81 replies to this topic

[tiger99]

It is an ambiguous situation because the battery box is excess weight as far as the basic monocoque is concerned, because it does not materially add to the strength and stiffness of the boot floor. Yet it is within the prescribed distance from the subframe mount, so if it was rusty it could be a MOT failure, despite not being structurally important (e.g. if you fitted the battery somewhere else).

Was there not a similar debate here recently about rear valance closing panels? Again, near the subframe mounts, amd if rusty are a failure. But If I recall correctly they did not originally carry a stiffener for the subframe mount, and shells pre 1976 or thereabouts only had the top side stiffener to the wheel arch. At the time the abominable rubber mounts for the front subframe were introduced, the rear rubber mounts were changed, and I am fairly sure that coincided with the underside stiffener being added. That would suggest that the extra stiffening is to reduce flexing, and is basically for noise reduction, not primary structure integrity, so the valance closers are no more important on a late shell than they were on an early one.

So now we have two different parts in the same general area which are thought to be unimportant structurally, but if rusty will result in MOT failure. But what if they are not there at all? And if a steel battery box need not be there, why can't it be replaced by any arbitrary material? What is more, are some people not running cars on the road with carbon fibre or aluminium boot floors? (I think that is going too far structurally, and will cause fatigue cracking somewhere.)

The problem basically lies with the MOT tester's manual not explaining in sufficient detail to cover thsi situation the difference between a repair of a stressed part, which we probably all agree needs to be properly welded, and the replacement of an only marginally stressed part by something entirely different, or even its complete removal. But a strong battery box, whether glassfibre, metal or anything else, should pass IVA, and once it had passed IVA, the MOT tester would be unable to fail it, as long as it was in good condition.

What we should have, to solve this and other problems, is a cut-down IVA for modified cars, as opposed to kit cars, which only tests the modifications, and does not require the entire vehicle to be brought up to present day standards. That would solve many other problems, such as those associated with radical engine transplants too..

[Brams96]

I agree with you about the rules sucking. I think I will risk it and put in a fiberglass battery box, at the end of the day if it is all painted & waxoyled under the car the MOT man will probably miss it being FG anyway.

Now back to Stainless steel panel discussion . . . . ;) (sorry for the hijack OP)

[Carlos W]

I'm cutting the battery box out, welding a piece in the hole and fitting one of these somewhere else

http://www.ebay.co.u...#ht_2499wt_1015

[tiger99]

Now there is a challenge for the MOT inspector! A properly seam welded blanking plate in the hole where the battery box should be....

Actually, I suspect that many younger MOT testers will not know much about Minis, and would be unaware that a steel battery box was missing, so it would pass.

[Carlos W]

Once it's stone chipped painted etc, you'll never know it was there (I hope)

[mini-luke]

Now there is a challenge for the MOT inspector! A properly seam welded blanking plate in the hole where the battery box should be....

Actually, I suspect that many younger MOT testers will not know much about Minis, and would be unaware that a steel battery box was missing, so it would pass.

Especially if you butt welded it and painted over, you'd never know it was there. Would be much stronger than a hole with a heavy battery floating about in the bottom.

EDIT: Carlos posted whilst I typed

Edited by mini-luke, 01 January 2012 - 10:15 PM.

[Carlos W]

Now there is a challenge for the MOT inspector! A properly seam welded blanking plate in the hole where the battery box should be....

Actually, I suspect that many younger MOT testers will not know much about Minis, and would be unaware that a steel battery box was missing, so it would pass.

Especially if you but welded it and painted over, you'd never know it was there. Would be much stronger than a hole with a heavy battery floating about in the bottom.

A hole corroded by battery acid, as it is now!

[tiger99]

I have done a bit more Googling about welding stainless to mild steel. It seems that people are having more success than official welding sites will admit to, even joining exhausts, which are subject to a fair bit of stress and vibration. Best results are with specific MIG wire or TIG rod, 316L stainless, or even just 316, but some people have got good results with soft grades of mild steel MIG wire. So I guess the stainless battery box will be just fine, considering it can't fall out anyway.

I am now beginning to wonder if we could safely replace the most corrosion-prone parts of the shell with a corrosion resistant grade like 3Cr12, provided we do the welding with 316L. All we need is for the panel suppliers to actually start pressing sills, floorpans etc in 3Cr12. Probably not going to happen.....

[Bungle]

but what would you do to stop the corrosion from electrolysis ?

[tiger99]

Good point! That is what paint, seam sealer and waxoyl are for. But the corrosion problem where stainless is in contact with, or welded to, mild steel is not as bad as it would be between say steel and copper. And, something like 3Cr12 welded to mild steel is not so bad.

Ideally we would have a complete 3Cr12 shell. But pigs would fly first, I think. Unless, of course, Heritage had an order for 20,000 shells fabricated from 3Cr12, at maybe 8k each. Then it would likely be viable.

[midridge2]

and what are the problems when trying to paint ss?

[firstforward]

but what would you do to stop the corrosion from electrolysis ?

I don't in any way know about this subject but with my limited connection with sea going boats they have problems of corrosion by electrolysis and install a sacrificial anode a metal component that is softer than the other metal, I think they install Zinc that dissolves to stop the hull corroding, can something like this not be employed on a car with stainless steel.......just a thought.

[Brams96]

How did the DeLorean get around the electrolysis problem?

[Bungle]

but what would you do to stop the corrosion from electrolysis ?

I don't in any way know about this subject but with my limited connection with sea going boats they have problems of corrosion by electrolysis and install a sacrificial anode a metal component that is softer than the other metal, I think they install Zinc that dissolves to stop the hull corroding, can something like this not be employed on a car with stainless steel.......just a thought.

would i then have to soak the mini in salt water ?

[Bungle]

How did the DeLorean get around the electrolysis problem?

it was all stainless steel