How do you measure rust ??
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Electron

Original Poster:

605 posts

248 months

Monday 17th December 2012
quotequote all

I'm rebuilding a set of TR4 suspension. There are essentially four wishbones and upright and a spring pan for each side.

The lower wishbones are cast with no rust - the top wishbones have very minor pitting and the uprights are ok.

The spring pan however has what I would describe as "deep pitting" ie after sand blasting none of the surface is in any way smooth however there is a good thickness of metal left. (To be honest they're cheap I'll scrap them and start again ..)

But I was wondering how you decide what is an acceptable level of rust on a critical component ??


HustleRussell

26,484 posts

189 months

Monday 17th December 2012
quotequote all
Safety critical and 'deeply pitted', plus easy and inexpensive to replace? To me that equals 'definitely replace'. I take a fairly common sense attitude towards this, I look at what the part does, I decide if it would cost me time/money/inconvenience/injury if it were to fail, and if it stacks up I'll replace it.
The only way you'll know how bad corrosion is will be to remove the oxide as you have done and inspect it against a new part. There will be no minimum thickness spec published for a part like that but normally common sense tells me.

Electron

Original Poster:

605 posts

248 months

Monday 17th December 2012
quotequote all

This is the front nearside suspension on the Gilbern after "repair" .. it is actually nearly 100% replacement ...

The tubes had rotted from the inside out so looked solid but were thin in places ..


na

7,898 posts

263 months

Monday 17th December 2012
quotequote all
Electron said:
The spring pan however has what I would describe as "deep pitting" ie after sand blasting none of the surface is in any way smooth however there is a good thickness of metal left. (To be honest they're cheap I'll scrap them and start again ..)
a lot of parts can be cheap to buy but expensive to own as they don't last long, don't fit or work well - not always but a lot of times it's better to refurbish original/exiting parts than to replace with new unless there's a specialist producer manufacturing to a higher standard than the cheapest parts

RicksAlfas

14,493 posts

273 months

Monday 17th December 2012
quotequote all
Electron said:
How do you measure rust ??
Can you see through it?
hehe

LordBretSinclair

4,306 posts

206 months

Monday 17th December 2012
quotequote all
na said:
lot of parts can be cheap to buy but expensive to own as they don't last long, don't fit or work well - not always but a lot of times it's better to refurbish original/exiting parts than to replace with new unless there's a specialist producer manufacturing to a higher standard than the cheapest parts
I agree Nigel. Years ago I bought some "new" bumpers for an MGB. Lord only knows where they were made but they were the most awful fit ever and in the end I gave up on them.

More money later ( but well spent ) I had the original ones re-chromed.

Edited by LordBretSinclair on Monday 17th December 16:50

Electron

Original Poster:

605 posts

248 months

Monday 17th December 2012
quotequote all
Ahhh so I got it right then .....



shows where you can see through after I cut the body off .....

velocemitch

4,019 posts

249 months

Tuesday 18th December 2012
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Blimey that chassis doesn't half look flimsy, no cross bracing to speak of at all. How much does the Body contribute to stiffness?.

Sorry gone off topic a bit....

Electron

Original Poster:

605 posts

248 months

Tuesday 18th December 2012
quotequote all

Actually it's sort of still on topic a little bit ....

The inner fibreglass tub is riveted to the chassis. If the chassis is 100% everything works.

As the chassis rots it weakens ... as it weakens it flexes weakening the rivets and pulling them out of the chassis ... eventually you end up with something soggy.

The challenge is spotting rotten tubes when they're covered by the body (especially the sills).

The car looked ok on the surface but was sh*te once the fibreglass tub came off.

I was also surprised that the front suspension mount points were as bad as they were ....

As I mentioned in the "safety" thread the addition of a roll hoop with two rear tie bars should stiffen the chassis up a bit.

This is the Gilbern Genie ... the Gilbern Invader chassis is a bit stronger (but heavier) to counter some of the above .....


velocemitch

4,019 posts

249 months

Tuesday 18th December 2012
quotequote all
I took my 68 Alfa 1750GTV off the road three years back (nearly 4 actually) after I found the main cross member at the front, which carries the engine and the front suspension, was no longer connected to the inner wings.

Large areas of metal had just evaporated, yet the Car had just past an MOT and I'd been driving to hard for some time. It had also been (un)professionally repaired following a frontal impact and despite being in their workshop for a few weeks they still missed the rot.

I'm not saying this is a good thing, but you might be surprised how much redundancy is built into Cars, at least those designed without the aid of computer analysis.

DJRC

23,563 posts

265 months

Wednesday 19th December 2012
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RicksAlfas said:
Electron said:
How do you measure rust ??
Can you see through it?
hehe
No, you measure rust in units of RPL.

RPL = Rusts per Lancia smile

Skyedriver

23,320 posts

311 months

Wednesday 19th December 2012
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Usually measure by the shovelfull

Electron

Original Poster:

605 posts

248 months

Thursday 20th December 2012
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I have a very technical answer from someone who is into Ford Escort Mk2's.

To test the front strut mounts for rust he hits the mount with a hammer

"Ding" it's good.

"Thud" it's probably rotten

Not sure I would try this on a Lancia as I understand they went thud from the factory ...