The future of Hydrolastic suspension

[mab01uk]

Some interesting but not directly Hydrolastic info here on the closely related Moulton Hydragas suspension system and the benefits of interconnection......

While reading about the development of the R6 K-Series Rover Metro/100 on AROnline recently I came across this extract below explaining how Alex Moulton's research greatly improved the performance of the later 1990's Rover Metro/100 Hydragas suspension over the original Austin Metro Hydragas setup by reverting to installing front to rear interconnection pipes, as were used on his earlier BMC/BL designs.....but were omitted from the 1980's Austin Metro range as a cost saving exercise.

Metromorphosis - R6 (Rover Metro/100)
With the question of engine and gearbox choice answered, the only real headache that the R6 posed was what suspension system would be needed. When launched in 1980, the Metro’s Hydragas system gave it class competitive ride quality and handling – as well as a degree of “chuckability” that endeared it to its buyers. But times had moved on: the Peugeot 205 especially, had shown that smaller cars had grown, but also that small car ride and handling had become significantly more sophisticated. Because of these huge leaps and bounds made by the opposition, there were still unanswered questions on what was the preferable system to use in the R6: on one hand, work was completed on adapting the conventional set-up used in the AR6 for the R6, but as the Metro’s floorpan would require expensive (and extensive) re-engineering to accomodate the AR6 system, this was not an ideal solution. With this in mind, work also continued in-house on refining the existing car’s Hydragas set-up.

Swiftly, the configuration of the R6 was set: K-series engine, PSA gearbox, and a slight increase in wheel track, front and rear – only the suspension layout was yet to be settled. That is, until the homemade efforts of Doctor Alex Moulton were brought to the attention of Rover.

As the inventor of Hydragas (and Hydrolastic before it), Moulton was keen to demonstrate the benefits of his system: the suspension units were more compact, and therefore easier to package. Besides, Rover knew that in order to use a conventional system in the R6, a degree of re-engineering in the floorpan would be needed. As explained briefly in the Metro story, Moulton had modified his own W-registered Metro to accept front/rear interconnected Hydragas suspension.

Why front/rear interconnection as opposed to the vestigial side to side as it was on the existing car (“vestigial” meaning a small pipe interconnecting the two rear displacers, eliminating the “three legged stool” effect of zero-interconnected Hydragas – a decision taken out of safety consideration)? When the front wheel encounters a bump and rises, the suspension fluid will rush from the front suspension unit to the rear. The rear wheel will resultantly lower, lifting the tail of the car and allowing a level ride. Citroëns demonstrate this trait perfectly when encountering a “sleeping policeman” – the whole car rises in unison and suspension “see-sawing” encountered in conventional cars (and the original Metro) is eliminated.

Why this ideal arrangement was omitted from the original Metro can be best summed up by Moulton himself, “I was struggling to show how an interconnected Hydragas Mini, for all its diminutive size could give better results than a VW Polo. But BL’s Spen King, a very strong-minded and knowledgeable automotive engineer, didn’t like it. He preferred absolutely conventional cars. Yet I was persistently and consistently offering something superior in Hydragas.” In fact, the original Metro was so compromised by its non-interconnected Hydragas arrangement, that Moulton felt that at best, the solution would only produce a car that was average.

“All they’re doing is substituting the conventional spring and damper with a Hydragas unit” and that because of the compromise engineering in making this system work, needless complexity was designed in anyway, “Anyone coming in from outside would take one look, pronounce it burdened with nasty costs to no advantage and get rid of it.” Of course the real reason that Spen King adopted non-interconnected Hydragas for the original Metro was that the extra piping of the system employed on the Allegro and Princess would have cost extra money. So it was dropped – and it has to be said that the decision to do so was a rather questionable one. King himself recalled recently that, “we all had guns to our heads…”, which would go some way towards explaining the immense pressure he was under as the company’s Technical Director.

Doctor Moulton invited CAR magazine to drive his modified Metro, which they did… and they were stunned at the difference that interconnection made to the package. How Rover’s own engineers heard about the car is an interesting tale in itself: during July 1987, Moulton had received Sir Michael Edwardes as a guest at his house, and during the meeting, Moulton invited Edwardes to drive his interconnected Metro… like CAR magazine, Edwardes was very impressed, and he telephoned Graham Day up to tell him that they, “should incorporate the system and charge £100 extra for it!” Duly alerted about the existence of the Moulton solution, and allied with the painful decisions that the company had made over the AR6 and with question of the what the configuration of the R6 needed to be still to be unanswered, a viewing of Moulton’s solution would prove irresistible for Rover.

And so it was. Rover took the car away to Canley and engineers thrashed it around, before rapidly deciding that Hydagas did indeed have a great deal of life left in it and that following the example set by Moulton, with careful development, the system could be developed into a class-leading package. The decision was easily made: the R6 would be launched with Moulton’s interconnected version of Hydragas – and in taking that decision, Rover demonstrated that lateral thinking sometimes produced results far in excess of corporate compromise…

If the press were disappointed at the styling of the new car – oh, so familiar inside and out, they found the driving experience something of a revelation.
An example of this was the verdict reported by What Car? magazine, who after testing the Rover Metro 1.1L against such luminaries as the Peugeot 205, FIAT Uno and their then Car of The Year, the Ford Fiesta pronounced an easy victor.

“The New Metro is a quantum leap, and on several accounts. For a start it’s light years ahead of its predecessor, far more so than its obvious family resemblance would suggest. But, more important still, it sets new standards of quality, ride and refinement for the class… In its chassis dynamics – ride and handling – it takes on the acknowledged masters of the art, the French, and beats them. It’s probably the quietest, smoothest, most refined car this side of £10,000 or even a bit higher.”
The Full Story here:-
https://www.aronline.co.uk/cars/rover/r ... t-history/

[69k1100]

I'm not sure why we are comparing displaced to field guns and earthmoving equipment?

the best thing functionally to compare with is a shock absorber.

You need two components, a spring and a damper.

Or the rubber spring and the valve.

These two components contribute to three features of any suspension

Spring Rate, compression and rebound.

Springrate is a determined by the spring shape and material

compression and rebound are controlled by the valve, exactly as in a coil over.

The front back interconnect will play some role in this, but someone please do the calculations on the outlet diameter on the displacer and the actual flow rate when a simulated log appears at an agreed speed. Inertia probably has more to do with keeping the car level. It's no use imaging suspension dynamics in a Tesco carpark, unless that's where you do all your driving.

As I was saying before, there's no use burying your head in the sand and believing the rubber will last forever. It won't, don't kid yourself. Rubber bands dry out, so will displacers from the outside in.

A valve on the interconnect won't work for two reasons, it doesn't affect the dampening inside the displacer. If you treat it as fluid transfer then you are missing the point of suspension. You want different rates for bound and rebound because it's important for the suspension to be able to react quickly, transferring energy into the spring and to release that energy slowly, so the car doesn't bounce like a lowrider. You can't control compression and rebound with a common valve.

[Peter Laidler]

While I don't want to labour or argue the point but the point of someone makes of using JCB's as a point and me the field gun analogy is purely illustrative, where you can actually SEE hydraulics at work....... Hydra...., hydrolastic..... see it now! And you cannot see hydrolastic in isolation. It is two connected units like I said...., otherwise you've got a 70's era bloody space hopper toy!!!!!!! You're stating the what my mum used to call '....the bleedin obvious' 69K. We all KNOW that rubber won't last for ever, that's why a) the units are failing and b), everyone is trying hard to find an answer. Forgive me for being a bit harsh, but it must be said. There's been a LOT of input on this 13 page thread and it has to be said equally, a LOT of background/behind the scenes burning the midnight oil and PM'ing by the main contributors. Let me see now..... you've made three contributions so far. You've come over as a defeatist when there WILL be an answer somewhere and hopefully the optimists will crack it.

[nileseh]

There's a lot of really helpful information in this string of posts. I'm still rebuilding some of these things, but thanks to some of these entries, I may have been able to avoid some errors. Particularly the one about degradation of the rubber spring. I think it was Peter who made this note. I was not at first sure that it was valid because all of the displacers I opened looked and felt about the same. However, thanks to the post, I went about measuring the spring rate and the hardness of the spring rubber and by golly there is a substantial difference. I also can now see the displaced set (flattening) on some of the units. I measured hardness from 68 to 80 Shore A scale, spring rate from 2747 to 5730 lbs/inch and displacement from what I believe to be original position of up to .20". I'm glad I checked.
The good news is that I've got 4 that appear to be usable. I think the hardness that will work is about 70 A, and the spring rate is about 2800 lbs/inch. The worst case was 80 A and rate of 5700 lbs/inch. The 4 parts I can use do not appear to have any flattening (the spring cannot move any further down). Also there are 2 at 2750 lbs/inch and 2 at 2875 lbs /inch so I can use the stiffer units forward and the softer rear and will have good side to side symmetry.
The bad news is that not all of the old units will be candidates for rebuild. Too bad. Be calm and carry on.
I'll switch to the use of the best candidates, the valve apertures are are being machined, most of the plating is complete (except for the alternate spring units) the aluminum clamping assembly is ready so I'm getting close. We'll see how it goes.

Oh. Yes, my end game for now is to rebuild, but based on that experience it may be possible to recreate. We now know that the springs will need to be recreated, and that includes the upper housing. That may be pretty easy with two component compounds available now as opposed to the whole vulcanizing bit. The diaphram and sealing membrane is another matter. I'm working on disassembling one of these now to see if it can be done with the components intact. The paper someone noted above gets pretty detailed on the geometry of the housing and the intent (the whole variable area for the diaphragm bit). Really helpful. I can envision an machined aluminum unit that bolts together and duplicates all the features of the original, perhaps even with adjustable valving like an adjustable shock. But vision is easier than implementation. And my bottle of Scotch may empty before that happens........

[Glacier white]

Niles, it was me that have mentioned originaly that old displacers that were under pressure for a good number of years have their rubber spring permanently deformed.
Interresting that you have found such big differents in the spring rates between the displacers. It certainly ties up with the difference in comfort between a car with tired displacers, and another with new(ish) ones.
If we can open and close again the displacer like you did, i believe that it would not be that difficult to remove the old rubber from the upper part, and cast in the original housing a new spring from suitable rubber.

[nileseh]

Sorry Glacier. I didn't bother to re-read the whole string. So much information.

I agree, the upper could be replaced. To open the device it is the upper shell cut to remove the crimp. I'm no so sure about the ease of removing the rubber. It is pretty well bonded to the shell and the inner cone. However it is probably the easiest part to remake and attach to the lower diaphragm assembly. A replacement could redesigned with a more elegant coupling mechanism that I was able using the original welded and formed tube.

I may start looking into replacement materials. We use 2 component silicone materials all the time in the composite shop, but they have a rather low durometer. I'm not sure anything is available at 60-70. And then I've really got no way of determining the reliability of these materials in this application. I read the article by Moulton above and apparently a significant effort was involved in getting the compound right for the rate and longevity. But we work with what we have.

[geroch]

Very interesting, I'm a press operator and with rubber rollers it's everyday use. I know very well that a plastic is never the same, aging is a VITAL factor.
I follow the discussion with interest.

[69k1100]

I always envisioned it being stamped or spun on a mandrel. You can design it without undercuts, so both the upper and lower could be stamped.

It might have been made from readily available pipe originally, or perhaps they did this a means to better control wall thickness.

The shape of the upper / lower Housing isn't indicative of the whole manufacturing cycle.

There wouldn't have been any undercuts, the rubber then compression moulded directly into the steel cone, and then finally crimped on the lower valve assembly using a large hydraulic pipe press (with custom profiled dies), I think I even eluded to this in a previous post, you can see the witness marks form the hydraulic press. If you want to re-use the Rubber spring, then yes, you would have to flare the crimp. and then bash it back on?

But why?

Once you remove the crimp, cut/burn/dissolve the rubber and then recasting the rubber, wouldn't it be far easier to to punch/spin some new upper housings?

Any why not contact Dunlop? Perhaps they know the original formulation, Or maybe it was patented and so you would be able to do a patent search.

[Spider]

Any why not contact Dunlop? Perhaps they know the original formulation, Or maybe it was patented and so you would be able to do a patent search.

Maybe not Dunlop but the company who is making the Valley Rubber branded (dry) Rubber Cones. I did have a contact for them, but can't lay my hands on it. I suggest these guys because they claim what they make (in terms of the cones) to be to the original recipe and on original tooling. I have tested the rubber cones and unlike all others found them to have the same characteristics as the originals.

So, they may or may not have the original rubber recipe for the Hydro Displacers ??? and they clearly know how to bond rubber to steel. If they don't have the recipe, I'm of little doubt they would be able to work it out.

Perhaps initially, some old failed united could be recycled for their steel work.

[winabbey]

Any why not contact Dunlop? Perhaps they know the original formulation, Or maybe it was patented and so you would be able to do a patent search.

Maybe not Dunlop but the company who is making the Valley Rubber branded (dry) Rubber Cones. I did have a contact for them, but can't lay my hands on it. I suggest these guys because they claim what they make (in terms of the cones) to be to the original recipe and on original tooling. I have tested the rubber cones and unlike all others found them to have the same characteristics as the originals.
So, they may or may not have the original rubber recipe for the Hydro Displacers ??? and they clearly know how to bond rubber to steel. If they don't have the recipe, I'm of little doubt they would be able to work it out.
Perhaps initially, some old failed united could be recycled for their steel work.

Spider - you mentioned your Valley rubber cones in this thread, which is an interesting read - http://www.mk1-forum.net/viewtopic.php?f=3&t=9261

Minisport in Australia mention the cone patent number in their part description - http://minisport.com.au/mini-genuine-ru ... one-single

[Spider]

Spider - you mentioned your Valley rubber cones in this thread, which is an interesting read - http://www.mk1-forum.net/viewtopic.php?f=3&t=9261

Minisport in Australia mention the cone patent number in their part description - http://minisport.com.au/mini-genuine-ru ... one-single

Hi Doug,

The Avon Branded Cones had the original Patent No. on them and I *** think *** that Avon bought the rights and / or design and / or Patent (my best guess), however both in test and in use I found them considerably inferior to the Valley manufactured types and not in line with tests I did years ago on OEM Dunlop Cones. The blurb I read on the Valley Rubber website (and somewhere else) did say that they made them to the original recipe and on original tooling. I have their website book marked on an old PC (I think) I'll see if I can find that. You could google 'Valley Rubber' but they don't come up under that. I forget their trading name.

Somewhere M-parts have, I think, bought in to them in some way in more recent times.

<Edit: I just looked up their Trading Name or Parent Company, it was a company called Weightwash. They seem to be an Industrial Laundry of all things. I'm not sure if they still have this 'Valley Rubber' division under their umbrella. >

[mab01uk]

I always envisioned it being stamped or spun on a mandrel. You can design it without undercuts, so both the upper and lower could be stamped.

It might have been made from readily available pipe originally, or perhaps they did this a means to better control wall thickness.

The shape of the upper / lower Housing isn't indicative of the whole manufacturing cycle.

There wouldn't have been any undercuts, the rubber then compression moulded directly into the steel cone, and then finally crimped on the lower valve assembly using a large hydraulic pipe press (with custom profiled dies), I think I even eluded to this in a previous post, you can see the witness marks form the hydraulic press. If you want to re-use the Rubber spring, then yes, you would have to flare the crimp. and then bash it back on?

But why?

Once you remove the crimp, cut/burn/dissolve the rubber and then recasting the rubber, wouldn't it be far easier to to punch/spin some new upper housings?

Any why not contact Dunlop? Perhaps they know the original formulation, Or maybe it was patented and so you would be able to do a patent search.

A couple of years ago I did try contacting 'Dunlop Systems' via email to ask if they had any historic information or old photographs in their company archives, showing the factory manufacturing process and tooling used in the production of the Dunlop/Moulton Hydrolastic suspension units as used on cars of the BMC /British Leyland /Austin Morris range of cars, especially the BMC Mini's from 1964-1970 and does any of the original tooling or engineering development material or engineering detail drawings survive or was everything scrapped?
Sadly as expected there was no reply......

Dunlop History
"The Dunlop Pneumatic Tyre Company opened its first factory in the Hillfields area of Coventry in 1890. In 1908, following the acquisition of the neighbouring Stevenson Wheel Company, the Coventry factory was renamed the Dunlop Rim & Wheel Company Limited. The company relocated to the Holbrook Lane site in Coventry in 1919, where over the years it developed its engineering contribution to both the automotive and aviation industries. In 1959, collaboration between the British Motor Corporation, Moulton Developments and Dunlop saw the launch of the Mini motor car (ADO15). This was fitted with Dunlop manufactured cone spring suspension which, due to its success, quickly resulted in Dunlop forming a Suspensions Division in Coventry. The partnership continued with the launch of the BMC 1100 (ADO16) in 1962, followed by the 1800 (ADO17), both of which were fitted with Hydrolastic suspension manufactured by the Dunlop Suspension Division. With the change to Leyland cars in the 1970s came a further development, with the introduction of hydragas suspension on the Allegro, Princess, Metro, Ambassador and MGF vehicles. In 1970, The Suspension Division enlarged to include the further development and manufacture of the Pneuride® & Flexolink® air suspension systems, initially having levelling valves, to serve the commercial and public service vehicle market. With the introduction of Electronically Controlled Air Suspension (ECAS) in 1990 for Range Rover, the company extended the Pneuride range to include the sports utility market.
During 2007 Dunlop Systems and Components was formed as a management buyout of the Dunlop Coventry suspension division factory from previous owners Trelleborg AB. In the spring of 2014, the company moved to an all new, purpose built factory at Prologis Park in Coventry so ending a 95-year history at nearby Holbrook Lane."
http://www.dunlopsystems.com/about.html

Dunlop Systems and Components
Central Boulevard
Prologis Park
Coventry
CV6 4QJ
Phone: 02476 889900
Email: info@dunlopsystems.com

Does anyone know of any films, photos of the Hydrolastic Unit manufacturing process or factory machinery in the UK or elsewhere?
Does anyone perhaps know someone who worked in the original production process or what happened to the tooling....almost certainly scrapped.
There must have been some impressive machines and processes to produce millions of those unique suspension units in such a wide variety of shapes and sizes but sadly there seems to be very little record of it today.....I believe Heritage (BMH) have all the technical drawings, etc.

[Spider]

Sorry, just found this !!

EXACTLY Seamist...... the rubber casing acts as a shock absorber! See my para 2(d). Pulling teeth or what?

The rubber spring is a rubber spring.
It is not a rubber casing, it is not a damper, it is a spring. It is pre-loaded and holds energy.
It is the part that carries the load and deflects to absorb bumps.

Yes, the Rubber's Primary purpose is to act as a spring, however a side benefit of Rubber is it has natural self damping qualities.

This was discussed recently in another thread.

It's also why many who fit the Coil Springs (in place of the rubber cones) report back about 'body roll' and a 'more complain ride' which I read as softer and under damped. If one wants to run coils, they also need to run stiffer dampers.

[Seamist Green 1100]

Sorry, just found this !!

EXACTLY Seamist...... the rubber casing acts as a shock absorber! See my para 2(d). Pulling teeth or what?

The rubber spring is a rubber spring.
It is not a rubber casing, it is not a damper, it is a spring. It is pre-loaded and holds energy.
It is the part that carries the load and deflects to absorb bumps.

Yes, the Rubber's Primary purpose is to act as a spring, however a side benefit of Rubber is it has natural self damping qualities.

This was discussed recently in another thread.

It's also why many who fit the Coil Springs (in place of the rubber cones) report back about 'body roll' and a 'more complain ride' which I read as softer and under damped. If one wants to run coils, they also need to run stiffer dampers.

Yes, rubber is self damping to a degree. Your example of coils is correct. Just like if you removed the coils and fitted airbags you would need to increase the damping even more.
Leaf springs also have a degree of self damping.

But on a Hydrolastic displacer the damping is controlled by the internal valve body, just like a rubber suspended Mini it is controlled by the damper even though there is some self damping in the rubber spring.

[Bodge]

The Avon Branded Cones had the original Patent No. on them and I *** think *** that Avon bought the rights and / or design and / or Patent (my best guess), however both in test and in use I found them considerably inferior to the Valley manufactured types and not in line with tests I did years ago on OEM Dunlop Cones. The blurb I read on the Valley Rubber website (and somewhere else) did say that they made them to the original recipe and on original tooling. I have their website book marked on an old PC (I think) I'll see if I can find that. You could google 'Valley Rubber' but they don't come up under that. I forget their trading name.

Somewhere M Parts have, I think, bought in to them in some way in more recent times.

Hi Spider

You've got most of the facts right but I thought I would fill in some of the gaps.

Back in 2008, Dunlop ceased production of the original Moulton rubber cone. With a certain amount of foresight, John Lloyd from M Parts negotiated to buy the original rubber cone tooling along with the test and production line equipment. There are very few manufacturers that have the expertise to bond rubber to steel and John built a relationship with Valley Rubber to recommence low volume production. During the recession, Valley Rubber went bust but production of the rubber cone continued at a new company called Polyolia after there was a management buyout.

M Parts has manufactured in excess of 25,000 units for Mini Spares since then and they are made according to the original Moulton recipe.

I don't think that BMC relied solely on Dunlop for the supply of cones and maybe Avon Rubber had their own tooling for the rubber cone and also supplied BMC. I don't know whether this tooling still exists or not. The cones that Mini Sport supply are made by Avon but use Alex Moulton's prototype mould. Cones from this mould were never used on production cars.

So, they may or may not have the original rubber recipe for the Hydro Displacers ??? and they clearly know how to bond rubber to steel. If they don't have the recipe, I'm of little doubt they would be able to work it out.

I will ask John Lloyd about the rubber recipe for the hydro displacers and whether any paperwork still exists.

From memory I think that the tooling for the hydro units still existed in 2007 but was more than likely scrapped. Roger

[251 ENG]

The Dunlop hydrolastic factory was on Foleshill road in Coventry , just off the ring road . The building is still there , now split up and sells kitchens and a tyre fitting place .

When it closed in the 1980,s there were skips full of new units that went for scrap .

A well known poster on this forum could have bought as many as he want for £1 each but didn't

[Spider]

Cheers Roger for that.

Very Interesting.

Simon, we also had a Dunlop Hydrolastic Factory here too at Birkenhead Point (not far from were my Grandmother lived in fact). All long gone now, there was a fire there and then was redeveloped in to a shopping centre,,,,

[cooperess]

Wondering how nileseh is going with a replacement hydro bag.

[mab01uk]

Pete Bourne who worked for the BL Chassis Department, (see separate thread on the Rover Minki projects) kindly sent me the details and photo below which may be of interest to some here in the long running Hydrolastic thread:-

Electric Hydragas machine
"Thought you might be interested in this. I designed and built this probably about the same time as Minki Two. It is an electric Hydragas machine. Ride and handling development was a tedious job sometimes. You could spend weeks constantly changing spring and damper settings for the Engineers. On a conventional car it was bad enough, but on Hydragas it was very hard because the system had to be constantly emptied and filled. The service machine was not really up to these constant changes and neither were our knees! That's why I came up with this machine. It worked great and was used in the workshop for all the development work. It was made from whatever I could scrounge. The pressure pump was from a cabriolet Rover 200 powered hood and the Vacuum was supplied by a Range Rover air suspension pump. I even got paid £800 for the idea from our Rover suggestion scheme."
Pete Bourne

[mk1]

That is a very nice bit of kit. I have been thinking about making something similar as the vac side of both my hydro pumps is knackered, using a small electric vacuum pump makes perfect sense. To do the same for the pressurisation side is the next logical step.