All discussions relating to the Defenders end of production

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Originally Posted by Didge

Aluminium still corrodes unless protected properly but yes it will last longer than steel

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What do you mean by "protected properly"? The underside of my 2a's body has been unpainted for over forty years on (and off) the road, with no corrosion problem (the steel bits, carefully painted many times over the years, is a different matter!). My unpainted old aluminium caravan, now about sixty years standing in the weather and on the road, is virtually unmarked by corrosion - but again, the steel frame is another matter.

There are a few DC-3 aircraft still in operation round the world, with their aluminium structure still airworthy and with no corrosion after standing in the weather most of the time for at least seventy years.

Bad design with electrical contact between unprotected aluminium and other metals can result in corrosion, but the issues are well understood and easily avoided.

John

Visited our Dealer, ULR, yesterday, to arrange Gracie's next service & oil pump recall.
I was informed that all of their 90 allocations are gone, but they had a very few 110 spots available.
Upon leaving I noticed a somewhat unusual new Defender in the holding yard, it was a 110 dual cab, with the rear body (tray?) yet to be fitted. It was red with part leather seats. Very nice, can't be too many of them left. There were two 90s awaiting PD in the yard also.
Pickles.

Hi John, I'm thinking about the powdering of my doors in the 110 - but I guess that could be mainly due to galvanic reaction. Ally outboard motors still corrode which is why they have anodes attached to them. Yes, I take your point about the caravan and underside of the series., I've seen plenty of aluminium damaged by corrosion pitting over the years but to be honest it's mainly been boats. Maybe salt water is the real problem which is why aluminium windows need to be anodised if they're not powdercoated.
cheers gerald

Maybe salt water is a problem - but not too serious a one, provided you avoid bimetallic corrosion. I have a 'tinnie', used as dinghy for my yacht for thirty odd years, exposed to salt spray and general weather throughout that time - still does not leak, although certainly it is discoloured with corrosion. But comparing this to the (sandblasted, painted and repainted) steel hull of the yacht, there is no question that the unpainted dinghy has survived better - and steel is what you seem to be praising for car construction!

John

Not at all JD, not at all. I think car manufacturer's have persisted with steel because it does rust or at least their designs serve to accelerate it, or at least they did in the past and I did more than my fair share of repairing rust in my younger years. I have a secret fascination with aluminium - maybe it's the bright and light nature of it. Also, it's great strength to weight ratio and ability to be deformed into more extreme shapes than steel (I read that recently). I was gobsmacked at how well the Evoque survived that crash off the elevated roadway (under the LR videos thread on the forum - if you haven't seen it, you must). After re reading your comment I'm a more learned man - I didn't even think about all the still intact aircraft lying around in fields. I just got the impression from the earlier posting that the poster thought ally was totally immune to corrosion. I stand corrected :)

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Originally Posted by Didge

...... I think car manufacturer's have persisted with steel because it does rust.......

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No, car manufacturers have stuck with steel, simply because it is cheap compared to aluminium. The only reason Rover used aluminium in their first Landrover was because steel was rationed, and aluminium was not. They found that the the advantages of the alloy body were sufficient to stick with the material till the present, although in the last few years a number of panels formerly alloy have been replaced with steel.

As I have pointed out previously in another thread, Hartnett was building cars in Australia in the early 1950s with an entirely aluminium structure, so "all aluminium" cars are certainly not new.

Interestingly, if you analyse the requirements for a structural material, you find that the strength/weight ratio is not the critical figure, but the elasticity/weight ratio*. And this figure is almost constant for almost all feasible structural materials. Hence, for example, aircraft have been made from steel, wood, and aluminium alloys, with very similar performance - the choice depends on other factors, including that many parts have to have a minimum thickness to avoid being too easily damaged, susceptibility to corrosion, fatigue, heat etc., or ease of manufacture, repair or other factor.

The one exception to this rule is so-called "exotic" structural materials, most notably carbon fibre reinforced materials. These are not stronger for the same weight, but are much more rigid, so that structures, if properly designed, can be much stronger or lighter. (Worth noting though that the first Sydney-Hobart yacht race where there were a large number of yachts using carbon fibre had an unprecedented number of structural failures - designers did not understand the new material.)

John

*For most realistic structures, when designed for light weight, most of the mass is in those structural elements which are in compression. These elements will fail by what is known as Euler buckling. The only property of the material involved in calculating the resistance of the structure to this form of failure is its elasticity (Young's Modulus). A more elastic material will call for, for example, thicker material in proportion to the elasticity of the material.

Hi John, I know its cheaper but looking at all the well designed nooks and crannies and appropriately place rubber strips that conveniently catch silt and detritus in hard to reach places has, over the years, made me rather sceptical of the designers best intentions to produce a vehicle that might stand the test of time without diligent cleaning. I know cars these days are more resistant to rusting than they were in the 80's and earlier but the designs still make me suspect they are designing in a limited life (I guess they are anyway so they in the business of continued sales).
Carbon fibre, yes I have a quadcopter (drone if you like) and upon crashing numerous times have replaced a few of the strong yet brittle carbon fibre parts with aluminium that is far more elastic, cheaper and easier to source. :) Interesting - hadn't heard of Euler before. :)

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Originally Posted by Didge

.... Interesting - hadn't heard of Euler before. :)

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Leonhard Euler was an 18th century Swiss (but most of his life was in St Petersburg and Berlin) mathematician. Certainly the greatest mathematician of his time, and a worthy successor to Newton, Euler was possibly the greatest mathematician of all time.

John

That's a big call - better than Newton? He was scarily smart (as we all know) Didn't Newton devise calculus over a weekend to solve a problem posed to him? What do you think of Elon Musk? Owner of Tesla cars - now there's another genius - Nikolai Tesla. This is making me feel dumber all the time :(

[QUOTE=Didge;2398860]Hi John, I know its cheaper but looking at all the well designed nooks and crannies and appropriately place rubber strips that conveniently catch silt and detritus in hard to reach places has, over the years, made me rather sceptical of the designers best intentions to produce a vehicle that might stand the test of time without diligent cleaning. I know cars these days are more resistant to rusting than they were in the 80's and earlier but the designs still make me suspect they are designing in a limited life (I guess they are anyway so they in the business of continued sales).
Carbon fibre, yes I have a quadcopter (drone if you like) and upon crashing numerous times have replaced a few of the strong yet brittle carbon fibre parts with aluminium that is far more elastic, cheaper and easier to source. :) Interesting - hadn't heard of Euler before. :)[/QUOTE
]

I think many cars are only designed to outlast the warranty period so the manufacturer doesn't have to repair them under warranty.