Placed Under Duress – an X1/9 like no other.
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 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.
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….
 Now part of Rio Tinto, the world’s largest aluminium producer.
Check out www.roadster-life.com for a six-minute video.