helicopter flight time in teams of 4/5 experiment with the design of a helicopter to result in...
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Helicopter Flight Time
In teams of 4/5
Experiment with the design of a helicopter to result in maximum flight time
Money is only available for only10 prototype helicopters
What changes will you test to determine the best design?
Time 60 Minutes
Helicopter Design
Target: Maximise flight time
Y (seconds)
Changes allowed: (Design Parameters)
X’s (below)
X1: Wing length 90mm 115mm
X2: Wing Chord 55mm 65mm
X3: Weight 1 clip 2 clips
X4: Stiffness card paper
X5: Body length 85mm 100mm
X6: Body width 35mm 45mm
X7: Wing joint tape no yes
110 or 130 mm
35 or 45 mm
85 o
r 10
0 m
m
35 m
m
90 o
r 11
5 m
m
Paper clip
Standard Maximum
Wing Joint Tape
Helicopter
Proto Paper No. Taped Body Body Wing Wing FlightType Type Clips Wing Width Length Chord Length Test
Result
Strategy and Results
1
2
3
4
5
6
7
8Confirm
You have 60 minutes
You only have 10 attempts
How do you choose which experiments to run?
Go !
Who had the best time ?
Did The winner only use 10 prototype helicopters?
How do they do this in the real world?– The helicopters cost real money to build– They cost real time to build– You can’t just keep building new helicopters to find the best one
“One Factor at a Time”
Set baseline combination of conditions
Change one factor
If better, keep the change and try next factor
If results not improved, revert and try next factor
“One Factor at a Time” Strategy
ExperimentPapertype
No. Clips Tape
Bodywidth
BodyLength
WingChord
WingLength
1. Standard – – – – – – –
2. Paper Trial + – – – – – –
3. Clip Trial – + – – – – –
4. Taped Wing Trial – – + – – – –
5. Wide Body Trial – – – + – – –
6. long Body Trial – – – – + – –
7. Wide Chord Trial – – – – – + –
8. Long Wing Trial – – – – – – +
“Stick With a Winner” Strategy
Experiment Result
1. Standard – – – – – – – 2.0
2. Paper Trial + – – – – – – 2.4
3. Clip Trial + + – – – – – 2.2
4. Taped Wing Trial + – + – – – – 2.2
5. Wide Body Trial + – – + – – – 2.4
6. Long Body Trial + – – + + – – 2.6
7. Wide Chord Trial + – – + + + – 2.7
8. Long Wing Trial + – – + + – + 3.0
Papertype
No. Clips Tape
BodyWidth
BodyLength
WingChord
WingLength
“One Factor at a Time”
The results from changing one factor at a time could be plotted as the changes in the output Y against the change in a particular factor X
The “One Factor at a Time” approach can help to find the best design
But do the settings of the other Xs affect the amount of change in Y due to change in the selected factor?
Y
Paper typeX1
Y
Wing ChordX3
Y
Body lengthX2
Y
Wing SpanX4
Will these approaches always work?
Interactions between factors can and often exist.
Indeed, interactions can have a greater effect on the output than changes in individual factors
One factor at a time experiments cannot identify interactions between the Xs
If the optimum performance depends on interactions one factor at a time experiments will not find the optimum
Results can depend on the order of the experiments!
So “One Factor at a Time” or “Stick with a Winner” do not always work !
How do you find the best design ?
“One Factor at a Time” and “Stick with a Winner” approaches are good
They can reduce the number of experiments you need to perform
ie reduces cost
However they do not always work
If the factors are inter-related
Result can depend no the order you carry out the tests
“Test them All”
The best approach may be to test all possible combinations
How many prototypes would this need for our helicopter?
If you assume that each factor can only take on 2 values ie Body width 35mm or 45mm (not 40mm)
We need 128 prototypes to test every combination
That is way too many – way to expensive
How do you find the best design?
How do you find the best design?
every time?
With minimum number of prototypes?
Lowest cost?
Look up “Design of Experiments” on the web
– you might find a way
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