Technologies abandonnées

Throughout 2015, there were rumours that Citroën hasdecided to abandon hydropneumatics (the C5 Crosstourer would seem to bethe final iteration of this system).  In 2014, the Citroenianpublished a piece I had written on abandoned technologies and thispiece is based on that article.  Since Peugeot took over thecompany in1974,many of the core technologies that defined Citroën have beenabandoned as a result of enforced ‘banalisation’ of the marque.

In 2007, I was employed as a consultant for Citroën UK’s‘Different IsEverything’ marketing campaign and I was asked to come up with a listof ‘Citroën Firsts’.  For the UK company, this representedsomething of a U-turn.  In a bid to reinvent itself, the companyhad determinedly ignored its past - that is until the C6 waslaunched.  Here was a car that drew upon the technologicalinheritance of its forebears and, directed no doubt by the Paris HeadOffice, they decided to look back at their heritage.  The troublewas that in a Stalinesque rewriting of history, the company archiveshad been purged and there were few people left in the company who couldremember the pre-1974 glory days.  Which was why I was brought in.

Ian Hughes, Marketing Director atCitroën UK wrote a foreword to the Different Is Everything book:

My guess is that looking up your family's history must be fascinating.Discovering that you're connected so closely and directly to charactersrepresenting the full spectrum of personality traits could be eitheramusing or alarming, depending on your outlook, and what you find!

But working on this project - looking up our company'shistory, has hada quite different outcome. We have discovered so many incredible factsabout André Citroën  and his followers through the years that ithasgenuinely made us proud to say we're a part of the Citroën organisation.

André Citroën thought in a different way from everybodyelse, it's assimple as that. It wouldn't be an exaggeration to say that he was maybeone hundred years ahead of his time. He was responsible, almostsingle-mindedly, for putting ordinary people right across Europe intomotor cars. Where an industry didn't actually exist, he created it: cardealers, part-exchange, car finance, marketing and international salesoperations. In his factory he built a crèche and hospital and had botha subsidised canteen and shops, typical of today's caring management,but unthinkable in 1919!

The company went on to innovate inso many ways that 21st centurymotoring is still based on one of its earliest successes; with its verymany advantages, front wheel drive is now almost universal -Citroën conceived the first ever mass-produced car with this configuration withthe launch of the Traction Avant in 1934.

This wasn't thinking differentlyfor the sake of it, it was aninquisitive and analytical mind-set and the results were astounding.It's a philosophy we still practise today, as our current and upcomingmodels so clearly prove.

My list of 'Citroën Firsts' covered the obvious –

• the firstmass production car to feature unitary body construction;

• front wheeldrive;

• independent front suspension;

• torsion bar suspension;

• cardesigned according to aerodynamic principles (as opposed to so-called‘streamlining’);

• the first car to feature a high pressure hydraulicsystem offering a ‘total car’ solution that operated an infinitelyvariable rate, self-levelling suspension;

• fully powered steering;

• fullypowered brakes;

• powered operation of clutch and gearchange, etc. 

My list also included ‘firsts’ which I thought were importantin thehistory of the automobile such as:

• DIRAVI;

• single spoke steering wheel;

• headlamps linked to the steering;

• centre point/zero-offset steering;

• PRN ergonomics;

• anti-dive suspension geometry.

Citroën UK decided to edit my list so that the only technologiesmentioned were those that were, at the time, still in use.  Thiseffectively ruled out most of the technology used in the A Seriescars.  In a way, this was understandable.  Citroën UK haslong been ambivalent about the 2CV and its siblings; regarding itrather as one might an uncouth and provincial relative at a highsociety family gathering; a bit of an embarrassment.

The DS was okay although the ‘total car’ aspect of centralisedhydraulics was quietly ignored.  The Traction was safe since thatall happened long ago and British comedian Jasper Carrot hadn’t made acareer out of mocking it.

So, let’s start with the A Series.  My list comprised:
•   Front to rearinterconnected suspension  The great advantage ofthis is that the front wheel movement is transferred to the rear wheel– an upward movement as the front wheel encounters a bump results inthe rear wheel being provided with more travel and the result is a verysmooth ride.  The specifics of this system (a single, horizontallymounted coil spring) was not adopted by any other manufacturer but thefront to rear interconnection concept was adopted by BMC (later BLMCand then BL) in their range of Hydrolastic/Hydragas sprung cars.

•   Inboardfront brakes  One advantage of this is that it reduces theunsprung weight (and therefore the inertia) of the suspension. Another advantage is that this allows centre point/zero-offset steeringwhereby the pivot point of the steering (the vertical axis around whichthe front wheel rotates) runs through the centre of the tyre’s contactpoint with the road.  This leads to very precise and accuratesteering and furthermore, ensures that in the event of a front tyreblow out, the car remains on course and can be steered and braked tosafety.  Inboard brakes were not confined to the A Series ofcourse.  The D Series, SM, GS and GSA all made use of them. However, with the introduction of transverse engines, (from the CX on),there was insufficient room for inboard brakes or for centre pointsteering.

•   Frontsuspension geometry whereby the wheel leans over thereforeensuring that when body roll kicks in, the wheel remains perpendicularto the road surface. 

•   Anti-divefront suspension geometry whereby the lower pivot point ismounted forward of the perpendicular – under heavy braking, the carbody is forced upwards.  This geometry was used in all models upto those fitted with MacPherson struts.

•   Parkingbrake operating on the front wheels – this has the greatadvantage that it can be used as a very effective emergencybrake.  The disadvantage, when coupled with disc as opposed todrum brakes was the risk that the car would roll away if the brake wasnot firmly applied when parked on an incline.  This was caused bythe discs cooling and contracting.

•   Yoderhinge – used for the 2CV bonnet and bootlid.  I suspectthat increasingly stringent safety regulations were responsible for thedemise of this invention.

I then turned to the D Series and the list included:

•   Centre-lockroad wheels – I would imagine that these were abandoned sincemany tyre outlets did not have the appropriate machinery to allow themto balance the wheels.

•   Single-spokesteering wheel – this was effectively killed off by the need tofit an airbag in the steering wheel.

•   Directionalheadlamps – discontinued and then subsequently reintroducedafter the competition re-invented them.

•   Highlevel rear indicators – this item was retained by Citroën UK –somehow the marketeers made a connection between them and the boomerangrear light cluster of the C6 – they were both ‘unusual’: never mindthat the D’s lights were far more visible than indicators mounted in alower and more conventional location.

•   Removablepanels bolted to a skeleton frame  British car manufacturerRover adopted this type of construction for its P6 model in 1963.

•   Lightweight‘plastic’ body panels – initially used for the roof in the DSand later used on the Méhari (for the entire body) and AX and BX toreduce weight and thereby improve performance and economy.  Again,it is likely that safety regulations bore a large part in the death ofthis idea – although current cars do use plastics for some body panelssuch as bumpers and grills.

•   Centralisedhydraulics – as mentioned above, this was a ‘total car’solution; elements of which were abandoned, starting with the steeringin the BX and subsequent models and then moving to the brakes.  InCitroën marketing speak, this is a ‘decentralised’ system when it isconfined to the suspension.  From a purely economics perspective,it makes sense to build cars from a common parts bin.  At thetime, Citroën claimed that there were concerns about powering thebrakes off a central high pressure hydraulic system should the enginedie.  This is, of course, complete nonsense since the brakes havetheir own accumulator which provides power for the brakes in suchcircumstances and once that reserve is exhausted, the suspensionpressure can be used.

•   Mineral-basedhydraulic fluid – far superior to conventional brake fluid whichis intensely hygroscopic.

•   Articulatingunion (D rear brakes) This was developed at atime when conventional flexible tubing could not withstand the veryhigh pressures used in the Citroën hydraulic system.  A swivel wasmounted on the rear suspension arm in line with the middle of thesuspension arm bearings so that it could rotate with the arm in thebearings. The output half of the swivel was fixed to the suspension armand moved with it while the input side had an arm which was anchored tothe chassis, keeping that side stationary in relation to thechassis. The input side was of a larger diameter and fitted over the end of theoutput side with O ring seals between them and a dust seal over thejoin. An aluminium cap finished off the outer end and kept dirt awayfrom there.  When the brake is applied, fluid enters the pipethroughthe outer housing into the space between the outer and inner housings.There is a shallow groove in the inner housing that creates this spaceand an O ring on either side of this groove, mounted in their owngrooves in the outer housing, which prevented the fluid from leaking.The inner housing had a hollow centre and a hole from the shallowgroove into this allowed the fluid through. The inner housing had theoutput pipe attached through the side of it and the fluid can thereforeflow straight into the pipe and thence to the brake cylinder.

•   DIRAVIMovingon from the DS, the SM introduced the world to DIRAVI which is anacronym for "Direction à rappel asservi" (steering with power assistedreturn") which was marketed as VariPower in the UK and SpeedFeel in theUSA.  This was a fully hydraulic ‘steer by wire’ system with nodirect mechanical connection between the steering column and thesteering rack during normal operation although a mechanical connectionwould be established in the event of a loss of hydraulicpressure.  It provides automatic return to the straight aheadposition whenever the engine is running.  The centring forcevaries in relation to both vehicle speed and steering wheeldeflection.  The system requires minimal physical exertion and isa delight to use once one has got used to it.  It allows for veryhigh ratio (and therefore fast) operation with only two turns from lockto lock in the SM (2.5 in the CX and 3 in some LHD V6 XMs). Front tyreblowouts, potholes, and other road surface irregularities cannot affectthe steering since the direction of the steered wheels can only bechanged by steering wheel input.
Probably the reason for abandoning DIRAVI was that it took time tobecome acclimatised to it since there is no mechanical feedback to thedriver.  The feel is entirely artificial and bears no relation tothe actual forces acting on the front wheels.
DIRAVI was fitted to the SM, most CXs and some XMs and was also fittedto the SM’s Italian stablemates, the Maserati Quattroporte II andKhamsin.

•  Hybridchassis/body The CXwas fitted with a hybrid chassis/body arrangement whereby the front andrear subframes were connected and the bodyshell was mounted on noiseand shock-absorbing mountings.

•  Air-cooledboxer enginesOver the years, Citroën experimented withalternative engine configurations, starting with thehorizontally-opposed twin cylinder that powered the A Series.  Ahorizontally opposed six cylinder was proposed for the D Series but wastoo thirsty.  A four cylinder unit was developed for the GS, GSAand Ami Super but this suffered from noise since, being air-cooled, itlacked the sound damping effects of a water jacket. It was also thirstyand suffered from a relative lack of power. My C6 V6 diesel returnsbetter fuel consumption than my 1015cc GSX managed.

•   Wankel rotaryengine Citroën co-developed the Wankel rotary engine with NSUbut as was all too often the case with Citroën, there were insufficientfunds to develop the concept and overcome its shortcomings of excessivefuel consumption and emissions, not to mention the rotor tip wearproblems.  Mazda who stuck with the idea have been successful butthe vast majority of their cars use conventional engines.

•   PRN satellitesPRN(Pluie = Rain, Route = Road, Nuit = Night) satellites were first seenin production in the CX although they were first proposed by MichelHarmand in the stillborn Projet F in the nineteen sixties. Earlyversions of the Visa, the GSA (although on early UK versions of thiscar, the old GS set up was used) and Oltcit Axel and early versions ofthe BX used this highly ergonomic answer to the proliferation ofswitches and stalks that required twisting, pushing and pulling thatwere fitted to the majority of other manufacturers' cars.  All thecontrols were logically grouped around the steering wheel therebyallowing their operation without having to remove one's hands from thewheel.  Notwithstanding their superior ergonomics, a conservativeclientele preferred a more conventional set up and modern Citroëns arefitted with the by now traditional stalks.

•   Faired-in rearwheelsA commonly used styling motif was half-faired rearwheels; first seen on the 2CV and then on all subsequent models untilthe LN.  This conveys an aerodynamic advantage since theturbulence caused by the rotation of the wheels is reduced. Furthermore, in an era when nearly all cars were rear wheel drive, itemphasised the front wheels and thereby emphasised the fact that thecars were front wheel drive.

Many of the technologies invented or adapted or adopted byCitroën have become mainstream but a much larger number have beenabandoned.  Sometimes this is due to legislation and sometimes ithas been a matter of cost.  Sometimes however, I suspect thatPeugeot has philosophical objections – especially when the Citroënsolution is easier and cheaper to implement than the conventionalalternative and proves to be more effective. 
It seems to me that Peugeot wishes to sell to the lowest commondenominator – those people who would never dare to have consideredsomething so outré as a DS or 2CV.  Citroëns used to appeal tobuyers on a number of different levels – philosophical, intellectualand aesthetic. 
Under Peugeot’s management, the all-important thing was to make Citroënprofitable which meant that conventionally engineered cars at bargainbasement prices became the norm.  Recently, there has been a shiftaway from this paradigm but (with the exception of the soon-to-beabandoned C5 and the now obsolete C6), the appeal seems restricted toaesthetics. 
Citroën used to make cars which were mechanically and conceptuallydifferent from those built by other manufacturers.  ModernCitroëns are, for the most part, mechanically and conceptuallyconventional and, just like the competition, use electronics andstyling in an attempt to be different although the current C5 usesstyling in an attempt to be similar to the Teutonic competition. The DS range (now a marque in its own right) relies solely on stylingto make it identifiable. 
And as for bubble wrap and a touch screen on the C4 Cactus…