PJ wrote:Tim,
you refer to drilling a few discrete holes for rust protection purposes as 'vandalising' but then go on to casually refer to sawing a (presumably rust-free) Moke in half, as if it's a perfectly normal, everyday occurance!
Yep, my first Moke, it was pretty rough but I was very fond of it. It survived being torched by vandals, stolen three times, three engine transplants, two soft tops, rust repairs...but not a head on collision with a fast moving stoned teenager in a bigger car. Once I could walk again I decided that it wasn't a viable repair, but the back half was too good to get rid of. So I cut it across-ways just behind the seats and converted the rear into a trailer (which still isn't finished). I reasoned that I might need to repair the back half of another Moke one day and that was the best way to keep the good bits.
PJ wrote:
If the foam filling bonds to the steel inside the box section, not allowing damp to get to the steel, this would be a very effective rust protection but how can you be sure this is the case?
You cut it in half after a couple of years?
PJ wrote:
I would think that there is a risk that dusty contamination could prevent such a bond and allow moisture to spread between the steel and foam by capillary action - at least with a wax spray visual inspection is possible with a suitable probe.
Yes you are correct, and it would be much better to apply the foam onto new bright metal rather than rusty old metal. Although there are a couple of things in the favour of foam. Firstly it sticks like you wouldn't believe to any surface you can think of. You cannot peel it off. The other thing about it is that in order to harden it has to absorb moisture. When you spray waxoyl into a cavity the water is still there, but the foam actually absorbs it.
PJ wrote:
Also, what happens if you do need to weld - say for accident repair, even in you have eliminated the rust problem? Aren't these foams highly flamable?
PJ
Not sure about this one. I welded the 'trailer' after cutting away the mangled front half, and I did get a bit of smoke, but it didn't catch fire. If you had a big patch to weld it would be a simple matter to dig the worst of the foam out before welding. Obviously things like old paint, underseal and grease burn too and they are often on the other side of steel that we have to weld for rust repairs.
Apparently BMC filled the sills of some early Minis with foam to try to keep the water out. I remember reading that they bought some old bodies several years later and cut them open to see if it worked, and they were still bright inside. The repair manuals from that period tell you to dig it out before welding.
Re: Nigel's comment regarding climate, its true our cars don't rust as fast as yours but they certainly do rust, especially where I live. There are some protective sprays available, but as far as I can tell waxoyl doesn't work here, it melts in summer and drains away. Deodorised fish oil or lanotec, made from lanolin (cue sheep joke) seem to be most widely used.
Yesterday, when I was crawling around under my petrol tank failing to prove Nigel wrong, I noticed that the underside of my car is looking really bad. There was a period around '77 and '78 that Leyland seemed to have been mucking around with different rust proofing techniques. Mine must have been in the 'none what-so-ever" group. It will have to come off the road and be properly done in a couple of years. No problem with water buildup at the moment though, plenty of drain holes.
Tim