solutions to assignment #1 - university of...

MECH 350 – Engineering Design I Spring Term 2017

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Solutions to Assignment #1 Exercises on Problem Formulation In some cases, a client’s request may actually be the client’s perceived approach to solving a problem, and not actually the underlying fundamental “need.” Exercise #1: A plausible “need” for the request for a window with higher insulative properties, could be: Need: “There is excessive heat loss and heating costs for the client’s building.” Goal: “Conduct an energy audit to determine the cause and location of the heat loss. (Perhaps the windows are not the source of the problem). Upon finding the source of major heat loss, modify/redesign that source to reduce heat loss” Alternate Goal: “Install a more energy efficient heating system, such as a heat pump, to lower the heating costs for the building” Either of these goals may satisfy the “need” without requiring the design of new windows. Exercise #2: Like most client requests of this type, the request for car tires with improved grip may actually be the client’s perceived approach to solving a more fundamental “need.” A plausible “need” for tires with improved grip could be: Need: “There are excessive car crashes in the client’s community as a result of poor tire traction in bad weather conditions.” Goal: “Offer a safety course to teach safe driving skills for the community, for bad weather driving” Alternative Goal: “Increase signage in areas of high crash zones, to warn of bad traction in those areas” Either of these goals may satisfy the “need” without requiring the design of new tires. Exercise #3: A plausible “need” for the request for a new roadway with twice the lanes in both directions, could be: Need: “There is excessive vehicle traffic on the roadway, which results in long commute times.” Goal: “Conduct an analysis to determine the cause of traffic, including the average sources and destinations of people. Implement new public transit services to serve sources and destinations.” Alternate Goal: “Conduct an analysis to determine cause of traffic. Consider smart-sensor based stop lights, and bypasses/overpasses for local traffic, to prevent bottlenecks on main roadway.” Either of these goals may satisfy the “need” without requiring the doubling of roadway lanes in both directions. Exercise #4: A plausible “need” for the request for a computer that is 50% faster than current models, could be: Need: “The existing computer is taking too long to complete computationally intensive tasks such as video processing, or CAD.” Goal: “Check the existing computer’s resources such as available memory, hard-drive space, and running to many concurrent programs, to ensure there are adequate resources to perform the computational tasks.” Alternate Goal: “Evaluate the computational tasks to see if they meet the needs of the work, or if too much/excessive detail is being processed, where that level of detail is not actually needed.” Either of these goals may satisfy the “need” without requiring a computer that is 50% faster than current models.


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Exercise #5: A plausible set of Design Objectives for the “Alternative Goal” in Exercise #2 are:

Design Objective Description/Justification Value (Units)

Signage Size Size of signboard. Larger signs will be more visible and attract the driver’s eyes/attention to the sign.

2 x 2 (H x W) (m)

Signage Frequency Defined as the number of signs per km. A higher number indicates more opportunities for driver to notice/read it.

0.5 (signs/km)

Signage Clarity Signage should have a clear meaning, appropriate color, and a clutter-free appearance. The driver should be able to understand the meaning of the sign within 2 seconds or less, where this objective is measured in time to understand.

2 (seconds)

Signage Location Signage should be placed near areas that are know to be dangerous points on the road, or where accidents have frequently occurred in the past.

1 (kms prior to dangerous points)

Use Appropriate Warning Messages

Ensure message indicates problems: of poor traction, weather conditions leading to problems, and maximum speeds.

Yes (yes/no)

Speed Suggestion For signs indicating maximum speed, use a value of 50 km/hr or less.

50 (km/hr)

Exercise #6: Given the “Goal” described in Exercise #3, a set of information gathering steps are required prior to establishing the design objectives for the design of “Implementing new public transit services to serve sources and destinations”. The info gathering steps are: (a) Analysis of source of people, by recording number of people coming from each source, and location of each source, to understand traffic problem. (b) Analysis of destination of people, by recording number of people going to each destination, and location of each destination, to understand traffic problem. A plausible set of Design Objectives are:

Design Objective Description/Justification Value (Units)

Transit system capacity per route

The number of people/hour that a potential transit system can move per route.

1000 (People/hr)

Transit system cost per route

The cost of a potential transit system to build and install. 5 ($million/route)

Fee charged to rider of transit system

The fee charged to the rider of the transit system 1 ($/ride)

Rider satisfaction with system

Survey should be done each year to assess rider satisfaction 7 (happy units)

Government subsidy per route

Since public transit is the goal, the benefits of the system reduce traffic for all. Government will provide a subsidy.

100 ($thousand/ year x route)

Operating cost, per year, per route

The cost of operating the transit system per year, per route, including fuel/energy costs, driver/operator salaries, etc…

200 ($thousand/ year x route)

Maintenance cost, per year, per route

The cost of maintaining the transit system per year, per route 100 ($thousand/ year x route)


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Exercise #7 (See Page 4): The diagram on page 3 is one possible approach to the functional block diagram. There are many other possibilities. The key point is to identify the inputs and outputs, and to describe the main functions that transform the inputs into the outputs as can be seen below. Note: The blocks within the diagrams are “function-based”, and the arrows represent “components or parts.” Exercise #8 (See Page 5): The diagram on page 4 is one possible approach to the functional block diagram. There are many other possibilities. The key point is to identify the inputs and outputs, and to describe the main functions that transform the inputs into the outputs as can be seen below. Note: The blocks within the diagrams are “function-based”, and the arrows represent “components or parts.” Exercise #9 (See Page 6): The diagram on page 5 is one possible approach to the functional block diagram. There are many other possibilities. The key point is to identify the inputs and outputs, and to describe the main functions that transform the inputs into the outputs as can be seen below. Note: The blocks within the diagrams are “function-based”, and the arrows represent “components or parts.”

High Level Diagram

&ƵŶĐƟŽŶĂůůŽĐŬŝĂŐƌĂŵĨŽƌĂŝĐǇĐůĞ

Žnvert MechanicalŶĞƌŐǇƚŽDŽƟŽŶ

OperatŽr Input (Pedalling) OrientaƟŽn ŽĨ MŽƟŽn

Speed ŽĨ MŽƟŽn

NŽise & Heat KƉĞƌĂƚŽƌ/nput (Hand pŽsiƟŽn)

4. ƌŝǀĞWĞĚĂůƐƚŽDŽǀĞZŽůůĞƌŚĂŝŶ

OperatŽr Input (Pedalling)

NŽise & Heat

Mid-Level Diagram

1. Steering theĨƌŽŶƚǁŚĞĞů

ϱZŽtate theZĂƚĐŚĞƚDĞĐŚĂŶŝƐŵ

6. ZŽtate theƌĞĂƌǁŚĞĞů

KƉĞƌĂƚŽƌ/nput (Hand pŽsiƟŽn)

2. Engage the rŽllerĐŚĂŝŶŽŶƚŚĞƐĞůĞĐƚĞĚƐƉƌŽŬĞƚƐ

3. ApplǇ ĨricƟŽn tŽƐůŽǁĚŽǁŶƚŚĞƌŽƚĂƟŽŶŽĨǁŚĞĞůƐ OrientaƟŽn

ŽĨ MŽƟŽn

7. ZŽll Žn rŽadƐƵƌĨĂĐĞ

Speed ŽĨ MŽƟŽn

MŽving chain ZŽƚaƟng hub

Chain pŽsiƟŽn

ZŽƚaƟng ǁheel

FricƟŽn

>ŽǁĞƌͲ>ĞǀĞůŝĂŐƌĂŵ&ŽƌϰDrive WĞĚĂůƐƚŽZŽƚĂƚĞZŽůůĞƌŚĂŝŶůŽĐŬ NŽise& Heat

Chain pŽsiƟŽn

MŽving Chain4.1. ZŽƚĂƚĞ

ƌĂŶŬ4.2. ZŽƚĂƚĞŚĂŝŶZŝŶŐ;^ƉƌŽĐŬĞƚ^ĞƚͿ

4.3. ZŽƚĂƚĞZŽůůĞƌŚĂŝŶ

MŽving SprŽcŬetTeeth

OperatŽrInput (Pedalling)

^ŽůƵƟŽŶƚŽǆĞƌĐŝƐĞηϳMECH350 - Engineering Design I


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Exercise #10: This exercise clearly provides for a large number of possible solutions using any combination of the available resources. However, this exercise is designed mainly to illustrate the presence of a cultural barrier. In this sense, the “idea” of suggesting the solution of having the occupants of the room urinate into the pipe. It is interesting to see how many students would suggest that alternative when the exercise is used in the classroom and Individuals are called on to describe their solutions. More students are likely to include the urination option if the exercise is a written assignment in which they do not have to reveal their options to classmates. Exercise #11: For this question, there are an infinite number of possible solutions. Some examples include: Scissors Advantages:

• Great for cutting herbs • Shredding papers for creating arts and craft projects • Faster cut with multi blades • Multiple cut in one step • Shred confidential documents • Has more grip on paper so the paper will not slip • Can make small confetti

Coffee table Advantages:

• Easy to manufacture • Has a modern style • Easy to move • No sharp corners to hit legs • If material is elastic, the height of the table can be adjusted as desired • Good for a person on wheel chair (because no table legs get in the way)

Exercise #12:

1) clasp sheets of paper 2) tie clasp 3) barrette 4) key chain 5) jewelry (interlock to form necklace) 6) finger nail cleaner 7) bookmark 8) bag sealer 9) flathead screwdriver 10) substitute zipper handle 11) toothpick 12) lock pick 13) jump rope (long chain) 14) engraving tool 15) cigarette holder 16) To reset electronic devices (those with little holes to do it)


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17) Hold notes in cork or Styrofoam boards 18) As electronic wire (better if it has a plastic cover)

Exercise #13:

1) Steering for a car, whereby wheel turns pinion and rack moves wheels 2) Raise or lower windows whereby pinion rotation advances/recedes rack(window) 3) Open or close slider doors whereby pinion rotation advances/recedes rack(door) 4) Gantry style crane, whereby crane structure has pinion wheels that ride on a rack, and prevents

slip of crane when pinions are stopped. 5) Elevator whereby pinion is on elevator, which is in mesh with stationary racks 6) Press mechanism whereby pinion is turned by hand, using mechanical advantage to create high

force while driving the rack(press) downward 7) Window shutters, whereby each vane rotates on its own pinion, and all pinions are in mesh on

one rack. 8) Precision machine whereby rotating pinion precisely advances rack by specific amount of linear

distance. 9) Rail system for mining, whereby ore cars with pinion wheels are in mesh with a rack (part of the

track), allowing them to ascend/descend on steep inclines. 10) Metal forming machine whereby sheet metal passes between a rack and pinion to create folds

(impressions) with a precise pitch distance, on the sheet metal. Exercise #14:There are many acceptable solutions. One possible solution is:

Morphological Chart: New Ways to Harvest Wind Energy

Blade Technology Classic Windmill Airfoil Blade Windmill Helix Wind Turbine Wind Sails

Har

vest

Loc

atio

n Mountain Yes Yes Yes Ocean Yes Yes Yes Idea #3

Flat Field Yes Yes Yes

Tunnel Idea #2

Airborne Idea #1 Idea #4

Yes: Means there is an obvious/reasonable use of existing technology.

Blank: Means an idea could not be created from the combination.

Idea #1: Emergency turbine that could be deployed to generate power on aircraft, in case of main engine failure.

Idea #2: Some tunnels have natural/perpetual winds. Helix could occupy tunnel space to generate power.

Idea #3: Kite-like device that propels ship across the water. i.e. direct energy transfer for propulsion.

Idea #4: Kite-like device that acts as parachute to brake/slow down airborne craft.


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Exercise #15: There are many acceptable solutions. One possible solution is:

Morphological Chart: Vibration/Motion Energy Harvester

Available Vibration/Motion Source Person Walking Car/Machine Motion Water Motion Air Motion

Loc

atio

n of

Use

Building Yes Idea #1 Idea #2 Road Yes Yes Idea #3 Ocean Yes

Forest Yes Idea #4

Windy Hill Yes

Yes: Means there is an obvious/reasonable use of existing technology.

Blank: Means an idea could not be created from the combination.

Idea #1: Harvest waste water motion as it exits pipes from building

Idea #2: Buildings often have large drafts in vertical locations such as stairwells, elevator shafts, or other. Mount a wind harvesting system within these drafty locations in a building.

Idea #3: As a motor vehicle drives past the sidewalk, pedestrians can “feel” the air movement. Create a system on the sidewalk that harvests the air movement from motor vehicles.

Idea #4: Place spring-based oscillatory generator between two trees. As trees sway from the wind, they drive the generator to produce electricity.

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Exercise!#16!(See!page!11):!One%possible%solution%example%is%shown:%%%


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