The NIDO by Pininfarina rethinks automobile design

The Nido project was conceived through an intensive collaboration of the Pininfarina design and engineering departments, using extensive virtual product development to run computer simulations for static and dynamic analyses, structural and biomechanical crash testing and acoustic and vibration analyses. The objective was to increase the levels of safety for both the occupants and pedestrians. Current safety provisions in the event of a head-on collision focus on programmed deformation of components to absorb impact energy, leaving sufficient space for passenger mobility. But applying this principle in a compact vehicle poses more problems than in a larger car as the crumple zone is minimised. This in turn leads to problems with the design of structural components that must comply with strict legislation. The rigidity of a small chassis combined with the limited passenger space of most small cars means a significant proportion of energy is transferred to the occupants.

Pininfarina solved these safety issues through a total systems approach to automobile design. Rather than basing the safety characteristics of the car on its mass, as is done traditionally, the Nido follows a new blueprint consisting 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 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.

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. Simulations also 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.

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.

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