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M2 redux


Ian

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I took a look on the passenger side floor, expecting to find clean metal to receive my baseplates.  Unfortunately, it was not to be.  Once I removed the sound deadening and accompanying detritus, I found three holes that had rusted through the inner rocker.

PassCorner1.jpg

 

And then I remembered that when I bought the car in 1994 there was a rust bubble under the lower corner on the passenger side of the windshield gasket.  At the time I filled it with RTV and drove the car in blissful ignorance.  I wasn't until 2001 that I had the opportunity to cut the corner out of a parts car and have a shop weld in the replacement.  It appears that water leaked down between the two layers of the shell, collecting in the space between the inner and outer rocker.  The intervening years were not kind to the inner rocker!  A little exploratory surgery yielded a surprising amount of fossilized dirt and assorted agricultural byproducts from inside the rocker.

PassCorner2.jpg

 

It appears that the rust is localized to this piece of the rocker, but I have to check the area from the wheel well before proceeding with the repair.  

 

Moral of this story: prayer and RTV won't fix a leak  :)

Edited by Ian

Ian
'76 M2

'02 325iT

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I had to take the fenders off to see this corner from the outside. It was cold, and I couldn't find the seam at the front of the fenders, so I called my buddy Joe Ajavon, who has forgotten more about 2002's than I'll ever learn. And he's a saint, so at 8:00 at night, with temps below 20 degrees, Joe came over and helped me cut the seams at the front of the car to free the fenders. It turned out that the PO had welded the fenders at the front seam, so careful detective work found a crease in the paint to indicate where the seam should be, and judicious use of an air grinder with a cut-off wheel liberated the fenders. This seemed deserving of refreshments, so see knocked off work and substituted beer for welding for the night.

The next day I took a wire wheel to the accumulated grunge on the outside of the passenger footwell, and then realized this job was going to be a little bigger than I had planned. The front of the outer rocker had rusted through, as had the inner rocker.

OutsidePassCorner03.jpg

The outer piece was fairly complex, so this seemed like a good place to try making a flexible shape pattern (FSP) to guide my metal shaping. The idea is to make a 3-dimensional guide out of fiberglass tape. First you lay down a base layer of painter's tape that is easy to remove.

OutsidePassCorner05.jpg

Next, lay down a layer of fiberglass tape 90 degrees offset to the painters tape, and then a second layer of fiberglass tape 90 degrees offset from the first layer.

OutsidePassCorner06.jpg

You can then peel the entire piece off the body, and the fiberglass tape will retain its shape when its off the car.

OutsidePassCorner07.jpg

I cut a blank out of 18 ga steel, and using the FSP as a guide, I started forming the patch. A little time with a mallet and bag, a little wheeling in the english wheel, and a little shrinking and stretching and the patch is starting to approximate the contours.

OutsidePassCorner08.jpg

The patch needed a flange bent 90 degrees to the plane at the upper right corner, which gradually flattened out towards the bottom. I put a tipping wheel in my bead roller and tipped the edge to get the flange.

OutsidePassCorner09.jpg

This shape is not bad; it needs fine tuning and trimming, but first I need to get the hole in the car sorted out.

OutsidePassCorner10.jpg

I cut out all the rust, and trimmed the outer patch to fit. Now I need to cut a patch for the inner rocker. The rocker measures .065" thick. I don't have any steel in that thickness, but I did have some .095" (13 ga) that I bought for the roll cage baseplates, so I cut a blank, bent an edge over, and trimmed to fit. But now I'm cold and I can't feel my fingers, so welding will have to wait until tomorrow.

Edited by Ian
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Ian
'76 M2

'02 325iT

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Got the inside rocker piece cut and welded.  I had to mostly stitch weld again, to avoid burning through the thinner 18 ga floor.   On the inside I ground the weld bead down, so the baseplates for the cage will sit flush.  Here is the intact inner rocker, probably more solid than it's been for 15 years.

OutsideCornerPass1.jpg

 

On the outside I left the beads intact, except on the forward edge, where the flange of the outer rocker will meet the inner rocker.

OutsideCornerPass2.jpg

 

With the inner rocker done, I started shaping the outer rocker again.  I wanted to do some stretching and smoothing with my ewheel.  I needed to make a fixture to get my 1" anvils right to the edge of the upper wheel, in order to get clearance.  Nothing fancy, but a piece of flatbar from the cut-off pile did the trick, and allowed me to move the yoke for the lower anvil outboard just enough.

OutsideCornerPass3.jpg

 

A quick test-fit shows promise, but the patch needs a fair bit of tweaking before it will be ready for welding.

OutsideCornerPass4.jpg

Ian
'76 M2

'02 325iT

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Well, I worked on the corner piece of the outer rocker a bit and managed to over-stretch it while smoothing with the english wheel.  So I decided to shrink the stretched area with an oxyacetylene torch.  I went back and forth a bit working on the shape, but never got the corner back into shape.  At this point I decided to confront my inner OCD, and start over with a simpler piece.  After all, it's a corner on the bottom of the car, hidden by the fender.  An nobody is going to confuse this car with an unrestored original  :)  So I recut the blank, and this time just broke the piece in a straight line for the corner angle, and then shaped the sides to meet the body.  Here is the replacement tacked in place.

OutsideCorner31.jpg

 

And after a little massaging, welding and grinding, here is the completed patch. Finally, the rocker is solid and ready for the base plates for the cage.

OutsideCorner32.jpg

Ian
'76 M2

'02 325iT

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Beautiful work on that rocker Ian; I'm really hoping I'm not going to have a problem there in my car. I did want to ask you about your seat mounting though. Specifically the area against the transmission tunnel and how you've cut in patched it, like so:

Dash_Bar%20copy.jpg

 

I'm currently in the middle of a very similar process, and since I'm using SRD's like you, they need to be pushed as far inboard as space will allow. What I've found is that the bulge coming from the transmission tunnel is what's stopping the seats from going any further inboard. What I've done is sliced the bulge open, beat it in, then rolled the top lip back over it. Now it looks like that should give me enough room to play with, but I'd like to know how you went about cutting it out entirely and patching it. The main question is, what did you do for the center support bearing mount since that's the reason that bulge is there in the first place?

Alex
-'75 2002 with M42

-Spec E30

-'91 318is

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don't know if you have looked at my build to see how I did this, but i have some fairly wide seats (sparco ergo II and sparco pro2000 II). I use seat mount brackets that are offset to the inside. seats are as close to the tunnel as is possible and still be able to get at the seat bolts. i was worried if they would be low enough, but not an issue. actually raised then a notch so i could see over the steering wheel. ( i am 6ft tall).

no cutting of the center bearing hump needed.

2xM3

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don't know if you have looked at my build to see how I did this, but i have some fairly wide seats (sparco ergo II and sparco pro2000 II). I use seat mount brackets that are offset to the inside. seats are as close to the tunnel as is possible and still be able to get at the seat bolts. i was worried if they would be low enough, but not an issue. actually raised then a notch so i could see over the steering wheel. ( i am 6ft tall).

no cutting of the center bearing hump needed.

 

I had looked at your mounts before, but I went ahead and took another look to refresh myself. I think the issue is that the SRD's aren't boxed off towards to bottom like the fixed back seats are. The sides and bolsters seem to spill over onto the tunnel. Now I'm going about mounting the seats the same way that Ian did, just with angle iron instead of rectangular tubing. I'm pretty sure I wont' have any issues with fitment now that the bulge is flattened out a bit. There may not have been an issue in the first place, it may just be that since the seat wasn't elevated and squared when trying to take measurements of where it's going to sit we weren't able to get an accurate estimate. It seemed like we weren't going to get much more clearance on the B-Pillar than the stock mounts would have given us. Either way, they should fit alright now.

Sorry to clog up your thread Ian.

Alex
-'75 2002 with M42

-Spec E30

-'91 318is

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Hi Alex,  Thanks for the kind words.  As you noticed, it's tough to get the SRD's to fit next to the tunnel.  My solution for the seat mounts isn't exactly what I would do now, but in my pre-welding days, I had a local fabricator cut the hump in the tranny tunnel out, and weld in a plate.  Then he welded the center bearing mounts to the inside of the plate.  Here is the transmission tunnel, with the offending hump.

Seatmount1.jpg

 

And after surgery.

Seatmount2.jpg

 

And here is a shot from under the car.

DSCN0001.jpg

 

I'm not real happy with the job the guy did, and am going to have to spend some time cleaning up the edge on the inside of the tunnel, where he did not weld to the plate.  I think he over-engineered the setup, really all we needed was to beat the tunnel down as you suggested, and then reinforce with a piece of 13 or 14 ga steel.  Instead, I got this big honkin' piece of bridge superstructure, and then some big square tube braces.

 

The other end of the square tube was welded to the rockers.  I needed to raise the seats by about 2", so I cut some short sections of square tube to use as spacers.

Seatmount4.jpg

 

To mount the seats as close to the tunnel as possible, I cut the adapters at an angle, to get them as close to the tunnel as possible.

Seatmount5.jpg

 

Then I bolted the Recaro sliders to the spacers, and voila!  Seating!  Here are the seats, with the wings just fitting inside the door.  

Seatmount6.jpg

 

It's a tight fit and a tad heavy, but it works.  I think after I get the car running I'll cut the square tube off about 2" from each side, and use the square tube as a bracket to mount some lighter tube or angle.  I will also have to check the alignment of the center bearing support, and possibly fix that.

Ian

Edited by Ian

Ian
'76 M2

'02 325iT

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With the floors and rockers solid, it's time to turn my attention to the baseplates.  I needed to raise a slight edge on the inside next to the corner, in order to accommodate raised seam in the floor.  I turned to some high-tech tools for this phase.  I clamped the baseplate to the base of a t-dolly, and hammered the outside of the plate down to the steel table, to create a drop.

Baseplate1.jpg

 

After putting in the contour, I had to correct the front corner, which had pulled in during all the hammering.  Another high-tech solution; I clamped a piece of angle to the corner, and hammered the edge over the end of a 2x4 held in my bench vise.  Not much finesse, but it made a nice corner.

Baseplate2.jpg

 

And here is the baseplate sitting on the floor, with a demo A-pillar tube.  To get the correct contour on top, I used a contour gauge against the wall at the top of the rocker, transferred that pattern on to the top edge of the baseplate, and then bent the baseplate over a 1.5" tube to put in the shoulder.

Baseplate3.jpg

 

I'll tack the baseplate in place, and gradually hammer it into it's final contour before perimeter welding the entire piece.  The real A-pillar tube will be cut to the contour of the rocker for welding, and can even be welded a bit up the side wall to tie into the area above the rocker.

 

 

Ian
'76 M2

'02 325iT

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  • 2 weeks later...

Worked on the baseplates a bit more this week. First up, make the passenger side plate. Fortunately the 2002 is approximately symmetrical (although less so each year of existence!), so I flipped the cardboard template upside over and reproduced the passenger-side baseplate. This plate is just thick enough (.095") that I can't reasonably use tin-snips to cut it out, so I rough-cut the shape out with a jig saw, and then did a finish-cut using the Beverly shear. There are three models of the shear, and I have the middle B-2 model, which can cut up to 10 gauge like paper. I bought a used Beverly off of eBay several years ago, and even though mine is at least 30 years old, it effortlessly cut the .095" plate straight, left, right or any combination.

Baseplate22_1.jpg

I got the fit close, then bent over the top as before to match the contour of the lower rocker. To get the contour of the upper panel, I used the contour gauge to get the profile, then transferred the profile to the baseplate, and cut the profile with the Beverly shear.

Baseplate21.jpg

Fortunately, the baseplates for the main hoop will be much simpler. I'll run them up and over the rocker as in front, but there is much less origami involved in their production. Here is a paper mockup. The plates will incorporate the nut that anchors the brace from the subframe mount.

Baseplate23.jpg

Unfortunately, the passenger side looks like it suffered a little worse for the flooding that we got a couple of times back in South Florida. When I pried up the sound-proofing tar, there was noticeable rust just behind where the vertical divide for the rear seat used to be, and the rust holes went through the floor.

Baseplate24.jpg

More welding, oh joy!

Edited by Ian

Ian
'76 M2

'02 325iT

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