88 replies to this topic

[Guineapiggy]

Let's start with the basics of my question: In Formula 1 between the late 80s and early 90s various Formula One cars ran active suspension, I think I'm right in saying that the purpose of active suspension is to get better ride height of the car, yes?

Now, the problem I'm having is that I can't work out how this was put in to practice effectively. If a car reacts to ride out every single bump by maintaining the same ride height it needs to jack the suspension up by the right amount, yes? The problem I can see is the idea that it's putting an 'opposite' force through the suspension by doing so that surely would cancel out the spring and make the car very erratic over bumps? Is this the case? And if not or indeed if so how did they overcome it?

[Greg Locock]

Imagine that you are coming up to a single wheel bump. As you approach the bump, lift the wheel so it just skims over the bump, distribute the slight extra load from accelerating the wheel upwards between the other three wheels. Then do the same for the rear wheel.

That essentially is the magic carpet ride you are aiming at.

The problem is that without millimetric radar you can only sense the bump once it starts to happen, so you are always shooting from behind the eightball.

Now that millimetric radar is available for cars, you might expect a resurgence of interest in active suspension. Or perhaps it has outworn its welcome.

[saudoso]

I nerver really got into understanding it, but if I where to develop it I would go around riging a bicicle and try to figure out what my legs and arms where doing to try to keep my head steady as the wheels bump around rocks on the dirt.

The other experiment would be getting a ride in a car with a cup full of hot coffee, cap off, obviously.

Basically you try to keep a steady force on each support point, and let the arm or leg move up & down to compensate for the bump.

With cars even if you are not measuring all the heights at all the four corners, you know the position of each one of the wheels, and you can tell wich one if off.

[canon1753]

During the time active suspension or active ride suspension was usable in F1, Lotus (especially, since they were the first to develop it and were the only one with production road cars ) would always say active suspension would work so much better on road cars, yet there are few, if any road cars that use (or claim to use) this technology. Why is that? Is it too expensive or was it a technological blind alley?

Thanks

[murpia]

My understanding of F1 active ride was that it worked more like controlled self-levelling suspension than Greg's 'magic carpet'.

Consider that bump inputs are high frequency and so try not to transmit them to the chassis, using the equivalent of 'soft' conventional springs and dampers.

The chassis movements (and the ride height targets with speed and distance round the lap) are low frequency by comparison and are handled by the hydraulics of active ride. Roll control comes for free with this setup, although it probably represents the upper bound of the low frequency range of movements. How roll couple distribution is handled I don't know.

I believe this was done with one or more small hydraulic accumulators on each corner (piston separating a gas pressure from the fluid). Small high frequency movements activate the accumulator, while the 'average' position of the suspension depends on the controlled hydraulic pressure.

It's also possible that active 3rd springs were used with conventional side springs, then the car would roll as usual with roll couple is dictated by the mechanical setup.

Anyway, maybe someone who knows for sure can comment?

Regards, Ian

[J. Edlund]

There is a U.S. patent issued for Williams active suspension in 1989, it has patent number 4,861,066.

Basically the system is described as a gas-hydraulic system where a linear potentiometer measure the postion of each gas-hydraulic strut. An on board computer get the data from each potentiometer, and if there is difference between the actual value and the predetermined value of strut position a proportional servo valve control the flow of hydraulic fluid so that the strut will return to the predetermined position.

[mariner]

The avowed goal of Lotus F1 active was to keep a constant ride height for underbody aerodynamics but still allow some real suspension movement. It was a complicated way ( purely in the racing context) to do what the Lotus 88 twin chassis car did with simple design.

I once had cause ( for reasons entirely unconnected with cars) to talk to Darin Dellinger of Delphi who was, I think, one of the architects of Magna ride, the infintely variable MR damper.

He clearly referred to "sky hook" damping which was I think one way used originally to define Active suspension. I guess that ideally requires forward radar etc. but my impression of the conversation with Darin Dellinger was that the computers for MR dampers could get close to that IF you could define the environment. For example if you wanted to run a Corvette flat out in Alaska ( feasible from a traffic viewpoint) you would need an algorithm which recognised the frost heaves on Alaska roads or else you could shoot off the road. Again it was a non car conversation but he seemed to think MR could get a long way towards active.

As I recall the drawback with Lotus active was the power needed to operate the Moog valves and pump up the struts against very heavy downloads at racing speeds. If you want an interesting ( at at times very funny ) commentary on Lotus active read the Tony Rudd autobiograhy " it was fun".

On a slightly different note it is said that Fred Lanchester , who was maybe the first guy to apply basic engineering principles to car design at the beginning of the 20th century, decided on the ride frequency by estimating the natural gait of a man and setting the spring rates to acheive that. I dont know if that is true but if so he is possibly the first numbers driven ride and handling engineer.

[phantom II]

Great post. I don't mean to high jack yet another thread, but Lanchester was one hell of a man. My first introduction to him was thru aviation circles and a book called Aircraft in Warfare. His combat tactics are still studied at FPS today. He developed the math that demonstrated turn abilities of various birds. Why a hawk can't catch a sparrow, etc. We talk about Cof G and Cof P in aircraft and race cars. That was him who first discovered the importance of the relationship between the two and how birds move these two points for maneuverability.
A friend of mine was an aerodynamicist at NASA and his hobby was plotting flight dynamics of high performing birds. He died before completing his Puffin pusher aircraft. It is in the EAA museum now. He had all of Lanchester's books on flight dynamics and was inspired by the man.
A real must if you visit England, is the Imperial War Museum and the RAF Museum where there is a section dedicated to Lanchester. Also see the Battle of Britain Museum. I visit these places most every year. His theories of flight and combat was the reason Japan became so powerful in aviation and industrial innovation between the wars. He beat Henry to a mass produced car and Leland's Cadillac to interchangeable parts.
He invented disc brakes, fuel injection, turbo charging, power steering, etc.

The ZR1 has the most advanced Magna-Ride active suspension to date.
Resume normal navigation.

http://en.wikipedia....liam_Lanchester

http://lanchester.me...xt/volume3.html Books.

Originally posted by mariner

On a slightly different note it is said that Fred Lanchester , who was maybe the first guy to apply basic engineering principles to car design at the beginning of the 20th century, decided on the ride frequency by estimating the natural gait of a man and setting the spring rates to acheive that. I dont know if that is true but if so he is possibly the first numbers driven ride and handling engineer.

[jpf]

if you wanted to run a Corvette flat out in Alaska ( feasible from a traffic viewpoint) you would need an algorithm which recognised the frost heaves on Alaska roads or else you could shoot off the road. Again it was a non car conversation but he seemed to think MR could get a long way towards active.

re: active ride and Alaskan frost heaves, that's one thing that I think is really interesting about active ride, which is that it introduces software engineering into suspension dynamics as the vehicle operates (rather than in the development of an ultimately passive system). This is true of MR dampers too, just to a lesser extent.

I think the idea of taking data streams of suspension positions, velocities, and accelerations, and measurements for the same from the sprung mass, incorporating throttle demand, steering input, etc. and defining behavior modes is really cool. Not least because of the ways it ends up examining and defining the intensions behind the driver's control inputs, and trying to accommodate them. This is the real heart of modern technological innovation -- developing systems that explicitly try to work at the underlying matter, rather than developing tools for particular tasks.

I'm sure it's complicated stuff to add on top of the normal kinematic complexities of suspension design. But, it's all the same stuff that is used in stability control, and the work being done there might be useful in developing the behavior modes that describe the system responses. I'll tell you what, it really makes you appreciate the fact that they were able to make workable systems at all 20 years ago. That was really cool work.

[sblick]

Active Suspensions have been doomed because of the power needed to drive the pumps. On the order of 20-40 horsepower the last time I heard. So maybe someone like Bugatti or Rolls could sacrifice some power for ride but I don't think you will see Active Suspensions in a normal car. The MR shocks I think will be the closest a normal car will get to Active. A fun thing might be to crack the software on the shocks and tune them like you do an ECU for your engine, or possibly buy codes for certain tracks. I would be up for spending 200 or so for a track specific shock tune.

[manchild]

What made FW cars superior was the fact that on the straights active suspension greatly reduced drag and increased speed by raising the ride height. In corners, the ride height was set as low as possible enabling more downforce, lower cog, leveled car and stiffer suspension on the outer side of the car (relative to corner direction).

[Gerald Ryan]

Active consumes about 5 - 7 bhp, usually less. Do the maths and don't forget to put a hydraulic accumulator or two in the circuit to deal with transient peaks.

The main reason active didn't get into production was that the large car makers did not want to invest the cash. The Americans didn't think the public would care enough to notice the difference (although GM got close at one stage to putting the system in the Corvette, their own general incompetance in chassis matters put paid to that project) and the Eurozones didn't want to pay royalties. The manufacturers have since wandered about developing various half-way-house systems. The final nail in the coffin was that servo-valve manufacturers were not keen to reduce cost of their valves to the point they would become suitable for cars. They feared that allowing such cost reductions to occur would make the things ubiquitous and wreck existing industrial markets for components and technical services. {A servo-valve suitable for your car's active suspension will cost around US$7,500. You need four, possibly five.}

To be fair to the servo-valve guys, it has to be admitted that the car industry has not been kind to its suppliers, squeezing them mercilessly over many years. Far easier to deal with a small high price market instead.

BTW it is important to understand that there are several suspension systems known as "active" that were utilised in F-1. Only the Lotus was a true active one. The Williams system is best considered a form of semi-active. Their mechanism consisits of a gas spring and a column of hydraulic oil in series. The active intervention is to alter the quantity of oil in the column. Think of a Citroen self-leveling system operating fast and you'll have a reasonable approximation of it. Such a system remains partially passive as its gas spring reacts to bumps. The alteration of oil quantity in the column can only be done within certain limitations (for example you must avoid exciting the spring to resonance or getting stuck in a situation where all that the additions and subtractions of oil achieve is to work the gas spring). The Williams system was called "reactive" by their own engineers and that's probably a fair description of it.

The only fully active system in F-1 was the Lotus. It used solid hydraulic struts at each corner of the car. When springs were used, they were in parallal with the hydraulic struts, not in parallel. The springs were used to save energy required to operate the suspension and also removed a particularly nasty failure mode.

Note that, as well as using their more widely known full active suspension, Lotus also employed a semi-active suspension system in F-1 for a time. These were two completely different systems.

Fantastic stuff which should be in our cars by now instead of all this airbag and telematics nonsense.

Regards


Gerald

[phantom II]

I don't think you can have an active suspension with springs. The Cadillac and the ZR1 have springs. The ZR1 spring is much softer than the Z06 spring so the MAGNA shock acts as a spring and a damper. I think active means keeping the chassis level.
I don't think that there should be any resistance to the wheel motion in bump and droop provided the body is where it should be. Air Ride Technologies in Indiana build fast reaction double convoluted air spring suspension systems. The spring and the damper are one and electronically controlled much the same as the Citroen Mercedes system. ART only acts on the individual wheel but all the systems are in place in OEM to make them completely active.
I was skiing in Jackson Hole over Xmas and I pretend I am a car. I paid attention to my muscle activity and I observed that the damping force is only activated at the extremities of motion and mostly in full jounce when the amplitude of the moguls is regular. You can brace yourself for a big mogul and initiate resistance in advance. Moguls in a dip with a concave radius is tough on the old leg muscles. This is where radar is needed in a car. I also tried it with my eyes closed for brief moments. The leg muscles react almost the same way but you would bottom out on a big mogul. Both methods are reactive if conditions are uniform. If you ski in bright sunlight, mogul profile definition is invisible and you don't ski quite as well but your head stays level anyway. I think cars systems can re act faster and most of the time, pre bracing is not necessary. Mercedes tighten seatbelts and pressurize bakes if the radar detects objects ahead. Maybe the suspension is also put on alert.
At all times, there is muscle energy keeping the ride height or my head even. A KERS accumulator system on cars can be part of energy retention saving the compressor motor.

Originally posted by Gerald Ryan
Active consumes about 5 - 7 bhp, usually less. Do the maths and don't forget to put a hydraulic accumulator or two in the circuit to deal with transient peaks.

The main reason active didn't get into production was that the large car makers did not want to invest the cash. The Americans didn't think the public would care enough to notice the difference (although GM got close at one stage to putting the system in the Corvette, their own general incompetance in chassis matters put paid to that project) and the Eurozones didn't want to pay royalties. The manufacturers have since wandered about developing various half-way-house systems. The final nail in the coffin was that servo-valve manufacturers were not keen to reduce cost of their valves to the point they would become suitable for cars. They feared that allowing such cost reductions to occur would make the things ubiquitous and wreck existing industrial markets for components and technical services. {A servo-valve suitable for your car's active suspension will cost around US$7,500. You need four, possibly five.}

To be fair to the servo-valve guys, it has to be admitted that the car industry has not been kind to its suppliers, squeezing them mercilessly over many years. Far easier to deal with a small high price market instead.

BTW it is important to understand that there are several suspension systems known as "active" that were utilised in F-1. Only the Lotus was a true active one. The Williams system is best considered a form of semi-active. Their mechanism consisits of a gas spring and a column of hydraulic oil in series. The active intervention is to alter the quantity of oil in the column. Think of a Citroen self-leveling system operating fast and you'll have a reasonable approximation of it. Such a system remains partially passive as its gas spring reacts to bumps. The alteration of oil quantity in the column can only be done within certain limitations (for example you must avoid exciting the spring to resonance or getting stuck in a situation where all that the additions and subtractions of oil achieve is to work the gas spring). The Williams system was called "reactive" by their own engineers and that's probably a fair description of it.

The only fully active system in F-1 was the Lotus. It used solid hydraulic struts at each corner of the car. When springs were used, they were in parallal with the hydraulic struts, not in parallel. The springs were used to save energy required to operate the suspension and also removed a particularly nasty failure mode.

Note that, as well as using their more widely known full active suspension, Lotus also employed a semi-active suspension system in F-1 for a time. These were two completely different systems.

Fantastic stuff which should be in our cars by now instead of all this airbag and telematics nonsense.

Regards


Gerald

[jpf]

I disagree; I think the Lotus method of having a spring in parallel is a very good solution. Whatever extra work you have to do to pull against the spring, you get back when it helps you push the wheel back down (minus whatever internal damping is in the spring). Plus you get the safety factor of having the car remain supported in the event of a hydraulic failure. I can imagine doing without this in a well-sorted race environment where you're trying to trim all of your margins, but I'd certainly want the redundant spring in a productionized system. I like the idea of using a KERS system to help run the hydraulics, though.

Does anyone know if using an active system might give more latitude in tire construction? Could a properly tuned active system help mitigate the downsides to run-flats, for example? Or is the high frequency stuff that gets absorbed in compliant sidewalls too fine-grained for active to handle well? It seems to me that as tire design gets more and more well understood and fully modeled, the interplay between tire construction and a fully parametrized active system might be really fruitful.

[Todd]

There is one fully active system that may still make it to production, and it was developed by a supplier to many an automaker. Bose does without servo valves, hydraulics, or air springs, instead substituting linear electromagnetic motors seving as struts. You can see their system at work here. They've been at it since 1980, and the final product has been two years from production since 1990, but maybe someday.

[Gerald Ryan]

Whoops, I made an error. I wrote, "The only fully active system in F-1 was the Lotus. It used solid hydraulic struts at each corner of the car. When springs were used, they were in parallal with the hydraulic struts, not in parallel."

I should have said,"...When springs were used, they were in parallal with the hydraulic struts, not in series"

Putting the springs in parallel with the struts reduces power consumption considerably. If you take a look at the Lotus road car prototypes fitted with active you'll soon see that the hydraulic struts and springs were in parallel.

BTW it was discovered that the active system does not need to deal with frequencies above 20Hz or so.

[Greg Locock]

20 hz- no **** sherlock, you are trying to drive the system via the unsprung mass, wheelhop is essentially undamped and is at 12 hz or less. Trying to maintain control through a lightly damped resonance in series with your actuator is an elaborate form of suicide. Human beings may be able to supply drive type inputs at 5 Hz (being generous).Incidentally we used to use Zonic servo valve controlled hydraulic shakers for modal analysis, which used a 1/2" hydraulic ram with 6" stroke, at frequencies up to 100 hz. For some reason the active guys never asked us about the (well known) control issues.

I don't remember seeing coil springs on the Lotus active cars, there again I was more of an interested spectator on the hydraulics side of things.

The Active Corvettes were going to be a limited edition of 200 units. The hoods were locked down. Frankly it wasn't GM's fault they didn't go ahead, the installation was totally unsuitable for lawsuit prone Americans, or indeed, any customer expecting to drive on public roads.

[Todd]

Anyone know whether or not Bose has issues with linear electromagnetic motor durability or not? Serving as a strut on the front of a large car seems like a tough life for an electric motor.

[Fat Boy]

Originally posted by manchild
What made FW cars superior was the fact that on the straights active suspension greatly reduced drag and increased speed by raising the ride height. In corners, the ride height was set as low as possible enabling more downforce, lower cog, leveled car and stiffer suspension on the outer side of the car (relative to corner direction).

Do you think no one else considered this? It was a number of things that the '92 and '93 FW cars did better than the others which made for their success. The basic ideas that you have stated were used by everyone, though.

[Fat Boy]

Originally posted by Greg Locock
20 hz- no **** sherlock.....

BTW, I _did not_ hi-jack Greg's screen name. I know this response sounds like me, but it's not.
__________________________________________-

And...the open wheelers that I've had the ability to test properly (on a shaker) have had their wheel hops come in a bit higher than 12 Hz. More like 18 or so, but your point is made. The active suspensions are really at their best when used for relatively low frequency work.

[Fat Boy]

Originally posted by phantom II
....so the MAGNA shock acts as a spring and a damper.....

Which is another way to say it has a lot of hysteresis. I've heard (no first hand knowledge) than this is a real problem with the magnetic dampers.

[Greg Locock]

I really like the potential of the magna ride system, it is a very cluey sideways step around the fundamental problem.

"Anyone know whether or not Bose has issues with linear electromagnetic motor durability or not? Serving as a strut on the front of a large car seems like a tough life for an electric motor."

I think these things are more like giant solenoids than motors.

Not that I'm biased, but I have a strong distaste for Bose. And I really don't like the way they are 'selling' these things. They do make one good product, their antinoise headsets. I am not convinced that they are worth so much more than other people's but they do actually deliver. At which point everybody here who has a Bose sound system will pile in and tell me how electronics is better than physics....(PS I'm ****ing pissed off, my beautiful B&W speakers have started to break down after 26 years, thankfully they can be rebuilt).

[Greg Locock]

FB (laughs) - Ah, is that measured wheelhop on the road, or on a rig?

There is a huge difference (not that I'm saying you are wrong). There are two reliable ways of measuring wheelhop - either average your vertical accelerometer spectrum over a long time, or add an out of balance to the wheel and do a sweep in speed. The latter is cleaner but less representative. Typically the tire stiffness is about 30% less when rolling than on a static rig... but that is a very bodgy number.

[Terry Walker]

Bentley began using what they called active ride in the late 1980s, to give the Bentley Turbo R the luxurious boulevard ride needed in gentle travel, and the taut responses needed in the fast twisty stuff. As I understand it, they used a sort of two-speed shock at each corner, which rested on the "soft" setting until the ECU detected sudden or strong steering loads, when it switched them instantaneously to "hard".

This along with self-levelling suspension achieved what Bentley was looking for. I suspect however it's not the sort of active ride you guys are talking about. I've never driven an active ride Bentley Turbo R so I can't talk from experience.

[Greg Locock]

Yeah, that's what happens when marketing meets engineering. Switchable shocks (or even MagnaRide) aren't really proper grown-up active suspensions, normally we'd try and call them semi-actives, which is meaningless. The useful boundaries to my mind are (1) is the suspension controlled by external sensors? (2) is the suspension able to add energy to the system ?

Switchable shocks pass (1) and fail (2), but I'd agree that if push comes to shove there are plenty of 'active' systems that don't meet (2).

Quite often people use active to mean 'reconfigurable on the fly', and that is not unreasonable. But is a swtchable intake manifold active? Or a variable intake system? Or a knock limited spark advance? Not really, I think.

Oh, and before you start, yes I am aware that you can use shocks to pump the car up, so they can add energy to the system. But for some reason that doesn't really feel like an active system to me.

[dosco]

Originally posted by Greg Locock
normally we'd try and call them semi-actives, which is meaningless.

But isn't this the term Peter Wright used to describe the Williams suspension when compared to the Lotus?

[Fat Boy]

Originally posted by Fat Boy
And...the open wheelers that I've had the ability to test properly (on a shaker) have had their wheel hops come in a bit higher than 12 Hz. More like 18 or so, but your point is made. The active suspensions are really at their best when used for relatively low frequency work.

Now you made me go check notes.....

About 18 Hz on the road and about 22 Hz on the rig.

[cheapracer]

FWIW

On a TV show many years ago (maybe 5 or 6?, not sure) I saw a front engined road Ferrari being tested and it had some form of active susp.

They made a point of showing it going around the long turn 1 at Eastern Creek (Sydney Australia) and you could see it self-leveling.

[Greg Locock]

20% difference. That's about the same as a production car. Ta.

[Gerald Ryan]

Greg, was that really you? If so, why be rude? I certainly didn't set out to offend you, so why the hostility?

I related what I was told by the principals involved in the Lotus active project. They’d know exactly what occurred one would expect….



When the first prototype cars were built it was expected that the actuators would have to be controlled well beyond 20Hz and into the 80 – 100Hz region. They were pleased to discover that this was not necessary. That was not initially obvious at the time. Subsequently limited compliance was introduced between the actuator and the chassis. That made it difficult to get reliable data from the load cell measuring corner force, but the problem was overcome. You can look up the patent record to see how, should you wish. The reduction in dynamic range necessary (back to ~20Hz) reduced the system power requirement.

Apart from a very early prototypes (and some F-1 cars, previously mentioned), Lotus always put the road spring in parallel with the hydraulic actuator. This was made public at the time. It was mentioned in the literature and also in the patents. The arrangement is clearly visible in photographs published in Car (Oct 86) and Fast Lane (Jan 87). It was clearly described in the accpanying text. Go check them out at the library.

The GM project engineering and management staff responsible for the active Corvette project were given a running example built for them by Lotus. It was decided to alter many of the critical components, arrangements and specifications. The resulting vehicles did not perform properly. Examples of alterations included mounting accelerometers on portions of the body that were flexible and that resonated, replacing data comms cable runs with regular automotive accessory wiring (resulted in corruption of data and loss of command), alteration of geometry, alterations to specification of bushes and mounts, lots of details changed without understanding why they were as they were in the first place etc. etc. In the end the modified active suspension could not perform properly, as there was too much wrong with the installation. It wasn't working out and senior management then proceeded to claim that American drivers couldn’t have discerned the difference between active and passive anyhow. Other rationalisations followed and the project ceased. Grapes? Sour? Arse covering? Corporate politics?

Seems like a wasted opportunity that had the potential to have turned the Chevrolet Corvette into the best handling road car.


Gerald

[Todd]

Originally posted by Greg Locock
I really like the potential of the magna ride system, it is a very cluey sideways step around the fundamental problem.

"Anyone know whether or not Bose has issues with linear electromagnetic motor durability or not? Serving as a strut on the front of a large car seems like a tough life for an electric motor."

I think these things are more like giant solenoids than motors.

Not that I'm biased, but I have a strong distaste for Bose. And I really don't like the way they are 'selling' these things. They do make one good product, their antinoise headsets. I am not convinced that they are worth so much more than other people's but they do actually deliver. At which point everybody here who has a Bose sound system will pile in and tell me how electronics is better than physics....(PS I'm ****ing pissed off, my beautiful B&W speakers have started to break down after 26 years, thankfully they can be rebuilt).

I worked for Crutchfield 15 years ago or so, and we used to torture the Bose reps. Even the managers were in on it, going ahead to a restaurant and running up huge bills for the Bose reps to pick up even before we joined them following Bose product training peppered with sarcastic questions about the active equilizer required to make 901s sound like something other than the 18 '62 Oldsmobile dash speakers that they were, or the 801s that looked like shopping mall ashtrays(back when such things existed) and must have had internal heat sinks to deal with the 50 watts continuous consumed merely to produce ambient noise, or pointed questions about the dismal reviews Bose speakers received in audiophile magazines. Still, is that enough to justify not even looking at the viability of their active suspension technology? If it is as good as Bose' marketing methods, then it could be a viable concept. It seems just as viable as any of the other systems tried elsewhere.

[Greg Locock]

Sorry Gerald, I wasn't having a go at you, I was laughing at the naive assumption (in retrospect) that you could put a hydraulic actuator between a tire (resonance 12 Hz ish in my experience) and a body (any number of resonances from 25 Hz up) and expect to maintain control at a frequency of 20 Hz.

The Corvette installations that I saw were unfit for any duty off a test track. Maybe they had a production ready version I never saw. Fair enough.

[275 GTB-4]

Sir Alex Moulton.

[Fat Boy]

Originally posted by 275 GTB-4
Sir Alex Moulton.

The bike builder?

[mariner]

I think ( but I am not absolutely sure) that a low rider ( as beloved of part of LA's population) meets Greg's two tests as they clearly have controls capable of jacking up each corner of the car. I believe that they have used Moog valves in some installations and I seem to recall battery packs and hydro pumps in the trunk.

I am not "into" low riders but to give them credit they do seem to meet Greg's two tests. Not too sure about the handling though!

[Gerald Ryan]

Greg

Yes, I understand what you mean. It's a big ask. I'll have to find out more about what the thoughts and expectations were as they started development of active. Sometimes it's difficult to capture the context of the situation people were operating within. That gets lost over time. Still, the whole active suspension area is fascinating. When it was first announced I thought we would be seeing production versions within only a few years. That it so nearly occurred is frustrating. I really would have liked to get a car with that. Still want one.


Gerald

[Guineapiggy]

AS usual it's a lot to take in but it's extremely helpful, thanks to y'all. A more specific question though: Lotus first ran active suspension in the 99T, yes? Did they drop it after that? I can't find any evidence of them running active suspension on any other car after that one.

[silverc4s]

I will probably regret bringing this into the discussion, but I was once the proud owner of a brand new Infiniti Q45a (small a for active suspension), in the early 90's. This great behemouth of a car handled exceptionally well on public roads, and was especially fun in town, as it was very tossable for a 4100lb sedan. It had a 285 hp 32 valve V8, and the hydraulic pump was good for about -2 mpg, as I recall, over the normal version.
Does anyone know of this system's technical merits?? It had two ride heights, actuators at each corner in parallel (I think) with a coil spring. It wuld corner almost eeriely flat...

[Fat Boy]

Originally posted by Gerald Ryan
When it was first announced I thought we would be seeing production versions within only a few years. That it so nearly occurred is frustrating. I really would have liked to get a car with that. Still want one.


Gerald

In F-1, it was a way to control aerodynamics. A means to an ends, if you will. It's just so much less important on a street car that I doubt if an OEM could realistically justify the expense. Just take 1/10th that money and spend it on making your existing passive system better and the gains will be very, very similar and easier to sell to the public. -2 mph is huge, they couldn't possibly ignore that.

[Greg Locock]

I remember that they dragged us all into a conference room when the Inifinity came out (must have been earlier than 92), and showed us the video. There were two reactions I remember

(a) it's only a low bandwidth low authority system (I think it was 2 or 3 Hz from memory)

(b) we're screwed

It is no coincidence in my mind that they sold the production car active project to Moog soon after. (b) was probably the right answer then.

Interesting that Nissan didn't follow up.

[Fat Boy]

Originally posted by Greg Locock
There were two reactions I remember

(a) it's only a low bandwidth low authority system (I think it was 2 or 3 Hz from memory)

(b) we're screwed

(b) was probably the right answer then.

Since it's been essentially a non-player since then, why do you say (b)?

[Todd]

In the JDM, 90% of Q45 buyers signed up for active suspension, as opposed to 15% in the US market. Toyota was shocked into offering 300 active Celicas, much as Nissan today offers Toyota Synergy drive in their Atlima. Is it possible that Nissan's domestic executive barge still offers 'active' suspension? This is a company that still sells 4WS, if I'm not mistaken. Nissan is the place where pointless technology goes to die.

[Greg Locock]

I meant that the higher ups in Lotus probably thought (b) and so sold the technology. The technical guys were the ones saying (a).

Actually we needed the dosh for the Elan launch as well.

[Gerald Ryan]

FatBoy

Lotus revealed a 30% increase in cornering force from a car with active suspension in the absence of aerodynamic downforce. Worthwhile? Probably. Don't forget the ride would be much improved over the passive suspension vehicle also.

Gerald

[Greg Locock]

I've got a bit of a problem with that number. Under what circumstances?

[Gerald Ryan]

Greg

Looks to be regular road surface, uneven, dry. Two cars (one passive and one active) are driven through a series of interlinked chicanes at various speeds. Final attempt is at maximum effort, without loss of control (although the passive car driver abandons the course before the end). Lotus literature states 30% advantage to active. Advantage is claimed to be greater on road surfaces with more bumps and uneveness.

I have a VDO of a similar demonstration. The violence of uncontrolled body motions of the passive cars are always a surprise. No question this sort of thing results in loss of control incidents and smashes. The active car drives flat regardless of what it is being asked to do and regardless of the road surface. In another test a mid-corner dip causes loss of control for the passive car and requires quick intervention by the test driver. Not so for the active vehicle. Passive is clearly inferior and even looks unsafe in some circumstances.

After viewing the Lotus literature and VDO some years ago, I was convinced active should have been the next major development for cars. It was disappointing when it didn't come to pass after all. A shame.

Regards

Gerald

[Paolo]

Interesting topic.
At the time, it was claimed that at least some active suspension systems would also alter rear-front stiffness distribution to correct oversteer-understeer.
This was allegedly exploited better by Mansell than Patrese at Williams in 1992.
Poorer teams were said to have simpler systems that just kept the car level (in Italian "correttori di assetto").
Yet none of the "high end" systems I've seen described seems able to perform this roll stiffness splitting.
Or are they?

[Fat Boy]

Originally posted by Gerald Ryan
FatBoy

Lotus revealed a 30% increase in cornering force from a car with active suspension in the absence of aerodynamic downforce. Worthwhile? Probably. Don't forget the ride would be much improved over the passive suspension vehicle also.

Gerald

That was a bullshit claim. I'm not exactly sure how it was bullshit, but trust me, one way or another it was bullshit. 3% would be hard to swallow, but 30% is absurd.

[Gerald Ryan]

FatBoy

I'm not one to accept arbitrary claims. Having viewed the VDO comparison of active versus passive cars undertaking the same tests, having discussed active with some of those responsible for creating and developing the system, and having reviewed the literature on the subject, I am inclined to believe the Lotus claims.

Regards

Gerald

[Ben]

Originally posted by Gerald Ryan

Lotus revealed a 30% increase in cornering force from a car with active suspension in the absence of aerodynamic downforce. Worthwhile? Probably. D
Gerald

And you uncritically believe that claim...?

Ben