Designing Safer Small Cars: Pininfarina’s Nido
11 May 2005
Treehugger reports on Pininfarina’s work to develop a safer small car— one that, as Treehugger puts it, removes the sense that:
...driving in a small car can make you feel like some tiny rodent in a predator-prey relationship...
Pininfarina’s resulting Nido (“nest” in Italian) ultra compact car consists of three primary elements:
A chassis with a deformable front section and a rigid safety cell surrounding the occupants.
A shell sled that contains the driver and passenger, together with driving controls and instruments, that sits within the cell. This shell sled runs horizontally along a central runner within the rigid cell.
Two energy dissipating absorbers with controlled rigidity achieved by the combination of three honeycomb sections of different density (think big springs) connecting the cell and shell sled.
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 passengers 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 passengers.
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.
According to Pininfarina, computer simulations of crashes with the Nido system 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.
To guard against injury in T-bone collisions (lateral crash), Pininfarina uses a larger than usual underdoor side member that incorporates a number of crashbox elements to absorb energy in a lateral collision.
Despite the larger size, the side member is designed so that it 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.
All that said, increasing the safety of drivers and passengers in smaller cars—of which there will probably be an increasing number—will require design changes on the part of large vehicles as well.
As researchers concluded in a paper presented at the 17th International Technical Conference on the Enhanced Safety of Vehicles, in 2001:
To reduce the number of vehicle fatalities there must be a paradigm shift in thinking in regards to the crashworthiness design of the whole transport system rather than individual sub-components such as a sedan vehicle. No longer can the car and occupants be considered as an isolated system crash tested in a pristine laboratory environment in accordance to a certification procedure that in some cases bears little relationship with reality.
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