How much metal thinning is OK

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somewhatspritely
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Joined: Mon Mar 08, 2021 11:46 pm

How much metal thinning is OK

#1 Post by somewhatspritely » Mon Mar 08, 2021 11:55 pm

I'm cutting out the frilly bits of a Sprite. After cutting around the front web I measured the panel thickness adjacent to the cut out and I got just over 1mm. I believe the panel would have been about 1.2mm (18gauge) originally. Is this degree of thinning likely to be OK or should I be removing and replacing anything this thin? (There may be no car left if I do) Hopefully the attached pic illustrates what I mean.

Many thanks for any thoughts.
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Luxobarge
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Location: Horne, Surreyshire

Re: How much metal thinning is OK

#2 Post by Luxobarge » Tue Mar 09, 2021 10:46 am

Firstly, welcome to the forum!

OK, so a few years ago I restored a Midget (same thing really) which was in even worse condition, so I was often faced with the same dilemma. It really depends on your standards and what you are trying to achieve I suppose. I did my restoration project with the ethos of wanting it literally as good as new, and in some cases in some areas I swear I got it better than new, in the sense of stronger metal and better rust protection than it would have had from the factory. So if you want to do a really good job that will last, I'd say you need to cut out substantially more metal than that - I usually cut back to pretty much where the original paint was still intact, or at least not far off, then removed every single trace of rust from the remaining metal, if any. This kind of surgery is far more daunting - at one point I had only the centre part of the transmission tunnel connecting the front and rear halves of the car! I did weld in bracing struts to the door openings though, which were later removed, so it did actually remain the same shape. However, although it's more daunting and usually involves more complicated fabrication of repair pieces (unless they're available from MG parts suppliers, which many are) it's more satisfying, much easier to weld onto original thickness metal and much less chance of rust bubbling through in the future - my car was started in the 90s, completed in 2002 and is still immaculate, without a single spot of rust anywhere. Generally I'd say that if there is a repair piece available or making one is relatively straightforward then cut back plenty of the old metal, the extra time in doing longer welds is probably less than the time it would take to properly clean up original rusty bodywork.

On the other hand, if you're just wanting to get it back on the road for a few more years with the body reasonably rigid then you can go ahead with less metal removal and you'll probably get away with it - but I'd lay good money that as you're welding you'll get further holes blow in the metal and wish you'd gone back further! it certainly looks as if you'll need to cut back further to the right in the photo, that really doesn't look great, and a lot depends on how thoroughly you clean the rust off the remaining metal - you can't be too thorough here! I can't stress that enough, rust is like cancer - if there's ANY remaining, it will find a way to bubble through eventually in my experience.

Not a very definitive answer I'm afraid, but I reckon there's no hard and fast answer to this kind of question, it all depends on your objectives, your skill, your patience, time availability and availability of repair pieces I guess. Hope that helps?

All the best with it - how about posting up a blog-type thread on your restoration, we love that sort of thing on here!

Cheers :D :D
Some people are like Slinkies - they serve no useful purpose, but they still bring a smile to your face when you push them downstairs.

somewhatspritely
Posts: 5
Joined: Mon Mar 08, 2021 11:46 pm

Re: How much metal thinning is OK

#3 Post by somewhatspritely » Tue Mar 09, 2021 12:08 pm

Thanks for the welcome. I will try to figure out the blog thing at some point.

The how far to replace question is a tough one. The car is pretty horrific. It's a '62 quarter elliptic. Floors are gone, footwells etc are toast.
This webbing area is available as complete replacement but I have been a tiny bit underwhelmed by the quality of some of the replacement panels I have sources so far, I also have a sentimental desire to retain as much original metal as possible.

I bought the car as a restoration project 25 years ago. After a year of initial effort it languished. (Had a family etc.) Around August of last year I was reviewing life and my projects. I decided it was now or never for the sprite, It's a 1962 Mk2. My ambition is to have it back on the road in 2022 as that will be sixty years since registered. It has just taken me 5 months to do some basic preliminaries like make space for it in the garage, so 2022 is looking a little optimistic.

The photo with wheels is from 25 years ago. The photo with an electric heater far too close to a bowl of water (I am so dumb sometimes) is contemporary.

The car is straight in terms of suspension mounting points but needs repair or replacement of almost every panel. There is impact damage to the rear as well. I'm planning to brace the car and treat it as six sections, replacing/repairing each section as much as possible before moving on. My intention is to get rust free and then use epoxy primer for a long rust free life. I'm looking for solid and straight over pretty.

In terms of modifications I plan to keep the look and spirit of '62 as much as possible, but use bolt-on changes (1275 engine/g'box, disk brakes, etc) to make the car a little safer for modern traffic.A key thing is that any 'upgrade' should be reversible if desired in future.
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Luxobarge
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Re: How much metal thinning is OK

#4 Post by Luxobarge » Tue Mar 09, 2021 1:09 pm

I like your approach, that looks like a proper restoration, nice one. The first photo is a view I'm very familiar with! I also have that roll bar fitted - spoils the aesthetics of the car a little but in the event of a roll I'd rather keep my head attached to my torso, so it's staying.
I know what you mean by the quality of repair panels, but my personal view is that I'd still go that route, or at least find a happy medium - after all, if the new metal isn't that great, it's still probably better than the rusty metal you showed in the first photo. I'd share photos of my resto too, but unfortunately they're all old-school hard copy "analogue" photos, and I just don't have time or the equipment to convert them to digital.

Looks like yours was originally mustard colour or beige, but has had bits of red panels added - Mine was originally the BL standard mustard colour, but I wanted a red one so the whole thing (even bits you can't see) was re-sprayed red, you'd have to dig extremely deeply to find any original colour on it now. I know purists might object, but there are plenty of these cars around in original condition and that's what I wanted. Regarding upgrades, I took a similar approach to you, I did polybushes and a rear shock absorber conversion, but engine-wise I wanted to retain the original character of the mechanicals, so I used a fast road cam, electronic ignition, stainless multi-branch exhaust and silencer etc., oil cooler, electric radiator fan etc. but kept the carbs standard and it's still got the original A-series character, but sounds more like an MGB and goes very well - very well indeed to be honest! There are probably a few other mods I've forgotten, but they're all reversible and in my view "in character".

Keep up the good work - look forward to seeing more of it on here if you can. Cheers!
Some people are like Slinkies - they serve no useful purpose, but they still bring a smile to your face when you push them downstairs.

somewhatspritely
Posts: 5
Joined: Mon Mar 08, 2021 11:46 pm

Re: How much metal thinning is OK

#5 Post by somewhatspritely » Tue Mar 09, 2021 2:24 pm

Thx. I believe the car was originally blue. Someone painted it red. (or as much of it as they could see) The previous 'restorer' subsequently painted much of the car with beige primer. The attached photo of front chassis shows the original paint.

You've convinced me on replacement.The front of foot well front and outside panels need to be replaced and it will be a lot easier to do that with the webbing and inner wing temporarily out of the way.

Before that I need to get the car raised a little higher, supported level, and braced. It's a little hard to work out what I will brace to as almost everything will go at some point.
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