1. Jarrett Dunn SOLAR CAR CHALLENGE
Solar Car Suspension
Jarrett Dunn
SOLAR CAR CHALLENGE

2. Agenda Introduction Suspension Types Key Terms Measuring Toe
Ackerman Steering
Best Practices

3. Common Suspension Types
MacPherson Strut
Solid Axle
Dual A Arm

4. Less Common Suspension Types
Torsion Axle
Radius Arm
Mountain Bike Fork

5. Vocabulary Toe Caster Camber Scrub Radius
Angle of the wheel and tire pointing away from the centerline of the vehicle
Caster
The angular displacement of the steering angle for the vertical axis
Camber
The angle of the wheel and tire with respect to the vertical axis
Scrub Radius
The distance between where the steering angle intersects the ground and the contact patch of the tire

6. Vocabulary Contact Patch Steering Axis
Oval shaped area where tire contacts the road
Steering Axis
Line between two pivot points of of the wheel

7. Toe (Neutral)
Center Line
Front

8. Toe (In)
Center Line ∅
Front

9. Toe (Out)
Center Line ∅
Front

10. Camber (Negative)
Vertical ∅
Front

11. Camber (Negative)
Vertical ∅
Front

12. Caster (Positive)
Vertical θ
Front

13. Scrub Radius (Positive)

14. Toe Affects Tire Wear Toe Out Toe In Improves Steering Response
Improves Straight line stability

15. Camber Affects grip and stability in cornering
Not applicable to solar car racing
Camber Gain

16. Caster Creates straight line stability Positive Caster Negative Caster
Steering wheel feedback
Makes Car harder to turn
Causes wheels to self center
Negative Caster
Unstable

17. Scrub Radius Coffee Cup Experiment Harder to Turn
Increase wear on tire
Positive
Cause center seeking

18. Measuring Toe Front ∅= sin −1 𝐷𝑖𝑠𝑡 𝐴−𝐷𝑖𝑠𝑡 𝐵 2 𝐷𝑖𝑠𝑡 𝐶 A2 A1
Dist A A2 A1
T𝑜𝑒= 𝐷𝑖𝑠𝑡 𝐴−𝐷𝑖𝑠𝑡 𝐵
Dist B C B1 B2

19. Measuring Toe A1 A2
Front C B2 B1
∅= cos −1 𝐷𝑖𝑠𝑡 𝐵−𝐷𝑖𝑠𝑡 𝐴 𝐷𝑖𝑠𝑡 𝐶

20. Ackerman Steering

21. Best Practices Consistency is key Make Dedicated Tools
Date
Tire Pressure
Driver
Toe
Consistency is key
Be methodical
Do the same thing every time
Make Dedicated Tools
Solar cars racing is about efficiency
Small or zero angles

22. References Tune to Win, Carrol Smith Design to Win, Carrol Smith
The Winning Solar Car, Douglas R. Carroll
The Leading Edge, Goro Tamai