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Dune Buggy Suspension and Steering Design. Nate Dobbs Steve Myers Faculty Mentor: Dr. Richard Hathaway Industrial Mentor: David Myers. Overview. Problem Goals of Project Terminology Analysis Optimization Final Design. Current Design Instability. Current Suspension Shortfalls. - PowerPoint PPT Presentation
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Dune Buggy Suspension Dune Buggy Suspension and Steering Designand Steering Design
Nate Dobbs
Steve Myers
Faculty Mentor: Dr. Richard Hathaway
Industrial Mentor: David Myers
OverviewOverviewProblemGoals of ProjectTerminologyAnalysisOptimizationFinal Design
Current Design InstabilityCurrent Design Instability
Current Suspension Current Suspension ShortfallsShortfalls
Goals of ProjectGoals of Project
Re-design current front suspension and steering.
Maximize performance in a sand environment by optimizing:
Camber Gain Bump Steer Roll Center Height Ackermann Steering Toe-In
Existing SuspensionsExisting Suspensions Volkswagen
Trailing arm - most common
Swing-Arm – Original Swing-Arm – Original DesignDesign
Camber GainCamber Gain Tilt of wheels
towards vehicle. Ideal setup keeps
wheels perpendicular to ground.
Bump SteerBump Steer The tie rod path
follows a fixed radius.
Wheel travels on a separate path
The difference in these two causes the wheel to turn.
Rack and PinionRack and Pinion
Wheel Wheel TravelTravel
Steering Tie RodSteering Tie RodPathPath
Roll CenterRoll Center
Point at which Lateral Loads act upon the vehicle
Angle dictates force distribution
Location change is critical
Center of GravityCenter of Gravity
Roll CenterRoll Center
Suspension GeometrySuspension Geometry
Roll Center and Center of Gravity LocationsRoll Center and Center of Gravity Locations
Front WheelsFront Wheels
Effects of Roll Center Effects of Roll Center Height on SuspensionHeight on Suspension
Roll Center to C.G. distance is related to force seen by springs/dampers
The distance from the ground to the roll center is force seen by the geometry.
60%60%
40%40%
Ackermann SteeringAckermann Steering Steering angles to
travel perfect concentric circles
Shown in the form of a percentage.
Ackermann angle is between the two wheels
0% is with parallel front wheels
Ackermann SteeringAckermann Steering
Percent AckermannTurn Radius (feet) 12 14 16 12 14 16 12 14 16Inside Wheel Angle (degrees) 37.1 31.5 27.4 37.1 31.5 27.4 37.1 31.5 27.4Outside Wheel Angle (degrees) 30.9 26.8 23.6 34.6 29.6 25.8 37.1 31.5 27.4Ackermann Angle 6.2 4.7 3.8 2.5 1.9 1.6 0 0 0
50 20 0
i = steering angle inside
o = steering angle outside
100 = outside wheel angle at 100% Ackermann
%Ackermann i o
i 100100
Rack & Pinion SelectionRack & Pinion Selection
The rack and pinion changes rotational motion of the steering wheel into linear motion.
Ford Escort Rack and Pinion was 2.45:1 ratio. 1 revolution of the wheel resulted in 2.45
inches of linear travel.
Rack & Pinion SelectionRack & Pinion Selection
A smaller ratio means more movement to make a tight turn.
A 5:1 ratio rack and pinion was incorporated into the design
Full Range of Wheel motion in less than one full turn of the wheel.
Benchmark (Trailing Arm)Benchmark (Trailing Arm)
Excellent for minimal camber gain.
Inexpensive and widely available.
Poor Bump Steer characteristics.
Poor Adjustability.
Original DesignOriginal Design
Swing Arm configuration. Custom – more expensive, not adjustable Unacceptable Bump-Steer
SuspensionGen AnalysisSuspensionGen Analysis
Trailing Arm configuration from benchmark data.
Could not analyze 12 inches of travel.
Poor results in all areas.
SuspensionGen AnalysisSuspensionGen Analysis
Original Swing-Arm Model
Poor results at extremes of suspension travel
Large Camber Gain, bump-steer
Final Design OptimizationFinal Design Optimization
Final Design OptimizationFinal Design Optimization
17 configurations were evaluated
Varied A-arm location points within geometry.
Selection 3D gave the best results.
• Optimized Camber Gain• Good Roll Center Height• Poor Toe-in and Bump
Steer
1 Y Location Z Location Y Location Z Location
A 10.5892 9.577 2.91 2.88B 8.038 8.691C 8.369 7.034D 8.872 4.218
Orig 2.91 2.88
2
A 10.5892 9.577 4.04 1.0B 8.038 8.691C 8.369 7.034D 8.872 4.218
3
A 10.5892 9.577 5.04 1.0B 8.038 8.691C 8.369 7.034D 8.872 4.218
4
A 10.5892 9.577 8.04 1.0B 8.038 8.691C 8.369 7.034D 8.872 4.218
Upper Control Arm Lower Control Arm
Steering ArmsSteering Arms
20% Ackermann Steering Arm Length
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
0 10 20 30 40 50
Turning Radius (feet)
Ste
erin
g A
rm L
eng
th (
inch
es)
20% Ackermann
Steering arm length graphed with turning radius. Based on 20% Ackermann configuration. 12 foot turning
radius was desired. This resulted in a
5 inch steering
arm.
Bump Steer/Toe-in Bump Steer/Toe-in AnalysisAnalysis
Bump steer and toe-in vary with rack positioning. Angle between tie rod and wheel axis gives
Ackermann Steering The steering
arm and suspension move about similar radius, minimizing bump steer.
SuspensionGen AnalysisSuspensionGen Analysis Final Design Analysis performed with
12 inches of travel. Good results in roll and
vertical displacement.
New DesignNew Design
New DesignNew Design
Finite Element AnalysisFinite Element Analysis
AISI 1020 Steel was used due to availability and cost.
FEA analysis was used to determine material size
Shows results of these forces in displacements and stresses.
A 0.189 inch wall thickness tubing was used and allowed for a significant factor of safety.
SuspensionGen ComparisonsSuspensionGen ComparisonsToe-In vs. Displacement in Jounce
-20.00
-15.00
-10.00
-5.00
0.00
5.00
10.00
15.00
-7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7
Wheel Displacement (inches)
To
e-I
n (
de
g)
Original Design
Trailing Arm
New SLA Design
Toe-in vs. Roll Angle in Roll
-4.00
-2.00
0.00
2.00
4.00
6.00
8.00
10.00
-15.00 -10.00 -5.00 0.00 5.00 10.00 15.00
Roll Angle (deg)
To
e-i
n (
de
g/d
eg
of
roll)
Original Design
Trailing Arm
New SLA Design
SuspensionGen ComparisonsSuspensionGen ComparisonsCamber Gain vs. Displacement in Jounce
-3.00
-2.50
-2.00
-1.50
-1.00
-0.50
0.00
0.50
1.00
-10 -5 0 5 10
Displacement (in)
Cam
ber
Gai
n (
deg
/in o
f tr
avel
) Original Design
Trailing Arm
New SLA Design
Camber Gain vs. Roll Angle in Roll
-3.00
-2.50
-2.00
-1.50
-1.00
-0.50
0.00
0.50
-20.00 -10.00 0.00 10.00 20.00
Roll Angle (deg)
Ca
mb
er
Ga
in (
de
g/d
eg
of
roll
)
Original Design
Trailing Arm
New SLA Design
SuspensionGen ComparisonsSuspensionGen ComparisonsRoll Center Height vs. Roll Angle in Roll
-10.00
0.00
10.00
20.00
30.00
40.00
50.00
60.00
-15.00 -10.00 -5.00 0.00 5.00 10.00 15.00
Roll Angle (deg)
Ro
ll C
ente
r H
eig
ht
(in
)
Original Design
Trailing Arm
New SLA Design
Roll Center Lateral Migration vs. Roll Angle in Roll
-10.00-8.00-6.00-4.00-2.000.002.004.006.008.00
10.00
-20.00 -10.00 0.00 10.00 20.00
Roll Angle (deg)
Ro
ll C
en
ter
La
tera
l M
igra
tio
n (
in)
Original Design
New SLA Design
ResultsResultsRoll Center Lateral Camber Tread Toe-In Roll Height (in) Migration (in) Gain (deg/in) Change (in) (deg) Steer (deg)
Max 2.19 0.43 0.36 10.47 1.64Min -2.74 -0.3 0 -0.89 -5.17Max 23.48 -2.26 4.74 11.34 -0.86Min 6.61 -2.51 -8.7 -16.03 -1.48Max 13.74 0.46 2.58 1.14 0.2Min 3.74 -1.74 -4.88 -0.87 -0.12
% Change VW 89.11% 87.80%% Change Original 120.35% 45.57% 89.95% 123.26%
Roll Center Lateral Camber Tread Toe-In Roll Height (in) Migration (in) Gain (deg/in) Change (in) (deg) Steer (deg)
Max 53.14 1564.08 0.06 0.34 7.8 -0.01Min -0.01 -1564.08 -0.02 0 -0.89 -1.82Max 16.23 7.32 -2.39 0 -0.59 -1.05Min 13.5 -7.32 -2.49 -1.98 -2.35 -1.15Max 9.28 2.06 -0.64 0 0.3 0.08Min 8.32 -2.06 -0.91 -1.15 -0.59 0.03
% Change VW Large 95.60%% Change Original 255.34% 173.63% 72.17% 298.31% Large
New Design
Suspension Model
Suspension Model
Volkswagon
Original Design
Roll
Jounce
N/A
N/A
N/A
Volkswagen
Original Design
New Design
ReviewReviewSand Dune Buggy StabilityEvaluated 3 designsDeveloped Short-Long Arm SolutionOptimized Geometry, Steering, and
handling characteristicsAll original goals were met.
Questions?Questions?
