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MG Midget and Sprite Technical - Floor and rear bulkhead replacement

About to start work on 1500 midget need to replace floor sills and work on rear bulk head. Want to start off by removing floor. Whats the best way of doing this.
Jack Smith

Hi Jack,

I can help for sure on this having replaced mine fairly recently.

I have taken loads of photos for my blog which will hopefully help you:

https://1965mgmidgetrestoration.blogspot.com/

Before you cut anything out make sure that you weld supporting brackets across the doors to ensure the door gaps remain good. (assuming they are ok at the moment!)

To remove the floor you will need to drill out all the spot welds that attach the floor to the rest of the chassis. You will need a couple of really good quality spot weld drill bits. It will probably be easier to cut sections of the floor out first with a 1mm metal cutting disk on an angle grinder rather than attempt to get it out in one big section.

How much of each panel you cut depends on how badly rusted it is.

If you can post some photo's we can advise you further.

I decided to repair the rear bulk head first and work forwards to the cross member, end and side panels in the footwell. Then attached the inner sill, then the floor, then the outer sill. Again it just depends on how much you need to replace.

You can either buy new whole or part panels or make bespoke repairs to parts if the rust doesn't go to deep.

Good luck and keep us posted!

James
James Paul

Hi James
Thanks for your reply. I will add some photos tomorrow. Are the spot welds attacked from above or below the car.
Regards
Jack
Jack Smith

Jack, just to add to James's advice, which is very good. If you run a flap wheel lightly along each flange or seam to be dismantled, the dimples of the spot welds will stand out, become very apparent and it makes drilling them out far easier.
Study the photos on James's site - there are lots of them! - as that will help you see how it all fits together and where best to cut out rusted panels.
GuyW

Hi Jack,

Just to clarify a spot weld can be drilled out on either side of the two joining pieces of metal. You should see the weld clearly when you remove dirt and some paint as Guy describes. I also use a rotary wire disc used on a drill to clean up the metal.

Another tip is if the car is straight and you need to repair the crossmember is to try and replace this before you remove the sills so that that the jacking points become your guide. I found it helps with welding this in straight.

Please note that on my car mine wasn’t straight at all due to the heavy rust, accident damage and bodge repairs, so didn’t brace the door gaps and cut out more metal than I would recommend. The risk of a twisted chassis is something you’ll want to avoid.

Once you have braced the door gaps with steel tube you should be able to but the car on its side which should make the car more stable. Or you can made a rotisserie which will allow you to rotate the chassis up to 360 degrees.

James
James Paul

Hi Jack

Some excellent advice given in the previous replies, I dont have anything in add in that respect.

I have been through replacing sills on my 1500 as well as a multitude of other welding repairs, and then onto paint etc. I'm also in Gloucestershire (Thornbury). Once this lockdown has eased, if you need any help, loan of tools please feel free to contact me on my email or via the forum.

Good luck
Chris Madge

Jack
All the best with the car. I'm re-building a Frogeye although I cheated and started with a new basic shell but most of what you can see is original. I've still done a fair bit of welding though although of variable quality! Like Chris I'm in Gloucestershire (south) so maybe not far from you.
Bill Bretherton

Thanks very much guys. Im in moreton in marsh. Added some photos just cut abit of floor away today just to have a look. Drivers side looks like its been replaced before and has a seem weld along the flange as well as spot welds so need to decide how im going to approach thus. First restoration i have done so its alot of learning i think alobg the way. Will try and remove the rest of the floor this weekend. Want to get it jacked up properly first and remove rear axle for better access





Jack Smith

If the doors still close and the shutlines are OK then you really should brace the door gaps now, before you jack it up and remove the axle.
David Smith

My door closes but the gaps are not brilliant. Whats best to do still brace
Jack Smith

My door closes but the gaps are not brilliant. Whats best to do still brace
Jack Smith

I made up door braces with a threaded bolt and some nuts welded at one end so it could be adjusted for length. One at the top and one at the bottom of each door. Then hung the door parallel to the sill and then just micro - adjusted the nuts to get the gaps right before welding.

Before jacking put a beam of some sort - a 2" X 4" works well, along the length of the car under the sill,and Jack on that. It will help to stop it sagging or bowing in the middle.
GuyW

Thanks guy, have you got a picture of your brace
Jack Smith

Not a good photo Jack, but you get the idea.




GuyW

Do you have 1 top and bottom
Jack Smith

Yes, you can just see the angle iron of the top one at the edge of the photo. Initially the bracket at the end was bolted to the door opening flange but subsequently I added some tack welds which held it more firmly and are easily ground off when the sills and floors were all finished.

I have said this several times in the past, but I find the best thing is to build the sills and A and B posts around a door, using it as a template to get the spacing and the angles correct. Its easier than welding it all together and then finding that the door doesn't fit the hole, or that the corner angles are all wrong!
GuyW

This thread was discussed between 05/05/2020 and 06/05/2020

MG Midget and Sprite Technical index

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