The Hydragas Problem - seeking a solution

[jonny69]

Genuinely completely stupid idea here. If you've got a dead displacer with perished rubber and really need to be gotten out of a stitch, if you drilled in your tyre valve and squirted in a can of instant tyre repair, what would be the likelihood of it buying you a few days/weeks/months motoring?

We're all joking about filling it up with bathroom mastic and expanding foam, but is there anything else you might be able to squirt in to actually seal it up? It's almost like you want to be able to squirt something in that can form a new membrane skin on top of the old one. Like I said, I really don't know much about the subject so it's just a stupid idea

[vulgalour]

I'm tempted to give it a go if I can get hold of enough dead displacers in all honesty.  A flexible rubber type material could be a sensible solution providing it doesn't mix with the fluid side and clog the pipes up.  I also wondered what would happen if you injected a small portion of rubber and swilled it around to seal the chamber before refilling it, thus repairing the diaphragm at minimal cost.

[danthecapriman]

You can get a chemical that swells old rubber up. I bought some once to re seal the front crank seal on an old Volvo I had and it worked. It was meant for cars and you just poured it into the engine oil.

Maybe you could get some into one of the displacers?

I've used similar stuff at work too and it does work, but obviously it'll only do so much. If the seal is too worn or actually damaged it's pointless.

 

Edit:

http://www.americantechnology.co.uk/stop-leak-anti-leak-oil-additive---oil-anti-leak-250ml-30-p.asp

The stuff I used was similar to this.

Sounds like snake oil but it worked for me!

[Asimo]

For a rubber spring to work, the rubber has to change shape, it doesn't change volume. If the gas space of a Hydragas unit is filled up with an elastic material, it will be a very poor spring, it will be virtually solid. The gas volume of the top chamber changes a lot from bump to rebound.

 

I think the biggest issue with re-gassing is removing an ancient Hydrages unit from the car. That done, it is just a simple engineering fitters job with readily available gas fittings and a bottle of gas.

 

Impossible if you havn't got the kit or the skills, but then so is skimming a cylinder head.

[tooSavvy]

Impossible if you havn't got the kit or the skills, but then so is skimming* a cylinder head.

Some rumours exist of IMP ally heads + plateglass + wet or dry....

 

Well, how would I know

 

 

TS

[Noel Tidybeard]

it all seems that everyone is just assuming the mgf spheres are a no go- has any one actually tried?

[Eddie Honda]

As an ex-Hydrasag driver. I'm wondering if this problem is just being over-thought and isn't really a problem.

 

Yes, they haven't been made since nineteen-canteen, but there are still cars on the road and still "bottles" stashed in garages/sheds/lofts.

 

I got some Schrader valves stuck on top of a set of displacers on a Maxi. Worked perfectly, didn't fail. If a displacer is shagged to start with, then it obviously won't work, that's probably the failure in question (rather than sticking a valve on it making it fail). I don't think we've suffered hyperinflation in ten years, but 90 quid a corner is outrageous. Can't remember exactly how much I paid, but it was more like 50 or 75 quid a set of four, not 360 quid.

 

 

The problem with the MGF spheres is they are tiny and that's because it's a relative of the Metro, which it robbed the subframe and 3-3/4" wheel PCD from (or something along those lines). Now I suppose a support ring could be machined up to stop it flapping around a big hole, but then I'm not sure what the leverage ratios are on the units. Maxi units are the same as the Princess in diameter and indeed for a big soft wallowy ride front Princess units will fit in a Maxi subframe, even though they have a taller dome. I seem to remember the rear ones could be fitted with valve straight on top, but you'd be buggered filling it with gas in-situ, so right-angling them was the solution. Front ones could stick out of the top. Can't remember what size the 'leggy bottles are, but either they are the same as the Metro or fall inbetween the sizes.

 

Maxis at least have the benefit of having been made up to 77MY with Hydrolastic, so retrofitting is an option there. As mentioned above Hydrolasticing a Hydrasag subframed Maxi is possible with support collars for the front subframe. There rears sit in clamps anyway.

 

If I had a Hydrasag car now*, I'd be hoovering up spare displacers at ever turn (well at least a car set) and modifying them with Schrader valves before they got buggered and re-charge them every year. I know with a Maxi displacer the book pressure for the gas was only something handy like 13 bar. Not a busting pressure for a diaphragm to deal with compare to the pressure loss suffered by a Citroen green bottle which is pressurised to five times greater the pressure.

 

Whatever the outcome, I'd keep the car on it's original suspension system even if it cost me an arm and a leg. Replacing it with something else would lose so much of the character and essence of the car it might as well be parked up in a field and a bag of salt thrown over it to speed things up.

 

(*Highly unlikely. I've had two and prefer Hydrolastic TBH)

[vulgalour]

There is another solution*.  Mod Rod.

 

[Lacquer Peel]

Princess shell over Xantia underpinnings?

[Bear]

Activa V6

[vulgalour]

I have just learned that the Scimitar and Princess have VERY similar wheelbase dimensions.  It's entirely possible that I could plonk* the Princess body and interior on Scimitar chassis and mechanicals.

 

PRINCESS ANNE

[Eddie Honda]

My memory is coming back. Those thread bosses for the valves on those bottles were brazed on. I remember where I got them done at the time. They're in Berkcestershire and they are:

 

http://www.speedweld.co.uk/

 

I supplied the fittings, explained the score and they done a good job. Initially I was able to get 11 bar into them using a bicycle track pump.

 

Thinking about it, find a local Citroen specialist who does re-gassing and fit their sort of valves instead. Then you don't have to worry about a gas bottle/regulator.

 

 

 

JOHN REID

 

[The Reverend Bluejeans]

Another Moultonesque solution would be air springs. These can be bought for around £95 each brand new for the BMW E39 Touring that has rear air springs. They are about the same dimensionally as a Hy Drag Ass displacer. You'd need a pair of air pumps, one in the boot and one in the front unless you could find an X5 pump for a model that had front and rear air springs. Then you'd need the self levelling set up - the control box (£25 used), the wiring and the small switches that have small rose jointed linkages that clip onto a wishbone. An air spring will work upside down, on it's side, whatever.

You'll pay about 50 quid for an air pump, loads on Ebay.

 

A lot of fabrication and pissing about but the end result would be quite excellent. A nice air suspension ride, no interconnection, no fluid plus zero maintenance and almost never ending parts supply.

 

 

[twosmoke300]

Couldn't you just charge up the air springs and not have to have all the pump and leveling kit ? Or do they leak a lot

[Bear]

E39 also has an air reservoir in the boot that sits inside the spare wheel.

[Asimo]

Air springs are long travel things, Hydragas are levered to about 10% - 20% of wheel travel. Dampers required with air springs too.

[cobblers]

Yeah, there's no way air springs or any conventional airbag would work on these, the actuation ratio is way out and they wouldn't take the pressure required to lift the car off the ground.

 

I reckon a spring conversion like they do to minis would be your best bet, with some dampers cobbled on wherever possible.

They won't ride as good as on gas, but the practicalities of developing a custom airbag and damper to fit (and an air system that will supply the pressure) would be a nightmare.

Hydraulics with remote springs would probably be more practical than airbags, but they will ride like absolute shit as the damping would be a nightmare to get anything like proper.

[Mr_Bo11ox]

i say just get some ordinary hydragas displacers re-gassed for a few hundred groat, and enjoy the main reason for driving round in one of these old crates in the first place

[vulgalour]

Which is fine in the short term, but they will fail and eventually there won't be replacements so I'm trying to find a long term solution.

[Mr_Bo11ox]

i think there will always be more serviceable displacers in existence than there are serviceable princesses (oo-er missus etc)

[vulgalour]

I disagree.

[Eddie Honda]

The sky isn't going to fall in though? There's no need to worry about a long-term solution. (I'll be pushing up the daisies when there's a real displacer crisis)

 

Folk were grumbling about this 25 years ago.....

[PhillipM]

Can you get me some good, clear photo's of the room they're installed into, the way they fit and the rough leverage they have over the wheel?

 

I think I have something that might suit - I've a set of race dampers here I'm revalving for a friend and they have internal airsprings - but the price may be too high.

[Taff]

Princess shell over Xantia underpinnings?

 

re-bodies like that throw up some registration issues when done legally (read correctly),  although there are a few kicking about . Mk 2 Zeph onto a Granada 4X4 floor pan had been done a few times. There is also a PA Cresta on a jag floorpan doing the rounds 

[plasticvandan]

The simple problem is no one at BL expected the company to last 5 years,let alone the cars still running 40 years later.