The other active suspension cars - Leyton House

[autogyro]

I spoke to Frank Dernie in the paddock at Estoril early 90s.
I cant remember the exact year but we had a fairly long discussion about whether to choose a V12, V10 or V8 for the following year if that helps.
He said that Williams had tried a few different systems for active so Scarbs only has part of the picture.

[Tim.Wright]

I have an issue of Motorsport magazine from a few years ago which had some in depth interviews with Patrik Head and Adrian Newey. I recall some discussion on the Leyton House system - so I will try to dig this info out when I'm back home on the weekend.

[R_Redding]

but from what I could tell it was not exactly the same arrangement shown in the photo of R_Redding's post.

Note that figure 3 of the patent shows a hydraulic strut with only one fluid port, as opposed to the hydraulic struts in the photo above that show two fluid connections.

Fig 3 does seem to be quite accurate .. Once you note the rear wheels are at the bottom.

The single acting struts/cylinders shown at the bottom are for the rears .. the double acting struts/cylinders are at the front wheels , cross linked to the rears.

Rob

[DaveW]

riff_raff: Apologies, but I really don't know how the reply to your Friday's (12/6) post. First, I am pleased that you read the original patent, but your conclusions are a bit misguided. For example you state

...The patent documents describe a digital-electric (Moog!) servo valve regulated hydraulic actuation system that uses nitrogen gas primarily for dampening and compliance, but the suspension movement is still controlled by hydraulics.

The statement is true in the first part (kind of), true in the second part (note that nitrogen is used for compliance), but the last part is certainly not true. The suspension movement is controlled by sum of the "hydraulic actuation system" - average ride height position - the compliance of the nitrogen and the damping of the system. The trapped nitrogen will compress with increasing pressure. It will therefore act as a rising rate spring...Hence the "series" action (controlled average ride height acting in series with a passive spring & damper). The spring rate can be set by altering the volume of nitrogen and presumably the damper settings are also adjustable, but both are servicing (pit lane) actions.

....This would seem to imply that roll control is electronically regulated.

Well it is, but only on average, see above....

I spoke to Frank Dernie in the paddock ... He said that Williams had tried a few different systems for active so Scarbs only has part of the picture.

I'm sure that would be the case, and the end result was very good, but I doubt that WGP would have changed from a series to a parallel system...

[Tim.Wright]

Some notes on the Leyton House system from the December 2012 issue of Motorsport magazine (Article on Adrian Newey)

• They started work in 1989.
  
  Was a "platform control system, which is purely aimed at trying to control ride height through speed and downforce variation instead of trying to deal with road inputs, and left conventional springs and dampers to deal with those"
  
  "The system we used on the Leyton House was very simple. You put an actuator under the spring platform, and compensated the tyre and suspension squash by extending the actuator.
  
  This type of system was used by McLaren in 1993.

Some notes from the March 2012 issue of Motorsport magazine (Article on the FW14B)

• The active system was originally proposed by AP in 1984: "The AP system managed ride control of a 'three-legged' platform via valves controlling the flow of high pressure hydraulic oil, the valves being controlled by linkage to the suspension and a parallel inertia-based system"
  
  First test car was made in winter 1985 based on an FW09. The active suspension was then put on the back burner for a season because the passive car was looking like being competitive in 86. An active test car based on the FW11 was tested pre-season in 87.
  
  Newey arrived in 1990 and continued the development of the three-legged system depite being of the opinion that the platform control concept from Leyton House was a better system.
  
  "[the Williams system] basically had 2 front springs and a single rear spring. And then the bump side of the single rear actuator was connected to the rebound side of the front actuator and that's what gave you the roll stiffness."
  
  In 91 they moved from gas springs to disc springs which resolved the high speed bouncing on the tyre sidewalls due the non linear stiffness of the gas springs (at high aero load they were too stiff).
  
  This system had a fixed front/rear roll stiffness distribution, so the balance was adjusted actively using the ride height.

Honestly, some of the things above are not so clear. Particularly the note on the roll stiffness of the Williams system (however it does explain the connection to the rebound side of the front actuators).

In the pictures of the Williams article I see 2 accumulators connected to the 2 rear pushrod actuators. The rear actuators seems to be only single acting.

But it does seem to indicate the the Williams roll control has passive elements to it and is not adjustable or controllable in terms of roll stiffness distribution.

Seems a bit of a strange way to go honestly. In my opinion the 3 channel system was devised by AP with a view to commercialising it in production cars. In this case there would be significant cost savings in using a 3 channel system as opposed to a 4 channel system. But it seems it was quite compromised for use in a racing application.

[autogyro]

https://en.wikipedia.org/wiki/Hydrolastic

During the period covered, I was working closely with AP developing electronic shift control systems for their automatic transmissions fitted to Leyland cars.
I was supplied a number of cars from Leyland to modify.
Most of the ideas for constant ride height racing systems started with consideration of the hydrolastic and hydrogas systems being fitted to leyland cars.
I had meetings with Williams, Ferrari and Lotus around this time mainly on transmission ideas that eventually resulted in the current semi auto gearboxes in use both in racing and road application.
We did dabble with modified hydrolastic and gas systems, mainly in variable geometry suspensions for non aero racing applications.
There was huge potential in the Leyland systems but sadly like all superior engineering in the UK it was scrapped when the companies folded.

[DaveW]

Most of the ideas for constant ride height racing systems started with consideration of the hydrolastic and hydrogas systems being fitted to leyland cars......

Not true, I'm afraid...., though they may have been considered for FRIC systems.

We did dabble with modified hydrolastic and gas systems, mainly in variable geometry suspensions for non aero racing applications.
There was huge potential in the Leyland systems but sadly like all superior engineering in the UK it was scrapped when the companies folded.

With whom did you dabble? I believe that the IP on both was owned by Alex Moulton, & he was still trying to sell them in this century (2013)....

[autogyro]

We 'dabbled' with the hydrolastic mini set up replacing the rear subframe with various geometries connected to the displacer units.
Sadly the ideas we had to use electronic control on the gas systems that I discussed with Tony Rudd at Lotus never reached a car.
Leyland remained helpful until the end.
We had a Leyland Special Tuning department at Bushey Transmissions.
John Davenport was our contact at BL a colourful career.

I think you will find that most designers working on ride height control looked at the Moulton system in at least basic principle.
The rubber spring cones and later cup washer springs were an essential data source for active springing.

[riff_raff]

riff_raff: Apologies, but I really don't know how the reply to your Friday's (12/6) post. First, I am pleased that you read the original patent, but your conclusions are a bit misguided. For example you state

...The patent documents describe a digital-electric (Moog!) servo valve regulated hydraulic actuation system that uses nitrogen gas primarily for dampening and compliance, but the suspension movement is still controlled by hydraulics.

The statement is true in the first part (kind of), true in the second part (note that nitrogen is used for compliance), but the last part is certainly not true. The suspension movement is controlled by sum of the "hydraulic actuation system" - average ride height position - the compliance of the nitrogen and the damping of the system. The trapped nitrogen will compress with increasing pressure. It will therefore act as a rising rate spring...Hence the "series" action (controlled average ride height acting in series with a passive spring & damper). The spring rate can be set by altering the volume of nitrogen and presumably the damper settings are also adjustable, but both are servicing (pit lane) actions.

....This would seem to imply that roll control is electronically regulated.

Well it is, but only on average, see above....

I spoke to Frank Dernie in the paddock ... He said that Williams had tried a few different systems for active so Scarbs only has part of the picture.

I'm sure that would be the case, and the end result was very good, but I doubt that WGP would have changed from a series to a parallel system...

Here's the full text of Dernie's US patent: https://docs.google.com/viewer?url=pate ... 861066.pdf

If you look carefully at the system schematic, you'll see that the amount of nitrogen gas in the circuit is fixed, while the flow of hydraulic fluid in/out of the circuit is variable. So positioning of the system is regulated by active control of the hydraulic fluid, while the compliance in the system is provided by nitrogen gas displacement that is passively regulated by mechanical valving. The compressible nitrogen gas volume is needed since a pure hydraulic system would be far too stiff for a race car suspension.

While the patent schematic appears to show a fluid coupling between the F/R actuators (item 9), I can't see any similar fluid coupling from L/R.

[DaveW]

If you look carefully at the system schematic, you'll see that the amount of nitrogen gas in the circuit is fixed, while the flow of hydraulic fluid in/out of the circuit is variable. So positioning of the system is regulated by active control of the hydraulic fluid, while the compliance in the system is provided by nitrogen gas displacement that is passively regulated by mechanical valving. The compressible nitrogen gas volume is needed since a pure hydraulic system would be far too stiff for a race car suspension.

One more try....You appear to make the assumption that the nitrogen gas will have no effect on ride height. It will, just like a spring will.....one reason for controlling the volume of hydraulic fluid is to compensate for that change, but it doesn't happen instantaneously. If it did (happen instantaneously) then it would be like having no gas volume. Even that might not be a complete disaster. The first actively suspended car to win a GP was a Lotus (99T), with a "parallel" system (see above) and no gas compliance - but that is another story.....

While the patent schematic appears to show a fluid coupling between the F/R actuators (item 9), I can't see any similar fluid coupling from L/R.

The patent doesn't necessarily show all (why would it...). The video you posted clearly shows the front suspension rolling into a corner (apparently to compensate for tyre deflection). How might they achieve that with no left-right coupling?

[riff_raff]

One more try....You appear to make the assumption that the nitrogen gas will have no effect on ride height. It will, just like a spring will.....one reason for controlling the volume of hydraulic fluid is to compensate for that change, but it doesn't happen instantaneously. If it did (happen instantaneously) then it would be like having no gas volume. Even that might not be a complete disaster. The first actively suspended car to win a GP was a Lotus (99T), with a "parallel" system (see above) and no gas compliance - but that is another story.....

I did not assume the trapped nitrogen gas would have no effect on ride height. The nitrogen gas is a compressible fluid, and as you correctly noted, all other things being equal, this nitrogen gas functions similar to a metal spring as its volume is compressed/expanded. But if you bothered to look closely at the schematic shown in the patent you'd have noted that the nitrogen gas volume was part of a gas-over-hydraulic device. The compression of the nitrogen gas is controlled by a combination of the hydraulic fluid flow in/out of the working volume under the gas membrane, and the force transferred through the suspension members.

As I said, the nitrogen gas in the circuit serves primarily in a compensation function, and not as a suspension positioning mechanism. For example, if greater bump force was applied thru the suspension, more hydraulic fluid could be admitted into the working space between the pushrod and gas diaphragm. The nitrogen gas would be compressed and its pressure would be increased, but bump travel of the wheel would still be limited due to the change in actuator length provided by the hydraulic system.

The more difficult task of any active suspension is compensating for the effects of tire compliance.

[DaveW]

But if you bothered to look closely at the schematic shown....

If you say so, riff_raff - where is Mr. Newton when we need him?

He might have edited the last couple of sentences to read:

But if you bothered to look closely at the schematic shown in the patent you'd have noted that the nitrogen gas volume was part of a gas-over-hydraulic device. [Over the working range of the device] the compression of the nitrogen gas is controlled by [deleted] the force transferred through the suspension members.

[PlatinumZealot]

I'm fairly sure it was electro (moog-valve) -> hydraulic control.

On this pic of the front suspension and tub ,you can see the double acting (brass coloured) actuator cylinders and the moogs sat on the hydraulic manifold.
http://i897.photobucket.com/albums/ac18 ... 0zzqnh.jpg

Are you sure it is double acting?
Might not need to be. The primary load usually acts in one direction. Hard to see the system needing to "pull up" a wheel.

[PlatinumZealot]

One more try....You appear to make the assumption that the nitrogen gas will have no effect on ride height. It will, just like a spring will.....one reason for controlling the volume of hydraulic fluid is to compensate for that change, but it doesn't happen instantaneously. If it did (happen instantaneously) then it would be like having no gas volume. Even that might not be a complete disaster. The first actively suspended car to win a GP was a Lotus (99T), with a "parallel" system (see above) and no gas compliance - but that is another story.....

I did not assume the trapped nitrogen gas would have no effect on ride height. The nitrogen gas is a compressible fluid, and as you correctly noted, all other things being equal, this nitrogen gas functions similar to a metal spring as its volume is compressed/expanded. But if you bothered to look closely at the schematic shown in the patent you'd have noted that the nitrogen gas volume was part of a gas-over-hydraulic device. The compression of the nitrogen gas is controlled by a combination of the hydraulic fluid flow in/out of the working volume under the gas membrane, and the force transferred through the suspension members.

As I said, the nitrogen gas in the circuit serves primarily in a compensation function, and not as a suspension positioning mechanism. For example, if greater bump force was applied thru the suspension, more hydraulic fluid could be admitted into the working space between the pushrod and gas diaphragm. The nitrogen gas would be compressed and its pressure would be increased, but bump travel of the wheel would still be limited due to the change in actuator length provided by the hydraulic system.

The more difficult task of any active suspension is compensating for the effects of tire compliance.

This is how I understood it from reading the paper. The nitrogen tank is just an adjustable spring.

[DaveW]

Are you sure it is double acting?
Might not need to be. The primary load usually acts in one direction. Hard to see the system needing to "pull up" a wheel.

Peter Wright has written a book entitled "Formula 1 Technology", illustrated by (the enviable) Tony Matthews. Appendix C is entitled "Active Suspension". With apologies to both, I have taken the liberty of copying a page taken from this Appendix.

Figure C1 illustrates a passive suspension (with all the "extras" omitted).

Figure C3 illustrates the Lotus "parallel" active suspension, with the damper of the passive system replaced by a true double acting hydraulic actuator (the ports are connected directly to an EHSV). If the parallel spring is designed to carry (roughly) the dead weight of the vehicle and the aero, then it is clear (hopefully) that the actuator must be double acting.

Figure C2 illustrates what Peter describes as "semi-active", & I have referred to earlier as a "series active system". Tony has drawn the actuator as "double acting", but Dernie's patent shows that the rear suspension actuators are "single acting", but the front suspension actuators are "double acting". In Dernie's patent, the spring of Figure C2 is the compressed nitrogen, and the damper is explicit (see figure 3). Arguably, the actuator of figure C2 is neither single nor double acting in Dernie's case, because it acts as an hydraulic rocker controlling the distance between sprung mass and the top of the suspension in Tony's schematic.

The differences between the two systems are interesting. On a flat road, and with a changing down force, the series system must consume energy to maintain ride height, but the parallel system does not. On the other hand, with road inputs, the series system will consume little energy, but the parallel system must consume energy to maintain control (if that makes sense).