Rusty front Damper Mounts - B*****

[Fatboy]

HI Everyone,

I've finally got round to starting to get my Mini back on the road, and found this nasty bit of rot when I decided to take off the front damper mount to get a better look at a crack in the front panel:



Now I've found this I'm going to pull out the front subframe to check what else I might find, make sure I don't miss anything, but what I was wondering is, assuming that the damage is just the rotten area in the photo, can I get away with just using a piece of flat steel sheet to repair that section (I'd chop it out all the way to the top) or do I need to use a repair panel, as the area looks pretty much flat?

I was just thinking that steel sheet is cheaper than repair panels :-)

Also, ages ago I remember Cooperman talking about strengthening the front subframe mounts by double skinning them, anyone have any more input on this, as I can't find the old post...

While I'm at it, does anyone have a suggestions for a good supply of nuts and bolts to have available (i.e. 1/4" unf etc, high tensile/standard etc) when doing this - I have plenty of metric nuts and bolts, but no imperial so thought it would be an idea to start building up a supply ready for that last minute panic moment when I need some new bolts

[Cooperman]

Hi Grant.
I think I was referring to the strengthening of the tie-bar mountings on the front of the front sub-frame. You do this by welding in a triangular piece of steel, about 1/8" thick.
However, the damper top mounting brackets can also be strengthened by extending the base section, i.e. the face which sits against the inner wing and effectively making a new web so that instead of sitting on a damper attachment shaft which is cantilevered from the bracket, you have 3 webs and the damper sits between the forward 2. Then you use an extra 2 bolts through the inner wing and weld a new nut-plate inside the inner wing onto which you put the extra 2 bolts. If I had a scanner I would do a drawing, but I haven't.

[Cooperman]

Sorry, meant to add, for a selection of UNF nuts and bolts you can buy on-line from Namrick and they have an excellent web site. In fact, they do a 450 piece UNF bag of assorted UNF nuts, bolts & washers for about £15. Good quality stuff too.

[Fatboy]

Thanks Peter,

I phrased that 'double skinning' bit very badly, I meant the rear front subframe mounts - where they bolt into the floorpan by the driver's and passenger's feet - IIRC the MK1 & 2 had a double skin on the front of the floorpan where the back of the front subframe bolted on?

I think I remembered you saying you often welded in some reinforcing there on later rally cars? I need to do something as I put a crack in that section of floor during an overly-enthusiastic trip over a hump-backed bridge

Cheers,

Grant

[Cooperman]

Yes, the Mk 1 & Mk 2 and early Mk 3 had the front sub-frame mounted solidly onto the floor at the joint between floor and bulkhead. The loads then went into the bend line which is very strong. However, on the later cars the sub-frames were rubber mounted and the fixing was entirely into the bulkhead panel. The result can be a split bulkhead. I re-inforced the one on a 1991 rally car I built with two large pieces of 16 swg (that's 0.064" thick) steel sheet. I shaped it to meet the inside of the wheel arch and took it well past the mounting points on the in side. Then I plug and seal welded it for good strength, ground it back and painted it. If you are putting it on the inside you don't need to worry about accuracy of fitting for the frame afterwards. Don't plate over the rack mounting bolt holes!
It's worth going to solid mounts then, if you haven't already, as it will be strong enough to take the loads without the rubber pads.

[Fatboy]

Thanks Peter,

I have already gone to solid subframe mounts (when I converted to a flip-front) - I think I'll probably plate the front and back of that area for strength, to spread the load as best I can - I make 16SWG to be about 1.6mm, so I'll get something similar.

Cheers for your help again!

Grant

[Cooperman]

Yes, that's about 1.5 mm for you younger guys!!!
If you put a plate on the outside of the bulkhead you could have a problem re-fitting the sub-frame mountings as the panel face will be 1.5 mm further forwards. Just on the inside is fine so long as the welding is both plug and seam.
If it is already split, weld up the seam and grind that back before welding the plate on.

[Fatboy]

A bit more help please - I've found some more dodgy looking bits, especially the upper engine steady mount on the crossmember - see below:



I first thought that the mess you see below was just seam sealer or something, but having cleaned it all off with a wire brush, it's weld (fairly messy welding at that!) there also appears to be another bracket behind it hidden under the weld, with the crossmember dented inwards.

Is the crossmember supposed to be flat behind the steady mount? Could this have been bodged in when it was converted from a 998 to MG Metro lump, with then new steady just welded on over the old?

Due to the shoddy nature I'll want to cut it all out and replace with new, but I just wanted to check what thickness of steel I should use for the repair panels - both here and elsewhere on the shell?

I've also got the area around the lower front subframe mounts cleared off, and there is quite a lot of cracking and a bit of surface rust. With the cracking, am I OK to just weld up the cracks, or do I need to cut it out and patch in a panel, given that there is rust round the cracks therefore probably inside the crack as well? Or could I just use a thin grinding disc to remove the small amount of metal in the crack and (carefully) plug it up with weld?

As another aside, removing the pedal box I had to deal with more of those annoying shear bolts - why to they use them? (Genuine question, I just can't see the point).

Thanks in advance!

Edited by Fatboy on Saturday 24th October 16:02 to add new pictures!

Edited by Fatboy on Saturday 24th October 16:38

[guru_1071]

id guess the bracket has ripped out the bulkhead so the fix has to be plate the bulkhead up first, then weld the reamins of the bracket back onto the plate.

id cut the whole lot off, patch it better, then weld a new bracket on - they are fairly cheap

[Fatboy]

Hello again

Another issue here - started cleaning up the inside to find that there were already some plates on the inside of the bulkhead behind the subframe mounts (left pic below) - as these were spot welded in I'm assuming they were original, but does anyone know more about these?

But there was no seam sealer round the edges, so some corrosion behind them (second picture) and they were nowhere near wide enough to stop the cracking!.

Anyway, I drilled out the spot welds and promptly killed my angle grinder removing the rust - looks like just surface, so once I've repaired the cracks (last picture) it'll be time to put in some new plate on the inside as per Cooperman's post above...

[guru_1071]

those plates are the factory fitted reinforcers fitted to the later rubber mounted shells. they always crack when the mounts are worn as the subframe 'works' at the toeboard.

a couple of nice big thick patches will do the job!

[Fatboy]

Thanks!

When I put the reinforcing plates in, should I put them between the bulkhead and the lip of the floorpan, then plug/seam weld them up, or just butt them up to the seam of the floorpan?

Instinct tells me to put the patch between the bulkhead and floorpan (as per the factory patches) for strength, but I'm not sure...

Also, I was looking at the area to patch and reasoned that if I stuck a single piece of 1.6mm steel (thickness as per recommendation above) to run from one side to the other (with a cut out for the tunnel, as below) it would be stronger than two unconnected patches - is there any reason not to do this?

Also, how regularly should the plug welds be for the reinforcing patch - I was thinking every 50mm in all directions and seam welded at the edges?

Edited by Fatboy on Sunday 25th October 22:43

[guru_1071]

id make them just a little bigger than the std ones, theres no need to put a huge plate in. once the frame is held in with either a solid mount kit or new rubbers it wont move at all.

[Fatboy]

I'd fitted solid subframe mounts when I did the flip-front conversion, and don't remember seeing the cracks then - first time I remember noticing them was after an overly enthusiastic trip over a hump-backed bridge...

Hence I thought it might be best to add a lot more strength, but if I wouldn't gain anything from one large solid brace then I'll save the steel I tend to go by the maxim "If it's worth doing, it's worth over-doing" (thanks to Garfield for that one ).