1. 4th Edition
Chapter 24
Design Step #4:
The Design Details

2. What You Will Learn
Use math when you can to pin down operation of your concept
Experimentally model other unknowns
How to prepare detailed drawings of wht you have accomplished.
Exploring Engineering 2

3. Detailed Design Analysis of design Detailed drawings
Mathematical models as needed
Models of parts of concepts as needed
Detailed drawings
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4. Analysis
You have a boat made of a material of thickness 0.10 m and thermal conductivity 1.50 W/m°C with a power source on board that is producing 150. watts/m2 of heat. The surrounding water is 20.0°C. The boat material cannot exceed 100.°C. Should you risk the operation of your design without estimating the maximum temperature?
Ts, power source
0.01 m
20.°C
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5. Analysis Fourier’s Law of Heat Conduction:
Even if the model is crude in this case the leeway is sufficient to say the material will be OK.
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6. Experiments That Remove Uncertainty
Often make a crude model of what you want to design and use it to get the bugs out.
“Dueling Duffers” device
to deposit balls onto a board
against an opposing team
Model used in the experiment to
determine how to deliver balls
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7. What Model Experiments Will Help?
Sources of Risk and Uncertainty
1. Will all 10 balls fit in the top half of the 2-liter bottle?
What is the optimal height from which to dump the balls?
3. Will all 10 balls drop into the hole when dumped in this manner?
4. Is it important to have the vehicle perfectly positioned before dumping the balls?
5. Will the machine travel slowly enough that its position can be easily controlled?
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8. Detailed Drawings Normally engineering drawings:
Are not hand drawn unless very neat
Drawn to scale
At least two orthogonal views
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9. Detailed Drawings Concluded
Show hidden lines as dashes when they enhance clarity.
Show only essential dimensions that either have a direct impact on performance or needed to demonstrate geometry constraints are satisfied.
Use notes or labels to indicate material specification, part type, and assembly directions.
It is acceptable if the manufacturing details are incomplete. Students who lack the experience to fully specify them have to discover those details by trial and error during building.
If an electric circuit was designed, show it in the form of a neatly hand-drawn but fully specified circuit diagram.
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10. Design Milestone: Detailed Design
Assignment
1. Use analysis, experiments, and models to help establish dimensions and proof of concept.
2. Prepare detailed drawings of the design concept you selected.
Documentation
Write the analysis details in the usual format, stating all assumptions. For each experiment (a) state the purpose of the experiment, (b) describe the experimental procedure, (c) present results, and (d) state conclusions.
Summarize useful information yielded by models and turn in models.
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11. Design Milestone: Detailed Design
Grading Criteria
From examination of the detailed drawings, does the design have a chance of working?
Have opportunities to reduce the level of risk (through analysis, experiments, and models) been fully exploited?
Is there enough information in the detailed drawings to manufacture the design?
What is the overall quality of the detailed drawings?
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12. Design Composition Tips
Time spent upfront on analysis, experiments, models and detailed drawings pays off later in fewer design iterations during manufacturing and testing.
Of the four methods for reducing risk, good detailed drawings reap the most rewards in a freshman design project.
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13. Summary Analyze with numerical answers where possible
Experiment with models to reduce design risk
Computer or carefully hand draw detailed design (Remember someone has to read this to build it!)
Document what you have done