The team designed a suspension system for an SAE Mini Baja vehicle with 11 inches of travel front and rear. The suspension uses a dual A-arm design to allow full travel without interference while maintaining optimal camber. It is adjustable for ride height and stiffness via the pushrod connection on cams. Analysis and modeling showed the design can withstand impacts of 4 feet drops and 2000 pound horizontal impacts on each wheel, with a minimum safety factor of 2.34. The presentation provided details on the final specifications, component designs, analysis results, budget and schedule.

1. Detailed Design Presentation
Mini Baja Suspension Group
Rob Johnson, Cheng Jin, Robert Perry, Eric Petersen, Ryley Nelson
Senior Capstone MET/MENG 490A

2. Introduction
Baja Suspension Team
● Design and Build Suspension System for
Eastern’s SAE Mini Baja Vehicle

3. Needs, Functions, and Features
● Minimum 10” of travel, front and rear
● Adjustability:
o Ride Height
o Suspension Stiffness
● Sustain 3’ jump without bottoming out
shocks or breaking related components

4. Final Specifications
● 11” of travel, front and rear
● Designed to withstand:
o 4’ drop onto 4 wheels
o 2000 lb horizontal impact on each wheel (front to back)
○ Lowest factor of safety present: 2.34
○ Maximum factor of safety present: 5.1
● k values for shocks:
o Front: 160 lbs/in
o Rear: 200 lbs/in
● Ride height (distance from lowest point of vehicle to ground):
o Max: 17 3/16”
o Min: 10”

5. Description of Solution
● Dual A-arm style control arms front and rear
o Allows full travel of suspension w/o interference
o Creates optimum camber angle for entire travel
o Light weight
● Adjustable ride stiffness and height
o Location of pushrod connection on cam dictates this
● Designed optimum geometry so that each
component can withstand required loads

7. Front Upper A-Arm (Drop Force)
Vertical Force - 800lb
Factor of safety - 2.764
Max Stress - 22.8 KSI

8. Front Upper A-Arm (Frontal Impact)
Horizontal Force - 1000lb
Factor of safety - 4
Max Stress - 15.8 KSI

9. Rear Upper A-Arm (Drop Force)
Vertical Force - 800lb
Factor of safety - 2.47
Max Stress - 25.5 KSI

10. Rear Upper A-Arm (Impact Force)
Horizontal Force - 1000lb
Factor of safety - 2.34
Max Stress - 25.5 KSI

11. Pushrod Buckling (Max Force)
Force - 1500lb
Static FOS > 5
Buckling FOS - 4.47

12. Front Cam Analysis
Force - 1500lb x 2
Von Mises Max - 12.9 ksi
FOS- 2.8
Material- A36 ¼” plate

13. Rear Cam Analysis
Force - 1500lb x 2
Max Von Mises - 13.8 ksi
FOS- 2.6
Material- A36 ¼” plate

14. Front Carrier Analysis (Drop)
Force - 800lb
FOS - 5.1

15. Rear Carrier Analysis (Drop)
Force - 800lb
FOS- 4.987

16. Summary of Evidence
● Hand calculations provide evidence of
o Forces at wheel (worst case, 4 foot drop)
o Force thru carrier bearings/hubs (worst case)
o Force thru pushrod (worst case)
o Force thru cam (worst case)
o Force into spring and required K value (worst case)
● Solidworks modeling provide evidence that
o Needed suspension travel is achieved
o Suspension geometry is desirable through full motion
o Factor of safety in weakest member is 2.34
○ In rear upper A-arm when dropped from a height of 4 feet

17. Budget and cost analysis

18. Schedule of Milestones and Major Tasks
Start: April 1, 2015
Finish: May 29, 2015

19. Questions?