We return to our two stars of the spring 1969 season with a look at the different approaches to chassis design adopted at Longbridge and Lingotto. One car defied convention, the other defined the new orthodoxy.
Raw facts first: The Fiat 128 uses MacPherson struts at the front, with coil springs and a transverse anti-roll bar, and a fully independent system at the rear, comprising a transverse leaf spring, struts, and a single wishbone per side. The Austin Maxi has Hydrolastic springing and interconnection, with upper and lower links in a parallelogram arrangement at the front, and fully trailing arms at the rear.
That disregards the detail, which is significant in the understanding of the designers’ mindsets.
There are two important things to understand about Hydrolastic / Hydragas suspension. The first is that interconnection is more fundamental to the system than the springing medium. The second is that it went through a process of constant evolution. The 1100 and Mini were most similar, the 1800 brought a near-complete rethink, eliminating front and rear subframes, and placing the front displacers horizontally, high on the front bulkhead.
The Austin 3 Litre, launched in October 1967, had self-levelling, and introduced a new type of displacer in which the front to rear connecting pipes feed below the damper partition, rather than above it, to allow separate control of pitch damping through sizing of orifices in the front and rear interconnection pipes.
The 3 litre’s displacers were found to be a worthwhile improvement, and were adopted for the Maxi. The Maxi’s front suspension follows the subframeless 1800’s principles, but with a subframe which incorporates a tube enclosing the horizontal ‘back to back’ displacers.
This arrangement facilitated off-line assembly of the complete powertrain and suspension.
To the same end, the Maxi’s rear suspension was a bolt on-unit with wide-based trailing arms shaped like an asymmetric letter T. Unique in the Hydrolastic pantheon, the rear displacers are centrally located, side by side. At the time of the Maxi’s introduction, it was speculated that the arrangement could facilitate the addition of a self-levelling system, though none ever appeared. There’s evidence of intelligent cost-saving and production simplification – wide based suspension arms to simplify bearing design and use of pressings instead of forgings.
Two other details are worthy of note in the Maxi’s rear suspension. Items 30 and 35 are ‘trim bars’, small torsion bars which are used to control pitch.
Item 60 is an arch spring, effectively a refined bump stop which removed the need for self-levelling. Alex Moulton’s developments in rubber suspension had their origins in the railway buffers produced by his family’s business, so there is a nice piece of historical continuity in these items.
It is a matter of regret that the Maxi was the last Moulton / Issigonis collaboration on suspension. Issigonis’ abortive 9X Mini replacement used steel springing, while Dr. Moulton continued to work with Harry Webster on the Allegro and 18/22 Series, and on into the Metro / MGF era.
Regrettably the Maxi’s steering let it down, being low geared and yet also heavy.
Autocar is either being kind here, or simply ignoring the plainly obvious. The Maxi’s wheel is tilted at least 40 degrees to the vertical – around the same angle as the 1800. There is a good reason for this – the angle facilitates putting more physical effort into the wheel, disguising the ‘weight’ of the system. It is a form of “poor man’s power steering” more usually found on commercial vehicles. The Maxi would have benefited greatly from a power steering option, but never got it, unlike the 1800, on which hydraulic assistance was available from March 1967.
Steering apart, the Maxi’s chassis seems to have been thoroughly competent in ride and handling characteristics. It’s a pity that the “platform” did not find wider use at BLMC. The Moulton / Issigonis spat and the Stokes-era drive to cut costs slowed the momentum of development. The 1973 Allegro’s Hydragas system was compromised by cheapening to the point where it had no real advantage over a well-designed steel sprung set-up.
Dante Giacosa has been consistently praised for his modesty, decency, and sympathetic character, but wasn’t above making the occasional side-swipe at his rivals in his memoirs. In 40YODWF he wrote: “As far as I was concerned, I had played about with various designs for pneumatic and hydro-pneumatic elastic suspension systems but I came to the conclusion that cost and risk of defects were against it. The traditional system of metal springs is simple, reliable, and cheaper, therefore preferable in my opinion, even though it does not keep the level of the vehicle constant as the load varies.”
The final sentence typifies Giacosa’s mindset – simplify, refine, do not accept cost effectiveness and functional effectiveness as being mutually exclusive.
Peugeot and Honda had already shown how MacPherson struts could work with front wheel drive; Giacosa and Cordiano’s task was to do more with less.
The 128’s front suspension has no wishbone per se, rather a forged transverse link and an anti-roll bar of substantial section forming the front part of the triangle, insulated from the transverse link by a flexible bush. Rack and pinion steering is used, with the rack mounted on the front bulkhead.
Some time in early 1968, Dante Giacoasa and Ettore Cordiano had a mild disagreement over the rear suspension of the Fiat 128. Surprisingly, given his reputation as a chassis wizard, Cordiano favoured a beam axle on longitudinal leaf springs, as used on the Autobianchi Primula. Giacosa insisted on all-round independent suspension, citing the need to match the ride quality of French competitors.
Giacosa prevailed, and he and Cordiano developed a deceptively simple design of remarkable effectiveness, with the struts set up to provide some passive rear wheel steering, and the transverse leaf located to be able to ‘float’ to give roll resistance and accommodate adversely cambered surfaces.
The biggest design problem was accommodating the difference in weight distribution between driver-only use and fully laden conditions in a light car with its heaviest masses concentrated over or just ahead of the front axle. Judicious choice of spring rates, and the use of progressive bump stops as an active element of the suspension addressed the problem effectively – Dr. Moulton would have approved.
Giacosa was rightly proud of the design and wrote in 1979:
“I consider the rear suspension of the 128 and the ‘138’ (the Ritmo) to be one of the most functional, economical, and simple of all. And when the transverse spring can be made of a single layer of synthetic material reinforced with glass fibre or some equivalent, a further step forward will be taken in reducing its weight.”
Look upon the 128’s suspension and it looks slim to the point of fragility, but it performed effectively, and was not just copied closely by other manufacturers, but was also used as a benchmark for ride and handling for the upcoming generation of front wheel drive cars.
Reference sources: See part one