Atomic Element 13

Placed Under Duress – an X1/9 like no other.

The Superlight now resides at the Volandia Museum near to Milan’s airport. Images found
The Superlight now resides at the Volandia Museum, near Milan’s airport. Image:

Cars are expensive for a reason. When shelling out the hard-earned one expects the thing to function, which calls for a punishing test regime to iron out defects. Nothing new there but almost forty years ago, plans were afoot to structurally place aluminium in a car almost at the end of its production life – introducing the Bertone built X1/9.

Wishing to demonstrate proof of concept, Canadian company Alcan[1] turned to Bertone to produce five replica models in what would appear to be a drive towards using the ever-abundant silvery grey material. However, your author could not ascertain whether this was merely a material exercise or a serious attempt for future production.

Starting as would a mass-produced steel vehicle, a nine tonne roll of PVC wrapped aluminium entered the rolling mill. Pre-lubricated and requiring no cleaning, blanking and stamping occurred with the film intact, removed on assembly. The single part rubber-based epoxy resin, developed from Alcan’s long association with the aero industry, and applied by both robot and human, cured only when structurally complete.

The Bertone X1/9 required reinforcement due to the replaced materials’ characteristics. Doublers were placed in front and to the rear of the passenger compartment with another behind the mid-placed engine bay. Assisting stiffness, the sills became double box section. Averting the dreaded scuttle shake and unacceptable door fitting problems, the front shock absorber areas along with seating scuttle were beefed up by spot welding extra brackets. However, some of those doublers needed removal due to the manufacturing process. Increasing gauge thickness and extra bonding eliminated such hurdles.

The aluminium/magnesium alloy AA5251 ranging in thickness from 0.7-2.5 mm provided the body in white’s majority. Bonnet, doors and boot lid derived from AA6010-T4 alloy, often used for skin panels. A consideration to factor in being that normal press dies and tooling were not changed. Inspections revealed most of the forming was almost identical to its steel counterparts with little wrinkling or splitting. The Tig welding teams were not much in use in this first instance, subsequently utilised for spot-welding sub-assemblies. Steel remained in use for small brackets, clips and fasteners, phosphated and electroplated to avoid galvanic corrosion.

Prior to spot-welding, the adhesive required squeezing away; difficult when several panel gaps needed upwards of 3mm – a dilemma accordant with low numbered experiments. Manufacturing complete, the body in white was placed in Bertone’s oven, and baked at 180° Celsius for half an hour. Four bodies continued along the phosphate, paint and trim lines, with all five being motorised. 

Unpainted aluminium. Image:

Initial postproduction measurements were taken in Turin, the cars heading later to Britain for substantial and exhaustive testing. The alloy-bodied machine weighed in at 136.6 Kgs to steel’s 196.9 Kgs. Having the last laugh though was steel, with an 18% stronger bend stiffness. Torsional stiffness fell marginally the way of aluminium.

Static stiffness tests were held at Gaydon, then under Austin Rover’s jurisdiction. Vehicle roof removed, the body in white was placed on a steel test rig where a mass of 280 Kgs was suspended from each suspension turret. 

Dynamic testing must have been most time consuming. Measured over thirty-six body locations for both steel and alloy versions in the following categories: body in white, total vehicle without roof, total vehicle with roof. Modular frequencies were found to be higher in the aluminium structure, between 5-10%. 

A solitary Bertone example was chosen for High Load Durability Testing. With a kerb weight of 902Kgs, a 77Kg driver (of stout heart) was installed as was a dummy 68Kg passenger. Luggage at fifty kilograms tipped the scales to 1,097. The prosaically named ‘pot hole braking test’ is not for those of a faint stomach. From a speed of 70-80 Kmh, the alloy-bodied car entered a 610mm diameter pot hole, 50mm deep, the front right wheel leading the way, performed fifty times.

Track testing came next. Twenty laps, equating to 45 Kms on the ride and handling circuit, the driver tasked with driving enthusiastically. Seventeen passes on the wave pitching track troubled the suspension followed by twenty passes on an angled ramp. 96 Kmh saw the entire car airborne momentarily with not unsurprisingly the left side rear suspension wishbone bracket failing, three quarters into the program. The bond failures lay between the steel bracket and paint layer. More adhesive, along with 6.5mm rivets proved sufficient enough to continue. Later inspection found a handful of minor cracks within the glue but no problems at all with welded/bonded joints.

Adding insult to injury, the 1,609 Km (1,000 mile) pavé test found the tops of both front and rear suspension turrets cracking severely at 579 and (most apt?) 666 Kms, necessitating heavy repair. A repaired in manufacturing crack also required welding along with an exhaust pipe bracket. 

Spare a thought for the non-painted car. The Gaydon Accelerated Corrosion Test was equivalent to a six year life in “typical Montreal or Detroit environments” conducted over a twelve week period. Six two week cycles subjected the Bertone to 150 miles of rough road: 50 Highway, 50 wet, muddy road followed by 50 passes through a salt spray zone. Next, a temperature scale of 42/48/42° Celsius change per hour for 168 hours with another 150 hours spent in high humidity. Barring some early bodywork staining, no further deterioration occurred. Corrosion was found in small crevices, nuts and brackets. The engineers concluded more accurate paint layers would cure this.


The Acocks Green Hot Climate Centre roasted the car in 40° ambient temperature for four hours with the engine running. Results were favourable. Back in Italy, the Belgian pavé example was also subjected to a frontal 30 mph impact test. Dashboard and steering wheel deflection was minimal, however the bonnet disengaged from its lock. The doors functioned afterwards, and no fuel escaped. The same speed rear impact test saw the vehicle’s body collapse, spilling fuel, luckily with no fire. Again though, the engineers believed that with thicker material, satisfactory resilience could easily be achieved. 

Bowled over by the massive weight savings and overall impressive performance, the ASVT was considered an Alcan success though many moons waxed and waned before aluminium was comprehensively used.

As to the Bertone five, one example survives, residing at the Volandia museum, Milan. Once part of Bertone’s collection, one could not differentiate a steel from aluminium X1/9 – unless one introduced a magnet. That and the silver Super Light decals on the front….

[1] Now part of Rio Tinto, the world’s largest aluminium producer.

Check out for a six-minute video.

Author: Andrew Miles

Beyond hope there lie dreams; after those, custard creams?

15 thoughts on “Atomic Element 13”

  1. Many thanks for this interesting article.
    I didn’t know about these experiments but they show how Alcan searched for partners willing to show the usability of aluminium in car manufacture. That fits in with the story that Alcan promised thousand million Dollars to the company putting an aluminium car in mass production (winner was the Audi A2).
    The X1/9 stor shows that an aluminium car has to be designed as such from ground up and that its design should be completely different from a steel bodied car.
    The X1/9 shows that it’s not easy to convert a steel car to aluminium and the Honda NSX shows that a car designed like a steel car but made from aluminium doesn’t fully exploit the advantages of the light material.
    If you want to make an aluminium car then build it from extrusions and cast nodes that are bonded together like in Audi’s ASF space frame or like the chassis of the Lotus Elise and please don’t weld it like the Renault Spider. Then you get oprimum stiffness with low weight and you can produce it with a precision far better than wold be achievable by welding together stamped and bent steel.

    1. Good morning Andrew and, as Dave said, what an interesting story. Using the X1-9 (or any convertible) as the basis for an aluminium car was an odd choice, as the targa roof would compromise torsional stiffness. I wonder why Alcan didn’t give Bertone a free hand to design from scratch something more suitable for aluminium construction? Perhaps the company was determined to produce something as ‘normal’ and familiar looking as possible?

    2. Wasn’t the issue with the Renault Sport Spider that the aluminium needed to be a certain thickness in order to be welded? And thicker tubes wouldn’t necessarily lead to a stiffer chassis compared to the Elise?

    3. The Renault Spider’s welded chassis suffered from heat distortion of the parts in question during the welding process. This limited the precision with which the chassis could be made and which was no better then for the rest of the industry.
      The Elise’s chassis was bonded (the rivets arent load bearing and their only purpose is to prevent the bonded seam from peeling of under shear forces) and could be made to tolerances of around one millimetre and otherwise impossible in the industry and the chassis could be set up accordingly.

  2. Amazing – thank you, Andrew (ASD@DTW*). Here are some pictures I found which may be of interest.

    I would’ve thought that this was just a proof of concept by Alcan (and a pretty daring one, at that), with no real intention of putting the car in to production. As the X1/9 wasn’t engineered to be suitable for aluminium, there were bound to be problems. Repairing damaged aluminium requires specialist skills, too, and there’s the Fiat dealer network to consider…

    Still, no rust, which would’ve been a big benefit. Unless the aluminium came from Russia, of course.**

    I always thought that the X1/9’s design suggested it had a metal superstructure clad with lightweight panels.

    * Another school day – I say it so often I’m beginning to think I need an abbreviation.
    ** I’m really pushing my luck.

    1. Very interesting article!
      Panhard was famous in buildung cars with an aluminium body. Years after the death of Panhard, Porsche bought some Panhard Dyna to study the french skills in building a series car with an aluminium body. Some rumours are saying Audi did the same 20 years later.

      Maybe they took the Fiat X1/9 because of its angular shape, ideal for a paper model car too.

    2. Until the arrival of the Audi A8 D2 the largest part made from aluminium in the automotive industry was the Citroen DS’ bonnet.
      Audi’s ASF combination of extrusion and cast nodes has nothing in common with whatever Panhard had used. It was the first design that took full advantage of the properties and strengths of aluminium. Audi paid a high price for pioneering this technology because they had to invent a whole set of production processes twice – once for the introduction of the A8 and a second round after a year or so when they said that they would have to do a complete re-launch because everything had changed so much.

  3. When I was a student I once had a job in my semester break at a company making all kinds of extrusions from bronze, brass and aluminium. Their products were known as expensive but the best of their kind in terms of quality – they were the leading supplier of waveguides for Gigahertz high frequency current in radar and satellite technology.

    One of their products were aluminium extrusions used by different manufacturers in truck beds.
    Properly executed these extrusions can withstand enormous forces and last forever but need know how to design and make and cost some money.
    One day a trailer manufacturer sent in some profiles with a complaint about their quality.
    On inspection it was immediately visible that the profiles in question weren’t extrusions but folded aluminium sheet material which had bent and cracked very quickly under the load. They got their samples back with the comment that they should complain at the supplier of these sub-standard material or buy the proper stuff.

  4. Great read Andrew, I never knew 5 aluminium bodied versions were made. I was an auto electrician when these were launched. We had contracts with 2 FIAT dealers at the time and we were allowed to see them and drive one before they went into the showroom. I thought they were fantastic and very futuristic, especially for a FIAT. Of course, it wasn’t too many years before the tin worm set it. They have an enthusiastic following here in the U.K.

  5. Another school day for me too. Thanks to DTW and to the author.
    (Until then, I was not even aware of the Alcan company.)

    I also think it was a proof-of-concept on the part of Alcan, which is why they used any vehicle.
    The X1/9 was probably a good choice because Bertone, as a (small) manufacturer, was a better candidate for this exercise than the large manufacturers – who were probably less able to simply go through the production process with another material, in this case aluminium.

    What I wonder about is the function of the electrical system in this vehicle. A car body always has the function of the negative pole. Aluminium has a completely different conductivity than steel.
    (I’m probably outing myself as a complete idiot now and the question would answer itself if I had listened better to my teachers at the time, who tried hard to impart knowledge to me. Be that as it may).

    1. If I was Alcan, I would use a x1/9 as a starting point: if a convertible made by not the most considered automaker regarding structural integrity could be made to succeed, that might be a proof they were on the right path.
      In less words: if they had started with a SAAB 900, what would they learn?

      Or maybe the reasoning of said choice was quite the opposite, now that I thought about it…

      Speculation is allowed on DTW, God bless you😉

  6. Quite interesting and as Dave says, proof that you need to design an aluminium structure from the ground up instead of adapting an existing one. A truth, by the way, that is as old as the first switch in materials used very early in humanity’s development (pottery vs. stone, bronze vs. stone, etc.).

    You also need to be well versed in the various strengths and weaknesses (literally) of the material you use to make the most of a design. I seem to remember (perhaps wildly incorrectly) that aluminium Jaguars aren’t that much lighter than some well designed steel counter parts.

    What a lovely car the X1/9 is, by the way.

    1. Aluminium Jaguars as well as the Honda NSX aren’t much lighter than a car made from steel because they don’t make proper use of the material. Therefore they have to use much more of it, losing most of the weight advantage. The biggest progress made by the Jaguars was the invention of punch rivets that don’t need pre-drilled holes but use a process of punching the holes and riveting together the parts in one go.
      Audi’s A8 and A2 and the Lotus Elise show how aluminium should be used. Make extrusions and cast nodes and join them bonding or stretch fitting. Sounds expensive and was before Audi together with Alcan reworked their ASF technology for cheaper production by use of fewer parts.

    2. Thanks, Dave. That was indeed the point about the Jaguars, I think: that they’d made a lot of noise about the aluminium construction, but that they hadn’t done it very well. Disappointing about the NSX, though. You’d expect Honda to do better.

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