93 replies to this topic

[chrisgold]

Why cant you fix it? Why cant you just weld/ bolt / bond (you catch my drift) A completely new mounting point in??? To say something cant be fixed seems a bit daft to me....

Its corroded, so cut it out and weld or bolt a new plate in and make it stronger? Am I being stupid here? Just seems common sense to me? Surely you could fix it, Yeh, it would not look the same, but it would do the job???

must agree.i read the thread on seloc and thought then,unrepairable,new chassis.hmmmm!!!

Yeh no chance in hell I would be scrapping my car for that little washer problem

I would have something else welded and bolted back in its place, It might not look pretty and it may weigh more, but im sure I would get it done....

Edited by chrisgold, 09 January 2012 - 07:06 PM.

[Arno]

Its corroded, so cut it out and weld or bolt a new plate in and make it stronger? Am I being stupid here? Just seems common sense to me? Surely you could fix it, Yeh, it would not look the same, but it would do the job???

It's the wrong alloy type and too thin to weld the ali and retain enough strength (it loses a *lot* of strenght when heated), you also damage the glue/bonding in the area around the welds of the chassis causing them to fail, etc. etc.

Only repair you could do was to de-bond the whole 'tube' that the mounting points are made of, clean all the surfaces, prep properly (extremely importand) and bond in a new extrusion with a new high strenght glue.. And you need one that doesn't need heating to about 120-150C like the stuff it's original built from..

Now.. The problem is: lotus does not approve any repairs to any part of the bonded ali chassis/tub and as a result does not sell individual parts or extrusions.

It *may* be possible/feasible to cut off the old mount, insert a whole new designed and CNC'ed from a billet mount inside the chassis 'tube' and then bolt or bond that in place instead of repairing the chassis itself, but I'd like to see a structural engineer's report on that first.

As it stands at the moment, just like most front end suspension damage on these cars, this writes off a chassis as there is no 'approved' repair and you need a re-chassis to 'fix' it.

Bye, Arno.

[chrisgold]

Its corroded, so cut it out and weld or bolt a new plate in and make it stronger? Am I being stupid here? Just seems common sense to me? Surely you could fix it, Yeh, it would not look the same, but it would do the job???

It *may* be possible/feasible to cut off the old mount, insert a whole new designed and CNC'ed from a billet mount inside the chassis 'tube' and then bolt or bond that in place instead of repairing the chassis itself, but I'd like to see a structural engineer's report on that first.


Bye, Arno.

Yeh new aluminium "tube" inserted inside there and bolted, would be good as new and just as strong (as you can see in pic above there is plenty of space)

Well if mine go you can guarantee I will be repairing them fcuk Lotus!

[Initial D]

this might help http://www.lakesidee...s Corrosion.htm

[FLD]

I've seen htis one before. It is an issue that should be considered. I found a pit in the floorpan on mine where a coin had been under the seat for some time. The best bet is to use things like duralac, anti-corrosion grease and ACF50 appropriately. If I'm tinkering around the tub I might give it a little clean and ACF50 whatever alloy is visible. I'd rather do this than polish the outside.

[chrisgold]

If I'm tinkering around the tub I might give it a little clean and ACF50 whatever alloy is visible. I'd rather do this than polish the outside.

me2

Polish?

[FLD]

Things like this are not covered in a 'service'. FSH is a waste of time IMO.

[Exmantaa]

Like said, ideally you should replace that whole front beam and re-bond with a suitable cold curing adhesive. Lots of work involved and no spare front beams available. But if my car suffered something like that, I would definately make an insert and bond that into the beam. Probably is just as, if not stronger than original and the loads on the upper pick-up points are normally not that high...

And for a track car you can be less precise. Just something that gets the job done :

[FLD]

Like said, ideally you should replace that whole front beam and re-bond with a suitable cold curing adhesive. Lots of work involved and no spare front beams available. But if my car suffered something like that, I would definately make an insert and bond that into the beam. Probably is just as, if not stronger than original and the loads on the upper pick-up points are normally not that high...

And for a track car you can be less precise. Just something that gets the job done :

Carbon clam, aeroquip hoses on the rad??? There's some money spent there!

[s-express]

The same corrosion happens where the rear of the tub meets the steel rear frame.

[Slippy_fish]

I must admit this has got me a little worried as my car has spent at least the last 5/6 years outside and has done over 100k, think I'll take a look at the weekend........ Like others have said though, there is no way I will right it off if there is a problem, I really cant see a problem in manufacturing a suitable repair .

[Exmantaa]

The same corrosion happens where the rear of the tub meets the steel rear frame.

Probably why Lotus put some "special" thin plates between the galvanized steel frame and alu tub...

[Exmantaa]

Carbon clam, aeroquip hoses on the rad??? There's some money spent there!

Maybe better post this under the "spoiler" section, but some serious efforts there... :

[siztenboots]

epic rear wheels there

[joshua]

Not sure where that company Lakeside got there info from but 316 stainless steel is one of the worst materials to use for inserts in the ally chassis, far more reactive even than untreated mild steel. And stainless and aluminium are rarely found together in any aircraft structure unless a galvanic buffer is used. I never understood why Lotus used a steel shim between subframe and chassis as the zinc coating on the subframe is less reactive than steel for most aluminium alloys. Cadmium is one of the least corrosive metals to aluminium and sits amongst aluminium alloys in the metal reactivity table. (closer together the better). Aircraft fasteners are almost always alloy steel with a heavyish coating of cadmium, this treatment is passivation which as the name suggests calms the potential for reaction between dissimilar metals or between eg the steel and aircraft alloy. Stainless steel is difficult to passivate. The problem with cadmium is not being compatible with all epoxys perhaps explaining why Lotus chose not to properly passivate the chassis inserts. Ideally I would treat the area with a corrosion remover like Deoxidine 624, then use a chromate substance like Alocrom 1200 to reprotect similar to the original anodizing, then coat with Rocal px32 which is a high spec alloy protection wax. Trouble is these products are pricey and difficult to get hold of in small quantities.

[ghand]

Not sure where that company Lakeside got there info from but 316 stainless steel is one of the worst materials to use for inserts in the ally chassis, far more reactive even than untreated mild steel.
And stainless and aluminium are rarely found together in any aircraft structure unless a galvanic buffer is used.
I never understood why Lotus used a steel shim between subframe and chassis as the zinc coating on the subframe is less reactive than steel for most aluminium alloys.
Cadmium is one of the least corrosive metals to aluminium and sits amongst aluminium alloys in the metal reactivity table. (closer together the better).
Aircraft fasteners are almost always alloy steel with a heavyish coating of cadmium, this treatment is passivation which as the name suggests calms the potential for reaction between dissimilar metals or between eg the steel and aircraft alloy.
Stainless steel is difficult to passivate.
The problem with cadmium is not being compatible with all epoxys perhaps explaining why Lotus chose not to properly passivate the chassis inserts.

Ideally I would treat the area with a corrosion remover like Deoxidine 624, then use a chromate substance like Alocrom 1200 to reprotect similar to the original anodizing, then coat with Rocal px32 which is a high spec alloy protection wax.
Trouble is these products are pricey and difficult to get hold of in small quantities.

So copper slip is a waste of time then ? What would be the best common stuff that folk may have that would help the problem.

Would spraying say penatrating oil or silicon grease spray be a waste of time.

Are we talking a strip down to have any full effect ?

[Exmantaa]

Not sure where that company Lakeside got there info from but 316 stainless steel is one of the worst materials to use for inserts in the ally chassis, far more reactive even than untreated mild steel.
And stainless and aluminium are rarely found together in any aircraft structure unless a galvanic buffer is used.

Had the same thoughts when I read about the stainless & alu. (Ask a sailboat rigger...)
Same with replacing rivnuts in the alu tub; never use stainless there!

Edited by Exmantaa, 10 January 2012 - 09:43 PM.

[NickB787]

oK so what are the best/freely available bolts to use in aluminium? Just all the bolts I have a re stainless which was a group buy some time ago.

[fezzasus]

oK so what are the best/freely available bolts to use in aluminium? Just all the bolts I have a re stainless which was a group buy some time ago.

zinc plated. zinc is much more inert than bare stainless steel.

[slindborg]

The problem with cadmium is not being compatible with all epoxys perhaps explaining why Lotus chose not to properly passivate the chassis inserts.

And that cadmium is sodding expensive and iirc not meant to be handled much by hoomans. I know missiles get cadmium treatment and there are lots of safety issues that go with using it.