimate tensile strength<b><i> </i></b>because
as strain increases, the material becomes thinner and thinner. As this necking down process continues, the
amount of load that can be supported decreases and the material breaks.</p>


<p>In addition to these intrinsic materials factors, an
The <b>ultimate tensile strength</b> is the maximum stress a material can undergo. The <b>fracture stress</b> is the point at which the material breaks. Fracture stress is lower than the ultimate tensile strength of a material because the material has reached that level of stress and has already begun to fail. The cross-sectional area is constantly decreasing until the material finally breaks.
engineer must consider the behavior of materials as they age and are used in
service. These factors do not relate
directly to the design of your "one-time-use" boom, but they need to be taken
into consideration when deciding what material to use for an actual
design. The loss of desirable properties through use, called fatigue, is
often an important issue.  Non-static
loads, repeated loading and unloading, or loads that include vibrations,
oscillations etc., may lead to failure in service.  Special care must be taken with live loads
and situations where small motions may be magnified by design features.</p>


<p>The first aging factor is chemical degradation and, in particular, <b><i>corrosion</i></b>.  Light and  
In addition to these intrinsic materials factors, the behavior of materials as they age and are used in service must be considered in boom design. These factors are not applicable to the boom design in this lab, but they must be considered when deciding what material to use for  a design. The loss of desirable properties through use, called <b>fatigue</b>, is important. Non-static loads, repeated loading and unloading, or loads that include vibrations or oscillations will eventually lead to failure in service. Special care must be taken with live loads and situations where small motions may be magnified by design features.
<!--<p>The first aging factor is chemical degradation and, in particular, <b><i>corrosion</i></b>.  Light and  


chemicals present in the
chemicals present in the
Line 150: Line 78:
rust results when iron or simple steel is exposed to water, or just even humid
rust results when iron or simple steel is exposed to water, or just even humid
air.  Rust is particularly damaging
air.  Rust is particularly damaging
because it flakes off, thinning and weakening the underlying material.  Careful choice of material will minimize the effects of chemical degradation.  However
because it flakes off, thinning and weakening the underlying material.  Careful choice of material will minimize the effects of chemical degradation.  However,
cost is often limiting factor and cheap counter measures like paint and other
the cost is often limiting factor and cheap countermeasures like paint and other
coatings are often employed.</p>
coatings are often employed.</p>


Line 160: Line 88:
process.  Care in the design process can
process.  Care in the design process can
help minimize the effect of erosion.  
help minimize the effect of erosion.  
Again cost is often the limiting factor and coatings are often employed
Again the cost is often the limiting factor and coatings are often employed
to protect an object.</p>
to protect an object.</p>


Line 166: Line 94:
cycling</i></b>.  Materials in an object
cycling</i></b>.  Materials in an object
will routinely warm up and cool down while in use (especially device that
will routinely warm up and cool down while in use (especially device that
generate heat internally), over the course of a normal day, or even over a
generates heat internally), over the course of a normal day, or even over a
year.  This thermal cycling is
year.  This thermal cycling is
accompanied by physical expansion and contraction of the object.  Different materials expand and contract by
accompanied by physical expansion and contraction of the object.  Different materials expand and contract by
different amounts and this can lead to internal stress and strains, and
different amounts and this can lead to internal stress and strains, and
ultimately failure.  Careful choice and
ultimately failure.  Careful choice and
matching of materials can minimize the effects of thermal cycling, but cost may
matching of materials can minimize the effects of thermal cycling, but the cost may
limit the choices.  Accumulations of
limit the choices.  Accumulations of
water, which can freeze and thaw, can be very damaging and coatings are often
water, which can freeze and thaw, can be very damaging and coatings are often
Line 188: Line 116:
treatment (annealing) and in general, material properties can be improved
treatment (annealing) and in general, material properties can be improved
significantly through heat treatment and mechanical working.  For example, the familiar Pyrex<sup>TM</sup>
significantly through heat treatment and mechanical working.  For example, the familiar Pyrex<sup>TM</sup>
glass is specially treated to avoid thermal shock.</p>
glass is specially treated to avoid thermal shock.</p>-->


<p>There are many factors to consider in any design project. When designing and
There are many factors to consider in any design project. When designing and constructing the boom for this competition, consider the materials being used and what might cause those materials to fail under a load.
constructing your boom for this competition, remember to consider the materials
you are using and what might cause those materials to fail under a load.</p>


<h2>COMPETITION RULES</h2>
=Competition Rules=


<p>The competition rules must be followed at all times during the competition.
The competition rules must be followed at all times during the competition.
Violation of any of these rules will result in the disqualification of your
Violation of any of these rules will result in the disqualification of the
team.</p>
design.


<ul>
<ul>
<li>Your boom must extend at least 1.5 meters horizontally from the front edge of
<li>The boom is to be secured (i.e. anchored) to the white plastic anchorage provided at the front of the lab
the anchorage.</li>
<li>The boom must extend at least 1.5 meters horizontally from the front edge of
 
the anchorage</li>
<li>You have 2 minutes to anchor your boom.</li>
<li>The boom must be anchored in 2 min or less</li>
 
<li>The boom may not touch anything but the anchorage</li>
<li>Your boom may not touch anything but the anchorage.</li>
<li>The boom’s performance will be assessed by its anchor time, boom weight, boom length, and the weight it can support before deflecting 0.20 m vertically</li>
</ul>


<li>The
The <b>basic weight ratio</b> (3) for the competition uses the weight supported in grams divided by the boom weight in grams. This ratio should be greater than 1.
basic weight ratio for the competition is:</li>


<math>Weight\ Ratio = \frac{Weight\ Supported}{Boom\ Weight}\,</math>
<center><math>Weight\ Ratio = \frac{Weight\ Supported\left[\text{g}\right]}{Boom\ Weight\left[\text{g}\right]}\,</math></center>
<p style="text-align:right">(3)</p>


<li>The winning design will be determined based on the following weighted design ratio:</li>
The winning design will be determined by the <b>weighted design ratio</b> (4), which uses the weight ratio, anchor time in seconds, and boom length in meters. Each component ratio should be greater than 1.
</ul>


<math>Design\ Ratio = \frac{Weight\ Supported}{Boom\ Weight} \times \frac{60\left[\text{s}\right]}{Anchor\ Time\left[\text{s}\right]+30\left[\text{s}\right]} \times \frac{Boom\ Length\left[\text{m}\right]}{1.5\left[\text{m}\right]}\,</math>
<center><math>Design\ Ratio = \frac{Weight\ Supported\left[\text{g}\right]}{Boom\ Weight\left[\text{g}\right]} \times \frac{60\left[\text{s}\right]}{Anchor\ Time\left[\text{s}\right]+30\left[\text{s}\right]} \times \frac{Boom\ Length\left[\text{m}\right]}{1.5\left[\text{m}\right]}\,</math></center>
<p style="text-align:right">(4)</p>


<h2>Design Considerations</h2>
=Design Considerations=
* Which aspects of the competition formula are most advantageous?
* Which aspects of the competition ratio are most advantageous?
* How can the boom be built and/or reinforced to prevent as much deflection as possible?
* How can the boom be built and/or reinforced to prevent as much deflection as possible?


<p>Note: You and your partner are to design a boom.
=Materials and Equipment=
The boom is to be secured (i.e., anchored) to the white plastic
anchorage provided at the front of the lab.
The boom must extend at least 1.5 m from the front edge of the anchorage
and deflect as little as possible when loaded.</p>


<h2>MATERIALS AND EQUIPMENT</h2>
<ul>
<ul>
<li>2 Thick Dowels (1.1cm x 122cm)</li>
<li>Two thick dowels (1.1 cm &times; 122 cm)</li>
<li>2 Thin Dowels (0.8cm x 122cm)</li>
<li>Two thin dowels (0.8 cm &times; 122 cm)</li>
<li>6 Bamboo Skewers (30.5cm)</li>
<li>Six bamboo skewers (30.5 cm)</li>
<li>3D Printed Dowel Connectors</li>
<li>3D printed dowel connectors</li>
<li>Cellophane Tape</li>
<li>Cellophane tape</li>
<li>Kevlar String</li>
<li>Polyester string</li>
</ul>
</ul>


<br /><font color="red"><b>'''NOTE: A saw is available to cut the dowels. Ask your TA for assistance, as students are not allowed to use the saw.'''</b></font>
<font color="red"><b>'''Note: A saw is available to cut the dowels. Ask a TA for assistance, as only TAs may use the saw.'''</b></font>


= Procedure =


== Part 1. Boom Design and Construction ==


[[Image:lab_boom_15.jpg|thumb|400px|frame|center|Figure 9: 3D Printed Dowel Connectors]]
# Assess the materials and consider the design options, keeping in mind the competition specifications. Preliminary sketches must be completed during this process.
# Sketch the basic design in pencil using the lab notes paper provided by a TA or on the EG1003 website. Label the design clearly and have a TA sign and date it.
# Construct the boom based on the completed sketch and the available materials. A TA will provide the materials allowed for the design. If the design is modified during the construction phase, make sure to note the changes and describe the reasons for them.


<h2>PROCEDURE</h2>
== Part 2. Competition ==


<h3>Boom Design and Construction</h3>
<p><b>Note: </b>Attaching the boom to the anchorage is a critical phase of the competition. Anchoring will be timed. Making  a plan to anchor the boom quickly will improve its standing in the competition. Practice anchoring before the trial begins. The boom will be disqualified if anchoring the boom takes more than 2 min.


<ol>
# When the TA says "Go," attach the boom to the anchorage and shout "Done" when the boom is anchored. The TA will only stop the timer once there are no more hands are touching the boom. The TA will give the anchoring time that will be used to compute the boom's design ratio.
<li>Assess your materials and consider your design options, keeping in mind the
# A TA will measure the boom length and record the length in the competition spreadsheet for the section.
competition specifications. Make sure you make preliminary
# A TA will attach a basket to the end of the boom and add weights until the boom deflects (bends) 0.20 m vertically. The load supported will be weighed on the lab scale and recorded in the competition spreadsheet for the section.
sketches during this process.</li>
# A TA will weigh the boom and record the weight in the competition spreadsheet for the section.
# The design ratio for the in-person boom design will be used to decide the winner of the competition.


<li>Now sketch your actual basic design in pencil using the graph paper sample
<p>A TA will prepare an Excel file with the section's results. It can be accessed in the [http://eg.poly.edu/documents.php Lab Documents] section of the EG1003 website. This chart must be included in the PowerPoint presentation and in the Data/Observations section of the lab report. The lab work is now complete. Please clean up the workstation. Return all unused materials to a TA. Refer to the Assignment section for the instructions to prepare the lab report.
provided on the EG website. Label your design clearly and have your TA <b>sign and date </b>it.</li>


<li>Construct your boom based on the sketch you just completed and the available
=Assignment=
materials. Your TA will provide the materials allowed for your design. If you
decide to modify your design during the construction phase of your boom, make
sure to note the changes and describe your reasons for them.</li>


<li>Your TA will weigh your boom and record the weight in the competition
== Individual Lab Report ==
spreadsheet for your section.</li>
{{Ambox
</ol>
| type  = notice
| text  = <h4>Extra Credit Opportunity</h4>Students who perform well on this report have the opportunity to replace a lower score on an earlier lab report with their score on this report.}}


<h3>Competition</h3>


<p><b>Note: </b><i>Attaching your boom to the
{{Labs:Lab Report}}
anchorage is a critical phase of the competition. You will be timed. Making
sure you have a plan before you start will help you anchor the boom quickly and
improve your standing in the competition. You may want to practice before your
trial begins. Remember you will be disqualified if anchoring your boom takes
more than two minutes.</i></p>


<ol>
* What factors were considered in designing the boom?  Discuss the background information that was used
<li>When the TA says "go," attach your boom to the anchorage and shout "done" when
* Describe the competition rules in the Introduction. What impact did the rules and ratios have on any design decisions?
your team is finished. The TA will give you your anchoring time. You will use this
* Describe the function of each component used in the design
number to compute your boom's design ratio. </li>
* Describe the advantages and disadvantages of the boom design
* Discuss potential design improvements. How can the design be optimized (i.e. improve the design ratio) from this lab experience?
* Which elements of the boom were stressed by the load? Describe the load’s direction and if the load contributed s to the failure?
* Include the Excel spreadsheet with all the boom designs in the class. Discuss other designs in the class
* Contribution Statement


<li>Your TA will measure your boom and record the length in the
competition spreadsheet for your section.</li>


<li>Your TA will attach a basket to the end of your boom and add weights until the
{{Labs:Lab Notes}}
boom deflects (bends) 0.2 m. The load supported will be weighed on the lab
scale and the weight recorded in the competition spreadsheet for your section.
See Figure 9.</li>
</ol>
[[Image:lab_boom_5.jpg|frame|center|Figure 10: Sample Competition Spreadsheet]]


<p>Your TA has prepared an Excel file with your section's results. Go to the [http://eg.poly.edu/documents.php Lab Documents] section of the EG Website. This chart must be included in your
<h3>Team PowerPoint Presentation</h3>
PowerPoint presentation and in the data section of your lab report.  Your lab work is now complete.  Please clean
 
up your workstation.  Return all unused materials to your TA.  Refer to section <b><i>3 Your Assignment</i></b>
for the instructions you need to prepare your lab report.</p>


<h2>ASSIGNMENT</h2>
{{Labs:Team Presentation}}
 
<h3>Team Lab Report</h3>
<!--
* For EG1003: This is a REQUIRED TEAM Lab Report
*: <b>Note:</b> You will be writing a team lab report rather than an individual one. See the [[Team Authoring Strategies]] page in the <i>Technical Communication</i> of this online manual for guidance of how to do this.
* For EGED I: This is a BONUS INDIVIDUAL Lab Report
-->
 
<p>Follow the lab report guidelines laid out in the page called [[Specifications for Writing Your Lab Reports]]
in the <i>Technical Communication</i> section of this manual.
As you write, the following discussion points should be addressed in the appropriate
section of your lab report:</p>


<ul>
<ul>
<li>Describe the rules of the competition in your introduction. What consequences did the rules have for
<li>How can the boom design be improved?</li>
your design decisions? Use the appropriate equations in your answer.</li>
<li>Other than the examples given in this lab, what are other boom examples in the real world?</li>
 
<li>Which elements of the boom (e.g., wooden dowels, 3D printed dowel connectors, Kevlar string, etc.,) were stressed by the load, in what directions, and could potentially lead to the failure?
<li>What factors did you consider in designing your boom? Did you use any of the
background information?</li>
 
<li>What was the weight ratio and design ratio for your design?</li>
 
<li>What do you think would be the maximum design ratio for this project? Compare
your results with this ideal ratio.</li>
 
<li>What important design characteristics should a winning boom include to achieve
the highest possible weighted ratio?</li>
 
<li>Describe how the components you have chosen function in your design, and describe its overall height/length/shape/etc.</li>
 
<li>Discuss design improvements. How would you optimize the design (i.e. improve the ratio)
based on experience?</li>
 
<li>Which elements of the boom (e.g., wooden dowels, 3D printed dowel connectors, Kevlar string, etc.,) were stressed by the load, in what directions, and contributed to the failure?
 
<li>Include spreadsheet with every team's results. Describe the results and talk about other designs in the class.
 
</ul>
</ul>


{{Lab notes}}
= References =
 
<h3>Team PowerPoint Presentation</h3>
 
<p>Follow the presentation guidelines laid out in the page called [[EG1003 Lab Presentation Format]]
in the <i>Introduction to Technical Presentations</i> section of this manual.
When you are preparing your presentation, consider the following points:</p>
 
<ul>
<li>How would you improve your boom design?</li>
<li>Other than the examples given in this lab, what are other examples of booms?</li>
<li>Which elements of the boom (e.g., wooden dowels, 3D printed dowel connectors, Kevlar string, etc.,) were stressed by the load, in what directions, and contributed to the failure?
</ul>


<h2>Footnotes</h2>
<i>How Stuff Works</i> website. 2003. SHW Media Network. Retrieved July 28, 2003.
http://science.howstuffworks.com/tower-crane3.htm


<p><sup>1</sup> <i>How Stuff Works </i>website. 2003. SHW Media Network. Retrieved July 28<sup>th</sup>, 2003.
Jennings, James. 2015. “Up, UP in a Crane: What Life is Like as a Tower Crane Operator.” Philadelphia. Accessed 14 January 2020 from www.phillymag.com
<i>http://science.howstuffworks.com/tower-crane3.htm</i></p>


<p><sup>2</sup> Serway, R., Beichner, R., <i>Physics for Scientists and Engineers with Modern Physics, 5</i><i><sup>th</sup></i>
Serway, R., Beichner, R., <i>Physics for Scientists and Engineers with Modern Physics, 5</i><i><sup>th</sup></i> Edition. Fort Worth, TX: Saunders College Publishing, 2000
<i>Edition</i>. Fort Worth, TX: Saunders College Publishing, 2000</p>


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{{Laboratory Experiments}}

Latest revision as of 17:33, 23 March 2022

Objective

The experimental objective of this lab is to design and assemble a boom. This is a competition lab, and the booms will be judged by a design ratio that uses boom weight, boom length, weight held, and anchor time. The highest design ratio wins the competition.

Overview

A boom is used to lift and move heavy objects, often objects that are much heavier than the boom itself. Distributing the load being lifted over the length of the boom is the main problem in boom design. The design must consider the maximum load the boom will be required to lift, how high the load will be lifted, and whether the boom will be moved or remain stationary while loaded.

Examples of Booms

Certain types of bridges use booms. A cantilever bridge uses two booms extending from a common base. One type of cantilever bridge is a cable-stayed bridge (Figure 1).

Figure 1: A Cable-Stayed (Cantilever) Bridge

The Ed Koch Queensboro Bridge is a double cantilever bridge (Figure 2). It has two bases with two booms extending from each base and the cantilevers placed end to end.

Figure 2: Ed Koch Queensboro Bridge (Double Cantilever)

The Grand Bridge over Newtown Creek is a swing bridge, also known as a rotating bridge (Figure 3). This bridge has two booms mounted on a base that rotates.

Figure 3: Grand Bridge (Swing Bridge)

Figure 4 shows a bascule bridge, more commonly known as a drawbridge, where it is clear that the bridge uses a big, very flat boom.

Figure 4: Bascule Bridge

Not all bridges are booms. Suspension bridges use a deck that is supported by steel cables, not booms. Examples of suspension bridges are the Brooklyn Bridge, Manhattan Bridge, Verrazano-Narrows Bridge, and the George Washington Bridge.

Cranes are the most common example of booms. The crane pictured in Figure 5 is a tower crane. These cranes are a fixture on construction sites around the world. A tower crane can lift a 40,000 lb load. It is attached to the ground by anchor bolts driven through a 400,000 lb concrete pad poured a few weeks before the crane is erected (Howstuffworks.com, 2003).

Figure 5: A Tower Crane (Jennings, 2015)

Stress and Strain

The design of a boom must consider the properties of the materials used to build the boom. The mechanical properties and deformation of solids are explained by stress and strain. When an external force is applied to a material, it changes shape (e.g. changes length and cross-section perpendicular to the length). Understanding how deformation will affect materials is a critical consideration in boom design.

According to Serway and Beichner in “Physics for Scientists and Engineers,” stress is the external force acting on an object per unit cross sectional area. Strain is the measure of deformation resulting from an applied stress (Figure 6).

Figure 6: Material Under Tension

The expression (1) for tensile stress shows the relationship between an applied force and the cross-sectional area.

(1)

In (1), σ is the stress, F is the applied force, and A is the cross-sectional area of the object perpendicular to the force. The resulting strain (2) is calculated by dividing the change in length of the object by the original length.

(2)

In (2), ΔL is the change in length and L0 is the object's original length.

There are three basic types of stresses; tensile (pulling or stretching), compressive (squeezing or squashing), and shear (bending or cleaving). Consider a straight metal beam. If a tensile stress is applied to both ends, its length will increase in both directions of the force, while its cross-sectional area perpendicular to the force applied will decrease. Under compressive stress, the opposite will occur. If the beam is subjected to shear stress, it will bend towards the direction of the applied force, and both the length and cross-sectional area of the beam will become distorted. Figure 7 depicts a graphic representation of the three common forms of stress.

Figure 7: Example of Cylindrical Material Under Three Common Modes of Stress

Strain is proportional to stress for material dependent values of strain. If the material is known, it is possible to derive strain from measured stress, and vice-versa, up to a certain level of stress. This proportionality constant is referred to as the elastic modulus, or Young’s modulus. The moduli of different materials is an important factor to consider when designing or building any form of structure that will be under stresses.

Stress-Strain Curve

A stress-strain graphically shows the relationship between the stress and strain of a material under load. Figure 8 shows the stress-strain curve of a common metallic building material. In the elastic region, the material will regain its original shape once the stress is removed. The elastic region in Figure 8 is fairly linear. The slope of this linear portion of the stress-strain curve is the elastic modulus.

Figure 8: Stress-Strain Curve of a Material Under Tension

The elastic limit for a material is the maximum strain it can sustain before it becomes permanently deformed (i.e. if the stress is decreased, the object no longer returns to its original size and shape). In the plastic region, the material loses its elasticity and is permanently deformed. A linear approximation with the elastic modulus is no longer accurate.

The ultimate tensile strength is the maximum stress a material can undergo. The fracture stress is the point at which the material breaks. Fracture stress is lower than the ultimate tensile strength of a material because the material has reached that level of stress and has already begun to fail. The cross-sectional area is constantly decreasing until the material finally breaks.

In addition to these intrinsic materials factors, the behavior of materials as they age and are used in service must be considered in boom design. These factors are not applicable to the boom design in this lab, but they must be considered when deciding what material to use for a design. The loss of desirable properties through use, called fatigue, is important. Non-static loads, repeated loading and unloading, or loads that include vibrations or oscillations will eventually lead to failure in service. Special care must be taken with live loads and situations where small motions may be magnified by design features.

There are many factors to consider in any design project. When designing and constructing the boom for this competition, consider the materials being used and what might cause those materials to fail under a load.

Competition Rules

The competition rules must be followed at all times during the competition. Violation of any of these rules will result in the disqualification of the design.

  • The boom is to be secured (i.e. anchored) to the white plastic anchorage provided at the front of the lab
  • The boom must extend at least 1.5 meters horizontally from the front edge of the anchorage
  • The boom must be anchored in 2 min or less
  • The boom may not touch anything but the anchorage
  • The boom’s performance will be assessed by its anchor time, boom weight, boom length, and the weight it can support before deflecting 0.20 m vertically

The basic weight ratio (3) for the competition uses the weight supported in grams divided by the boom weight in grams. This ratio should be greater than 1.

(3)

The winning design will be determined by the weighted design ratio (4), which uses the weight ratio, anchor time in seconds, and boom length in meters. Each component ratio should be greater than 1.

(4)

Design Considerations

  • Which aspects of the competition ratio are most advantageous?
  • How can the boom be built and/or reinforced to prevent as much deflection as possible?

Materials and Equipment

  • Two thick dowels (1.1 cm × 122 cm)
  • Two thin dowels (0.8 cm × 122 cm)
  • Six bamboo skewers (30.5 cm)
  • 3D printed dowel connectors
  • Cellophane tape
  • Polyester string

Note: A saw is available to cut the dowels. Ask a TA for assistance, as only TAs may use the saw.

Procedure

Part 1. Boom Design and Construction

  1. Assess the materials and consider the design options, keeping in mind the competition specifications. Preliminary sketches must be completed during this process.
  2. Sketch the basic design in pencil using the lab notes paper provided by a TA or on the EG1003 website. Label the design clearly and have a TA sign and date it.
  3. Construct the boom based on the completed sketch and the available materials. A TA will provide the materials allowed for the design. If the design is modified during the construction phase, make sure to note the changes and describe the reasons for them.

Part 2. Competition

Note: Attaching the boom to the anchorage is a critical phase of the competition. Anchoring will be timed. Making a plan to anchor the boom quickly will improve its standing in the competition. Practice anchoring before the trial begins. The boom will be disqualified if anchoring the boom takes more than 2 min.

  1. When the TA says "Go," attach the boom to the anchorage and shout "Done" when the boom is anchored. The TA will only stop the timer once there are no more hands are touching the boom. The TA will give the anchoring time that will be used to compute the boom's design ratio.
  2. A TA will measure the boom length and record the length in the competition spreadsheet for the section.
  3. A TA will attach a basket to the end of the boom and add weights until the boom deflects (bends) 0.20 m vertically. The load supported will be weighed on the lab scale and recorded in the competition spreadsheet for the section.
  4. A TA will weigh the boom and record the weight in the competition spreadsheet for the section.
  5. The design ratio for the in-person boom design will be used to decide the winner of the competition.

A TA will prepare an Excel file with the section's results. It can be accessed in the Lab Documents section of the EG1003 website. This chart must be included in the PowerPoint presentation and in the Data/Observations section of the lab report. The lab work is now complete. Please clean up the workstation. Return all unused materials to a TA. Refer to the Assignment section for the instructions to prepare the lab report.

Assignment

Individual Lab Report


Follow the lab report guidelines laid out in the EG1003 Writing Style Guide in the Technical Writing section of the manual. The following points should be addressed in the appropriate section of the lab report.

  • What factors were considered in designing the boom? Discuss the background information that was used
  • Describe the competition rules in the Introduction. What impact did the rules and ratios have on any design decisions?
  • Describe the function of each component used in the design
  • Describe the advantages and disadvantages of the boom design
  • Discuss potential design improvements. How can the design be optimized (i.e. improve the design ratio) from this lab experience?
  • Which elements of the boom were stressed by the load? Describe the load’s direction and if the load contributed s to the failure?
  • Include the Excel spreadsheet with all the boom designs in the class. Discuss other designs in the class
  • Contribution Statement


Remember: Lab notes must be taken. Experimental details are easily forgotten unless written down. EG1003 Lab Notes paper can be downloaded and printed from the EG1003 Website. Use the lab notes to write the Procedure section of the lab report. At the end of each lab, a TA will scan the lab notes and upload them to the Lab Documents section of the EG1003 Website. One point of extra credit is awarded if the lab notes are attached at the end of the lab report. Keeping careful notes is an essential component of all scientific practice.

Team PowerPoint Presentation

Follow the presentation guidelines laid out in the EG1003 Lab Presentation Format in the Technical Presentations section of the manual. When preparing the presentation, consider the following points.

  • How can the boom design be improved?
  • Other than the examples given in this lab, what are other boom examples in the real world?
  • Which elements of the boom (e.g., wooden dowels, 3D printed dowel connectors, Kevlar string, etc.,) were stressed by the load, in what directions, and could potentially lead to the failure?

References

How Stuff Works website. 2003. SHW Media Network. Retrieved July 28, 2003. http://science.howstuffworks.com/tower-crane3.htm

Jennings, James. 2015. “Up, UP in a Crane: What Life is Like as a Tower Crane Operator.” Philadelphia. Accessed 14 January 2020 from www.phillymag.com

Serway, R., Beichner, R., Physics for Scientists and Engineers with Modern Physics, 5th Edition. Fort Worth, TX: Saunders College Publishing, 2000