Mr Whippy
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| posted on 20/11/14 at 12:24 PM |
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Oil or CO2
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]
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britishtrident
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| posted on 20/11/14 at 01:15 PM |
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Co2+water = carbonic acid
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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liam.mccaffrey
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| posted on 20/11/14 at 01:18 PM |
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Nitrogen you want, nitrogen is used in industry to do exactly this.
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cliftyhanger
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| posted on 20/11/14 at 02:07 PM |
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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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Mr Whippy
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| posted on 20/11/14 at 02:08 PM |
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quote:
Originally posted by britishtrident
Co2+water = carbonic acid
ohhh well I didn't know that
Nitrogen then sounds a bit friendlier then
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Mr Whippy
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| posted on 20/11/14 at 02:14 PM |
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quote:
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...
Well yeah but this landy is going to be living the good life and not be used in winter and it's kept in the garage and only used on warm sunny
days!
The chassis is totally undersealed outside but I just want to protect the inside and any area’s I burnt the paint off modifying it.
[Edited on 20/11/14 by Mr Whippy]
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Angel Acevedo
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| posted on 20/11/14 at 02:36 PM |
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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
Beware of what you wish.. for it may come true....
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FuryRebuild
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| posted on 20/11/14 at 02:49 PM |
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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.
When all you have is a hammer, everything around you is a nail.
www.furyrebuild.co.uk
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Mr Whippy
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| posted on 20/11/14 at 03:39 PM |
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quote:
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
This is the last landy I'm rebuilding and the one I'm going to keep for myself so should be driving it 30 years from now
One of the reasons I'm currently modifying it so it's safe for my daughter driving it and she's not even 2 yet! which sounds
ridiculous until you think well the cars 35 years old already, what's another 16 years...
Great idea using gas pressure to detect leaks, though I can imagine the confused look on the MOT testers face when he sees a pressure gauge fitted to
the side of a landrover chassis...WTF!?!
In theory though, just like a pumped up drinks bottle having some pressure in the chassis should make it stiffer? 
[Edited on 20/11/14 by Mr Whippy]
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jollygreengiant
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| posted on 20/11/14 at 05:49 PM |
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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.
Beware of the Goldfish in the tulip mines. The ONLY defence against them is smoking peanut butter sandwiches.
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Mr Whippy
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| posted on 20/11/14 at 07:05 PM |
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quote:
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.
the lift may be dangerous round corners...
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motorcycle_mayhem
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| posted on 20/11/14 at 08:35 PM |
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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.
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Grimsdale
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| posted on 24/11/14 at 12:30 PM |
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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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Mr Whippy
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| posted on 24/11/14 at 12:39 PM |
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quote:
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.
No it’s not the welding shut what's meant to stop it rusting...
It's afterwards replacing the air inside with something other than air which in theory should make it rather hard for bare metal inside to
oxidise, nitrogen being a good candidate
[Edited on 24/11/14 by Mr Whippy]
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mcerd1
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| posted on 24/11/14 at 01:09 PM |
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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]
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Grimsdale
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| posted on 24/11/14 at 05:22 PM |
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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
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