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Decision Presentation:
Frame
Tyler Bork
Friday, February 10, 2006
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Agenda
• Frame– Past to Present
• Assembly• Mock-Up • FMEA• Stress Analysis
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Initial Frame Design
Redesigned Initial DesignInitial Design
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Refined Frame Design
New Design from Scratch
Final Design
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CAD Assembly
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Full-Scale Frame
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Operator Position
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Mock-up Conclusions/Plans
• Overall Visibility: good• Accessibility: good• Overall Look: Is something consumers
would like/approve
• Future Plans include adding weather protection for further visibility questions
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FMEA
• Roll cage collapse due to frontal crash• Roll cage collapse due to roll over• Collapse of control-arm frame posts• Steering linkage disengagement• Loosening of seat• Overloaded bending of steering column• Roll cage bending when supporting weight at contact point• Floor support bend due to sudden shock• Storage compartment overloading• Adjustable seat malfunctions• Impact failure to control/swing arm connections• Tipping due to off center loading• Person stands on edge and vehicle tips over onto them• Seat belt connections loosen• Suspension spring failure• Environmental protection tearing/breaking when hit with object• Seat springs overload/break• Detachment of motor and housing
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Detailed FMEA Analysis
Worst-Case Stress Application Frame Failure
Failure ModeSEV
OCC
DET
RPN
Swing Arm Connection Failure 8 5 8 320
Recommendations: add some sort of additional support that would keep swing arm temporarily functional in the event of a failure
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Stress Analysis Concentration
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Rear Forces
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Free Body Diagram
½ Fr
½ Fr
FD
FD
Fy
Fy
Fx
Fx
Front ofVehicle
0
θ1
θ1
θ2
θ2
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Worst Case Scenario
• 15 ft radius, 10mph
• Weight Transfer or Body Roll
• Accelerating into turn (max Torque)
• Estimate Loads @ 4 different points
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Weight Transfer for Turn
Total Weight 800 lb (Team Skid Mark)Weight transfer =
( acceleration x Weight x Height of CG ) / Track width
215.6 lb
277.75 lb
144.4 lb
162.25 lb
100 lb
535 lb
80 lb
70 lb
180 lb
220 lb
180 lb
220 lb
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Material Selection
xzτ
- Unknowns = D, d- Use manufacturer value
xσ
( ) ( )
( )
( )2
8.12
6
2
464
2
22
22
2
2244
dDd
dDd
Q
QT
dD
F
dD
DM
xz
x
AxialBendingx
−+⎟
⎠⎞
⎜⎝⎛
−⎟⎠⎞
⎜⎝⎛
=
=
−+
−
⎟⎠⎞
⎜⎝⎛
=
+=
π
π
τ
ππσ
σσσ
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Material Selection
• Use Factor of Safety of 3- Model approx. represents system- Fairly representative material test data
• Inquire machineability, cost, availability• Create MatLab Program• FEA Validation• Analyze other potential worst-case scenarios
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QUESTIONS
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Refined Mock-up Materials
• Materials Used:• Finalized Frame Design (Solid Edge drawing)• Schedule 40 ½” PVC• Tape Measure• Duct Tape• Metal Tie Wire
Total Material Cost: $25
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System of Equations
)cos*()*()cos2
*()cos2
*()*(
)sin(22)sin2
(2
)cos(22)cos2
(2
25413121
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θθθ
θθ
θθ
Dxrr
xyo
Dxr
Dxr
x
FlFlFlFlFlM
FFFFy
FFFF
++−−=
++=
++−
=
∑
∑
∑
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½ Fr
½ Fr
FD
FD
Fy
Fy
Fx
Fx
Front ofVehicle
0 θ1
θ1
θ2
θ2
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Future Analysis
• Creation of shear and bending moment diagrams
• Analysis of stress due to bending moment and selection of suitable material– Based on material strength needed vs. tubing
thickness• Create MatLab or Microsoft Excel Program• FEA Validation
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