On Thu, 10 Feb 1994, Marcus Tooze wrote:
> I will be welding in a new floor pan this weekend. How should I attach
> the pan to the rocker panel for welding??
>
> Marcus
Dear Markus,
On your Spridget, right? I assume you are welding in the replacement half
pans, not the whole bigosh pan. If you have not already removed the old
pan, that's going to take you a while because there are beaucoup spot
welds and you have to end up with clean flanges.
For spot welds, I recommend getting a *bunch* of 1/8 or 3/16 drills, or
some carbide ones. Drill the center of the spot weld, starting the hole
from the side you will eventually discard, if you can. Drill until you
are completely through the 1st piece and have made a considerable dimple
in the second (if you go completely through, don't worry). Do this for
every weld you can find. Then separate the pieces, using max care to
avoid ruining the flanges you want to retain. You never completely
eradicate the spot weld, so you have to chisel the pieces apart. (Yes, I
have tried a spot weld cutter; it didn't work well for me.)
I have tried screwdrivers, even a special order floor chisel, and the best
way bar none was a very good sturdy putty knife made by HYDE that had a
tang running trough the handle, so I could hammer on it. They have rather
thick, stiff chrome blades, and black handles. Anyway, they will slide
between the sheets without bending them much and do a fair job of cutting
any remaining spot weld. You can hammer on them like crazy, and when it
is all over with, you can file the battered edge smooth and use it for
putty.
Cut through the old floor pan parallel to the drive shaft tunnel, leaving
enough floor pan on either side of the tunnel to overlap the replacements
generously. Do final trimming later, to leave about 1/2 inch overlap of
the new panel and the center of the old panel.
To get to your main question. All surfaces have to be clean, bare metal,
including the old inner rocker. That may not be easy, because if your old
pan rusted out, there's likely to be some pitting of the inner surface of
the inner rocker. You really want to get rid of that rust--at least you
must have clean spots every inch or so, to weld to. MIG welders work
badly, if at all, on rust. If need be, lather it with naval jelly, wire
brush it, and repeat until the metal is *clean*.
Then, the only trick is to nestle the welding flange of the new panel
tight up against the inner rocker. The inner rocker is far thicker than
the new floor. If there is a gap between them, you will melt the flange
of the new floor long before the weld sticks to the inner rocker. So fit
everything up, make sure the front of the pan is tight against the flange
across the front of the floor pan, it is tight up against the bottom
flange of the toe board, get everything right. Tack here and there, and
recheck. If necessary, tap the side flange against the inner rocker until
there is *no* gap.
| |
| |_X
| | |
| | |<-----B
| | |___________________
|___|---------------------
A
Above, A represents cross section of inner rocker, B represents the
turned up welding flange of the new floor panel. Angle your MIG
torch so it heats the inner rocker more than the flange, and run
approx 1/2 to 1 in beads at the point marked X, fusing the welding
flange to the inner rocker. I would weld 1/2 inch, skip an inch,
weld 1/2 inch, etc. No need to seam weld it; you can seal it later
with seam sealer.
Where the floor panel front flange fits against the old flange, you have a
problem. It will *not* be easy to weld along the edges. Here, you want
to drill or punch 3/16 inch holes in the new panel flange, butt the new
flange tightly against the clean old flange, and then simulate spot welds
by turning the power a little on the high side, and welding through the
new panel, filling the 3/16 hole with weld that fuses to the old flange
(and the edge of the hole).
If you want to look this up in a book, look for plug welding or rosette
welding. Do the same at the rear, where the floor fits against the
vertical panel ahead of the rear axle. In the center, along the tunnel,
overlap the new and old panels about 1/2 inch. I offset one panel with a
joddler, so the inside surface is flat and seam welded along the whole
seam on the bottom of the car, but you can do short welds and use seam
sealer to make the seam water and gas proof if you prefer.
Ray Gibbons
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