Car Body Design and
Aerodynamics
Automotive Engineering
Prof. Andrea Tonoli
Politecnico di Torino,
Dipartimento di Ingegneria Meccanica e
Aerospaziale
andrea.tonoli@polito.it
Aim of the course
Introduction of the main aspects that influence the car body
design taking the mutual constraints into account.
Packaging ergonomics
Ergonomics
Visibility (direct and indirect)
Structural aspects
Structure configurations
Structural analysis
Noise and vibration
Passive Safety
Restraint system
Crash and energy dissipation
Course organization
Classroom lectures exercice
Keynote presentations Case study:
(industrial practice) Packaging of a vehicle
Visits Visual requirements
verification
Structural analysis (FEM) of a
car body (static parameters)
Case study results
Technical reports and
drawings to illustrate the
Exam: obtained results
Oral and/or written discussion
(the exercice reports are integral part of
the exam and of the evaluation)
Packaging
Establishing the required interior
space, and arranging interior and
structural components (seats,
controls displays, ...) to guarantee
driver and passenger safety,
comfort, convenience and
accomodation.
Comfort
Controls accessibility
Cabin and trunk accessibility
Powertrain, suspension and
structure positioning
Requirements (standards)
Front side Back side
Cervical
Thoracic
Lumbar
Sacrum
2.2 -1
2.2 - 2
Anthropometric data
Anthropometric measurements are statistically distributed
( approx. Gaussian distribution). The distribution can be defined
from the average and standard deviation.
Percentile: if 100 people are ordered from the least to the
greatest for any given measurement, the 1st percentile is that
exceeded by 99% of the group, the 70th percentile is that exceeded
by 30% of the group....
Different databases (and percentiles) can be gathered for male and
female population. To reduce complexity dimensions used for
automotive anthropometry are based on 50% male 50% female
population.
The anthropometric data change with time !
2.3 - 3
2.3 - 4
Manikin percentile models
SAE J826 manikin (H-point machine)
EU manikin for R point definition
Percentile 10th 50th 90th 95th 99th
A [in] 15.37 16.40 17.46 18.10 18.74
B [in] 16.05 16.99 17.94 17.99 18.69
Task oriented models
Task oriented: head contours
Task oriented: eyellipse
Task oriented: control reach
Body base grid for vehicle measurement
USA
EU
Basic postures
seated reclined cramped
+ longitudinal size + vertical size
+ vertical size
+ control reach + load on backbone
+ longitudinal size
+ visibility + vibration and fatigue
- control reach
- vertical load on backbone - longitudinal size
- vibration and fatigue
- vibration and fatigue - in/out of the cabin
- in/out of the cabin
- vertical size - visibility
- visibility
Angles for automotive postures
() SAE Wisner Wyse RENAULT
Alfa 85-95 85-95 90-110 90-110
Beta 105-115 95-120 95-135 90-135
Gamma 95-105 85-100 87-103 95-120
Delta 15-28 15-25 20-30 25-30
Packaging procedure
1. Pedals setup and operation
2. Mechanical constraints
3. Definition of heel point (HP)
4. R point definition (driver)
5. Check Interference with steering column and dashboard
6. H point definition (second and third row)
7. Head contours
a1) a2)
HP HP
b)
c1) c2)
T
SR
P
GB
FW
SA
TR
3035
25 27-30
95th 95th
R G
330-400
20-30
HP
150-200
1000 800-850
2.6 - 3
148 9 Ergonomics and Packaging
Fig. 9.11. SAE J1100 dimensions relative to drivers posture.
The backbone is the structure that transmits the vertical load of the upper
2.6 - 4verte-
body to the legs. The transmitted force increases from the cervical
brae to the lumbar ones that, in comparison, are the most heavily loaded
as indicated by their larger size 9.1.
2.6 - 5
SAE J1100 Package dimensions
elbow
hip
Package definition
9.4 Pedals Functionality and Positioning 155
Fig. 9.14. Test bench to investigate the postural seating comfort (seating buck ).
The bench is representative of the position of the driver and the main cockpit ele-
ments: pedals, seat, steering wheel and allows to measure the angles between the body
segments.
Factors influencing seat comfort
Subjective and
psycological
Physical attributes
10% Of the seat
Pressure
9%
distribution
9% Backbone support
54%
9% Thermal behavior
9% Vibration isolation
2.7 - 1
Seat comfort
Factors influencing comfort for still vehicle
Body support
Perceived contact stiffness;
Lateral support
Possibility to adjust the posture
Tactile perception
Aestetics
Factors influencing comfort for moving vehicle
Vibration isolation
Avoid limitations to the drivers motion
Reduce the dynamic loading of backbone and contact regions
2.7 - 2
Pressure distribution
(comfort index for still vehicle)
cushion Seat back
rear
front
Seat back
Upper
y = 56,1 RA + 11,25 RD 16,16
Lower
Comfort index
2.7 - 2
2.7 - 3
Vibration insulation of the seat
(comfort index for moving vehicle)
Power spectral density of the
transmitted acceleration
1
Wi ( f )
G SS ( f )Wi 2 ( f )df
SEAT % =
100
G ff ( f )Wi 2 ( f )df
Weight function
Power spectral density of the vehicle
structure (seat connections to the veh.
Body)
0.5 Hz < f < 80 Hz
a b
2.7 4
Automotive climate
Tester
Front view
Thermal Shield
Control system
Automotive climate
Pump Tester
Back view
Sweating patch
Temperature and
humidity sensor
2.7 - 5
2.8 - 1
2.8 - 2
2.8 - 5
2.8 - 6
2.9 - 4
2.10 - 1
Eye structure
Fig. 2.11-1
Limits of visual fields, obstruction
Fig. 2.11-2
Min transparency = 70%
source
p = 0 A( )
A0 n 2 sin 2
A( ) = 1
n 1 cos
eye
0 1.5'
= 60 = 1.5'2.85 = 4.3'
A(60) = 2.85
Fig. 2.11-3
source
d
c = B( )
r
eye d = 4.6 mm
4.6
r = 3000 mm = 3.57 = 5.46'
3000
B(60) = 3.57
Fig. 2.11-4
source
eye
Fig. 2.11-5
Fig. 2.11-6
Fig. 2.11-7
Fig. 2.11-8
Fig. 2.11-9
Fig. 2.11-10
Fig. 2.11-11
Fig. 2.11-12
Fig. 2.11-13
Fig. 2.11-14
Fig. 2.11-15
Fig. 2.11-16
Fig. 2.11-17
Fig. 2.11-18
Fig. 2.11-19
Inside mirror
h > 4 cm
1
a = 15cm
1000
1+
r
rmin + rmax
r= > 1200 mm
Outside mirror 2
h > 4 cm
1
a = 13cm
1000
1+
r
Fig. 2.11-19
