MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - Sill replacement

I have aquired a 1500 midget that has stood in a lock up for 17 years. It is in remarkably good condition but (inevitably) needs new sills.

At some time in the past a really thick plate mirroring the inner sill has been welded on from the inside. I presume the inner sill was left in situ but apart from that the job seems to have been done properly and is seam welded. The outer sill has just crumbled to nothing so this plate has probably helped maintain rigidity in the mid-section. Poking around inside the sill suggests to me that the original inner sill has also crumbled away leaving only the new plate, rusty but sound.

My question is this. Should I:
1) cut everything out and start again with a new inner and outer sill, or
2) leave the plate in position and after killing the surface rust on the plate fit a new inner sill alongside as was originally the case, or
3) kill the rust on the plate and regard as the inner sill and just fit a new outer sill.

I should add that the jacking point tubes, floor panels and everything else appears in good order. I think the need for new sills is a consequence of them not being removed when the orginal repair was carried out (oh those POs).

Chris
Chris H (1970 Midget 1275)

Hi Chris do you have any pictures? That would help, is the plate the same thickness as an inner sill would be? Personally if the inner plate is solid I would be tempted to leave it but if you have any doubt I would replace it otherwise it will be false economy as you will have to replace in a few years anyway.
C Carter

As long as it is sound, properly welded and the door gap is OK, you could probably just fit an outer. Is the seatbelt mount intact?
Dave O'Neill 2

Hi C Carter - I'm at work so can't send pictures at present.

Dave - yes, the seatbelt mount is rock solid. Compared to my Heritage shell Midget the metal in the 'false inner wing is heavier gauge!
Chris H (1970 Midget 1275)

Can anyone recommend a website with some good pictures of how to replace the sills? I found this one http://www.spiny.org/van_progress/. I found it very helpful. Any other suggestions?

Chris
Chris H (1970 Midget 1275)

Feel free to have a look round my Flickr account for the many, many pics I have taken of my re-build.

http://www.flickr.com/photos/53944874@N04/collections/72157626067600364/
S Overy

Thanks S Overy, a very good reference site for our red car that's underway at the moment. Whilst my welding isn't up to your standards, I'm learning how to do it slowly but surely and the welds are getting better and I'm finally getting "that sound" so it's good to see pics of how others do the things that we may have to do.

A.
Andrew McGee

I echo the thoughts of Andrew - thanks S. Overy for a very inspirational website. Just what I need.

Chris
Chris H (1970 Midget 1275)

Hmmmm. Some good news and bad news. Here a photo of the interior. A new 'inner' sill appears to have been welded in at some time. This seems very sound along its length e.g the seat belt mount withstood a lot of force to remove the belt retaining bolt.

Chris


Chris H (1970 Midget 1275)

However, there is rot right at the front where there is a space in front of the footwell/pedals. Seems sound enough around it.


Chris H (1970 Midget 1275)

Also some evidence of a patch near the rear spring box although seems solid now.

So overall, I'm still not quite sure which way to go - leave the replacement inner sill as it is (and patch that hole in the front) or rip the whole lot out and replace inner and outer sills (I admit I'm not keen on that).

Any opinions?


Chris 'I must need my head examined' H


Chris H (1970 Midget 1275)

If the car is straight, then just cut the rusty patch out of the inner sill and leave the rest, assuming it is properly attached. It appears to be seam welded along the inner edge, so it should be. I see no point in disturbing bits of the car unnecessarily, hence why on one side of my car, I only replaced the front half of the sill. Be warned though, any repair done this way MUST be seam welded to the rest of the existing panel.
S Overy

Thanks, S. Overy (we can't keep calling you that - it's too formal!).

I have two questions arising from your photos (forgive me if they seem simplistic but I'm a novice). These are:
1) what did you use to produce those fine/narrow cuts in the metal? I have a metal cutting disc for my angle grinder but it does not produce nice cuts like that1
2) what gauge steel did you use for items such as the inner sill, closing panel etc.

As I say, I'm such a novice but hopefully with a bit of advice I can learn by doing.

Thanks

Chris
Chris H (1970 Midget 1275)

Chris,

There's a clue in his email address to his name ;-)

Also I posted some pic's of my sill replacement on here:

If you use the archive facilty in the K series and TC area and search for (include all of these words two threads called:

XE Midget - Progress Elec / Fuel

Spridget - XE - Restoration cont'd...

Cheers

Spencer
S Deakin

Whereabouts are you in the West Mids?

Try these links to see if they take you to the two threads I mentioned:



http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=&mode=archiveth&subject=76&subjectar=76&thread=2011061021291417104

http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=61562636107008&mode=archiveth&subject=76&subjectar=76&thread=2009092616331822224

Cheers

Spencer

P.S. I think they only go to the link properly if you are logged in, if not you just get the Twin cam and K series latest posts
S Deakin

I'm in sunny/rainy Wolverhampton
Chris H (1970 Midget 1275)



Just seperated by the oasis that is M6 J10 ;)

S Deakin

As pointed out, my real name is Simon. ;)

For cutting the slots, I only ever use 0.9mm cutting discs. I guess you've got the more standard 2-3mm thick cutting discs, which do tend to leave nasty looking cuts. The thin ones aren't cheap, for my last set I paid £16 for 10 from Wickes, but I consider them well worth the money for the cleanness of the cuts. They also put much less heat into the panel, so they help avoid distortion too.

As for the gauge of the steel, that depends where on the car it was. The inner sill is 16 SWG (1.6mm), with most of the rest being 18 SWG (1.2mm). I figured that since most of the rust spots are what I'm fixing, replacing everything with slightly thicker steel than before is no bad thing. It's also easier to weld! Things like the new chassis rail bottom plates are 16 SWG to aid with the strength and stiffness, and all the new suspension mounts I'm making are 3mm.

Also, if this helps (or maybe won't), this is the first car I have ever restored. So it shows what can be done with a little patience, practice and forethought.
S Overy

Simon,

I think you can get the thin discs cheaper if you shop around. I often get them from J&L when they have them on sale but ordering them on their own probably wouldn't save much, but I often order other stuff. Maybe asking at local fabricators might help as a friend says she knows one that buys in quantity and would sell to her at around 50p per disc. Do love them thin discs as they're much better than the thicker ones as you say, more fragile but less heat input.

IIRC the inner sill is 14swg (2mm).
David Billington

Another vote for thin discs, work like a knife through butter.

A comment on the inner sill: From the photo, what you can see inside the car looks good, but the important thing is how well is it linked in at the ends? At both ends of the sill there is a bit of double skinning of the transverse panel, and linking in properly to both of these is a critical area for the shells rigidity. If the sill was repaired by plating the new bit only over the part of the inner sill accessible from the inside it won't have reached the other end of each cavity (as evidenced by the rust hole you can see at the front end).

If you are going to all the trouble of renewing the outer sill, then this is the time to do the whole sill properly if there is a problem in this area.

If you are renewing the sill it is a good idea to brace the door opening from the windscreen attachment to both the rear spring mount and the B-pillar. It's imortant to attach the bracing while the car is set up with all the door gaps correct, and is best done before removing any old panels. (However, better late than never!)

B-pillar attachment of the bracing can be either to striker attachment (as the one shown in the photo) or to the hood frame attachment. The latter allows you to offer the door up to check the gaps as you proceed with the job.



Paul Walbran

This thread was discussed between 03/08/2011 and 08/08/2011

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.