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MG MGA - Chassis repair

Despite all my efforts, I have failed the MoT with some holes in the chassis under the near side door.

It looks like it was previously repaired as I ave to cut through some old welds to get to sound metal.

At the moment, it looks fairly straightforward with all the damage on the bottom of the chassis rail.

What thickness of metal should be used for chassis repairs?

It looks as if originally the chassis was made up of two parts welded together to make a box section as there is a ridge running down the middle. Do I need to replicate this or can I put in a flat section across the bottom?

thanks
Dan Smithers

Metal was 14g on the frame I believe.

You can buy repro sections of the frame from Todd Clarke of Clarke Spares, and probably from Metal Mickey or other suppliers.

It is pretty easy to make a section up that matches though using lumber as a break if you have to do the corner.

Cut out the rusted holes only as far back as sound metal and weld in patches rather than cutting out a whole section. It doesn't sound from your description like the damage warrants replacing a whole section of frame rail.

JIM in NH

AJ Mail

Dan,

Metal Mickey (Michael) at Sportscar metal works sells the chassis repair sections. They are folded and designed to go either side of the welded seam on the chasis, so as not to be to obvious.

Regards...John
J Bray

Dan, I would try to replicate the bottom seam. If your welding is good enough it will not even be noticed by the inspector that a repair has been done. (unless of course you get the same one). Missing the seam would draw attention to that area.
Art Pearse

Thanks for your suggestions. I'm going to try Metal Micky. On closer inspection, it appears that flat sheet had previously been used to reinforce the bottom face - welds running along the outside corner edge and either side of the seam.

How were the two pieces welded together originally?
Dan Smithers

The entire frame is 14 gauge (0.075" thick) steel. Original construction of the frame side rails was two C-shape sections with very small flanges, welded 100% along the center flanges of the box section. It is my understanding that MG Car Company, Ltd. contracted out stamping and welding of the two main side rails, then did the rest of the tube forming, stamping and welding in house.
Barney Gaylord

Getting ready to do the repair with some sections made up by Metal Mickey.

Can I do this as a continuous weld, or should I do it in short sections allowing time to cool in between?

Also, are there ventilation/drain holes in the chassis?
Dan Smithers

Best to make several tack welds to hold the part in correct alignment, then go at it an inch or so at a time to letting it cool in between welds to minimize warping. Body sheet metal can warp a LOT with continuous welding. Frame metal is thicker but can still warp with too much heat on one place.

There are a few small finger tips size vent/drain holes in bottom of the side frame rails.
Barney Gaylord

A lot of usefull information still exists on Eclectis's web site. http://www.eclecticmotorworks.com/mga.html
The methods they used were very helpfull. Reading their information will help prepare you to tackle a lot of the welding needed to restore a MGA.
R J Brown

This thread was discussed between 14/11/2011 and 24/11/2011

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