Much has been written about Fiat's brilliant mid-engined sports car. Still, I believe one of the most intriguing facets of X1/9 history is the one described in SAE paper no. 890718, whose rather clunky title reads: "The Building and Test Track Evaluation of an Aluminum Structured Bertone X1/9 Replica Vehicle."
The key word here is "replica:" The whole point of the experiment was to demonstrate how Alcan's adhesive bonding technologies could allow to more or less directly replace steel for aluminum, even in an existing body design.
The company approached Bertone in 1986, and the Turinese company built five aluminum-bodied X1/9s, equipped with standard suspensions and drivetrain components, for various performance and durability tests.
The aluminum panels were press-formed using Bertone's existing body tooling with similar gauges (between 0.7 and 2.5 mm) as their steel counterparts and then spot-welded, with bonded-in doublers added in specific locations to compensate for the lower strength of the material.
One of the aluminum bodies was then subjected to static testing, with results that make for interesting reading.
The experimental X1/9 aluminum body weighed 136.6 Kg, a whopping 30% less than its steel equivalent (197 Kg), while offering comparable torsional stiffness (3155 Nm/Degree vs. 3100).
However, it must also be said that the bodyshell's bending stiffness was instead far less convincing, with an 18% loss over its steel counterpart (2490 N/mm vs. 3040).
Driven to destruction
The five experimental X1/9s were fully trimmed and assembled by Bertone in its Grugliasco factory and then sent to the UK to be driven to destruction on the Motor Industry Research Association test track
This involved a lot of hard driving over the various proving ground features with the precise intention of inducing high bending, torsional, and impact loads upon the vehicle's structure. Sometimes, though, the results make for pretty grim reading.
For example, after nearly 600 miles on the infamously unforgiving Belgian pavè, both rear suspension turrets cracked so severely that they had to be repaired to allow testing to proceed any further.
However, the prototype aluminum bodies maintained their geometry throughout their various ordeals, and, given that the X1/9's body design hadn't been designed for aluminum and applying doubling panels had been impossible in some areas, that's very impressive indeed.
And that was precisely the point Alcan was trying to make: demonstrating that aluminum bodyshells were not only possible, but also compatible with existing production facilities, even if the way those X1/9s were built would undoubtedly make an Audi engineer squirm.
The lone survivor
One of the aluminum-bodied Bertone X1/9s survives to this day in the Volandia museum located in front of Milan's Malpensa airport, together with the other 79 vehicles and prototypes that once formed Bertone's company museum collection.
If it wasn't for the silver decals on the nose and the doors, there would be no way to tell it apart from the "regular" X1/9s parked alongside it, at least without bringing a magnet with you!
However, another prototype wasn't so lucky.
It was subjected to two crash tests at Fiat's laboratories in Turin: a full front barrier test and a full rear impact, both at 30 Mph.
In the frontal crash, the aluminum X1/9 performed similarly to its steel counterparts, which meant it would have complied with the period's rather weak regulatory demands by an ample margin.
The opposite was true for the rear end test, though, where the structure lacked the necessary strength and collapsed, leading to fuel spillage and consequent fire risk.
However, the company considered its X1/9 experiment a successful proof of concept, as the aluminum bodies delivered a comparable performance with the steel equivalent while weighing 30% less.
Had it been possible to redesign and optimize the X1/9 'shell for aluminum construction, it's likely the gains could have been even more significant.