Difference between revisions of "Boom Construction Competition"

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=Objective=
=Objective=


The experimental objective of this lab is to design and construct a boom following the specifications provided. The boom will be entered in a competition against other booms in the section. The competition will be judged by a ratio that uses boom weight and length, weight held, and anchor time. The highest ratio wins.
The objective of this lab is to design and assemble a boom. The performance of the boom will be judged by a design equation that includes boom mass, boom length, mass held, and anchor time. The team with the highest equation result will win the competition.


=Overview=
=Overview=


A <b>boom</b> is used to lift and move heavy objects, often objects that are much heavier than the boom itself. Distributing the weight of the object, or 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.
A <b>boom</b> is a device used to lift and move heavy objects that are heavier than the boom itself. Booms can be found everywhere in society, particularly in construction; cantilever bridges and cranes, for example, are common examples of booms.


== Examples of Booms ==
A common example of a boom is a cantilever bridge, which uses two booms extending from a common base (Figure 1).  
 
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).


[[Image:Lab_boom_13.png|650px|thumb|center|Figure 1: A Cable-Stayed (Cantilever) Bridge]]
[[Image:Lab_boom_13.png|650px|thumb|center|Figure 1: A Cable-Stayed (Cantilever) Bridge]]
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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.
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.


[[Image:lab_boom_10.jpg|frame|center|Figure 2: Ed Koch Queensboro Bridge (Double Cantilever)]]
[[Image:lab_boom_10.jpg|frame|center|Figure 2: Ed Koch Queensboro 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.
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.


[[Image:lab_boom_11.jpg|650px|thumb|center|Figure 3: Grand Bridge (Swing Bridge)]]
[[Image:lab_boom_11.jpg|650px|thumb|center|Figure 3: Grand 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 shows a bascule bridge, more commonly known as a drawbridge. This bridge uses a big, flat boom.


[[Image:lab_boom_12.jpg|650px|thumb|center|Figure 4: Bascule Bridge]]
[[Image:lab_boom_12.jpg|650px|thumb|center|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-pound load. 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 (Howstuffworks.com, 2003).
Cranes are another 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).


[[Image:Tower Crane.jpg|650px|thumb|center|Figure 5: A Tower Crane (Jennings, 2015)]]
[[Image:Tower Crane.jpg|650px|thumb|center|Figure 5: A Tower Crane (Jennings, 2015)]]
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== Stress and Strain ==
== 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.
Distributing the load being lifted over the length of the boom is the main challenge 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. The design of a boom must also consider the properties of the materials used to build the boom.


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).
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. The mechanical properties and deformation of solids are explained by stress and strain (Serway and Beichner, 2000). '''Stress''' is the external force acting on an object per cross sectional area. '''Strain''' is the measure of deformation resulting from an applied stress (Figure 6).


[[Image:lab_boom_1.jpg|frame|center|Figure 6: Material Under Tension]]
[[Image:lab_boom_1.jpg|frame|center|Figure 6: Material Under Tension]]


The expression (1) for tensile stress shows the relationship between an applied force and the cross-sectional area.
Tensile stress, &sigma;, is the relationship between an applied force, ''F'', and the cross-sectional area, ''A'' (1).


<center><math>\sigma = \frac{F}{A}\,</math></center>
<center><math>\sigma = \frac{F}{A}\,</math></center>
<p style="text-align:right">(1)</p>
<p style="text-align:right">(1)</p>


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.
The resulting strain (2) is calculated by dividing the change in length of the material by the original length. This equation finds the strain for a rod of a material. In (2), &Delta;L is the change in length and L<sub>0</sub> is the rod's original length.


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


In (2), &Delta;L is the change in length and L<sub>0</sub> is the object's original length.
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 of the beam, the length of the beam will increase, while the cross-sectional area of the beam 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.
 
There are three basic types of stresses; tensile (pulling or stretching), compressive (squeezing or squashing), and shear (bending or cleaving). If a rod of material is put under <b>tensile stress</b>, 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 <b>compressive stress</b>, 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 <b>shear stress</b>, it will bend in the direction of the applied force and its length and cross-section will be distorted (Figure 7).


[[Image:Lab_boom_7.gif|frame|center|Figure 7: Rods of Material Under Stress]]
[[Image:Lab_boom_7.gif|thumb|400px|center|Figure 7: Example of a Boom Under Three Common Modes of Stress]]


Strain is proportional to stress for small values of strain. The proportionality constant depends on the material being deformed and on the type of deformation. The proportionality constant is called the <b>elastic modulus</b>, or Young’s modulus. The moduli for different materials vary considerably and the various moduli for a particular material may also vary significantly. Concrete, for example, is very strong in compression, but less so in tension, and wood breaks quite easily when bent because its natural grain is anisotropic (properties depend on the direction of the material).
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 stress.


== Stress-Strain Curve ==
== Stress-Strain Curve ==


A <b>stress-strain curve</b> graphically shows the relationship between the stress and strain of a material under load (Figure 8). In the <b>elastic region</b>, the material will regain its original shape once the stress or load is removed. In the <b>plastic region</b>, the material loses its elasticity and is permanently deformed.
A graph of <b>stress-strain</b> 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.  


[[Image:lab_boom_2.jpg|frame|center|Figure 8: Stress-Strain Curve of a Material Under Tension]]
[[Image:lab_boom_2.jpg|frame|center|Figure 8: Stress-Strain Curve of a Material Under Tension]]


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). If the stress is greater than the elastic limit, the material will plastically deform and for sufficiently large stress ultimately fail. 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 under tension. Fracture stress is lower than the ultimate tensile strength because as strain increases, the material becomes thinner and thinner. As this necking down process continues, the load that can be supported decreases and the material breaks.
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.  
 
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 do not relate directly to the boom design in this lab, but they must be considered when deciding what material to use for an actual 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 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>The first aging factor is chemical degradation and, in particular, <b><i>corrosion</i></b>. Light and


chemicals present in the
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.
environment can cause chemical reactions with the materials chosen for a
design.  These reactions can cause a loss
of strength, flexibility or other desirable material properties. Corrosion
occurs when two or more materials or substances react with each other, in the
presence of an electrolyte.  For example,
rust results when iron or simple steel is exposed to water, or just even humid
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,
the cost is often limiting factor and cheap countermeasures like paint and other
coatings are often employed.</p>


<p><b><i>Erosion</i></b> is another
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.
factor in material failure. It is weathering caused by exposure to
environmental factors like wind driven dust or sand, rain or flowing water. The
smoothing of rocks by a river or the sea is a good example of this kind of
process.  Care in the design process can
help minimize the effect of erosion.  
Again the cost is often the limiting factor and coatings are often employed
to protect an object.</p>


<p>A third factor in material failure is <b><i>thermal
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.
cycling</i></b>.  Materials in an object
will routinely warm up and cool down while in use (especially device that
generates heat internally), over the course of a normal day, or even over a
year.  This thermal cycling is
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
ultimately failure.  Careful choice and
matching of materials can minimize the effects of thermal cycling, but the cost may
limit the choices.  Accumulations of
water, which can freeze and thaw, can be very damaging and coatings are often
especially vulnerable to thermal cycling as they may crack and peel off,
exposing the underlying material in need of protection.</p>
 
<p>A related but more dramatic mode of failure is <b><i>thermal shock</i></b>.
This can occur when objects made of certain
materials are exposed to extreme temperature changes over a short period of
time.  If the material is inhomogeneous
(i.e., properties not uniform throughout), thermal expansion or contraction can
be sufficiently non-uniform to cause cracking.
If the cracks spread far enough, the material will fail in spectacular
fashion.  Imagine quickly immersing a
very cold ordinary glass bottle in very hot water.  Often such failures can be avoided by heat
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>
glass is specially treated to avoid thermal shock.</p>-->
 
There are many factors to consider in any design project. When designing and constructing the boom for this competition, remember to consider the materials being used and what might cause those materials to fail under a load.


=Competition Rules=
=Competition Rules=


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


<ul>
<ul>
<li>The boom is to be secured (i.e. anchored) to the white plastic anchorage provided at the front of the lab
<li>The boom must be anchored to the white plastic anchorage provided at the front of the lab
<li>The boom must extend at least 1.5 meters horizontally from the front edge of
<li> The dowels must be used as-is; they cannot be cut further
the anchorage</li>
<li>The boom must extend at least 1.5 m horizontally from the front edge of
<li>The boom must be anchored in two minutes or less</li>
the anchorage for the entire run
<li> The boom must start at least 0.30 m from the ground after adding 15 grams of preload
<li>The boom must be anchored in 2 min or less</li>
<li>The boom may not touch anything but the anchorage</li>
<li>The boom may not touch anything but the anchorage</li>
<li>The <b>basic weight ratio</b> (3) for the competition uses the weight supported divided by the boom weight</li><br>
<li>The boom’s performance will be assessed by its anchor time, boom mass, boom length, and the mass it can support before deflecting 0.20 m vertically</li>
<li> A team can use any number of dowels, as long as their total length is less than or equal to the length of 4 uncut dowels (4 x 122 cm, or 488 cm)
</ul>
 
The '''basic mass ratio''' (3) is defined via the mass supported in grams divided by the boom mass in grams. The mass ratio must be greater than 1 to enter the competition.


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


<li>The winning design will be determined by the <b>weighted design ratio</b> (4), which uses the weight ratio, anchor time, and boom length</li>
The winning design will be determined by the competition equation (4) which includes the weight ratio, anchor time in seconds, and boom length in meters. The equation result should be greater than 1.
</ul>


<center><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>
<center><math>Competition\ Equation = (Mass\ Ratio)^2 \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>
<p style="text-align:right">(4)</p>


=Design Considerations=
=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?
* How can the boom be built and/or reinforced to prevent as much deflection as possible?
* In which instances should you use the thin vs thick dowels?
* What design aspects will maximize and minimize the design equation result?


=Materials and Equipment=
=Materials and Equipment=
The following materials are available to construct the boom.
<ul>
<ul>
<li>Two thick dowels (1.1 cm &times; 122 cm)</li>
<li>Thick dowels (diameter = 1.1 cm) </li>
<li>Two thin dowels (0.8 cm &times; 122 cm)</li>
<li>Thin dowels (diameter = 0.8cm) </li>
<li>Six bamboo skewers (30.5 cm)</li>
<li>3D printed dowel adaptors</li>
<li>3D printed dowel connectors</li>
<li>Cellophane tape</li>
<li>Cellophane tape</li>
<li>Kevlar string</li>
<li>String</li>
</ul>
</ul>


<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>
{| class="wikitable"
|+ Table 1: Materials Available for Boom Construction
!Item Name!!!!Dimensions!!!!Quantity
|-
|Dowel Length || || Dowel Diameter || ||
|-
|Full Length || 122 cm || Thick || 1.1 cm ||
|-
| || || Thin || 0.8 cm ||
|-
|2/3 Length || 81.2 cm || Thick || 1.1 cm ||
|-
| || || Thin || 0.8 cm ||
|-
|1/2 Length || 61 cm || Thick || 1.1 cm ||
|-
| || || Thin || 0.8 cm ||
|-
|1/3 Length || 40.6 cm || Thick || 1.1 cm ||
|-
| || || Thin || 0.8 cm ||
|-
|3D Printed Dowel Adaptors || || || || Unlimited
|-
|Cellophane Tape || || || || Unlimited
|-
|String || || || || Unlimited
|}


=Procedure=
= Procedure =


<h3>Boom Design and Construction</h3>
== Part 1. Boom Design and Construction ==


# Assess the materials and consider the design options, keeping in mind the competition specifications. Preliminary sketches must be completed during this process</li>
# 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
# Sketch the basic design in pencil using the lab notes paper provided by a TA. 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
# 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.
# A TA will weigh the boom and record the weight in the competition spreadsheet for the section
# Since anchor space is limited, each  boom  is only allowed to use an anchor for '''10 min''' at a time. The TAs will keep track of the time, and  booms  will rotate every 10 min to ensure that every  boom has access to an anchor. During the downtime, continue working on  the boom to make the best use of  the next anchoring opportunity.


<h3>Competition</h3>
== Part 2. Competition ==


<p><b>Note: </b>Attaching the boom to the anchorage is a critical phase of the competition. Anchoring will be timed. Making sure there is 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 two minutes.
<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.  


# 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 touching the boom. The TA will give the anchoring time. This value will be used to compute the boom's design ratio
# 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 all hands are off the boom. The TA will give the anchoring time that will be used to compute the boom's design ratio.
# A TA will measure the boom and record the length in the competition spreadsheet for the section
# A TA will measure the  horizontal length of the boom and record the length in the competition spreadsheet for the section. The boom must remain past the 1.50 m mark throughout the whole run in order to be an accepted run.
# A TA will attach a basket to the end of the boom and add weights until the boom deflects (bends) 0.2 m vertically. The load supported will be weighed on the lab scale and recorded in the competition spreadsheet for the section (Figure 10)
# 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 will be weighed on the lab scale and recorded in the competition spreadsheet for the section.
[[Image:lab_boom_5.jpg|frame|center|Figure 10: Sample Competition Spreadsheet]]
# Calculate the mass with [[Media: Lab_7_Student_Sheet.xlsx|this sheet]] by filling out the required values colored in gray. Students can also chose to calculate a preliminary mass ratio and competition result by filling out the sheet.
# The design ratio for the boom design will be used to decide the winner of the competition.


<p>A TA has prepared 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.
<p>A TA will prepare an Excel file with the section's results and upload it to the the [http://eg.poly.edu/documents.php Lab Documents] section of the EG1004 website.


=Assignment=
=Assignment=


Follow the lab report guidelines laid out in the [[media:EG 1003 Writing Style Guide.docx|EG1003 Writing Style Guide]] in the <i>Technical Writing</i> section of the manual. The following points should be addressed in the appropriate section of the lab report.
== Individual Lab Report ==
{{Ambox
| 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.}}


<ul>
<li> Describe the rules of the competition in the Introduction. What consequences did the rules have for any design decisions? Use the appropriate equations in the answer.</li>
<li>What factors were considered in designing the boom? Was any of the
background information used?</li>
<li>What was the basic weight ratio and weighted design ratio for the design?</li>
<li>Describe how the components chosen functioned in the design, and describe its height/length/shape</li>
<li>Describe the advantages and disadvantages of the boom design</li>
<li>Discuss design improvements. How can the design be optimized (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 the spreadsheet with every boom's results. Describe the results and talk about other designs in the class


</ul>
{{Labs:Lab Report}}
 
* What factors were considered in designing the boom?  Discuss the background information that was used
* Describe the competition rules, the ratio, and materials in the Introduction. What impact did the rules, the materials and ratio 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) using the experience  gained from this lab?
* Which elements of the boom were stressed by the load? Did the load deflect to the side, and if so, did that contribute to the boom failing? Describe the load’s direction and how  the load contributed to the failure?
* Include the Excel spreadsheet with all the boom designs in the class. Discuss other designs in the class
* Contribution Statement
 


{{Lab notes}}
{{Labs:Lab Notes}}


<h3>Team PowerPoint Presentation</h3>
<h3>Team PowerPoint Presentation</h3>


<p>Follow the presentation guidelines laid out in the page called [[EG1003 Lab Presentation Format]] in the <i>Technical Presentations</i> section of the manual.
{{Labs:Team Presentation}}
When preparing the presentation, consider the following points.</p>


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



Latest revision as of 17:21, 12 March 2024

Objective

The objective of this lab is to design and assemble a boom. The performance of the boom will be judged by a design equation that includes boom mass, boom length, mass held, and anchor time. The team with the highest equation result will win the competition.

Overview

A boom is a device used to lift and move heavy objects that are heavier than the boom itself. Booms can be found everywhere in society, particularly in construction; cantilever bridges and cranes, for example, are common examples of booms.

A common example of a boom is a cantilever bridge, which uses two booms extending from a common base (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

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

Figure 4 shows a bascule bridge, more commonly known as a drawbridge. This bridge uses a big, flat boom.

Figure 4: Bascule Bridge


Cranes are another 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

Distributing the load being lifted over the length of the boom is the main challenge 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. The design of a boom must also consider the properties of the materials used to build the boom.

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. The mechanical properties and deformation of solids are explained by stress and strain (Serway and Beichner, 2000). Stress is the external force acting on an object per cross sectional area. Strain is the measure of deformation resulting from an applied stress (Figure 6).

Figure 6: Material Under Tension

Tensile stress, σ, is the relationship between an applied force, F, and the cross-sectional area, A (1).

(1)

The resulting strain (2) is calculated by dividing the change in length of the material by the original length. This equation finds the strain for a rod of a material. In (2), ΔL is the change in length and L0 is the rod's original length.

(2)

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 of the beam, the length of the beam will increase, while the cross-sectional area of the beam 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 a Boom 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 stress.

Stress-Strain Curve

A graph of stress-strain 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 following rules must be followed to qualify for the competition. Violation of any of these rules will result in the disqualification of the design.

  • The boom must be anchored to the white plastic anchorage provided at the front of the lab
  • The dowels must be used as-is; they cannot be cut further
  • The boom must extend at least 1.5 m horizontally from the front edge of the anchorage for the entire run
  • The boom must start at least 0.30 m from the ground after adding 15 grams of preload
  • 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 mass, boom length, and the mass it can support before deflecting 0.20 m vertically
  • A team can use any number of dowels, as long as their total length is less than or equal to the length of 4 uncut dowels (4 x 122 cm, or 488 cm)

The basic mass ratio (3) is defined via the mass supported in grams divided by the boom mass in grams. The mass ratio must be greater than 1 to enter the competition.

(3)

The winning design will be determined by the competition equation (4) which includes the weight ratio, anchor time in seconds, and boom length in meters. The equation result should be greater than 1.

(4)

Design Considerations

  • How can the boom be built and/or reinforced to prevent as much deflection as possible?
  • In which instances should you use the thin vs thick dowels?
  • What design aspects will maximize and minimize the design equation result?

Materials and Equipment

The following materials are available to construct the boom.

  • Thick dowels (diameter = 1.1 cm)
  • Thin dowels (diameter = 0.8cm)
  • 3D printed dowel adaptors
  • Cellophane tape
  • String
Table 1: Materials Available for Boom Construction
Item Name Dimensions Quantity
Dowel Length Dowel Diameter
Full Length 122 cm Thick 1.1 cm
Thin 0.8 cm
2/3 Length 81.2 cm Thick 1.1 cm
Thin 0.8 cm
1/2 Length 61 cm Thick 1.1 cm
Thin 0.8 cm
1/3 Length 40.6 cm Thick 1.1 cm
Thin 0.8 cm
3D Printed Dowel Adaptors Unlimited
Cellophane Tape Unlimited
String Unlimited

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. 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.
  4. Since anchor space is limited, each boom is only allowed to use an anchor for 10 min at a time. The TAs will keep track of the time, and booms will rotate every 10 min to ensure that every boom has access to an anchor. During the downtime, continue working on the boom to make the best use of the next anchoring opportunity.

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 all hands are off 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 horizontal length of the boom and record the length in the competition spreadsheet for the section. The boom must remain past the 1.50 m mark throughout the whole run in order to be an accepted run.
  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 will be weighed on the lab scale and recorded in the competition spreadsheet for the section.
  4. Calculate the mass with this sheet by filling out the required values colored in gray. Students can also chose to calculate a preliminary mass ratio and competition result by filling out the sheet.
  5. The design ratio for the boom design will be used to decide the winner of the competition.

A TA will prepare an Excel file with the section's results and upload it to the the Lab Documents section of the EG1004 website.

Assignment

Individual Lab Report


Follow the lab report guidelines laid out in the EG1004 Writing Style Guide in the Technical Writing section of the manual. Use the outline below to write this report.

  • What factors were considered in designing the boom? Discuss the background information that was used
  • Describe the competition rules, the ratio, and materials in the Introduction. What impact did the rules, the materials and ratio 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) using the experience gained from this lab?
  • Which elements of the boom were stressed by the load? Did the load deflect to the side, and if so, did that contribute to the boom failing? Describe the load’s direction and how the load contributed 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. EG1004 Lab Notes paper can be downloaded and printed from the EG1004 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 EG1004 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 EG1004 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, 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