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MG Midget and Sprite Technical - Bending wing beading

I have a job to tackle and am looking for advice- ideally first-hand experience from someone who has done this already! Or at least knows how 'tis done.

I am fitting new rear wings to my frog. This involves fitting new beading along the join. The beading is that "T" shaped section, but the problem is how do I bend this so as to make a smooth progressive curve? The vertical stem of the "T" is about 5/8" so it doesn't just bend by hand - certainly not to form the tighter radius towards the rear of the wing.

I tried putting slits in the stem to enable it to bend. This sort of works, but creates slight kinks in the curve which just isn't good enough.

I guess the proper way is to use a flange shrinking machine, but I cannot afford one and wonder if there is another technique that works well?

Guy


Guy Oneandahalf Sprites

i've never done this, but i believe many people basically remove the flange and weld/solder the top bead on directly. I think Lindsay porter talks about this in his book on restoring sprites and midgets
Chris Edwards

Guy,
I haven't done this job on the rear wings but did so with new front wings. My bonnet was in a pretty bad shape when I had it. The wings were useless as was the lower front valance. The central shroud was good. Not having access to a spot welder I followed a non conventional route and decided to attach the wings to the shroud, with new T section between the two with U-pol 45, a two pack adhesive. I then bolted the three parts together. Bending the T section was a problem especially at the front part of the wings that have quite a sharp bend in them. I cut numerous slits in the section where the bend was the sharpest and took great care in bending the T piece. I then held these in position with clamps whilst the glue set (45 mins). This was five years ago and it has worked fine. An advantage I can see with this method is that no water can ingress between the joints as the glue has sealed this area. I accept that some might not like this method but it worked for me.

Neil (K series)

And the finished result

Neil (K series)

Chris,
Yes, I have done that myself when adding beading to the top of the rear wings when they are still in position, to avoid splitting the seam from the rear deck. Its a method that works well. But in this instance I am refitting the complete wing so was intending to assemble the beading in the proper fashion.

But thanks for the suggestion. I may have to revert to that method.

Guy
Guy Oneandahalf Sprites

Oh yeah and what it looked like before

Neil (K series)

Neil,
That's an interesting addition to the idea. You made a really good job of that!

I have the bonnet to do as well, fitting new front wings like that. I hadn't thought of using an adhesive as I wouldn't expect it to be strong enough. But it very apparently is! I may need to re-consider.

But the point that slitting did work for you without producing kinks in the bead edging is useful to know.

Thanks!
Guy Oneandahalf Sprites

Guy,

Not a job I've done yet but one I'm likely to have to do when I replace the rear shroud on the frog with the steel original centre at least, which I still have. From doing similar in the past I would do as follows.

What I would do is form a jig consisting of 2 plates spaced slightly wider than the leg of the T and radius them to 10% to 20% more than the maximum curve to account for spring back, have a fixed restraint at one end to stop the T lifting out of the groove, and then gently bend the section in small increments to suit the wing curve, I'd go for maybe 6" minimum more won't hurt. IIRC the top centre of the T has a slight pip so the restraint may want to be shaped to suit or made of something which is conformal.
David Billington

Guy

Most of every Audi you see out there is glued together I think

and many if not most other cars

Audi and others decided to glue (OK they call it "bonding" years back so that their carbodies could last longer. The Audi engineer who told me about this back in the eighties explained that almost all body rust on cars can be expected to start at welds and that manufacturers have been trying to eliminate that problem so they could improve their warranties in the battle for more sales

I've ceratinly seen plenty of re-rusts on my own cars over the years where new metal has been welded to old, so his story made big sense to me

The Tee sections are cut off and brazed on in Lindsay Porter's "how tos"

I'd be inclined to make many vee shaped cut outs along the flat plate section to allow tighter curves if I was welding OR gluing them to the wings


I am thinking of trying Neil's method in future if my car is up for more new panels

Modern cars even have their sills and other box sections bonded together, with the right adhesive I'm sure we could benefit from new technology too
Bill 1

The idea of using forms to control the bend is key: you can make them out of plywood. Cutting lots of darts where the bend is sharp is also important, if you don't have access to a stretcher. The forms will help prevent the end points of each dart causing "kinks" in the surface.

The idea of using adhesive in the joints will work, but because you do not have the benefit of an OEM working with brand new metal, and their large scale mixing equipment controlling the adhesive blend accuracy, it is also a good idea to include some nut/bolt fasteners in key places to help carry the worst of the loading. In case you don't get a perfect bond, this will help to prevent a stress crack from forming over time/use.


That is the benefit of spot welding, it is really dependable, and predictable. The whole challenge in making bonded bodies is the process control, which car companies have been working for years to steadily improve and bring the costs down. Note that bonded structures are immensely strong (F1 tubs), and also note that bonded automobiles are still very expensive (so far). I am sure this will gradually become more commonplace, and more cost effective, as the techniques improve.

Remember to keep the necessary minimum glue thickness inside of the joint (each glue will have its own minimum thickness that it will be strongest at). OEMs use little spacers to control this so that the clamps don't "over squeeze" things and result in weak joints.

The biggest problem with adhesive is that you can't tell if it is good or not, after it is cured. So, the process control is really, really important, to avoid unintended variables (temperature, glue mix, bonded surface cleanliness, bonded joint thickness) that can cause it to fail later. Nuts & Bolts in key stress points will prevent this from being too much of a concern in a bonnet assembly.

Norm
Norm Kerr

I suppose that ties in with the way I have been thinking Norm take the strain and help it all stay together

With industrial adhesives (as with the stuff you buy in the Home DIY stores too) you simply have to read the instructions

This shows even with Loctite in all its many variants, what works for Stud'n'bearing fit isnt the same rules for the thread adhesives

There's a whole new brave world out there if we take it on board

Many of the adhesives we can obtain will be DIYable and there is bound to be more availability in future

Guy consider the braze in option too :-)
Bill 1

As I intended using a spot welder the actual bonding wasn't really what I was asking about. But never the less I was interested to hear about the industrial adhesive method. The main advantage to me would be that the adhesive would spread through the joint filling any pockets and gaps and creating a sealed joint which sounds a very great benefit. So that's a useful by-product of the topic.

As for bending the beading I have tried cutting slits in the web which works, but I think may create a "thrupenny bit look" But I like David's jig idea (mental image: David, pint in hand, dancing on a table in a crowded Irish bar).

Pretty easy to make a small former of two pieces of 1/4" plate, ground to a French Curve to allow for changing radii, and then bolted together with a spacing washer to allow the stem of the T bead to slot into the gap. Given the delicacy of the beading, it should bend smoothly by hand, but may still need some short Dremel slits as the radius tightens towards the rear light cluster (or front indicators when doing the bonnet.
Something to play with on a sleety-wet day!

Guy
Guy Oneandahalf Sprites

One thing that may help is cutting slightly wider slots. That allows a more gradual change in the curve without the spikes that can form around a thin cut. Try fitting two blades to a hacksaw instead of the usual one and see if it helps.
S Overy

I have been practising. I did find that the slits need to be no more than half of the stem. If I continue them up to the root of the T then it creates a focus for the bend and this is visible. Half length slots are better. I see that wider slits would also help to disperse that focus.
Guy Oneandahalf Sprites

Guy . I've avoided the problem completely by welding the wings on and discarding the beading. A thin skim of filler has the top of the wing looking nice and smooth. Fine if you're building a custom but not much use if you're after concours authenticity. ;-)

Graeme

graeme jackson

Friend of mine who is a paint sprayer, when restoring his frog, totally removed the beading and filled any gaps between wings/ shoud and used a plastic stick on beading, once painted it was very difficult to tell the difference - slightly wider, and the benifit of no corrosion "under" the paint...
d brenchley

Well that is another approach. I don't like the look of no beading, but a plastic stick on might be ok. Any idea who supplies that ?
Guy Oneandahalf Sprites

Guy,

Shame you are so far away, mate restoring a TR2 has a shrinker/stretcher - its so simple to use and the results are really good.

Does anybody hire one locally ?

R.
richard boobier

Richard, Thanks for the thought! I have enquiries out locally about a shrinker, but if that fails I will try the other good ideas gleaned here.

Guy
Guy Oneandahalf Sprites

Richard,

I have a set of shrinking jaws I use in my fly press, they're a really neat tool to have. My neighbour asked me how I would tackle a certain job on a small stainless disc, about 4", that needed dishing and I immediately thought of them and showed him and he was amazed it was possible, he'd never heard of them before. It was a simple job of shrinking the outer edge to produce the dish. Probably something one would encounter occasionally in aircraft sheet metal, his background was at Stothert & Pitt.
David Billington

We're doing this job (replacing a rear wing) at the moment and I'd certainly planned on cutting the stem of the T off and then using Tiger Seal (from my U-pol stockist) to attach the remaining little bit of beading to the top. most of the advantages of the plastic beading (the tiger seal is actually an adhesive and a sealant, according to the tube) with regards to water penetration but with the correct look.
Of course, this also lets us stitch weld the wing on, much easier than getting a spot welder in, I'd have thought, especially towards the front of the car.
With the stem cut from the beading, there'd be no need to shape the bead as it'd bend the required small amount easily, I'd have thought.
Only just repairing the section where the boot extension attaches so still a bit away from this at the moment! So interested to hear what you end up doing.
-Craig
C Robertson

Guy,

I had to put curves in T-cap to repair some aircraft ribs. In this case, the cap did not get sandwiched between other parts, so it might not work in your case. But, I took a pair of pliers and brazed some welding or brazing rod to their jaws. I attached two pieces to one side of the plier jaws, and one piece to the other jaw that centered between the first two. Then, you just work your way along the flange with the pliers, and the T-cap starts to curve. It was a cheap solution.

Charley
C R Huff

Guy,

A heavy hammer some heat (not just red hot) and a piece of relatively soft wood (between hammer and T bar) helped a lot. I hammered with the T bar on the car and did not need a form. Heat was applied before and after bending (on the T bar only). I did not use splits.

Flip


Flip Brühl 948 frog 59

Flip,
Thanks for that. Looks a very neat job. But I am fitting a complete new back wing, so it is not a matter of dressing he beading down onto the wing - it somehow needs to be pre-shaped to the profile of the seam before the three flanges are clamped together for spot welding
Guy Oneandahalf Sprites

Guy,

If you made a ply/mdf former in say 6mm I could see if I could arrange to use the s/stretcher for you if that helps ?

Just a thought if other methods fail to get the result you want.

Probably a dry run on a scrap end first would be best !

No news of the 'Doctor' in Aus lately ?

R.

richard boobier

Guy / Richard....

All OK here but more rain and bad forcast for the forseeable.

http://www.weatherzone.com.au/qld/southeast-coast/biggera-waters

As for the beading, my view is to trim off most of the lip and soft solder it on after joining the wing to the shroud.

However I do like Flip's results...!

Mark.
M T Boldry

Mark,
That is exactly how I did the job last time, and used lead loading to seal and finish it off. Very effective it was too. At that time I was only replacing the beading - not the whole wing. Somehow as this time I am replacing the whole wing I was thinking I needed to fit the beading as per original. But of course I don't - I can weld the wing on first and then add the beading.

I always thought the triple-layer flange joint for the beading was an oddity. I think it is a relic from how bolt-on wings were fitted in earlier times - often with a rubber beading inserted. The top of an A30 front wing is almost identical, but using a flanged rubber bead insert in place of the Sprite's metal T bead.
Guy Oneandahalf Sprites

This thread was discussed between 03/01/2011 and 09/01/2011

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