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Chasis Design

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This document summarizes the conceptual design of an electrically assisted human powered vehicle. It evaluates different design concepts and materials for key components like the vehicle frame, impact mitigation members, body, and ingress/egress based on criteria like cost, reliability, safety, and performance. For the main frame, a double tube design is recommended for stiffness. Aluminum 6061-T6 is selected as the material. Air springs are selected to connect the upper body canopy due to better reliability.

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Electrically assisted human powered vehicle
Evaluation Criteria Cost (6) Reliability (9) Safety (5) Manufacture-ability (7) Design-ability (7) Performance (8)
Functional Decomposition Frame (Arshad, Keyush) Impact Mitigation Members (Erdal) Body (Jason) Ingress/Egress (Babak)
Main Frame Conceptual Evaluation Fabrication Rear Wheel Support Connections with Body Material selection Method for fore/aft torsion and bending transfer Battery/electrical support Front wheel support Crank shaft support
Fabrication In fabrication, welded joint gives better over all output compare to monotube and coupling in above characteristics. Weight Alternatives Monotube Welded Parts Coupling Cost 6 4 6 5 Reliability 9 7 7 6 Safety 5 8 7 6 Manufacture-ability 7 6 8 7 Design-ability 7 5 6 6 Performance 8 8 8 7 268 296 261
Rear wheel lower support (2 point connection) Out of above three alternatives longitudinal bar is proper choice. Weight Alternatives Rear - T bar Direct connection Longitudinal bar Cost 6 5 6 4 Reliability 9 8 6 9 Safety 5 5 5 5 Manufacture-ability 7 7 8 6 Design-ability 7 6 7 6 Performance 8 8 7 9 282 276 286
Rear wheel upper support (1 point) Decision Matrix From Single and double angle alternative single angle is ideal because above decision matrix. Weight Alternatives Single Angle Double Angle Cost 6 6 5 Reliability 9 8 9 Safety 5 6 6 Manufacture-ability 7 8 7 Design-ability 7 8 7 Performance 8 7 8 306 303
Connections with Body For connecting body bracket, bolt and rivet connection is mostly depend on application and location of connection. Weight Alternatives Bracket Bolt Rivet Cost 6 5 6 7 Reliability 9 9 8 7 Safety 5 6 5 6 Manufacture-ability 7 5 6 7 Design-ability 7 6 7 7 Performance 8 9 8 7 290 288 289
6061-T6 aluminum alloy is selected Light weight Proper physical and mechanical properties Corrosion resistance Weldability Material selection Criteria Weight Alternatives Steel Carbon fiber monocoque Aluminum Cost 6 9 5 7 Reliability 9 7 8 8 Safety 5 7 8 7 Manufacture-ability 7 8 5 7 Design-ability 7 7 5 7 Performance 8 6 8 9 Weight Total 305 276 319
Double structure is selected Redundancy Better torsional stiffness Simple structure to produce Better support of the components and the body Method for fore/aft torsion and bending transfer Criteria Weight Alternatives Center tube Double tubes Triangular assembled beam Cost 6 9 8 6 Reliability 9 5 8 9 Safety 5 5 7 8 Manufacture-ability 7 8 7 6 Design-ability 7 6 7 6 Performance 8 6 8 6 Weight Total 270 317 289
Batteries are located behind the seat Adjustability adds more complexity Close to the rider for concentrated CG Proper space behind the seat Battery/electrical support Criteria Weight Alternatives Underneath the seat Behind the seat Behind the seat and adjustable for CG Cost 6 5 8 6 Reliability 9 6 7 9 Safety 5 7 6 8 Manufacture-ability 7 5 7 5 Design-ability 7 6 7 6 Performance 8 6 8 7 244 303 290
90尊 tube bracket is selected Strong joint Proper load transfer Simple assembly Better support of the main tube Front wheel support Criteria Weight Alternatives T bar (hollow for hinge) 90尊 tube bracket Direct connection Cost 6 5 5 7 Reliability 9 6 8 6 Safety 5 6 8 7 Manufacture-ability 7 6 7 7 Design-ability 7 7 7 7 Performance 8 6 8 7 253 304 285
Single bar is selected Light weight Simple structure to produce Low cost Crank Shaft Support Criteria Weight Alternatives Single bar, same as typical bicycle Double beams Cost 6 8 5 Reliability 9 6 7 Safety 5 6 7 Manufacture-ability 7 8 7 Design-ability 7 8 7 Performance 8 8 7 308 282
Final Concept
3D model of the main body frame in NX
4 views of the main body frame
Stress analysis of main single tube The main tube is located between the back wheel and the axel suspended to the front wheels. This is a simple beam condition, there are no moments supported at the end points. Assumed CG is on 1/3 of wheel base measured from front wheels For different riders, CG changes, so the center of the tube is considered as the critical point for this analysis
Calculations Wheelbase: L= 1.5 m Total weight = 165 kg Frame and Body (40) Rider (100) Batteries (10) Electric motor (5) Chain drive system (10) Uncertainty factor= 1.1 Total force (Ft)= 165 x 9.8 x 1.1 Ft= 1778 N Reaction force at front wheel: Ff = Ft / 2 =889 N
Tube diameter and thickness Moment at the center of the tube M = Ff x L/2 = 667 Nm For tubular cross section maximum stress on the outer layer of the tube is: max =Mc/I (Eq.1) Al- 6061-T6 Tensile Yield Strength = 276 MPa max = yAl = 276 MPa c= do/2 (Eq.2) Second moment of inertia is: I= 仍 x do^3 x t/8 x (1-3t/do +4t^2/do^2) (Eq.3) Where t and do are wall thickness and outer diameter of the tube, respectively By solving equations. 1, 2 and 3 for t do is obtained as follow: t= 3 mm do= 36 mm t= 2 mm do= 42 mm
Bending stiffness for t= 2 mm tube thickness Kb= EI/L^3 (Eq.4) Al- 6061-T6 Modulus of Elasticity (E) = 68.9 GPa t= 0.002 m and do= 0.042 m Eq.3: I= 5 x 10^(-8) m^4 Kb = 1029 N/m Axial stiffness (Ka) Ka= AE/L (Eq.5) A= 仍 x do x t x (1-t/do)= .00025 m^2 (Eq.6) Ka= 11.54 MN/m
Torsoinal stiffness Kt= JG/L (Eq.7) Al- 6061-T6 Shear Modulus (G) = 26.0 GPa Shear Strength= 207 MPa J= 2I= 10 x 10^(-8) m^4 (Eq.8) Kt= 1733 Nm/deg
Torsional Analysis of the main tube 龍 =Tr/J (Eq.9) Considering 1/3 total length of main tube from front axel for CG location and Ft= 1778 N reaction force from center of axel is: 2/3x1778= 1185 N Reaction force of the front wheel (Fr)= 1185/2= 592 N On slope in turning and braking condition Fr is multiplied by 3: Maximum force (Fm)= 592 x 3= 1776 N Distance between the end of front axel and the wheel= 0.1 m Distance between wheels (Wd)= 1.2 m Torque (T)= 0.6 x 1776 N = 1065 Nm r= do/2= 0.021 m (Eq.10) J= 10 x 10^(-8) m^4 Maximum shear stress ( 龍 max)= 1065 x 0.021/ 10 x 10^(-8)= 224 MPa 224 > 207
=> 龍 max > Shear Strength This shows that single tube with specified dimension is not proper as a main tube. Minimum bending, torsional and axial stiffness 龍 =Tr/J (Eq.9) I= 仍 x do^3 x t/8 x (1-3t/do +4t^2/do^2) (Eq.3) J= 2I (Eq.8) r= do/2 (Eq.10) Torque (T)= 1065 Nm 龍 max= 207 MPa By substituting in eq.9 for t= 0.002 m do is 0.0418 m: t= 2 mm => do= 44 mm I= 5.8 x 10^(-8) m^4
Bending stiffness: Kb= EI/L^3 (Eq.4) Minimum Bending stiffness (Kb-min)=1830 N/m Axial stiffness: Ka= AE/L (Eq.5) A= 仍 x do x t x (1-t/do)= .000264 m^2 (Eq.6) Minimum Axial stiffness (Ka-min)= 12.12 MN/m Torsoinal stiffness: Kt= JG/L (Eq.7) J= 2I= 11.6 x 10^(-8) m^4 (Eq.8) Minimum Torsional stiffness (Kt-min)= 2011 Nm/deg
Source www.matweb.com/index.aspx (Material properties)
Results Considering 龍 max > Shear Strength specified t= 2mm and do= 42 mm tube does not satisfy the safe condition In motion 50% extra load is needed to compensate the impact in acceleration, breaking and turning for the main tube. To solve mentioned problems using two tube with t= 2 mm wall thickness and do= 42 mm outer diameter for the main tubes is recommended (sketch page 6)
Impact Mitigation Members Conceptual Evaluation Protection Methods Material
ROLLOVER PROTECTION Fully visible outside the rider silhouette when viewed from the front or rear, and conform to the following dimensions. Height above helmet - 150 mm minimum Width at top of helmet - 150 mm minimum either side of the helmet Width at shoulder level - 50 mm minimum either side of the shoulders Forward or rearward - no more than 150 mm of the rider's helmet Roll bar shall envelope the rider when viewed from either front or rear. The forward leg roll bar must protect the riders legs, knees and feet from being crushed in a rollover or side slide situation and must be mounted across the vehicle above the riders knee area. (Front side Protection) Composite Material Aluminum or CrMo
Side Bar Rollbar Composite Material ( Carbonfiber-Honeycomb core) Airbag Protection Methods for Impact Criteria Weight Alternatives S bar Air Bag Side Bars or Rollbar Composite Mat. for surface support None Cost 8 4 2 9 5 10 Weight 9 4 3 7 8 10 Safety 9 7 10 7 7 0 Reliability 9 7 9 7 7 0 Easiness of Mounting (Frame material is Aluminium) 6 8 2 8 3 10 Manufacturability 7 5 2 8 7 10 Design-ability 7 6 2 8 7 10 Complexity 6 5 2 8 7 10 Low C.O.G. 5 4 2 7 8 10 Affect to the Performance 4 6 3 7 8 10 Weight Total 393 288 532 468 520
SIDE PROTECTION * Minimum 50 mm clearance around the rider and shield the area between the riders hip and shoulder from contact with another vehicle and be constructed of material type, size and integral strength similar to the roll bars. Rollbar and Side Bar Materials Criteria Weight Alternatives Aluminum CrMo Composite Cost 8 7 8 5 Weight 9 6 4 7 Impact Absorption 9 7 8 7 Reliability 9 7 8 7 Easiness of Mounting (Frame material is Aluminium) 6 8 6 5 Manufacturability 7 8 7 6 Design-ability 7 8 8 7 Low C.O.G. 5 6 4 7 Affect to the Performance 4 6 5 7 Weight Total 450 425 413
Material is Aluminum 6061-T6 as used in frame. Tubing diameter is taken from Frame tubing diameter.
References: www.matweb.com www.alcotec.com http://www.racvenergybreakthrough.net/PDF/Handbook07/Handbook07-PartB-HPV.pdf
Body Conceptual Evaluation Vent Location Body Material
Front Inlet (Side View) Side Inlet (Top View) Corner Inlet (Top View) - Frontal inlet is selected - Highest static pressure and thus result in the greatest airflow at given speed. - Minimal impact on airflow over the surface Air Vent Location
Required Air Flow Rate - This study recommends that 6liters of air per minute be passed over a body during exercise to maintain an acceptable temperature. (assumes an ambient air temp of 20deg C. http://academic.uprm.edu/~mgoyal/fluidsjuly2004/cooneychapter5.pdf -It is assumed that 6 times this is required to maintain the electronics at 33deg C. - Assuming that the flow rate through the vent is 1/10 of the vehicle speed the vent area must be. 3.6cm^3
Body Material Selection - Fiber-glass is selected - Light weight and durable - Some risk of compounding injury in the event of a crash - Plexiglases will be used for the window material
Body Drag Analysis Methodology An elemental analysis was performed. Multiple 2D analysis were performed on slices of the body and these results were integrated to determine an estimate for the overall body drag
http://www.aeronautics.nasa.gov/docs/rpt460/discuss.htm Element (2D Symmetric Airfoil) Drag As a Function of Aspect Ratio (Thickness to Length)
Drag Results Frontal Force = 12N Pressure Centre = 0.5m Vehicle Height = 1.25m Vehicle Width = 1m Vehicle length = 2m Power as a Function of Air Speed
Ingress Egress Conceptual Evaluation Sealing Method Connection Method Note: Last week this style of ingress method was justified.
Sealing Method Self Sticking Vinyl Weather Stripping Tape Economical Applicable on irregular surfaces Meets General Motors Specification 6086M-IA; Ford ESB M3G 102-A; Chrysler MSAY 511-A, B and C Length: Each roll is 17 feet Cost: approx. $ 5 each roll Universal bulb style adhesive Backed Weather Stripping Very high sealing rate Dimension: 7/8" wide X 3/4" thick X 8' long Cost: approx. $ 16.05 http://www.pplmotorhomes.com http://www.metrommp.com/
Sealing Method Criteria Weight Alternatives Self sticking weather stripping tape Universal bulb style adhesive backed weather stripping Cost 6 5 6 Reliability 9 5 8 Safety 5 6 7 Manufacture-ability 7 8 8 Design-ability 7 8 8 Performance 8 5 8 257 319
Connection Method ( Air spring Vs. Coil spring ) http://www.stabilus.com
Connection method comparison In the above vehicle the upper body is lifted by two air spring and is kept in place with the hinge. The lower figure shows that the upper body is connected to the lower body just with two heavy duty hinges and coil spring
Decision Matrix for Connection method Connection method ( Canopy to the main body Shell) Criteria Weight Alternatives One central Hinge with the Air spring Two side Hinges with coil spring Cost 6 6 5 Reliability 9 7 5 Safety 5 6 7 Manufacture-ability 7 8 8 Design-ability 7 8 8 Performance 8 8 5 305 262

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Chasis Design

  • 1. Electrically assisted human powered vehicle
  • 2. Evaluation Criteria Cost (6) Reliability (9) Safety (5) Manufacture-ability (7) Design-ability (7) Performance (8)
  • 3. Functional Decomposition Frame (Arshad, Keyush) Impact Mitigation Members (Erdal) Body (Jason) Ingress/Egress (Babak)
  • 4. Main Frame Conceptual Evaluation Fabrication Rear Wheel Support Connections with Body Material selection Method for fore/aft torsion and bending transfer Battery/electrical support Front wheel support Crank shaft support
  • 5. Fabrication In fabrication, welded joint gives better over all output compare to monotube and coupling in above characteristics. Weight Alternatives Monotube Welded Parts Coupling Cost 6 4 6 5 Reliability 9 7 7 6 Safety 5 8 7 6 Manufacture-ability 7 6 8 7 Design-ability 7 5 6 6 Performance 8 8 8 7 268 296 261
  • 6. Rear wheel lower support (2 point connection) Out of above three alternatives longitudinal bar is proper choice. Weight Alternatives Rear - T bar Direct connection Longitudinal bar Cost 6 5 6 4 Reliability 9 8 6 9 Safety 5 5 5 5 Manufacture-ability 7 7 8 6 Design-ability 7 6 7 6 Performance 8 8 7 9 282 276 286
  • 7. Rear wheel upper support (1 point) Decision Matrix From Single and double angle alternative single angle is ideal because above decision matrix. Weight Alternatives Single Angle Double Angle Cost 6 6 5 Reliability 9 8 9 Safety 5 6 6 Manufacture-ability 7 8 7 Design-ability 7 8 7 Performance 8 7 8 306 303
  • 8. Connections with Body For connecting body bracket, bolt and rivet connection is mostly depend on application and location of connection. Weight Alternatives Bracket Bolt Rivet Cost 6 5 6 7 Reliability 9 9 8 7 Safety 5 6 5 6 Manufacture-ability 7 5 6 7 Design-ability 7 6 7 7 Performance 8 9 8 7 290 288 289
  • 9. 6061-T6 aluminum alloy is selected Light weight Proper physical and mechanical properties Corrosion resistance Weldability Material selection Criteria Weight Alternatives Steel Carbon fiber monocoque Aluminum Cost 6 9 5 7 Reliability 9 7 8 8 Safety 5 7 8 7 Manufacture-ability 7 8 5 7 Design-ability 7 7 5 7 Performance 8 6 8 9 Weight Total 305 276 319
  • 10. Double structure is selected Redundancy Better torsional stiffness Simple structure to produce Better support of the components and the body Method for fore/aft torsion and bending transfer Criteria Weight Alternatives Center tube Double tubes Triangular assembled beam Cost 6 9 8 6 Reliability 9 5 8 9 Safety 5 5 7 8 Manufacture-ability 7 8 7 6 Design-ability 7 6 7 6 Performance 8 6 8 6 Weight Total 270 317 289
  • 11. Batteries are located behind the seat Adjustability adds more complexity Close to the rider for concentrated CG Proper space behind the seat Battery/electrical support Criteria Weight Alternatives Underneath the seat Behind the seat Behind the seat and adjustable for CG Cost 6 5 8 6 Reliability 9 6 7 9 Safety 5 7 6 8 Manufacture-ability 7 5 7 5 Design-ability 7 6 7 6 Performance 8 6 8 7 244 303 290
  • 12. 90尊 tube bracket is selected Strong joint Proper load transfer Simple assembly Better support of the main tube Front wheel support Criteria Weight Alternatives T bar (hollow for hinge) 90尊 tube bracket Direct connection Cost 6 5 5 7 Reliability 9 6 8 6 Safety 5 6 8 7 Manufacture-ability 7 6 7 7 Design-ability 7 7 7 7 Performance 8 6 8 7 253 304 285
  • 13. Single bar is selected Light weight Simple structure to produce Low cost Crank Shaft Support Criteria Weight Alternatives Single bar, same as typical bicycle Double beams Cost 6 8 5 Reliability 9 6 7 Safety 5 6 7 Manufacture-ability 7 8 7 Design-ability 7 8 7 Performance 8 8 7 308 282
  • 15. 3D model of the main body frame in NX
  • 16. 4 views of the main body frame
  • 17. Stress analysis of main single tube The main tube is located between the back wheel and the axel suspended to the front wheels. This is a simple beam condition, there are no moments supported at the end points. Assumed CG is on 1/3 of wheel base measured from front wheels For different riders, CG changes, so the center of the tube is considered as the critical point for this analysis
  • 18. Calculations Wheelbase: L= 1.5 m Total weight = 165 kg Frame and Body (40) Rider (100) Batteries (10) Electric motor (5) Chain drive system (10) Uncertainty factor= 1.1 Total force (Ft)= 165 x 9.8 x 1.1 Ft= 1778 N Reaction force at front wheel: Ff = Ft / 2 =889 N
  • 19. Tube diameter and thickness Moment at the center of the tube M = Ff x L/2 = 667 Nm For tubular cross section maximum stress on the outer layer of the tube is: max =Mc/I (Eq.1) Al- 6061-T6 Tensile Yield Strength = 276 MPa max = yAl = 276 MPa c= do/2 (Eq.2) Second moment of inertia is: I= 仍 x do^3 x t/8 x (1-3t/do +4t^2/do^2) (Eq.3) Where t and do are wall thickness and outer diameter of the tube, respectively By solving equations. 1, 2 and 3 for t do is obtained as follow: t= 3 mm do= 36 mm t= 2 mm do= 42 mm
  • 20. Bending stiffness for t= 2 mm tube thickness Kb= EI/L^3 (Eq.4) Al- 6061-T6 Modulus of Elasticity (E) = 68.9 GPa t= 0.002 m and do= 0.042 m Eq.3: I= 5 x 10^(-8) m^4 Kb = 1029 N/m Axial stiffness (Ka) Ka= AE/L (Eq.5) A= 仍 x do x t x (1-t/do)= .00025 m^2 (Eq.6) Ka= 11.54 MN/m
  • 21. Torsoinal stiffness Kt= JG/L (Eq.7) Al- 6061-T6 Shear Modulus (G) = 26.0 GPa Shear Strength= 207 MPa J= 2I= 10 x 10^(-8) m^4 (Eq.8) Kt= 1733 Nm/deg
  • 22. Torsional Analysis of the main tube 龍 =Tr/J (Eq.9) Considering 1/3 total length of main tube from front axel for CG location and Ft= 1778 N reaction force from center of axel is: 2/3x1778= 1185 N Reaction force of the front wheel (Fr)= 1185/2= 592 N On slope in turning and braking condition Fr is multiplied by 3: Maximum force (Fm)= 592 x 3= 1776 N Distance between the end of front axel and the wheel= 0.1 m Distance between wheels (Wd)= 1.2 m Torque (T)= 0.6 x 1776 N = 1065 Nm r= do/2= 0.021 m (Eq.10) J= 10 x 10^(-8) m^4 Maximum shear stress ( 龍 max)= 1065 x 0.021/ 10 x 10^(-8)= 224 MPa 224 > 207
  • 23. => 龍 max > Shear Strength This shows that single tube with specified dimension is not proper as a main tube. Minimum bending, torsional and axial stiffness 龍 =Tr/J (Eq.9) I= 仍 x do^3 x t/8 x (1-3t/do +4t^2/do^2) (Eq.3) J= 2I (Eq.8) r= do/2 (Eq.10) Torque (T)= 1065 Nm 龍 max= 207 MPa By substituting in eq.9 for t= 0.002 m do is 0.0418 m: t= 2 mm => do= 44 mm I= 5.8 x 10^(-8) m^4
  • 24. Bending stiffness: Kb= EI/L^3 (Eq.4) Minimum Bending stiffness (Kb-min)=1830 N/m Axial stiffness: Ka= AE/L (Eq.5) A= 仍 x do x t x (1-t/do)= .000264 m^2 (Eq.6) Minimum Axial stiffness (Ka-min)= 12.12 MN/m Torsoinal stiffness: Kt= JG/L (Eq.7) J= 2I= 11.6 x 10^(-8) m^4 (Eq.8) Minimum Torsional stiffness (Kt-min)= 2011 Nm/deg
  • 25. Source www.matweb.com/index.aspx (Material properties)
  • 26. Results Considering 龍 max > Shear Strength specified t= 2mm and do= 42 mm tube does not satisfy the safe condition In motion 50% extra load is needed to compensate the impact in acceleration, breaking and turning for the main tube. To solve mentioned problems using two tube with t= 2 mm wall thickness and do= 42 mm outer diameter for the main tubes is recommended (sketch page 6)
  • 27. Impact Mitigation Members Conceptual Evaluation Protection Methods Material
  • 28. ROLLOVER PROTECTION Fully visible outside the rider silhouette when viewed from the front or rear, and conform to the following dimensions. Height above helmet - 150 mm minimum Width at top of helmet - 150 mm minimum either side of the helmet Width at shoulder level - 50 mm minimum either side of the shoulders Forward or rearward - no more than 150 mm of the rider's helmet Roll bar shall envelope the rider when viewed from either front or rear. The forward leg roll bar must protect the riders legs, knees and feet from being crushed in a rollover or side slide situation and must be mounted across the vehicle above the riders knee area. (Front side Protection) Composite Material Aluminum or CrMo
  • 29. Side Bar Rollbar Composite Material ( Carbonfiber-Honeycomb core) Airbag Protection Methods for Impact Criteria Weight Alternatives S bar Air Bag Side Bars or Rollbar Composite Mat. for surface support None Cost 8 4 2 9 5 10 Weight 9 4 3 7 8 10 Safety 9 7 10 7 7 0 Reliability 9 7 9 7 7 0 Easiness of Mounting (Frame material is Aluminium) 6 8 2 8 3 10 Manufacturability 7 5 2 8 7 10 Design-ability 7 6 2 8 7 10 Complexity 6 5 2 8 7 10 Low C.O.G. 5 4 2 7 8 10 Affect to the Performance 4 6 3 7 8 10 Weight Total 393 288 532 468 520
  • 30. SIDE PROTECTION * Minimum 50 mm clearance around the rider and shield the area between the riders hip and shoulder from contact with another vehicle and be constructed of material type, size and integral strength similar to the roll bars. Rollbar and Side Bar Materials Criteria Weight Alternatives Aluminum CrMo Composite Cost 8 7 8 5 Weight 9 6 4 7 Impact Absorption 9 7 8 7 Reliability 9 7 8 7 Easiness of Mounting (Frame material is Aluminium) 6 8 6 5 Manufacturability 7 8 7 6 Design-ability 7 8 8 7 Low C.O.G. 5 6 4 7 Affect to the Performance 4 6 5 7 Weight Total 450 425 413
  • 31. Material is Aluminum 6061-T6 as used in frame. Tubing diameter is taken from Frame tubing diameter.
  • 32. References: www.matweb.com www.alcotec.com http://www.racvenergybreakthrough.net/PDF/Handbook07/Handbook07-PartB-HPV.pdf
  • 33. Body Conceptual Evaluation Vent Location Body Material
  • 34. Front Inlet (Side View) Side Inlet (Top View) Corner Inlet (Top View) - Frontal inlet is selected - Highest static pressure and thus result in the greatest airflow at given speed. - Minimal impact on airflow over the surface Air Vent Location
  • 35. Required Air Flow Rate - This study recommends that 6liters of air per minute be passed over a body during exercise to maintain an acceptable temperature. (assumes an ambient air temp of 20deg C. http://academic.uprm.edu/~mgoyal/fluidsjuly2004/cooneychapter5.pdf -It is assumed that 6 times this is required to maintain the electronics at 33deg C. - Assuming that the flow rate through the vent is 1/10 of the vehicle speed the vent area must be. 3.6cm^3
  • 36. Body Material Selection - Fiber-glass is selected - Light weight and durable - Some risk of compounding injury in the event of a crash - Plexiglases will be used for the window material
  • 37. Body Drag Analysis Methodology An elemental analysis was performed. Multiple 2D analysis were performed on slices of the body and these results were integrated to determine an estimate for the overall body drag
  • 38. http://www.aeronautics.nasa.gov/docs/rpt460/discuss.htm Element (2D Symmetric Airfoil) Drag As a Function of Aspect Ratio (Thickness to Length)
  • 39. Drag Results Frontal Force = 12N Pressure Centre = 0.5m Vehicle Height = 1.25m Vehicle Width = 1m Vehicle length = 2m Power as a Function of Air Speed
  • 40. Ingress Egress Conceptual Evaluation Sealing Method Connection Method Note: Last week this style of ingress method was justified.
  • 41. Sealing Method Self Sticking Vinyl Weather Stripping Tape Economical Applicable on irregular surfaces Meets General Motors Specification 6086M-IA; Ford ESB M3G 102-A; Chrysler MSAY 511-A, B and C Length: Each roll is 17 feet Cost: approx. $ 5 each roll Universal bulb style adhesive Backed Weather Stripping Very high sealing rate Dimension: 7/8" wide X 3/4" thick X 8' long Cost: approx. $ 16.05 http://www.pplmotorhomes.com http://www.metrommp.com/
  • 42. Sealing Method Criteria Weight Alternatives Self sticking weather stripping tape Universal bulb style adhesive backed weather stripping Cost 6 5 6 Reliability 9 5 8 Safety 5 6 7 Manufacture-ability 7 8 8 Design-ability 7 8 8 Performance 8 5 8 257 319
  • 43. Connection Method ( Air spring Vs. Coil spring ) http://www.stabilus.com
  • 44. Connection method comparison In the above vehicle the upper body is lifted by two air spring and is kept in place with the hinge. The lower figure shows that the upper body is connected to the lower body just with two heavy duty hinges and coil spring
  • 45. Decision Matrix for Connection method Connection method ( Canopy to the main body Shell) Criteria Weight Alternatives One central Hinge with the Air spring Two side Hinges with coil spring Cost 6 6 5 Reliability 9 7 5 Safety 5 6 7 Manufacture-ability 7 8 8 Design-ability 7 8 8 Performance 8 8 5 305 262
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