Tesla Motors said Friday it will add three new underbody components to all Model S electric cars to add further protection against impacts from road debris, which caused a pair of fires in its cars last fall.
In 2013, two Model S collisions resulted in underbody damage that led to car fires. In both cases, the occupants walked away unharmed, thanks to the car’s safety features. The onboard computer warned the occupants to exit the vehicles, which they did well before any fire was noticeable.
To improve things, Tesla provided an over-the-air software update a few months ago to increase the default ground clearance of the Model S at highway speeds, substantially reducing the odds of a severe underbody impact.
Tesla felt it was important to bring this risk down to virtually zero to give Model S owners complete peace of mind. Starting with vehicle bodies manufactured as of March 6, all cars have been outfitted with a triple underbody shield. Tesla service will also retrofit the shields, free of charge, to existing cars upon request or as part of a normally scheduled service.
During the course of 152 vehicle level tests, the shields prevented any damage that could cause a fire or penetrate the existing quarter inch of ballistic grade aluminum armor plate that already protects the battery pack.
“We have tried every worst case debris impact we can think of, including hardened steel structures set in the ideal position for a piking event, essentially equivalent to driving a car at highway speed into a steel spear braced on the tarmac. We believe these changes will also help prevent a fire resulting from an extremely high speed impact that tears the wheels off the car, like the other Model S impact fire, which occurred last year in Mexico. This happened after the vehicle impacted a roundabout at 110 mph, shearing off 15 feet of concrete curbwall and tearing off the left front wheel, then smashing through an eight foot tall buttressed concrete wall on the other side of the road and tearing off the right front wheel, before crashing into a tree. The driver stepped out and walked away with no permanent injuries and a fire, again limited to the front section of the vehicle, started several minutes later. The underbody shields will help prevent a fire even in such a scenario,” said Tesla CEO Elon Musk.
The first of the three shields is a rounded, hollow aluminum bar that is designed to either deflect objects entirely or, in the case of a self-stabilizing, ultra high strength object, like a three ball steel tow hitch, absorb the impact and force it to pike upwards well forward of the battery pack. This pierces the plastic aeroshield and front trunk liner, but causes no damage affecting safety and the car remains in control and driveable before, during and after the impact.
This is followed by a titanium plate, which has exceptional strength-to-weight properties and is more commonly seen in aerospace or military applications. The titanium plate prevents sensitive front underbody components from being damaged and aids in neutralizing the road debris.
By this point, the vast majority of objects will have been deflected or crushed. For the rare piece of debris that remains intact, Tesla added a third shield, which is a shallow angle, solid aluminum extrusion that further absorbs impact energy, provides another layer of deflection and finally causes the Model S to ramp up and over the object if it is essentially incompressible and immovable.
Thanks to high speed cameras fixed underneath the cars during testing, we have a close-up view of what happens to the objects on impact. As illustrated in the slow motion videos below, the shields destroy everything from a solid concrete block to a steel alternator and safely capture and eject objects made of ultra-hard steel.