Sheet metal thickness for TR4A front wings.

[rogerowen]

I need to make up some repair sections for my front wings - guessing thickness of 1mm, ???

[MikeF]

0.04", 40 thou 19 swg.

That's a 90% yes from me

 

Mike

[boxofbits]

I usually use 20 guage sheet steel for fabricating repair panels, which is around or just under 0.9 mm.

 

Kevin

[Motorsport Mickey]

Far as I know TRs are 18 gauge that's 1.2mm and on a car that doesn't have much in the way of developed crumple zones I'd hang onto every thou of material you can get in the wing, it's the only stiffness and anti crash protection you can get there.

Stuart knows the thickness better than all of us, he'll have a worthwhile opinion.

 

Mick Richards

[boxofbits]

An interesting post from Iain McKenzie who used to be a fabricator at Morgan cars says: -

 

" A lot of areas with 'shape' in, ie: wings and inner wings are only 20g (1mm) as the strength is in the shape, though as has been said 18g is a good default size for repairs, unless you're doing sill steps and chassis legs.

beware when buying from motorfactors etc, a lot will stock 22g (0.8mm) suitable for modern cars (thinner steel, so lighter and more efficient) and of course used for nasty patch repairs for the MOT man.

A steel stockholder would sell you single sheets - depends how much you want. May have offcuts too. Think the smallest normal size is 6'x3' which woudl be cheaper than buying small bits over the counter. Worth trying fabrication companies too, depending what they make, they probably throw away as offcuts large enough pieces to repair a minor with. A donation to the tea and biscuit fund can work wonders! "

 

Kevin

[RogerH]

Hi Kevin,

your sums are dodgy -

20SWG = 0.9mm = 0.036"

22SWG = 0.7mm = 0.028"

 

19SWG is nice to work in as it bends quite easy.

18SWG is better for many repairs as you will not get a step in the mismatch between thicknesses, but can be a sod to bend.

 

Shape will give you strength but an 18SWG shape is stronger than the same 19SWG shape.

 

Be careful when ordering sheets of steel. 1mm (19SWG) may arrive as 0.9mm (20SWG) - the excuse being that it is within the rolling tolerance if 0.004"

(0.040" - 0.004" = 0.036 = 20swg)

 

Also be very careful of your wire gauges AWG (American) can be thinner than SWG as they are used for different things.

 

 

Roger

Edited April 18, 2017 by RogerH

[stuart]

Most motor factors these days only keep what they call "Half sheets" Which is nominally 4ft by 2ft so relatively easy to handle. I only use 18SWG for panel repairs as a matter of course as it puts some strength back into what are often panels that are getting very thin by now. I buy it by the full sheet as an 8X4 sheet only costs me about £30 +VAT.from my local steel stockholder.

Stuart.

[boxofbits]

Hi Kevin,

your sums are dodgy -

20SWG = 0.9mm = 0.036"

22SWG = 0.7mm = 0.028"

 

19SWG is nice to work in as it bends quite easy.

18SWG is better for many repairs as you will not get a step in the mismatch between thicknesses, but can be a sod to bend.

 

Shape will give you strength but an 18SWG shape is stronger than the same 19SWG shape.

 

Be careful when ordering sheets of steel. 1mm (19SWG) may arrive as 0.9mm (20SWG) - the excuse being that it is within the rolling tolerance if 0.004"

(0.040" - 0.004" = 0.036 = 20swg)

 

Also be very careful of your wire gauges AWG (American) can be thinner than SWG as they are used for different things.

 

 

Roger

Yes you're right Roger. I used the post Iain put on the MMOC forum, but having checked 20 guage is around 0.89 mm. As I'm restoring a Morris Minor van I'll check and measure some of the existing BL metal to see if it's the same as Standard Triumph.

 

Simple logic would suggest that since they were all under the BL corporation by 1971 ( the year of my LCV manufacture) that they would have used the same supplier and specification of steel. However, since there was very little logic in BL it will be of interest to find out.

 

I do wonder if the steel supplier, quality and guage for production of body'shells as previously sourced independently in the early/ mid '60's by both BMC and Triumph changed in any way when BMH and Standard Triumph merged into one company?

 

Regards

 

Kevin

[RobinTR]

I have been saving up a similar question for my TR6 restoration, (although more related to material availability), but this thread has answered most of my questions. Prompted by Stuart's comments I rang around to find local steel stockists (Camberley area) and found one who was helpful and said that they could cut to any size and even help put in angles etc. Interestingly, they said that while they stock 18 gauge steel (CR4), with nominal 1.2 mm thickness, it is currently being supplied closer to 1.1mm.

 

I presume that the older cars where manufactured when things were still predominantly to imperial measurements, so SWG was based on so many thou, whereas the current sheet appears to be metric, with the SWG referenced as a legacy size. However, from my reading of the size tables, the metric equivalent tends to be slightly thinner than the SWG specification.

 

I had to prepare scores of weld-in patches when refurbishing my Stag a few years ago and found that the most effective material came from a steel shelf from some industrial racking and the section dividers from an office filing cabinet. This steel appeared to be slightly thicker than the usual metric/SWG purchased on the net and seemed to be of a higher grade steel (may have been just my subjectivity).

 

I was happy to work with this slightly thicker material on small patches as it allowed surface finishing without leaving a hollow needing to be filled.

 

When talking about thickness for original items like rogerowen's wings, then what allowance would have been made to compensate for the pressing process? I assume that there would have been some measurable thinning on the wheel arch lips etc. Does this result in requirement for different thickness material depending on the position of the repair?

[Motorsport Mickey]

To complex, remember the "kiss" principle.

 

The TR shells were supplied in 18 gauge 1.2mm, do what you can to duplicate it, any shortfall is tough , you've done your best.

 

Mick Richards

[rogerowen]

Thanks guys - didn't mean to stir up a hornet's nest . I've already got some 1.2mm sheet left over from a Morris Minor project (possible was too thick for that one).

 

The shaping issue could be important though - as one repair section is around the grille curve - it's a tight bend with some complex architecture, and I can see how 1.2 might be a bit tough to bend and shape. Measuring the stock I have with a digital caliper gauge gives a pretty accurate 1.2mm, and offering it up to the wing top edge return confirms the thickness to 1.2mm (as far as I can tell).

 

Think I'll try with the 1.2mm and see how I get on.

 

Thanks again for the suggestions.

 

Cheers,

 

Roger

[boxofbits]

Hi Roger

 

Well as Mick has stated previously TR bodyshells where manufactured in 18 guage which is 1.27 mm according to various tables, so your 1.2 mm sheet should be about right.

 

I believe the Morris shell must have been made in 20 swg. I measured an old door skin and it came out to around 0.034", and when I bought some sheet steel for the van using part of the rear door pillar as a reference, the guy measured it up as 20 swg. So it appears that Standard Triumph possibly used thicker sheet steel than their corporate cousin Austin/ Morris at the time.

 

Kevin

[Drewmotty]

It's worth noting that the material can thin considerably by the time it has been shaped and linished.