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MG Midget and Sprite Technical - Warped Sill

Hi, Can anyone explain what would cause the inner sill and side panel to warp during welding. I have not had this issue before with other panels.

So had it all clamped in place beforehand, measurements all taken and correct with it fitting perfectly. Now the sill and side panel are bowing outwards. I took it really slowly so not to heat up any one area too much.

If anyone has experience of this issue I would be very grateful because this is the second attempt and before I drill out all the welds for the second time some guidance would be most welcome.

Thanks

James
James Paul

Do you have a picture James?
Malcolm Le Chevalier

Yes, i'll upload one in 30 mins or so. The section of sill below the door is fine?? Just around the footwell, Really annoying.
James Paul

Sounds like a problem with the A post on that side. Have you tried checking the vertical height of the A posts on either side of the car? did you prop the floor cross member to the underside of the scuttle before welding in the footwell side?
GuyW

Did you start welding at one end and progress up the sill to the other end? Or did you alternate, do one end, then other end, then middle, then halfway between etc?

I have a midget shell I was starting to do up and noticed on the drivers side the outer footwell side panel had a big bow inwards.

Interested in pictures also.

Rob
Rob aka MG Moneypit

here you go! Not the A-post, rust ate that!

The bottom of the sill is ok, it is just along the welding line. First time I started at one end and went along. This time started in the middle and then to each end. Same result.



James Paul

another view

James Paul

and another

James Paul

last one...

as i said it was fine when held in place with the clamps. I really don't want to drill it all and weld it again if it is going to keep happening.

Thanks

James
James Paul

I wasn't meaning the A post itself was wrong as such, but if it isn't there (as in rusted away or simply not welded in), then what supports the scuttle at that side? The scuttle will transfer load through the front bulkhead to the top of the footwell. I was thinking that load might cause that sort of buckling if the scuttle isn't sufficiently propped.

That said, the warping is less than I had expected when you first mentioned it. Its not that bad!
GuyW

My guess rob is your best friend for this project
Prop and the Blackhole Midget

Sorry last one didn't upload.

Thanks Guy, I was kind of hoping for perfection!

James Paul

Heat, When you weld, even with a spot welder, it is possible to get too much heat into the metal which will cause it to warp. Go slower next time and use tack welds to try hold the job in place.

When I'm welding I'll put, depending on the length of material, half a dozen tacks right along the workpiece.
A bit like this
1=first pass
2=second pass etc etc

______________________________________________
1 3 2 3 1 3 2 3 1 3 2 3 1 3 2 1

Easier to show than describe :)
J White

This might help

http://weldingdesign.com/welding-qa/tips-avoiding-weld-distortion-thin-sheet-0709
J White

This might help

http://weldingdesign.com/welding-qa/tips-avoiding-weld-distortion-thin-sheet-0709

http://www.weldingengineer.com/Distortion.htm
J White

LOL James. When l said its "not bad" l was just trying to be encouraging, not saying it was 100% acceptable! Just l have seen worse.
I think heat distortion is only part of the story as the length under the door hasn't distorted like that. Which is why l was lookingcfor some other imposed tension that would also affect it when it was heated.
GuyW

Thank you everyone! Looks like I am guilty as charged of rushing this.

So I'll drill the welds out and start again. Hopefully lesson learnt! 3rd time lucky!

Another story for my blog:

http://1965mgmidgetrestoration.blogspot.co.uk/

Kind regards

James
James Paul

J

nice looking beads... mine look like this :(

$$£€=&$(¥$&%×7&3:!*!&÷_÷

You mother F-ing son of a beeeeeeeeeeeeep

prop
Prop and the Blackhole Midget

I had a look online about warping / bowing metal and found quite a bit of information about "metal shrinking" using heat and cooling techniques.

Found this video: https://www.youtube.com/watch?v=t2ddTNrR8Ag that shows the process.

Also read up on this:
http://allmetalshaping.com/showthread.php?t=3913

So before I drilled out all the welds for a third time I decided to give it a go.

It turns out that the process does work. I used a blow torch to heat up the metal instead of a heat disk, but it worked all the same. I think that with the cold weather and the metal being so cold at the moment contributed to metal shrinkage, but not to say that I could have taken a little more time welding along the seem.

It's looking much better now, so a few more sessions and we should be good.

Thanks for all you help

James
James Paul

http://www.youtube.com/watch?v=t2ddTNrR8Ag
Bernie Higginson

That shrinking video is really interesting and informative, James. Thanks for posting it.
Bernie Higginson

Interesting. I have done it with a propane torch but it was slow and not very controlled. Using a disc make it look a lot easier. Especially if you follow the other link to the shrinking disc supplier's video.

http://www.wolfesmetalfabrication.com/sdisc.html

A new thing to try!
GuyW

Im no metal smith but i dont understand why he is using a sanding disk

Id just use a gas welder and heat a spot to cherry red and hit it with awet sponge.. with the sanding wheel he is taking metal off making the panal even more weak

i get the idea... the sanding wheel creats heat ... but so woukd a hair dryer
Prop and the Blackhole Midget

Prop,

It's not a sanding disc but rather a smooth metal disc that create heat by friction. There is the odd spark but no sign of any metal removal, maybe a bit of burnishing.
David Billington

Love the video, I especially love the use of electric power tools with a soaking wet sponge in hand. I watched that just waiting for a bright flash and a bang :D
J White

Thanks david.... i didnt realise that

Probably not much of a flash bang here in the states... it looks to be a 4.5 inch angle grinder and it only runs on grounded 110 volt probably pulling around 5 to 7 amp... but that water will screw up the bearings if it gets water over time

prop
Prop and the Blackhole Midget

James,

Heat the centre of it to cherry red, then either spray a compressed air duster tin upside down at it, that should shrink most it back.

Then if it hasn't pulled it back enough, do the same again around the welds, it should then shrink back the areas where the heat has caused it to stretch.

It is a very fine line between the shrinkage from the weld cooling down and warping due to too much heat. there is a nice balance in there, but finding it is different with every single panel you will ever do.

If you can't get an air duster, a rag soaked in cold water should suffice, but you may have to do it two or three times in various places to get the same effect.
Pete Moreland-Moore

Thanks for all the responses here. I have been trying out some of the techniques and it is nearly there now. i found by grinding the welds down and cooling them rapidly it helped a lot! Once the A-post, outer sill and footwell back plate are in I'm sure the bowing will be sorted.
James Paul

This thread was discussed between 07/03/2016 and 16/03/2016

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