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MG Midget and Sprite Technical - Replacing Floor - Putting Car on its Side?

Afternoon gentlemen,


I have ordered a new floor, both sides, from MGB Hive for my 1973 MKIII.

MY project started as just a few patch repairs in the footwell on the driver's side and one under seat patch. I started poking aggressively to make the worst of the damage as I was down there anyway.

The inevitable happened and patches became panels, with me now biting the bullet and just replacing the whole floor. The rear of the N/S was going too I discovered after the midget went in for a 'pre-MOT' check.

Anyway, I have access to the necessary tools (grinders, welders et al). But I only have axle stands...

I got a quote to weld in a new floor, I believe one plug welds them in. The garage said it would take them two days straight, so 16 hours labour at £640 inc VAT.

I thought £640 was a little steep for what I could see as no more than an hours straight welding.

Anyway, I was pondering the possibility of putting the Midget on her side. This would give me great access to top and bottom of the floor to do the work. Would this be at all possible? What would need to come off and what would need to be supported and where.

Also, does anyone have any tips/tricks for removing an old floor and putting two (separate) replacement panels in?



Any suggestions gratefully received,
- Richard

R L J Oakley

Hi Richard,
How stripped down is the car? If you have it stripped to a shell then you can just tilt it up on its side. A one-man lift. Get it securely fastened once it is up - ropes and props of some sort. I rolled mine onto an old mattress which was interesting when this subsequently caught fire from welding sparks! You could also roll it onto a couple of old tyres. If you still have the axles and wheels on it will be a deal heavier to lift but should still be possible, although oil might then run out past the rear axle seal.

If doing the floors in two pieces I would cut out and replace one half fully before starting on the other. Just to minimise possibility of it getting out of square.

Guy
Guy

If you can cut out the old floor and weld in replacement panels correctly in an hour, you're a better man than I am and you could make a fortune. You said you "believe" you plug weld them in. If you don't know for sure how to do it, I think it's a bit unfair to slag off a garage for charging too much, who one assumes would be doing it correctly. If you think that's dear, try getting a quote for an MGB four piece sill done properly.

Bernie.
b higginson

When I said 'believe' I was mearly being modest, remaining open to suggestions from other forum members. I know I'm going to plug weld it, as it's an OEM panel, it does not need to be seam welded.

Forget the cutting out, I've done half of it (although I'm still open to suggestion of best practice).

My original statement clearly said to 'weld in a new floor' There was no mention of cutting out the old as I would be doing that.

The garage even said they would not be doing it to any coach-work standard. 'It would be an obvious bodge' was the direct quotation.

So, please Bernie, if you're not actually adding to the thread I'd rather you didn't shoot your mouth off at me for questioning a garage's labour rates.



Anyway, back to the topic. Thank you Guy for posting so quickly. I'm afraid the car is pretty much in one piece. It's only the floor that needs doing. The car is a runner and all structural members are solid.

With this in mind, would it still be possible to tilt the car (after draining fluids say)? I'm more worried about the engine mounts, and body panels. Are they strong enough (with the cushioning of some mattresses).


Sincerely,
- Richard
R L J Oakley

the shell completly stripped can be tilted by one person (I too have done it myself). I laid mine against the garage wall with axle stands under it to stop it tipping back ontop of me.

How about if you drill out the spot welds from the inside (with the car on its wheels) can you not get the panel into place using a jack and then plug weld it from the inside.?

That said, you wouldnt be able to do the seam to the old floor under the gearbox tunnel and the welds to the back of the bulkhead... At least you would have most of the job done.

Bit of a tricky one I'm afraid Richard.

Cheers,
Malcolm
Malcolm Le Chevalier

Richard,

I am not sure that I would tilt it with the engine etc in situ. Even with fluids drained it is going to put a lot of lateral loading into the shell when it isn't at its strongest (bits cut out)

Having said that, I recall tipping our rally mini on its side one dark wet night on Anglesey to straighten out a front track control arm and sub frame mount after an argument with a wall. And that was without draining fluids or removing battery! It was only for a few minutes though - we were in a hurry to attend a meeting! (at the end of the Stage).

When I cut out the floors I leave the central section under the tunnel undisturbed (oily and solid). Cutting in a straight line rearwards from the wider section at the gearbox housing. Leaves a 1 1/2" ledge along the side of the narrower part of the tunnel. If the floors are gone enough to need replacing, then the rear suspension boxes are likely to need some repair also. Good time to paint inside of all those floor box sections (which the garage wouldn't do!)

I also found it easier and neater to re-bend the outer flange on the floor to go downwards where it attaches to the inner sill. Makes for a neater seam inside the tub and an easier job where the floor buts up against the cross member. I cannot remember if the originals did that - it seams more logical somehow - but my aftermarket floor panels were bent up on that long edge, not down.

I thought your garage price not that bad (£40 per hour inc) but didn't comment as I perceived you had already made that decision and were moving on from there. Didn't think you were wanting confirmation or otherwise on that one!
Guy

Richard. I had no intention of being offensive, but if you re-read you first post you may see that it was rather ambiguously worded as to what you are or are not capable of and what had or hadn't been done. You also didn't mention anything about the "obvious bodge" involved.
As for "shooting my mouth off", I only said I thought it was a bit unfair. If you think that is shooting my mouth off, you should see some of the stuff that gets put on here. LOL.
BTW. I have done all the work you mention on more than one occasion, so I do have some idea of labour times, but once again, no offence was intended.

Bernie.
b higginson

Richard. When I did my floors I did them with the flange upwards as per originals, but also tack welded along the seam underneath as well for extra srength, but Guy's method is also a good one. The original floor is as I'm sure you know all one piece where it forms the bottom part of the prop tunnel, so as you're putting in two separate pieces, where the inner edge of the new panel meets the old centre section it should be seam welded ie continuous welding, as MOT inspectors perceive that you are replacing part of a one piece panel. (Not my opinion,but their's) and must make it be as close to the original strength as possible.
Sorry if we got off on the wrong foot and if I can ever be of help I will. God knows I've had enogh help from people on here.

Bernie.
b higginson

That's quite alright, apologies for my ambiguousness.

Would it be easier to cut off the new panels section that sits under the tranny tunnel?

Excuse the explaining with out pictures that follows;
The replacement panel is 'L' shaped. The long section goes up to the front bulkhead, continuing back to the sporting mounts and kick of the 'L' makes the underside of the trans tunnel with it's mirrored counterpart.

This section is perfectly solid, as Guy said, it's nice and oil protected. Is there any point welding over the top or indeed cutting the good bit out?

I've got the panels now, I will go and have a look to decide if I'll go ahead with the seam bent up, or start bending it down as Guy said he did.

I'll get some snaps when I'm on the go, will help everyone I'm sure!


- Richard
R L J Oakley

Bernie,
I spot welded my down-turned flange along the bottom. The flange fits neatly within the depth of the drip-rail along the bottom of the sill to set the floor at the right height. It almost seemed to be designed that way! I then seam welded along the inside which then helps to avoid water working its way down into the joint when the cockpit fills with rainwater!

I realise this isn't original but it was easier for me. The only doubt I had is whether in re-bending that flange through 180 degrees, it might weaken the metal.

Guy
(am I still mixing mixing my seems and my seams?)

Richard, there is also an extra reinforcing piece at the rear edge of the tranny tunnel. Trimming straight down either side avoids any disturbance of that bit. Is that where your replacements are L shaped?
Guy

Richard. Hopefully this photo will be of some use. It shows the underside of my car with the floor completely removed. One word of warning thought...be prepared for more horror stories once it's out.

graeme


graeme jackson

tyres!

roll it on to tyres and brace it safely so it doesn't decide to redesign you later on.

I stripped mine of tank, engine and gearbox before I did but when stripped it will be remarkably easy to tilt.

I had simply to use my haltrac hoist under the sill and up and away she went.

Sadly I lost all my pictures of the re-build that were on my computer but somewhere there are a few on paper if you really need to see them.
Bill 1

Just picked up my new inner sills this morning from the city link depot. Sat here looking at them on the floor and I had a thought that related to this thread...

The long flange on the floor is bent upwards because if it was bent downwards it would have then interfered with the spot welding of the outer sill to the inner sill.

This might be a consideration if you are replacing sills too, you don't want to lay down heaps and heaps of weld all on the bottom edge of the sill.

And as has already been said, folding the edge through 180 degrees will probably weaken it a fair bit.

Cheers,
Malcolm

P.S. Picture of my shell on its side attached.


Malcolm Le Chevalier

Richard. As you can see from Graeme's pic, the prop tunnel is asymetric. Those are the seams which would need continuous welding if you cut them there.
On Malcolm's pic you can see the shape of the repair panels which are straight and end at the reinforcement channel. They are the same as mine. Are yours the same or do yours have more metal at that point. From your description it appears they may have.
On one side of mine I only needed to put in the floor from the gearbox crossmember forward and I plug welded it all round, but by the time I'd finished all the welding the MOT rules had changed so I had to re-do the cross member seam with continuous. I'll try and get a pic of a drawing of the outer edge panel positions on in a minute.

Bernie.
b higginson

Here's a rough drawing (very rough)of the way the cars came out of the factory as viewed from the front or rear. I've moved the panels apart a little for clarity. Guy's method is to turn the floor flange round and weld it to the inner sill where it meets the outer. As he then seam welded on top of the floor I'd say that the strength was not compromised in any way, in fact it could be stronger.
Have you got any pics of your repair panels?

Bernie.


b higginson

That drawing is really helpful. It's hard to see from rusty pictures and my own half cut half rusted shell. Thank you Bernie.

I have attached a picture of my repair panels. Apologies for the crap lighting, I'd just dumped them on the bed in the guest room.

Bernie (and Guy), if I wish to do the majority of welding (seam or plug) from the top (so with my head in the car), would it be best to leave the flanges turned up, or bend them down?

I have been thinking about cutting the, what I call, 'kick' of the L shaped panel off, leaving me a perfect rectangle. Is this sensible?


Regards,
- Richard



R L J Oakley

I am no expert and only bent the flange up because it looked neater that way. If you don't, then you will need to snip the flange off where it will interfere with the 3 chassis box cross sections. I did the floors after doing the inner and outer cills and then plug welded the floor in. In fact, I then went along the length of the floor on both the top and the underside with a bead weld. A bit belt and braces perhaps.

Bernies' little sketch is helpful. If you imagine that inner floor flange bent down it nestles against the inner sill and very tidily within that little edge fold in the outer sill. Also, my welding isn't very neat and it is a lot easier dressing off splatter etc on the underside rather than working into tight corners inside the shell! I have now done 2 tubs this way.

My floors were rectangles and didn't cover the central tranny tunnel bit, so are seam welded down those inner joints as well. Hopefully more waterproof that way quite apart from satisfying MOT man
Guy

Yeah, if you were going to seam weld inside too then I'm sure bending the flange down would be fine.

They look like the standard steel craft repair panels that everyone else uses Richard. If you cut off the 'kick' would the seam you have to weld interfere with the seat mounting?

It would perhaps look a bit untidy from the inside. but structurally the strength comes from the bulkheads, sills, gearbox tunnel and box section cross member, the floor just fills the gap and keeps your bum in the car so I would think it would be ok. Would you agree with this bernie/guy?

Malcolm
Malcolm Le Chevalier

Yes, I guess so. As I keep saying, I am not an engineer, but the floor panels must also stop the whole structure of box sections "lozenging". Keeps the various box sections all at nice neat right angles.

I cut the old floors out with a straight cut from front right through to the heelboard. From inside the car this cut goes flush to the tunnel flange at the front, but then continues in a straight line as the tunnel narrows, so leaves a wider flange made up of the edge of the centre panel of the old floor under the tunnel.

Not very clear, but you should see it in this photo:


Guy

Richard. If you didn't cut off the kick I assume the two panels would butt up to each other, in which case you'd have one long seam weld then have to plug weld from on top where the repair panels meet the prop tunnel on either side. So it's either cut the kicks off leaving the centre bit in and do two seams or leave them on, cut the whole floor out as in Graeme's pic and do one seam and two plugs. Catch 22? I suppose do which ever you think is easiest, because as Malcolm says, most of the srength comes from the parts he mentions, but every panel helps to stiffen the panel next to it etc.
I'm off to watch F1 qualifying now so I'll be back later to see what transpires.

Bernie.
b higginson

Richard. If you do choose to turn the flange down, is there any chance you could get your hands on an electric spot welder? It might make the floor to sill welds easier to do. I used one on my car for part of the restoration and for certain things they are very good. A bit expensive to buy though.

Bernie.
b higginson

I suppose I could hire one from HSS?

Do any of you have any ideas of best practice to get the spring hangers off?

There is no way the four bolts are undoing, they're rusted solid and I think welded in another life's repair.

I have thought about cutting round the spring hanger plate. What are the dangers? Where should the leafs be supported?


- Richard
R L J Oakley

Bernie,

Keep in mind that you can always sell the spot welder after the restoration and if bought 2nd hand you'll most likely recover most if not all the cost. If buying one you'll want to buy one capable of doing 2mm + 2mm as IIRC the inner sills are 14swg (2mm). Doing the spot welds along the top of the sill along the footwell sides may well require making long arms, I made my own years ago and someone else on the BBS did so more recently IIRC.
David Billington

me again!
I have a spot welder. An e-bay purchase really cheap as the windings were burnt out. I dismantled and re-wound the transformer with £12 of new wire and it is as good as new. Just checked out prices of these things new MM one is an eye-watering £538 and Frost a completely ludicrous £570!

I also made a longer set of arms although they take some juggling to use as the contact pressure on the electrode points is much reduced. Lesson I have learned is that it is vital to keep the electrodes clean and they need re-dressing after every couple of dozen welds if you want them to stay consistent.

Bernie, even with the floor edge turned down the electric welder doesn't make a good job of that particular bottom sill joint. The reason being the triple thickness of steel, plus the extra thickness of the heavier duty inner sill is just too much for my 2 + 2 welder. So I plug and seam welded instead. But the electric welder was great for the sill top joint and various others, but there are lots of places it won't work because of access limitations. But where it does work it is brilliant! Very quick and clean!

Guy
Guy

Richard. The spring hangers are a nightmare and whatever you try will most likely result in you needing new hangers at least. The front 2 bolts can be cut off from inside the car leaving the studs in the captive nuts on the hangers but the two rearmost bolts screw into threaded inserts that are part of the rear bulkhead reinforcing structure (moss part no aha7208). Hopefull the photo will show what I mean. the problem you will have is that these captive nuts are impossible to get at unless you're taking the floor off or replacing the rear bulkhead. If you cut the screw heads off to get the spring hanger out you would be able to weld in new captive nuts once you have the entire floor cut out vbut getting the old ones out will be difficult. Photo shows the new box reinforcement with captive nuts..

incidentally, the black paint is POR15 from frost. i wouldn't recommend using it anywhere you may want to paint over as the stuff is so hard nothing else will stick to it.

Graeme


graeme jackson

The electric spot welder that I used was not mine, it was the property of Manchester College of Art and Technology, where I did a course on metal body construction. It had lots of different arms for different applications, it even had arms for when you could only get access to one side of the panel. It was the absolute dog's wotsits. After a bit of blagging on my part, they even let me take my shell in there and I did a lot of the resto work in the classroom/workshop. If anyone is contemplating a big restoration and they are a bit worried about having the skills involved, I would thoroughly recommend seeking out a similar course. Lots of colleges run them in the day and evenings. Leeds college being a prime example.
Just on the subject of Frost. I've found that their stuff is usually good but very expensive.

Bernie.
b higginson


Hello Richard,

Further to the pics others have added, there are pics of my floor replacement here:

http://www.mhharris.org.uk/page12.html

The images have got reduced to quite a low res in putting them through whatever software I was using at the time,

I'm not an expert by any stretch of the imagination but mu approach was based on the advice I was given at the time - basically plenty of plug welds. you can see in the picture in the bottom right where I plug welded through, and also the stitches I put on the outside of the floor - when I put the shell back on it's wheels I also plug welded through the flange where it folds up.

Hope that's helpful?

Mark
MarkH1

Yes thank you.

Trouble is my car is in one piece and drivable.

It seems everyone who's been replacing their floors has had only a shell to work with.

Am I at a disadvantage through having everything attached?


- Richard
R L J Oakley

Hi Richard,
in answer to your question, "Am I at a disadvantage through having everything attached? "

My answer would be:
yes, because it will be difficult to roll over the shell with all of that weight in it, and it will be bad for the engine mounts, and the shell might get twisted when you cut out structure while hanging the weight of the engine (350lbs+) and rear suspension (150lbs+) on their sides

Two pieces of advice for your project:

1. get the tallest jack stands that you can buy, and do your work on your back (get a good mask and leather apron to keep the sparks off of you). Make sure the jack stands are perfectly level (if your floor is not level, then use shims between the stands and your fully assembled body to get it perfectly level before starting).

2. If you do go the route of getting a spot welder, don't try to spot weld through three thicknesses of steel, the strength of the weld drops greatly with each additional layer. OEMs work hard to make all of the welds to be between two panels, with only occasional 3 layer ones in low stress areas. This is why the floor pan flange points up, so each row of welds would be as strong as possible.


Norm
Norm Kerr

Richard
Drop me a line or call later tonight/evening. I can get/ have large axle stands etc and a spot welder I can 'borrow' from school and I live local - Beaford that is. I can also help with the welder /grinder if you need them as well.
Dave
Dave Price

I also have access to a high power impact driver that should get those bolts off as well. 01805spam603133 or email me.
Dave
Dave Price

I replaced the floors in a '77 3 years ago with everything in place. Smooth floor, jack stands, level everything. Do one side at a time. Weld as much as you can with the doors closed. Use them to aid alinement. Placement of a floorjack at different places to tweak the body for alinement. Open and close the doors several times to check the alinement. time spent before welding is well worth it. My floors looked good,but no pics. Good luck.
J Bubela

This thread was discussed between 09/09/2011 and 25/09/2011

MG Midget and Sprite Technical index

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