Hi

I have yet another a landy and have spent what seems forever welding up the chassis cos that’s what I do. I’ve now got to the point where its air tight, quite literally as on this one I have welded up all the jig alignment & drainage holes and fitted drain plugs. I then pumped it up and checked the pressure inside didn’t drop to check for leaks so far so good.

You may wonder why on earth I did that but the intention you see was to fill it up with oil (about 90ltrs), swirl that about inside and then drain it out so in theory so long as the chassis is looked after on the outside the inside could never rust…

But it occurred to me when getting welding wire that rather than using oil I could just flush the inside with CO2 from a welding cylinder so by removing all the oxygen from the air inside the chassis that should prevent rust. Plus it would not be as messy to do fortunately the chassis rails and cross members have holes which allow gas (and smoke) to travel right round the inside so the gas put in one end should travel all over the interior.

Some may say why didn’t you just buy a galvanized chassis but this one is hugely modified for crash protection, there are also doubled up plates which would not be possible to galvanizes due to the risk of explosion.

What do you think?




[Edited on 20/11/14 by Mr Whippy]

Co2+water = carbonic acid

Nitrogen you want, nitrogen is used in industry to do exactly this.

surely a good dose of dinitrol would be easier? I wouldn't trust a chassis not to gain a few holes (attaching stuff for a start) that would let trapped gases out. And dinitrol would deffo be better than oil...

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Originally posted by britishtrident
Co2+water = carbonic acid

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Originally posted by cliftyhanger
surely a good dose of dinitrol would be easier? I wouldn't trust a chassis not to gain a few holes (attaching stuff for a start) that would let trapped gases out. And dinitrol would deffo be better than oil...

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How long do you expect to keep the car??
May be overkill...
If it´s air tight, eventually the 21% oxygen will be depleted therefore anything else is pointless...
Maybe Nitrogen, a Tire valve and a gauge...
Then whenever the pressure drops, you go to a tire station and fill up...
I think this has been covered here Tubular chassis gas filled as early failure warning system.
AA

Porsche used to gas-fill their magnesium chassis for Le Mans cars, because there was no other way to reliably check that the magnesium hadn't cracked. IIRC, the chassis would last 1 to 2 races before having to be scrapped anyway.

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Originally posted by Angel Acevedo
How long do you expect to keep the car??
May be overkill...
If it´s air tight, eventually the 21% oxygen will be depleted therefore anything else is pointless...
Maybe Nitrogen, a Tire valve and a gauge...
Then whenever the pressure drops, you go to a tire station and fill up...
I think this has been covered here Tubular chassis gas filled as early failure warning system.
AA

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Why not be silly and fill it with a Gas like helium, should be inert and it would make the Landy that much lighter.

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Originally posted by jollygreengiant
Why not be silly and fill it with a Gas like helium, should be inert and it would make the Landy that much lighter.

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I am a Landrover nut as well, with an ex-military 109, 1967 vintage. Plenty of strengthening bits were also added for extended spring hangers (etc.) by the MoD. It spent most of it's life at a Scottish logistics base, then a spell in Ireland, before being released. I've had it for some 30 years now, complete with expletives still written by the squaddies visible on the inside. it's gained a Mazda 3.0 engine and a few other things in more recent years...... I fitted a Holden straight 6 when I took it over to Australia.... then back to the 2286 Diseasel, before the Mazda.

Whatever gas goes into the chassis, I believe, will escape eventually. Any air left in chassis will contain moisture, which will condense, any acids present won't go anywhere either. If you must fill the chassis with gas, dry nitrogen is the only choice.
Mine's full of waxoyl, sprayed in every few years, cut with white spirit. It's been a good thing.

The external paint on the chassis has been a problem, it all seems a bit brittle, needs touching up at times.

Your tactic of excluding oxygen by welding a structure shut has been tried time and again, and i have personal experience of seeing it on buses, trains and offshore wind turbines. None of those i've seen have been successful, and generally last a lot shorter time than those that use a decent coating system.

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Originally posted by Grimsdale
Your tactic of excluding oxygen by welding a structure shut has been tried time and again, and i have personal experience of seeing it on buses, trains and offshore wind turbines. None of those i've seen have been successful, and generally last a lot shorter time than those that use a decent coating system.

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I can't help thinking that it'll be nearly impossible to make all the welds 100% airtight and keep them that way (its not like its shaped like a pressure vessel)
especially on a chassis that's going to get bounced around on/off the road

a tiny bit of porous weld or maybe even a tiny fatigue crack would let gas out and water in and any water that got in would be trapped without a proper drain to let it out again



personally I'd spray something stickier than oil up the insides even if it meant adding more access points

then either block off all the major entry routes for water / muck - but leave some drain holes in strategic places
or block them all off with removable bungs of some kind (probably screw in metal ones) so that you can periodically open them up to drain it and spray more stuff in


if you just weld it up and hope it sealed then you've put all your eggs in on basket and left no way of inspecting it to find out if you were right until its too late

[Edited on 24/11/2014 by mcerd1]

Mcerd sums it up nicely, it's impossible to make a significantly sized welded structure completely defect free and prevent any nonstructurally signifcant cracks forming in service.

As an aside, if you did have a perfectly sealed system, you would not need to back purge as the amount of corrosion caused by the quantity if oxygen or water vapour retained would not be significant.

Andy