one for the engineers

[c.morewood]

I'm about to experiment with a cheap repair solution to the aluminium suspension cylinder corrosion problem... even cheaper than buying a second hand one!!
I'm going to file off the rim of the cylinder, which succumbs to the corrosion, salt I guess, and replace it with a dowty washer.
This washer has a bonded membrane to replace the rubber seal for the sphere and a hard metal washer to keep the rubber seal in place. hopefully the metal washer will act like the cylinder rim, but not succumb to corrosion.
They may have to be replaced every time I do a sphere change, but at less that £2.50 each its not going to break the bank.
My question is, What should the metal of the washer be made of to avoid promoting corrosion?
I'm aware that salt and ally do not go well but there's no point in encouraging corrosion by putting in the wrong metal.
Choices I've seen are Copper, Stainless or gun metal.

Thanks,

[Chlorate]

Ideally, whatever metal the cylinder is made of.
When you get dissimilar metals in contact you will get accelerated corrosion in the metal higher up in the electrochemical series.

http://www.npfasteners.com/pdfs/galvani ... -chart.pdf" onclick="window.open(this.href);return false; this appears to be quite a good chart for reference.

If the cylinder is mild steel, all of those metals will cause the cylinder to rust away at an accelerated rate.

[c.morewood]

Original post edited to show "aluminium" cylinder

[Chlorate]

Even worse unfortunately.

[c.morewood]

Check yours when you next do a sphere change

[citronut]

the problem i can see with using these dowty seals is, the rubber section will not be seated against anything,
as there is a gap between the inside edge of the cylinder rim and the thread of the sphere,
this gap is the width of the original seal profile,

so the only way it might work is by keeping the original seal in place,

[RichardW]

I think it'll work Malc - Chris is talking about filing the old rim of the cylinder off, so that you are effectively left with 2 flat faces (cylinder and sphere) to seal against - this is what the existing seal does, but is retained from bursting out sideways by the lip on the edge of the cylinder. If this works it will be a top repair, as it can be done in situ without having to remove the pin

I wouldn't worry too much about the metal Chris - if it corrodes it will do so slowly, and only on the outside - as long as some of the seal face stays intact it should still seal - it's not as bad the current affair whereby the lip is very thin, and failure results in the seal blowing out. It will outlast most Xantias now I expect!!

[citronut]

I think it'll work Malc - Chris is talking about filing the old rim of the cylinder off, so that you are effectively left with 2 flat faces (cylinder and sphere) to seal against - this is what the existing seal does, but is retained from bursting out sideways by the lip on the edge of the cylinder. If this works it will be a top repair, as it can be done in situ without having to remove the pin

then next problem in that case is how far the end of the sphere goes into the cylinder after removing the rim

[RichardW]

From work I did on mine there is plenty of room - sphere does not bottom out in the thread, and even then there is another 1/2" or so before you get to the top of the piston at low suspension height - you've got to get past the inlet port, which is well down the ram, as long as this is not obscured then it will be OK

[Richard_C]

Back to the corrosion question, my Hillman Hunter had an aluminium head on a cast iron block. The head gasket was a sandwich of copper and (I think) aluminium, which suggests copper might be a good answer to your first question.

[CitroJim]

Chris, I still have my plans to experiment but recently I've not been up to it so it's on the back-burner for a while...

[c.morewood]

"then next problem in that case is how far the end of the sphere goes into the cylinder after removing the rim"

I believe that the washer hard face, same depth as the rim will prevent the sphere going any farther into the cylinder than it does at the moment.


"If this works it will be a top repair, as it can be done in situ without having to remove the pin "

and a few more as well Richard

"which suggests copper might be a good answer to your first question."

That's what I would have thought Richard.. resistant to the very prevalent salty roads up here in the winter and easily moulded to take into account any slight high areas.. however looking at the chart it seems that stainless might be a bit better on the corrosion side of things.


"Chris, I still have my plans to experiment but recently I've not been up to it so it's on the back-burner for a while..."

I thought so Jim.. no probs. I just would like to get this tried before the Hydraflush cycle is up in 1300 miles.. middle of next month.. just so I don't waste too much LHM!!

Updates:
The "repaired" cylinder isn't leaking at all..as far as I can see .. so maybe it is possible that the Dremmel grinding worked.
The ride height adjusted after the FHC replacement .. slightly on the low side of perfect..seems to be working...I'm now on 500 miles on a half tank.. still smoking slightly and missing occasionally at idle.. but it can't be that bad for that MPG. I suspect it will get worse as the temperature goes down towards winter and I'm leaning towards the injectors being worn... but that's for another day....no.... month!!

[Richard_C]

The corrosion question got me interested. The washer isn't the worry, can be replaced, its the aluminium part that matters. There are lost of threads on yachting forums, they have aluminium masts and stainless steel fittings, but I found this very useful looking one on an airstream caravan forum. The second post has a useful lookup table, and it makes sense to me.

http://www.airforums.com/forums/f4/is-s ... 49955.html" onclick="window.open(this.href);return false;

Any chemical engineers on the forum (see small engineer joke below)

As it is unlikely your car will spend a lot of time immersed in the sea, I doubt you have an issue whichever you use. If you are planning James Bond Lotus like excursions, better think again. It's ages since I worked on spheres, are the rear ones exposed to road salt? If so you could probably cover the joint with a bit of Vaseline after assembly and it would outlast most other bits of the car.

I wonder, would copa- slip or similar help? Not sure you can get it now, used to be just the thing betwixt brake pad and piston on my Maxi front brakes.

Small not very good joke. Four engineers are travelling in a car, it breaks down. The mechanical engineer gets out and starts pulling and prodding at the accelerator linkages, the electrical engineer gets out and checks the wiring, the chemical engineer gets out and sniffs the petrol tank. The computer engineer sits inside and closes the windows and opens them then closes the windows then opens them then closes the windows then....

[RichardW]

RichardW CEng MIChemE

I love the smell of petrol in the morning.....

[c.morewood]

Slight downside to this
1st enquiry with Pirtek "you'd have to order a hundred!!"
Have we got 25 Xantias with the cylinder problem?
I'm awaiting a few more replies.....