2004 Pininfarina Nido
(from Pininfarina
Press Release) With the Nido project, Pininfarina has chosen to
rethink the current methodology of the car design process, resulting
in an innovative concept, which reexamines safety in small
automobiles.
The Nido concept builds upon Pininfarina’s grand tradition of
continuous investment in research and development programs in each
of the Company’s areas - Design, Engineering and Manufacturing - to
quickly and methodically tackle contemporary problems as they arise
in the automotive industry. For example, during the 70’s energy
crisis, the industry looked towards aerodynamics and alternative
energy sources to cut fuel consumption. Pininfarina responded by
developing the CNR Energetica 1 prototype, an ideal aerodynamic body
shape, and the electric powered Ecos. In the 80’s Pininfarina’s
pioneering research into lightweight material application bore the
Audi Quartz and Lancia Hit prototypes, which explored the use of new
light metallic and composite materials.
The 90’s witnessed to heightened environmental awareness, spawned
research into recyclability of materials, improved ergonomics and
more efficient vehicle packaging. Pininfarina offered solutions with
the Ethos macro-project, a family of three cars with aluminum
chassis, recyclable plastic bodywork and innovative, low emission
internal combustion engines, highlighted by the 1995 Ethos 3EV zero
emissions vehicle. More recently Pininfarina turned their attention
to hybrid vehicle research in the Eta Beta and Metrocubo projects
which, with reduced dimensions and modular cabins, also answered the
problems of both urban and medium range usage.
Today the industry is concerned with a problem that Pininfarina had
already anticipated with the Sigma, Alfa Romeo P33 and Sigma Grand
Prix prototypes: safety.
The Nido project dives into the concept of total design: coherent
integration of all aspects of the design and engineering of the car.
This concept was in fact conceived through an intense collaboration
between design and engineering, two poles often opposed, with the
singular goal of creating an attractive, small and safe vehicle.
By focusing and redefining their respective approaches on a singular
goal from day one, new innovative solutions were discovered in the
overlap between the aesthetic and the technical view points.
Nido demonstrates Pininfarina’s ability to combine user’s desires
with the technical feasibility that allows the project to be built.
It marks Pininfarina not only as an innovator today, but shows how
Pininfarina is providing solutions for a better tomorrow.
The principle of the nido project
When examining the issues of safety, we can no
longer simply consider the effects of a collision on a single
vehicle. Problems of incompatibility between vehicles of small and
large masses in collisions have taken on a fundamental importance in
automotive safety engineering. This is even more significant if we
consider current development trends in cars, which are getting
larger and heavier, in order to comply with increasingly severe
legislation and to offer more passenger space. In this context, the
safety of a small light car assumes particular relevance.
For this reason, the Nido project has concentrated on the
development and prototyping of new solutions involving both the
structure and the design of a small two-seater car with the
objective of increasing levels of safety for both the occupants and
pedestrians.
The principle normally applied to protect occupants in the event of
a head-on collision entails ensuring that sufficient space is
maintained to accommodate the biometric parameters of the
passengers, by using the programmed deformation of components to
absorb impact energy. This is achieved in part through the
deformation of the front of the vehicle, in part transferring the
remaining loads to the rear of the vehicle (via floor panels, side
members, doors and the structure as a whole) and in part with active
retention systems (seatbelts and airbags).
Applying this principle in a compact vehicle poses many more
difficulties than in a larger car, as there is very limited space to
accommodate crumple zones. This leads to problems in the design of
structural components that comply with increasingly strict
legislation. While the structure will withstand a violent impact,
the very rigidity of the chassis, together with the limited space
available, means that a significant proportion of the energy is
transferred to the occupants. As the dimensions of the front of the
vehicle cannot be increased, it is necessary to find an alternative
solution to reduce the forces of deceleration acting on the
occupants to levels comparable with those of larger vehicles.
Rather than basing the safety characteristics of the car on its
mass, as is the traditionally accepted method, Nido puts forward a
new principle.
Nido consists of three principal elements:
1/ A chassis, accounting for approximately two thirds of the total
vehicle mass, which supports all the mechanical components, such as
the front and rear suspension, the engine etc. This chassis consists
of a deformable front section and a rigid safety cell surrounding
the occupants.
2/ A shell for the occupants, accounting for approximately one third
of the vehicle mass. This shell holds the driver and the passenger,
together with the driving controls and instruments. This shell is
actually a sled which can run horizontally along a central runner
within the rigid cell.
3/ The rigid cell and the sled are connected in normal conditions by
a third element, consisting of two energy dissipating absorbers with
controlled rigidity achieved by the combination of three honeycomb
sections of different density.
In the event of a head-on collision, the vehicle absorbs part of the
energy with the deformable front section of the chassis, constructed
of two metal struts with internal plastic foam absorbers. These
components are shaped as truncated cones in order to dissipate the
energy over the cellular sheet metal firewall, which in turn
transfers the energy along the central tunnel and the side members.
The remaining energy, due to the mass of the dummies and the sled,
shifts the sled itself forward and compresses the two honeycomb
absorbers between the rigid cell and the dashboard of the sled
shell, resulting in the gradual and controlled deceleration of the
dummies.
The insertion of honeycomb absorber elements between the rigid cell
and the sled shell means that, in a collision, the deceleration
curve for the sled is lower than the curve for the rigid cell.
Additional, smaller absorber elements may also be fitted between the
rear of the sled and the rigid cell, to provide occupant protection
in the event of a rear-on collision.
This principle, applied here in a small, rear-engined two-seater
city car may also be used in a mid-engined two-seater sports car.
Virtual validation of the principle
During the Nido project, a strong cooperative relationship between
the different company divisions involved was established, and
Pininfarina’s experience in virtual product development was put to
full use, employing computer simulation for static and dynamic
analyses, structural and biomechanical crash testing and acoustic
and vibration analyses.
The working principle behind the rigid cell/honeycomb energy
absorber/sled system was validated using simplified virtual models.
Using these models to simulate a variety of types of crash (head-on,
lateral and roof crushing) made it possible to study the dynamics of
the Nido principle during a collision. The initial simplicity of the
model permitted a number of parameters for each of the three
elements (for example, the rigidity of the absorber element) to be
varied in order to discern the optimum characteristics and
configuration. The optimum rate of deceleration of the car was
defined by analysing the crash test results of other, similar
vehicles. Each structural component has been assessed individually
within simplified models, and optimised to achieve the objectives
set for the project.
The simulations showed that thanks to the mobile sled system, the
deceleration sustained by the occupants during a collision is low
enough to render the use of airbags unnecessary in certain cases,
meaning that the way in which they are currently used may be
reconsidered.
From the virtual model to the prototype
Translating the basic principle of the project into a fully
functional car meant conferring a sufficient degree of rigidity to
the lower section of the chassis, locating the engine at the rear of
the vehicle and optimising the use of internal space to leave enough
room to allow for the motion of the sled. To achieve maximum safety
cell rigidity, innovative cellular sheet metal technology was used
for the firewall, floor panels and central tunnel, which enables
sufficient space to be made in front of the occupants’ feet to allow
the forward motion of the inner shell in the event of a head-on
collision.
The overall architecture of the car was also chosen for
functionality: the single-box shape allows more room for the motion
of the sled shell and conveys an impression of a protective “nest” (nido
in Italian) surrounding the occupants.
The sled consists of a shell of structural plastic reinforced by a
sub-frame in stainless steel tubing to help keep the overall weight
of the system as low as possible.
The interior trim and fittings were not simply designed for style,
but have been developed in consideration of the impact dynamics of
the occupants during an accident.
The doors are fitted with rhomboid aluminium alloy hinges and are
oversized in comparison with average comparable components on other
cars to facilitate the exit of occupants after an accident.
The inner door panel has been designed so that there are no
hazardous protuberances during a collision.
Staying on the topic of the inside of the passenger compartment, a
number of parts are made from soft materials.
The door handles, for example, also function as emergency door
releases. They are fabric straps, which can be used to open the door
from whichever position the occupant is in after an accident. The
stowage compartments are fabric pockets.
The dash assembly serves a dual role: it houses the instruments and
is an integral part of the sled shell, acting to compress the
honeycomb absorber during a collision. Furthermore, the dash itself
also performs an energy-absorbing role, as its internal components
(heater, air pipes) have been designed to contribute to dissipating
energy in a collision. The underdoor side member is larger than
usual as it incorporates a number of ‘crashbox’ elements which
absorb energy in a lateral collision. Despite its larger size, it
has been designed so that it still does not impede access into the
car. The concept developed by the Nido project also includes the use
of suitably sized transverse structures in the sled near the dash
and at the base of the seats, which transfer lateral impact energy
from one side of the car to the other. As a consequence, the doors
rest on these transverse structures, an arrangement which also
prevents door intrusion.
To maximise the effectiveness of the Nido principle, the space
normally taken up by the steering column and traditional pedal box
has been freed up by the use of a ‘steer and brake by wire’ system,
which means that these components no longer intrude into the
passenger compartment and also allow the use of a spokeless steering
wheel. This last feature optimises instrument visibility, thus
further contributing to safety.
Style
The essential body styling of the prototype echoes the technological content of the project: the shape and finishings convey the concept and highlight the project’s consistency of shape and structure. The technological, structural and functional solutions adopted to maximise safety transpire through the vehicle’s volumes as three principal elements: the rigid cell, the sled and the energy absorber. The colour scheme also contributes to emphasise the elements directly correlated to safety and confers a friendly and reassuring character to the car.
The surfaces appear as a skin stretched over a structure, thus
emphasising the shape of the structure itself. The front of the
vehicle is characterised graphically by horizontal lines echoing the
motion of the sled shell, while the rear is more raked to confer a
dynamic quality. Remaining with the rear of the vehicle, the hatch,
which covers the triangular light clusters, is also the rear screen.
The screen itself is hinged under the spoiler.
The low waistline, very wide windscreen and transparent roof ensure
excellent visibility.
The front moulding is completely covered with a cushion of energy
absorbing material to present safer surfaces in the event of
collision with a pedestrian, and thus minimise injury; it houses,
among other elements, the windscreen wiper and windscreen washer
fluid filler cap. To reduce head injuries in the event of a
collision with a pedestrian, the windscreen pillar is also fitted
with a collapsible covering consisting of an external plastic
section to fit in with the rest of the bodywork and an internal
energy-absorbing section made of the same foam used for the cushion.
The headlights are mounted high to increase the deformable area
presented during collision with a pedestrian. In addition to an
indicator light, the wing mirror incorporates a white reflector to
ensure visibility at night when the vehicle is parked.
A veltex trim has been applied on the dash and tunnel, so that any
loose object (mobile phone, MP3 player, satellite navigator etc) can
be fixed by simply applying a Velcro type strip on the object
itself. On the one hand, this contributes to cutting the basic cost
of the car, by balancing off the greater expense of the safety
features with simpler internal trim, and on the other, it means that
the interior of the car can be personalised according to individual
tastes and requisites.
The full scale prototype
Starting with only the elements which are directly involved in the
functioning of the Nido principle, two developmental models were
built to correlate the simulated experimental results of the virtual
model with a physical model. A 1:1 scale prototype was then built,
incorporating both solutions developed specifically for this project
and other, already known and consolidated solutions. The decision to
use stainless steel for the structure was taken because of the
specific characteristics of this material, which has an excellent
energy-absorbing capacity in the event of a collision and which
increases in mechanical strength in relation to the degree of
deformation (strain hardening). As it requires no anti-corrosion
surface treatment, stainless steel also makes the industrial process
more flexible, and means that the cataphoresis treatment can be
completely omitted.
A new concept of chassis construction has also been developed,
replacing the traditional floor tray, tunnel and firewall
configurations with a structure in cellular sheet metal. The
advantages of this technology lie in its improved energy absorption
capacity in collisions and excellent torsional stiffness. Cellular
sheet metal technology consists of a sandwich made up of four or
more thin layers: flat sheets are used for outside sections, whereas
for internal parts, two or more ribbed sheets were assembled
together with their respective corrugations opposed.
Lastly, the use of solid coloured plastics for the external body
panels means that the painting process can be eliminated completely
and gives the Nido project a high environmental value.
The last stage in the project will consist in industrial feasibility
studies for a hypothetical production of 100-120 cars per day for a
total of 20,000 units over 5 years.
Pininfarina has applied for patents for the innovative safety
features developed as part of the Nido project.
Length 2890 mm
Width 1674 mm
Height 1534 mm
Max forward movement sled 350 mm
Max rearward movement sled 120 mm
Wheelbase 2068 mm
Front track 1363 mm
Rear track 1457 mm
Front tyres 175/50 16”
Rear tyres 205/45 16”
Body Composite, inox chassis
Drivetrain Rear engine, RWD
Gearbox Automatic