20 replies to this topic

[meb58]

I have seen some pictures of this car and it looks like an active suspension setup...but I am not entirely sure?

[desmo]

http://www.carbodyde...spension-lg.jpg

Active maybe in adspeak.

[meb58]

The upper portion that I saw is missing from that photo...there appear to be two crossed hoses running the top of the damper perch/pivot

[mikeyb]

The article that picture is from says "The dampers are interconnected hydraulically and provide adaptive responses depending on both road conditions and driver preference."
Another possible purpose for those hoses is "Proactive Chassis Control system, which features adjustable roll control which replaces the conventional mechanical anti-roll bars."

[SimonW]

More pictures here and the next 8 or so taken at Goodwood FoS this summer.

Simon

[benrapp]

I'm going to a launch event on the 15th at which I've been promised access to members of the design team, if anyone has any questions they would like me to ask.

[Greg Locock]

Active maybe in adspeak.

From memory Kinetic originally offered three generations of design of which the second is more active than most systems that claim to be active, but not as active as an active suspension. The first generation was 'just' cross linked shocks with remote valving, so they got selectable roll stiffness as well as variable rate shocks. That is a very attractive option for production cars, especially off roaders. I can't remember the details of the more complex versions, but I think they included gas springs, so could be considered to be active with the addition of a pump.

[meb58]

...I thought the hoses, crossed in the fashion that I can see in the photo, controlled hydro. SB as well...

[Alloyd]

I wonder if this is an implementation of the ideas of Professor Malcolm Smith of Cambridge University. McLaren came into contact with his work because the inerter came from him. In 2005 he co-wrote a theoretical paper on interconnected suspensions which describes as one of two implementation strategies a hydraulic interconnection of the suspension units.

[Greg Locock]

I wonder if this is an implementation of the ideas of Professor Malcolm Smith of Cambridge University. McLaren came into contact with his work because the inerter came from him. In 2005 he co-wrote a theoretical paper on interconnected suspensions which describes as one of two implementation strategies a hydraulic interconnection of the suspension units.

Kineic have been promoting their system, for 10 years or so. Moulton proposed various interconnected suspensions in the 60s using hydrogas or fluid units, and built them. It wouldn't exactly amaze me if Citreon or even Lanchester had some prior art there.

[StressedDave]

By my reckoning, Kinetic have been working on the system for a lot longer than 10 years. I remember driving around an MoD test track in 1993 in a prototype shipped over from Oz.

[DaveW]

I wonder if this is an implementation of the ideas of Professor Malcolm Smith of Cambridge University. McLaren came into contact with his work because the inerter came from him. In 2005 he co-wrote a theoretical paper on interconnected suspensions which describes as one of two implementation strategies a hydraulic interconnection of the suspension units.

I don't wish to belittle Malcolm Smith. He is clearly a highly capable & innovative control system engineer. It doesn't necessarily follow that his ideas are original, however. For example, the first inerter patent I know of was published in 1949, & I rig tested a passive, hydraulically linked, "modal" suspension fitted to an F3 vehicle in July 1997, designed & built by Louis Karmios. It worked & was occasionally faster than a conventionally suspended equivalent, but I suspect the intractable problem in his implementation was (a lack of) accurate ride height control with varying temperature in a "closed" system. I've not thought how it might compare with the Kinetic system.

I'm tempted to add that Cambridge & other Universities should concentrate on what were intended for - to accumulate & disseminate knowledge - & leave "big business" games to ... big businesses, but that would reveal my prejudices.

[ferrarifan2000]

Sorry if this is a dumb question, but what can this set-up do that a MR-fluid damper can't? AIUI, a MR damper can alter compression and rebound for different wheels in a similar way. Is the hydraulic ARB capable of adding energy into the system, giving it a wider range of motion and more control?

[Bloggsworth]

Almost sounds like hydrolastic suspension to me, we had that on our 1963 Austin 1100...

[ferrarifan2000]

I found this. The suspension uses a gas spring too:

"The MP4-12C’s clever suspension bits worked so well in Sébastien Loeb’s Citroën rally car that the FIA banned this technology in 2006. What looks like an ordinary shock absorber at each wheel is instead a hydraulic cylinder. In relation to wheel motion, a piston inside each cylinder pumps hydraulic fluid into and out of the chambers above and below the piston. All eight chambers are connected to two accumulators, each of which contains fluid and nitrogen separated by a bladder.

Unlike conventional shock absorbers, these pistons have no orifices or valves. Instead, the flow restrictors are located where the hydraulic lines attach to each cylinder. The size of the restriction, which is varied by an electronic controller, determines the amount of damping provided.
Hydraulic lines connect the four wheel cylinders to two accumulators.

The pressurized nitrogen contained within the two accumulators acts as a spring to resist roll motion; each accumulator handles one cornering direction. Individual wheel motion is resisted by the coil springs.

This technology saves the weight and complexity of conventional anti-roll bars, but more significantly, it’s a boon to tuning. Soft springs and gentle damping provide a pleasant ride. A high accumulator spring rate assures minimal body roll, which is further diminished by adding more fluid to each accumulator. When the driver turns a cockpit knob from the normal setting to sport or track mode, an electric pump adds the appropriate amount of hydraulic fluid. (Infiniti and Toyota also use versions of this Tenneco Kinetic system.)"

http://www.caranddri...ckledown_page_2

[Greg Locock]

(Infiniti and Toyota also use versions of this Tenneco Kinetic system.)"

Yup, Toyota use it in the Prado. Does what it says on the box.

[TDIMeister]

I think Audi among others have done such a hydraulically-linked damper arrangement, but they are connected diagonally, not left-right. Magneto-rheological fluid may also be involved, thus one could call it an active-suspension.

[Greg Locock]

I think Audi among others have done such a hydraulically-linked damper arrangement, but they are connected diagonally, not left-right. Magneto-rheological fluid may also be involved, thus one could call it an active-suspension.

The marketing people can call it whatever they like, but unless significant energy is added to the system via pump or the like then it isn't active in an engineering sense. The Kinetic system can be active, but usually isn't. MR fluid by itself just offers a rather better alternative to switchable dampers, often described by the almost meaningless term semi active.

The problem with the terminology is that the technology is a continuum, not many people would regard adjustable ride height or perhaps decouplable sta bars as active suspension, but until you start talking bandwidths then classifying the different systems is a mess.

[TDIMeister]

I'm just a messenger.
http://www.rpmexotic...RS6.pdf#page=46 (starting from page 46 of the PDF, 41 of the document)

[gruntguru]

The marketing people can call it whatever they like, but unless significant energy is added to the system via pump or the like then it isn't active in an engineering sense

Not sure if that is a useful definition. Typical suspension systems need to dissipate significant amounts of energy, so in theory a genuinely "active" suspension could be designed to utilise some of this energy.

[Greg Locock]

Not sure if that is a useful definition. Typical suspension systems need to dissipate significant amounts of energy, so in theory a genuinely "active" suspension could be designed to utilise some of this energy.

Sure, for instance the Bose electrical suspension could run on virtually no external power, on average, in theory. Or you can change your shock valves to one way valves to vary the ride height (that's a real effect, cars jack down on rough roads because rebound damping is greater than jounce damping). But in practice there seems to me to be a useful distinction that can be made between systems that directly power the suspension, and those that merely power control devices. However I agree it is all shades of grey and definitely is not worth going to the barricades for.

Edited by Greg Locock, 06 March 2011 - 03:51.