We conclude March’s theme by wondering if the engineering ideal of suspension that thinks for itself is any closer to reality now than it was thirty years ago.
Pity the unfortunate suspension engineer, saddled with the seemingly impossible task of reconciling the hugely complex operating range of the motor vehicle against the twin imperatives of providing a comfortable ride for passengers, while allowing sufficient body control to allow for accurate and consistent handling. Under such constraints, the successful melding of conflicting forces acting vertically in ride and horizontally in cornering and steering, can only result in unhappy compromise.
Physics will always win, no matter how clever our putative chassis guru might be. And some of them have been very clever indeed, although superiority in this sphere can often be as much a function of an intuitive proving engineer as any groundbreaking idealist. Take for instance, the ability to successfully marry tyre and suspension characteristics, often being a process tantamount to alchemy. According to Leonard Setright, who seemed to know about these things, what was good for handling was also good for ride, although in this respect I’ve never fully understood what he was on about.
But some things will always hold true – for instance a tired driver is a less alert one. Because despite what Alec Issigonis might have asserted, driver comfort was, is and remains a safety issue. Given there’s been better solutions to the conventional steel spring/damper suspension available for well over half a century, we really ought to have left it all behind years ago. But complications of cost and cowardice have allowed the motor giants to successfully soften up the motoring public to low expectations, a position now gleefully accepted without question. Harsh = sporty = good. QED.
With Citroen and BMC blazing a more virtuous trail decades ago, it’s clear that some form of computer controlled, hydraulically actuated suspension system was and remains, if not the holy grail, a decent stab towards it. Lotus began working on active suspension technology around 1980 during the ‘ground effects‘ era of grand prix racing, when the levels of downforce being generated were effectively doubling the car’s static weight at racing speeds and the required suspension stiffness rendered the cars virtually undrivable.
This led to work on ‘synthetic springs’, hydraulic arms powered by a pressure pump and actuated by computer controlled valves. There were no springs, more a series of links worked by what Lotus engineers described as muscles controlled by an electronic brain, responding to sensors and a series of control parameters. Basically, active ride allowed Lotus to decouple force from displacement and the results as reported by Car‘s Steve Cropley in October 1986 were, even allowing for his notable propensity towards hyperbole, pretty impressive.
Cropley observed that the test Lotus Excel; “…refuses to roll or dive, or lurch or pitch, whatever you do. The car felt, most eerily, to be in touch with the road… All you could conclude was that this was a car that didn’t have to obey the rules that other cars live by”. Car made it their cover story, proclaiming the Lotus’ active prototype as; “the greatest single advance in car engineering since the war.”
Having reached a stage in its development where car companies such as GM, Volvo and others were successfully running prototypes, why it failed to make the final hurdle to series production remains one of those automotive mysteries yet to be satisfactorily explained. Cost, complication, politics? Certainly, the results being reported in 1986 suggested its introduction was imminent.
In its absence, perhaps the nearest and best approximation is the excellent Tenneco kinetic system used by McLaren in their current road cars. Mercedes-Benz too, having experimented with air and a form of oleopneumatics themselves over the years currently expound upon what is cringingly referred to as ‘Magic Ride‘, which despite being undoubtedly clever, sounds like a decal you’d find residing beneath a side rubbing strip on a mid-80’s Mitsubishi Tredia.
Employing lasers to read the road ahead and telegraphing this data directly to the suspension’s electronic brain has certainly yielded notable gains in passenger comfort, but behind the microprocessors remains hardware that would not be unfamiliar to a 1950’s mechanic. But even active ride on the cheap is better than nothing at all and at least Daimler are making the effort, which is more than can be said for most.
But looking further ahead, what form of suspension design will the autonomous car of the future take? By decoupling the driver from the equation, surely such terms as ‘ultimate handling, steering feel and incisive turn in’ won’t butter too many parsnips. But I suspect ride comfort will. After all, while technology can envisage a world without rough edges, reality tends to rather annoyingly intrude. Because in our roseate binary future, road surfaces will continue to crumble beneath our wheels. Not everything’s going to get better.