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MG MGF Technical - why cant you rebuild a hydra gas unit

Hi all as you can see my question is why cant you rebuild a hydra gas unit.

Andrew
AR Cayzer

Well if you were to understand how they were constructed perhaps you would agreee that repair is very difficult. What skills do you have?

I suppose also that it depends on how they have failed. I would expect that 99% must fail on the nitrogen escaping it would not be too hard to engineer a way of refilling the sphere with N2 But why has it leaked? The sphere is half metal half rubber both halves are bonded together with N2 pressurized inside the resulting sphere. Redoing this sphere I would suggest by the home enthusiast is almost impossible
Robert (Bob) Midget Turbo

i didn't mean by me .

with all the problems slowly happening with the units in older cars i would off thought some body might work out how to do it
Andrew
AR Cayzer

Hi,
if you have a look at this article you will get a good appreciation of the complexity of the Hydragas system:
http://www.mgfcar.de/hydragas/ehydragas.htm
The rubber components are the ones which give up the ghost and these simply aren't available. Don't give up though, there are spring replacements coming on the market which will solve the problem and keep these cars on the road.
Pete Cornell

Fully agree.
Another impression give this pictures of the complex design, special the rubber membrane.
http://www.mgfcar.de/cut_unit/index.htm
I still keep the parts in the garage ;)

btw. there's still the other option of using front spheres instead of the no more available rears. Swap over the old rear alloy pistons to a new front spheres. This was done already by F'ers in Australia.

Regards
Dieter
Dieter

Thanks Dieter, they are graphic pictures of what can happen inside these units! It's hard to understand why a non-corrosive fluid could not have been chosen in the first place.
Pete Cornell

I'm with you. However they had no time or budget to develop improvements to the old reused Mini/Metro design and process, or material combinations.

An oil based fluid would have required a very secure sealed and creak protected system cause of the danger of splashing oil into the road in case of any damage.

Also the rust would be a minor problem in case the system always is evacuated and free of any air bubbles.
No oxygen, no rust :)
That's easy said and nearly impossible to provide.
Dieter

Yes, I hadn't thought through the implications of hydrocarbon fluids when they leak - not just road issues but fire risk as well. There are other possibilities such as liquid silicone but cost and technical difficulties might preclude them. Best answer - get rid of the system!
Pete Cornell

Why were they invented in the first place? Innovation and invention is supposed to improve something, or find a solution. So the bloke that invented these said “hey guys check this out, I have invented something to replace the leaf and coil spring. Its complex expensive to manufacture and will most definitely eventually fail causing the owner of the vehicle huge expense to replace them but by then the owner won’t be able to replace them because they won’t be manufactured anymore because they were absolute sh*t" "That’s awesome Barry lets fit them to our cars" I don’t know if the inventor’s was named Barry.
P Thomas

Couldn't agree more Paul and well said....;-)
Sue Wilson

Probably three reasons:
1. Ride quality and handling - vastly better performance than basic springs of any era.
2. Lightweight and compact dimensions.
3. Reasonably cheap if volume production continued.

I think the higher ambient temperature in your part of the world seems to bring forward the failure date, particularly the rears. Being a permanently pressurised system, it doesn't cope well with heat - either change or higher levels - not a problem in UK! Unlike a spring even a small failure in hydragas vehicle renders it unusable.
You were joking about leaf springs weren't you?
Remember the ride quality when it was brand new.
Charless

I too think the Liquid suspension as it is sometimes known as is far superior to springs. Pity it was faised out so that parts are becoming scarce.
As described if you can not find replacement units then it is not to difficult to replace them with springs. Its what classic car ownership is all about. :)
Robert (Bob) Midget Turbo

I don't believe it has anything to do with the higher ambient temperature that the system fails as I have no problems with mine....touch wood! Plus there are many early Mini drivers that have no problem with their system either. When it comes down to it for the MGF in Australia, it's getting available parts for the whole car at reasonable prices. Parts are very expensive or unavailable here.
Sue Wilson

Sue so your car has done over 190 thousand K's and your hydrogas is Aok? thats great. Your car must have been made on a good day indeed ;o) I heard the old morris's and mini's hydrolastic suspension spheres were made of steel or something, pretty much lasted the life of the car due to being so well made. These days however things are made to a budget and made to fail to keep the spare parts industry going. So I guess when hydrogas is good its very very good and when its bad its terrible :-O
P Thomas

I have two 15 year old Fs with over 200000 miles between them on their original, completely trouble free hydragas spheres. One has the original 'shock absorbers' and on the other I have adjustable gas dampers which (I think) help the ride quality.
Hopefully not famous last words! But don't be tempted to think that on a specific car forum the number of problem reports paints an overall picture.
Charless

Andrew,
See this link:
How to repair / service Hydagas Displacers
http://www.mgf.ultimatemg.com/group2/suspension/hydragas__depressurisation.htm
I have no idea if this has been done on a MGF unit.
Sue Wilson

This thread was discussed between 15/04/2011 and 18/04/2011

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