The future of Hydrolastic suspension

[mab01uk]

An interesting Hydrolastic 'DIY repair' thread with photos on the 'Elf/Hornet Register forum' (link below) which may be of interest.

Hydrolastic, keep repairing or change to dry cone?
https://elf-hornet.forumotion.com/t1303 ... o-dry-cone

[Peter Laidler]

Interesting. I note that several of the ideas have come from this forum. But why complicate things...... In the US bob-cat hydraulic deep-well hose re-fitting facilities are readily available.

As for all this talk of evacuation etc etc; they ought to simply flush out the units and pipes, refill, stopper the open ends and.......... Or read how to make a hydro vac and pressure pump for £25 on this forum!

[cooperess]

I just love hydrolastic suspension on my Cooper S. Lets keep this part of the forum alive, even though I can't make a contibution.

[Exminiman]

Interesting extract below from an article on Keith Dodd of Minispares attempts at getting the Competition and Standard Hydrolastic units remade back in the early 1980's:-
http://www.minispares.com/article/Minis ... Suspension

"Between 1978 and 1981 Dunlop USA spent $102 million on modernising its European tyre business. The British workforce was cut from 13,000 to 7,000 with departments being closed down, hence the probable loss of the hydrolastic tooling . It was after a disastrous merger with Pirelli in 1971 until 1981 that indirectly lead to the whole Dunlop group of companies being sold to BTR in 1985. BTR who also made the many rubber body seals for the mini gradually split them up and sold them off, with the Systems and Components division transferring to Trelleborg AB at the end of the 1990's, but a management buyout in 2007 allowed the company to modernise, culminating in the current building which was completed in 2014.

I had always been trying to get Alex Moulton to help in getting the competition hydrolastic units remade early 1980's and standard units again especially after Rover made them obsolete when stocks run out in 1989 but he had no interest at all saying they were too difficult to manufacture and that he would not part with any drawings or any help in the manufacturing process at any cost. Alex Moulton also reflected on the cost and scrap rate encountered, but my contacts in Rover etc were unaware of any major production problems. Unbeknown to me Dunlop had discontinued making displacers in 1978 and must have suffered any losses themselves as I never had any warning the huge testing equipment and tooling would be scrapped and as sales were quite low the "all time buy" by Rover allowed them to carry on selling them at £27 to Mini Spares and other main dealers for over 10 years without any increase. Rover all time buys were usually 10 years worth of stock holding where they are obliged to keep replacement parts and the tooling was often scrapped (a bad policy for classic car owners but saved companies large amounts of money on storage of machinery or tooling and their replenishment costs which made good business sense at the time). In 1994 I bought my last 200 displacers sourced by Tony Fitchet who was Rovers scrap and clearance contractor at £52 each. I paid a lot more for odd new units that I could subsequently find afterwards.

Having spoken to Alex on quite a few occasions about hydrolastic units I also enquired about the Innocenti suspension cones I had discovered wondering if with his contacts he could get them made. (Plus the standard type of course as the only source available were Rovers made by Dunlop which were expensive.)

Big mistake! As he hated anything being uprated or stiffened but I debated the fact that many car manufactures were now fitting anti roll bars and stiffer suspensions for better handling. (BMW). Later interviews and articles regarding Alex Moulton also showed or indicated his complete dislike for the New Mini with its firm suspension."

Innocenti 120 Rubber Cones:-
"During a trip in 1984/5 to Ivra the Mini and Innocenti parts manufacturer and stockist in Milan I noticed some strange shaped rubber suspension cones that transpired to have been used on the heavier Innocenti 120 mini, produced from 1978 that was fitted with the 1275cc British Leyland power plant producing 74BHP. The Mini 90/120 cars production had finished by 1982 and having never seen this shape cone before I was intrigued enough to buy 100 for trial and found positive results and great feedback from rally drivers and performance mini owners, so I purchased the remaining stock of about 800 in January 1986 which lasted until 1993. It transpired Dunlop developed this shape to stop body roll on this taller heavier hatchback model to help change the ride over the cobbled or undulating Italian streets.
I contacted Dunlop about these special rubber cones with patent number 620734 but they were very reluctant to offer any help as they held the patents with BL/Rover, but having had 5000 of the Cooper S Wheels 21A1286 remade in 1980 by Dunlop I managed to find out from my contacts the bad news that the tooling had been scrapped and they had no interest in resurrecting the product (the same old sad story would unfold similar to the hydrolastic units)."

Great article, makes you wonder if KD will write a book, maybe from a suppliers perspective ? TBH I had thought they had made the displacers into the 90s as they were still available. I hadn’t realised the last one was actually made in 1978 ……..so the youngest displacer is nearly 50 years old, amazing how they have lasted.

[Peter Laidler]

Seems like a suitable place to add a comment regarding maintenance of the units.

Regarding flushing the units out with clean water, usually by dunking in a bucket of water and hoping that they'll fill - and that you can purge them clear a few times, here's a better method:

Get a length of 12" long well used brake pipe and attach to one end a screw-on fitting suitable to screw onto a standard garden hose fitting. With me so far....? How you do it is up to you and depending on what facilities you have. But the fitting must be secure of course.

Then very slightly ovalise the other open end.

Attach the threaded end to the garden hose and wiggle the ovalised end deep into the bowels of the hydro unit and turn the tap on. This clean water, through the ovalised hole wlll loosen and flush all (?) the rust and shite which will find its way up, between the gap in the brake pipe and the hydro hose.

Call it a hydrolastic enema........ I few minutes of this high (?) pressure flushing will certainly expel most of the sewage and crap from inside the unit. Once clean, clear fresh water starts to come out, just shake the unit to release any residue, another minute, clean water again and you're home and dry.

Empty out, leave upside down for a few hours, operate the strut end a couple of times and that's it. Fill with fresh clean hydro fluid. Put wooden stopper in the end of the hose to prevent evaporation of the hydro fluid.

Time taken to make adapt probe, 30 minutes. Time to flush out, 10 minutes

[Ernst Blofeld]

Here’s a dumb question that I have often pondered but have been too ashamed to ask: could the larger (and more plentiful) ADO16 hydrolastic displacer be fitted to the Mini?

I am guessing not at the front, otherwise BMC would have done it, but what about at the rear?

Only reason I ask is this passage from the development story of the Minki K series Mini on the Austin Memories website: “We had converted the standard Mini rear suspension and subframe to take a hydragas unit very easily.”

Given that the the Hydragas displacer looks to be a bit bigger than any Hydrolastic unit, it set me on a course of possibly futile pondering until I could bear it no longer and had to ask.

[Peter Laidler]

I suppose that given a hacksaw, a hammer and a bit of will, then you could.......! But I'm not sure that the 11/1300 displacers are more plentiful - although I don't really know.

All that said, just remember that the same fate will eventually come to the large displacers too. Best the devil you know I say. But interesting question. I hope that others will come on board the discussion. What say you Spider Chris? You've had plenty of cut and shut experience with suspension

[Andrew1967]

ADO16 displacers are much larger than Mini ones.

I stand to be corrected but I think some ADO16 ones are the same physical size as the Landcrab rears.

[111Robin]

ADO16 units "should" be more plentiful given the volume produced but when the cars were scrapped (back in the day) no one would bother saving bits like this. If possible when scrapping one I used to remove the rear subframe and keep it (unless it was rotten) but more often than not we would just fit them to a customer car with a rotten subby rather than swap bits around, then the old subby assembly was just scrapped.

[Exminiman]

There is not very many 1100 or 1300 left, back in the day, it was often collapsed suspension that was the reason for a scraping

https://www.howmanyleft.co.uk/?q=Austin ... mit=Search

https://www.howmanyleft.co.uk/?q=Austin+1300

[mab01uk]

Reminded me of the photos below of an ADO16 rear subframe converted from Hydrolastic to rubber cones and then fitted in a Mini in the USA...not sure why someone would go to all that trouble, other than to get the wider rear track width...







ADO16 rear subframe in a Mini:-
https://mk1-forum.net/viewtopic.php?t=37761

[Spider]

Pete, the ADO16 Displacers will have quite different characteristics to those fitted to the Mini. Being a heavier car, the rubber springing in them will have a harder rate and the damping, if there's any left, will also be stiffer for the same reason. I don't know if it would be a successful / worthwhile conversion.

Ernst, the Hydragas units as fitted in the Metro, MGF etc were different in that that set up was designed for the units to operate independently and weren't interconnected like the hydrolasic system of the Mini, ADO16 and Landcrab. The Hydrogas used a Nitrogen gas chamber within them for the 'spring'.

I'll likely get a public stoning mentioning this here, but the Dry set up can be made to give a very good ride, easily equal to Hydro. It's true that the Mini Saloon was designed from the start to have Hydro but was fitted with Dry initially since the Hydro development was sill going on when the Mini first rolled off the line, the Dry set up was always going to be produced for the Van, Pick-up and Mini Moke. These being commercial vehicles, designed to carry weight meant they had a harder suspension. The rate of the dry set up, unlike that in the wet, is 'tunable', you can make the set up harder or softer as well as tuning the rate and just where the secondary rate that set up has, occurs. I've not looked at making the dry set up softer, but I have done this exercise to make the secondary rate harder and stiffer.

I'll add here too, that some of the hydro's ride characteristics comes from it being underdampened. It's been mentioned a few times in this thread that the damping in the bags has failed, those, the rubber springs of both wet and dry has damping qualities of it's own.

[Ernst Blofeld]

The Hydragas units of the A-Series engines Metro weren’t front/rear interconnected, but the units on the K-Series Metro and the MGF were.

Here is a copy of an article from Car magazine in July 1990, called “Told You So” and it explains how the system eventually came good in the K-Series Metro. (Sorry it’s a bit long…)

GRANDSON OF THE MINI,' IS HOW DR ALEX
Moulton sees the revitalised Metro, and you
can see the paternal pride in his eyes - he
was a creator of both the Mini and this, its
latest descendant. Moulton's contribution to
these cars is their suspension - the Mini's
rubber cone arrangements (and later
Hydrolastic) and the Metro's Hydragas
system which first turned up, and didn't work
too well, in the Allegro.

Though the original Metro had Hydragas,
it used the gas and water spring/damper
units without interconnection, and so never
embraced the principles of Hydragas as
Moulton conceived them, with the
consequence that the theoretical benefits of
the system never materialised. What the 1980
Metro really had was an expensive version of
a relatively conventional suspension. Or, to
be blunt, a (falrly effective) botch-up.

Initially, for Rover's Metro replacement,
there was talk of ditching the Hydragas
suspension in favour of a conventional steel
set-up, a choice that would probably have
produced suspension similar to the Polo's or
the Fiesta's. At which point, enter Moulton,
and his metallic brown development Metro
which we featured in April'86.

This car used Hydragas as it should be,
which is to say interconnected from side to
side, like a hydropneumatically suspended
Cltroen. The front anti-roll bar was removed,
though its ends were adapted to convert the
lower suspension arm into a proper
wishbone, inclined a shade to induce a
measure of anti-dive. The interconnecting
pipes ran down the centre of the car, and at
the rear a pair of coil helper springs were
added to keep the rump end up when loaded.

The brown Metro rode with much greater
suppleness, but didn't lose any of the original
car's agility. In fact, it handled rather better,
especially at high cornering speeds, when the
old Metro used to hop and lurch. We thought
it a great improvement.

A good thing then, that the brown Metro's
next port of call would be Longbridge and
Austin Rover's engineering department. The
people there were impressed. And here was a
chance to save millions of pounds, because
adapting the car to use steel suspension
would cost a fortune in re-tooling. Making
these alterations demanded very little in the
way of change to the body-in-white.

Moulton's Metro suddenly became very
important to the development of the R6, as
the project was known. Luck, happy timing
and a story in this magazine all helped
Moulton to a hearing, and final vindication of
his claim that, properly sorted, Hydragas
could endow a small car with a big car ride.

The main source of the improvement lies
in the side-to-side interconnection of the
Hydragas units. Put simply, this allows the
suspension to be set up more softly, so the
car rides better on rough surfaces. The
beauty of the Hydragas system is that it
doesn't allow the car to heel over
dramatically as it rounds a bend, the usual
result of very soft springing, To understand
why, you need to know how Hydragas works.

Essentially, each unit consists of two
spheres, one on top of the other, resembling
a figure of eight in cross-section. At the base
of the unit is a vertical tapered rod or piston
upon which the wishbone or trailing arm
bears. The piston in turn seats against a
diaphragm, which seals in the water-based
fluid housed in the lower sphere. This liquid
travels along the interconnected pipe when a
wheel rises in reaction to a bump.

However, the fluid can also travel, via a
metal valve, into the top sphere, where it
presses against a further diaphragm sealing
in nitrogen gas. Since nitrogen is
compressible, unlike water, it acts as a spring.

The system works like this: say the car is
travelling straight, and a front wheel hits a
gentle bump. This will displace the fluid in the
front Hydragas unit, sending it along the pipe
to the rear unit, which will in turn force the
rear wheel downwards as the front wheel
rises. The effect is to keep the car level.

If, however, both wheels on the same side
hit bumps simultaneously, fluid travels
through the valve into the top sphere where
it compresses the nitrogen. In effect, then,
each wheel is suspended by two springing
media - the displacement of the fluid along
the pipe, and the compression of the
nitrogen. The advantage of this is that you
can have two spring rates. They're known as
the pitch rate and the bounce rate. Pitch is
the movement of the car's body fore-and-aft
like a see-saw; bounce is self-explanatory.
With the Hydragas system, you can afford
to have a low spring rate, which means soft
and supple like a 2CV's, in the pitch mode.
But, in the bounce mode, more resistance
and therefore a higher rate, is required,
especially since this is the mode in which the
Hydragas units resist roll,too (because both
pistons are being pushed against their
diaphragms simultaneously). In practice, of
course, the system works using a combination
of both modes concurrently.

Damping is provided by the metal valve
between the two spheres, a very compact
solution. ln fact, compactness is one of the
major attributes of Hydragas, and is one
reason why the Metro has always had a
decently dimensioned boot-there is virtually
no suspenslon intrusion.

But why, you might ask, does the system
work well in the Metro when the principles are
exactly as they were for the Allegro, which
certainly wasn't the smoothest-ridlng, best-
handling car of the day? There are several
reasons. The main one is that the Metro has
sturdy sub-frames front and rear, whereas the
Allegro had none at the front, and a simple
tubular device at the rear.

This prevented the inclusion of anti-dive
and anti-squat into the equation, because
this geometry creates massive road noise
Without decent sub-framing to suppress the
din, the Allegro had to do without this
subtlety, something the new Metro does not.

Changes in the articulation of the rear
trailing arm, and rhe way in which it bears on
the Hydragas piston have allowed a longer
wheel travel, further improving the ride, and
there are revised camber settings for the front
wheels. This is tied in with the desire to rid the
Metro of its very expensive (though effective
four-pot brake calipers.

These were needed because the original
front-wheel geometry was such that if the car
were fitted with a conventional diagonal
dual circuit brake system, it would spin
should one circuit fail. To overcome this
meant a different combination of pipe
circuitry that called for two brake pistons per
front wheel, where most cars have one.

The new geometry produced superior
bump-steer characteristics, but the downside
was heavier steering, which meant ditching
the original, dellghtfully quick set-up for a
lower-geared rack, This, however, is one of
the few demerits of the new running gear.

For enthusiasts, perhaps the most
warming aspect of the whole affair is that
development of the ideas first seen in the
Mini continues, Or as Moulton puts it: 'In the
genetic evolution of the Mini, the good genes
have come through, and that is a joyous
thing. The good things are double wishbones
at the front, trailing arms at the rear, sub-
frames, anti-dive and anti-lift. It's got
everything.'

Just as the Mini was, the Metro is one of the
technically most intrigulng cars in its class.
What's also pleasing is that some of the
people who were involved with the Mini and
descendants in the '60s and '70s, worked on
this latest exponent of the lssigonis ideals -
not just Moulton, but chief steering aand
suspension engineer Rob Oldaker, whose
proiect this was, Which leaves you with the
nagging feeling that this new Metro is very
much an Austin. One of the best Austins, in
fact, ever built.

[Andrew1967]

Metros were interconnected at the rear but the fronts were independent.

[wantafaster1]

Metros were interconnected at the rear but the fronts were independent.

Absolutely correct, but later Metros were front to rear.
My auntie had A plus metros, I had a K series GTA, remember comparing them in 1993

[Andrew1967]

I wasn’t sure about Rover Metros but knew the earlier ones were as I mentioned .
Used to occasionally see an early Metro with its arse dragging along the ground going along the road. Easiest way to correct it without a hydro pump was to buy a complete inflated rear frame from the scrapyard and swap it over .. no inflating required. We had a pump so just a case of replacing what was necessary

[mab01uk]

I remember when the first season of the Metro Challenge race series started in 1980, many of the drivers like Chris Tyrrell, (who my brother Steve was mechanic for at the time), had switched from Mini Se7en or other Mini race series with well proven and sorted Minis and were suddenly all trying to make the original Metro go around corners without hopping and lurching on their Hydragas suspension....although it was quite entertaining for the spectators standing on corners like Paddock Hill and the Druids hairpin at Brands Hatch.
Metro Challenge & Group A 1980's:-
https://mk1-forum.net/viewtopic.php?f=4&t=10632

[Spider]

Yes, I should have clarified, the Metro units are interconnected across the Rears, but the line is small and the fluid transfer rate small. There's also conventional springs in the back of the Metro and conventional dampers on the fronts, since the Nitrogen doesn't have any self damping properties.

[Ernst Blofeld]

The K-series Metro did feature front/rear interconnection, though. and transformed the car’s ride and handling so much so that the usually cynical Car magazine raved about the car and, in the same issue as the Moulton interview I posted earlier, declared the R6 Metro to be the world’s best handling and riding small car.

They weren’t so keen on the Metro GTi which featured auxiliary telescopic dampers and anti roll bars both of which Moulton railed against (“they’ve crowded out my springs.”)

IIRC Moulton said that if Rover had wanted to achieve a sportier drive they should have increased the gas pressure in the Hydragas spheres and/or fitted a smaller diameter interconnection pipe.

Going back to my pondering about fitting ADO16 hydrolastic units to the rear subframe of Minis I wonder if Hydragas units could be plumbed in instead? These should be easier to obtain than hydrolastic displacer and can be recharged with gas.

[Exminiman]

Going back to my pondering about fitting ADO16 hydrolastic units to the rear subframe of Minis I wonder if Hydragas units could be plumbed in instead? These should be easier to obtain than hydrolastic displacer and can be recharged with gas.

This crossed my mind, I also, wondered if the Hydro liquid, could be replaced with air or gas in the standard ones ……appreciate the viscosity of the fluid would be lost, but still seems feasible.

Adjustable air or fluid suspension in a mini…….wasn’t there a works Safari car that had this ?