Essential Aspects of Engineering
Concepts of Planning & Designing
by
Tahiem Williams Office of Science, Science Undergraduate Laboratory Internship
Stanford University
Stanford Linear Accelerator Center Menlo Park, California
August 16, 2008
Prepared in partial fulfillment of the requirement of the Science Undergraduate Laboratory Internship Program for the Department of Energy, under the supervision of Bobby McKee in the Linear Collider Main Linac at Stanford Linear Accelerator Center.
Participant: ______Signature
Research Advisor: ______Signature
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Abstract:
Concepts of Planning and Designing. TAHIEM WILLIAMS (Bethune Cookman University, Daytona Beach, FL 32114) BOBBY MCKEE (Stanford Linear Accelerator Center, Menlo Park, CA 94025)
The field of engineering demands that a sequence of procedures be carried out before any practical design of a product is manufactured. These procedures consist of the following: recognition of need, definition of problem, synthesis, analysis and optimization, evaluation and presentation. Most of these procedures were performed during the completion of the projects that were assigned. The assessment of relocating a steel ladder required both analysis and optimization. The pursuit of a surveillance camera for End Station A required evaluation and presentation. Lastly, the installation of metal sheets on the Radio Frequency distribution structure to prevent sections of the structure from shifting required synthesis and evaluation.
Introduction:
Mechanical Engineering is an engineering discipline that entails the design, manufacture, installation and operation of engines and machines [1]. “Planning and designing,” are not only the essential parts in mechanical engineering but they are also known to be the fundamentals elements of general engineering. Without these key elements, nothing would get accomplished. Prior to anything that is designed (using advance computer software for instance Auto CAD) and then built, there are series of steps or phases that one must complete. The process begins by recognizing a need and decision to do something about it. Recognition is usually triggered by a particular adverse circumstance or a set of random circumstances which arise almost simultaneously [1].
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Second, the problem must be defined. There are many factors involved in getting from the need to the problem. One of these is to define a problem that can be solved within time and budget constraints. After defining the problem and obtaining a set of written and implied specifications, the next step in design is the synthesis of an optimum solution.
Synthesis cannot be done without both analysis and optimization because the system under design must be analyzed to determine whether the performance acts in accordance with the specifications [1]. The next stage of the design phase is evaluation. Evaluation is a crucial stage of the total design process because this phase involves testing of the design to ensure that it satisfies the needs. Presenting the design is the last and vital step in the design phase. Failure to effectively communicate with others to persuade them that your solution to the problem is better than others is simply a waste of time and effort. The three forms of communication are oral, written and graphical. A successful engineer will be technically competent and versatile in all three forms of communication. A key concept of engineering is being able to communicate effectively as well as work well with others.
There were three central projects that I was involved in. The first project consisted that I determined if 12 inch metal rods could withhold a 30 ft steel ladder (Figure 1) assembly in the End Station B 6 inches from the wall or not. The second project consisted that I managed the design of a surveillance camera in the End Station A. This consisted of, finding what materials to use, calculating the cost estimate, determining where the surveillance camera should be positioned in the End Station and choosing the surveillance camera that was high-quality at the same time low in cost and that would best accomplish the task at hand. The third project was to brainstorm ideas and methods
3 Essential Aspects of Engineering to keep the RF (Radio Frequency) distribution structure (Figure 2) from displacing while the structure was being relocated. Radio Frequency waves are injected into the RF structure from the Klystron, a microwave generator, and then divided into even proportions upon entering the beam line.
Method:
In order for me to find whether or not it was possible to reposition the 30 ft steel ladder assembly 6 inches from the wall using 12 inch steel rods (Figure 3), I had to find the weight of the steel ladder. Weight is defined by multiplying the volume and the
density of steel (W vladder steel ). Then I calculated the shear stress ( ) of each steel rod. Shear stress is defined as a stress which is applied parallel or tangential to a face of a
F material [1] and can be calculated by using the following formula, , where F is the A force applied and A is the area to which the force is applied. Then I calculated the moment of inertia of each rod. The moment of inertia is the rotational analog of mass [2].
The moment of inertia ( I ) of a slender rod is represented by the following formula,
d 4 , where d is the diameter of the rod. Next, I calculated the maximum deflection 64
FL3 of each rod by using the following formula, y , where F is the force applied, max 192EI
L is the length of the rod, and E is the elasticity of the material. Finally I calculated the bending stress ( ) of the steel rod which is represented by the following equation
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My . Where, M is the moment of fixed ends and y is the perpendicular distance to I the neutral axis.
The quest for an adequate surveillance camera entailed the usage of the internet.
The surveillance camera was selected by first making an excel spreadsheet (Table 1) of the surveillance cameras that I thought satisfied the minimum requirements. The spreadsheet consisted of only the important specifications of each camera. The spreadsheet was then presented to others to collect ideas and opinions in order to make the best decision.
Aluminum sheets (Figure 6) were installed on the RF distribution structure to keep the fragments from shifting. Measurements were made in order to supply the correct dimensions of the aluminum sheet. Next, using the measurements, a sketch of the aluminum sheet was drawn to send to the machine shop. Upon sending the sketches to the machine shop, the aluminum sheets were then installed.
Results:
i. Ladder Evaluation:
lb Density of Steel: 0.283 in3
Total Volume: V 2420in3
Weight:
lb W V x 2420.13in3 x 0.283 685lbs in3
Shear Stress:
F F 100lbs lb 2 2 509 2 A r 0.25in in
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Moment of Inertia:
d 4 0.5in4 I 3.07x103 in 4 64 64
Maximum Deflection:
FL3 100lbs12in3 y 0.01in max 192EI 19230x106 psi(3.07x103 in 4 )
Bending Stress:
2 Pab 2 d 2F ab 2 d 2100lb6in6in 0.5in L2 2 L2 2 12 in 2 2 My 3 lbs 3 4 24x10 2 I I I 3.07x10 in in
I measured the weight of the ladder to be approximately 684.9lbs. With the consideration that there was a steel rod on both sides, each rod would take half of the total load that was exerted on the ladder. Therefore, I calculated shear stress due to a 100
509 lb pound force being implied on each of the steel rods to be in2 . The rotational analog of the steel rods, moment of inertia, was3.07x103in4 . This gives a maximum deflection in the y-axis to be0.01in. The breaking point or ultimate stress of steel is said
58x103 lbs to be approximately in 2 . For safety precautions, it's important to have the bending stress of a material at least half or more than half of the ultimate stress to assure
24x103 lbs reliability. Since, I calculated the bending stress of the steel rods to be in2 ,
6 Essential Aspects of Engineering which is more than half the ultimate stress of steel, the 12 inch steel rods were capable of embracing the ladder 6 inches from the wall. The negative sign represent the negative moment, which is obtained using the right hand rule. Although the steel rods were completely capable of withholding the 30ft ladder several inches from the wall, L-
Brackets (Figure 4) were installed on the bottom of the ladder to reduce the stress on the rods for additional assurance.
ii. Surveillance Camera Design:
Unfortunately, none of the surveillance cameras mentioned in the excel spreadsheet were chosen to partake in the design. Instead, a surveillance camera that was previously used in End Station A was preferred in order to save money as well as time.
The surveillance camera that was chosen is illustrated in Figure 5. Upon being selected, the camera was immediately assembled in End Station A. The camera can be controlled by using an internet browser of the computer which matches the IP address of the surveillance camera and that is connected to the camera by an Ethernet Crossover cable.
The difference between a Crossover Ethernet cable and a Straight-Through Ethernet cable is simply just the wiring. They both have the same function.
iii. Installation of Aluminum Sheet
Upon receiving the aluminum sheets from the machine shop, the diameters of the holes were too small for the screws that were used to attach the aluminum sheets to the
Radio Frequency structure. As a result, the diameters of the holes were made larger by a power hand drill and then the sheets were installed. Figure 7 and 8 illustrates the aluminum sheets installed on the RF structure. The installation of aluminum sheets, were extremely expensive. The cost could have been reduced by using wood instead of
7 Essential Aspects of Engineering aluminum. Although wood is less expensive than aluminum, wood isn’t as durable as aluminum when it’s constantly being handled. Thus aluminum was chosen because of the fact that it’s durable as well as reusable.
Conclusion:
In conclusion, I learned a valuable lesson working under the direction of Bobby
McKee. Not only was he an expiring mentor, but he gave me insight to how it was like in industry versus how it was like in an research environment. As an engineer, it’s important to understand the significance of time and money management. I realized that large projects demand a massive amount of time and money. They also entail a collaboration with others that share the same or similar intentions, to complete the task at hand. This is why communication is the key to execution and completion
Acknowledgements:
This work was supported by the Department of Energy at the Stanford Linear
Accelerator Center. I would like to take this opportunity to express my sincere gratitude to my mentor Bobby McKee. I would like to thank Farah, Susan and Steve for their assistance and guidance throughout the internship and for making this internship such a wonderful learning experience. Additionally, I would like to thank the Department of
Energy, the Office of Science, and the SULI Program for allowing me to partake in this extraordinary internship program.
References:
[1] Joseph E. Shigley, Mechanical Engineering Design, Second ed. , St. Louis: McGraw- Hill Book Company, 1963.
[2] A. Johnson and K.Sherwin, Foundations of Mechanical Engineering, First ed. , Oxford: Alden Press, 1996.
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Figure 1: Steel Ladder Assembly
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Figure 2: Radio Frequency Distribution Structure
12” Steel Rod
Figure 3: Steel Rod
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L-Bracket
Figure 4: L-Bracket
Figure 5: Surveillance Camera
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Figure 6: Aluminum Sheet
Figure 7: Aluminum Sheet Installation (Front View)
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Figure 8: Aluminum Sheet Installation (Side View)
Table 1:
Surveillance Camera Price Dimensions(W x H x D)
SNC-RZ30N $1,158.00 5.625in x 7in x 5.75in SNC-RX550N(Japan) $1,749.00 6.375in x 6.375in x 9.125in Vivotek PZ6112 $552.99 4.1in x 4.1in x 4.9in VC-CA-IPPZ6114 $580.00 4.13in x 4.48in x 4.13in Samsung SPD-2300N $974.00 Ø155(W) x 243.4(H)mm + $590 w/ keyboard
Image Size (H x V) Pan Angle/Pan Speed
N/A -170° to +170° /2 sec. per 340° 640 x 480, 320 x 240, 160 x 120 (JPEG, MPEG-4, H.264) 360° endless motion/360° per sec.(max.) N/A ±135°/ 10° to 50° per sec. N/A ±135°/ 10° to 50° per sec. 811 x 508 360° endless/240° per sec
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Tilt Angle/Tilt Speed Number of pixels Zoom Ratio
-90° to +25°/1.5 sec. per 115° 6.8 x10^5 25x optical zoom, 300x w/ digital zoom 90° to 0°/300° per sec.(max.) 3.8x10^5(768 x 494) 26x optical zoom, 312x w/ digital zoom +90° to -45°/ 7° to 25° per sec. 2.7x 10^5 10x optical zoom, 10x w/ digital zoom +90° to -45°/ 7° to 25° per sec. 2.7x 10^5 10x optical zoom, 10x w/ digital zoom -4° to 184°/240° per sec 4.1x 10^5 23x optical zoom, 230x w/ digital zoom
Memory Focal Length Remote Maximum Frame Rate Signal System
SNC-RZ30N 32MB 2.4mm to 60mm N 30 fps max.(640 x 480) (NTSC) 3.5mm to 256MB 91.0mm N 30 fps max.(640 x 480) NTSC(Composite) 16MB 4.2mm to 42mm Y 30 fps max.(352 x 240) NTSC 16MB 4.2mm to 42mm N 30 fps max.(352 x 240) NTSC 3.84mm to N/A 88.4mm Y 30 fps (768 x 494) NTSC
Power Supply Protocols
DC 12 V via AC adaptor DHCP, TCP/IP, HTTP, ARP, FTP, SMTP, ICMP, SNMP AC 24 V/DC 12 V TCP/IP, HTTP, ARP, ICMP, FTP, SMTP, DHCP, SNMP, DNS, NTP 12 V DC UPnP, TCP/IP, HTTP, SMTP, FTP, Telnet, NTP, DNS, DDNS, DHCP UPNP, TCP/IP, HTTP, SMTP, FTP, Telnet, NTP, DNS, DDNS and 12 V DC DHCP 24 V AC PELCO-D, Panasonic, Vicon, Samsung Electronics
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