My Beetle Restoration

After searching for years for something that I could just purchase to use to replace the rusted-out tunnel rails on my chassis, I decided to just make my own. "Tunnel rail" is what I am calling the lip on the bottom of the tunnel where the tunnel bottom plate is welded and also where the floor pans rest on the tunnel. The closet thing I could find is a 15" tunnel section replacement that is made to replace the tunnel inside of frame heads. But they are around $35 each (plus shipping) and I would need at least 5 of those. Not only would this option be costly, but these aftermarket parts are way thinner metal than the original metal and the shape really doesn't match as well. I found that I could get a 12" x 48" x 2mm sheet of steel online for about $45 total, so I decided to purchase that and see if I could find a way bend it and make pieces to use. It came very well packaged and protected.

To bend the sheet metal and match the radius of the lip on the tunnel, I used two 18" long, 3/16" thick x 2" wide mild steel plates set at a 90 degree angle with a 1/4" round steel rod on the outer edge and welded them on the inside edge. This gives me a smooth rounded surface on which to pound the metal into shape. The sheet metal is 2mm thick and will take a lot of force to form it.

After the plates and dowel were welded together, I made a clamping plate, added clamping bolts, and mounted the unit on a 4" x 4" treated post. The post is dense and heavy and gives me something to hold on to when forming the shape. I used a large rawhide mallet to hammer it into shape. It was quite difficult to bend metal this thick without distorting it and to get it flat and even. With a lot of pounding, I was able to get it fairly flat and checked it against a tunnel section I had from a donor frame head. It matched well. The flange is longer than the tunnel flange, but it gives me more leverage to bend and form it and it can later be trimmed once the tunnel bottom plate is welded back on.

The next issue was how to cut the piece off and to get a nice, straight cut. I can't really do that well with an angle grinder with a cut-off wheel, so I decided to try to do this with my chop saw. I have an Evolution Rage 2 chop saw with a 14" multi-material blade that will cut steel, wood, and plastic. And although the blade is 14" in diameter, it doesn't go down far enough into the table to get a 12" long cut as I needed. So I took the clamping mechanism off of the table and attached a 1" x 4" piece of wood to raise the cutting area up and this made the cutting length about 12 1/4" which is sufficient. I then used some steel plate and 2 clamps to clamp the sheet down while cutting. It was a little difficult to make sure that the cuts were square, but I managed to get them close enough. I checked the first one against the tunnel and it matched well. I made another and it was very close to the first one. I made a few more and the results were good. I went ahead and made 12 of them. Good thing I did as I ended up using 11 of them to complete the tunnel.

Now that I have the repair pieces made to replace the tunnel rails, it's time to start cutting and welding them in. My plan is to replace the rail from the point that I removed the tunnel bottom plate, all the way to the end in the frame head. I made the pieces long enough on the tunnel side of the pieces to reach past most all of the rust damage. I will have to patch a couple of places where the damage extends upward past them, but these will cover almost all of the damage. I will weld these pieces in on both sides and ground them down on the outside, but leave the welds as is on the inside for strength. They will not be visible and I'm mainly interested in them being strong. I'm starting on the passenger side as it has the least amount of damage and is the least complicated.

The first section took quite a while to do as I tried different things to figure out the best way to do this. I first laid out a replacement piece on top of the rail, marked the length, and cut 1/2 inch or so through the lip down into the tunnel. After that I cut across between those two cuts to remove the lip. I then placed the piece on the tunnel, lined it up with the existing lip on both ends of the cut-out, and clamped it in place. With it clamped, I then used the piece as a guide to cut through the tunnel. I now had a cut-out just a little larger than the size of the piece. I first held the piece in place for welding using panel clamps, but after just a few tacks across the joint, the panel clamps were locked in tight from the shrinkage of the metal when cooling and I could barely get them out. From that point on, I just used vise grip style clamps. The first three sections were pretty much the same and just involved determining and making the cuts and clamping and welding the pieces in.

The fourth section on this side connects to a tube support bracket for the clutch tube, fuel line, and choke tube. I drilled a couple of spot weld holes in the piece to attach it to the support brace. Next, I will replace the same four sections on the driver side.

Now on to the driver side of the tunnel to replace the tunnel rail. This side is definitely the worst of the two sides. During the two decades that this car sat outside in the elements, water apparently pooled in the floor pans and there must have been water in higher volume and for a longer period of time on the driver side due to the damage. The tunnel on this side was rusted completely through to the inside in one area and this damage will be cut out on the first and second sections being replaced. In the first section, the cut-out for the piece did not extend high enough to include all of the damage, so I had to make two small patches. I welded them in first and ground down and dressed the welds. I then welded in the first section on both sides and ground down and dressed the welds on the outside.

Next I replaced the second and third sections. The third section had a little area that had a little pitting. Rather that patch it, I ground the area down to clean metal and filled it in with weld. I then welded the section in as usual.

The fourth section includes metal that goes in front of the pedal cluster support plate. Part of that support plate was severely rust damaged, so I first cut out for the tunnel rail replacement piece and then cut it out and welded in a replacement piece on the support plate. I had to grind out an area on that new piece to allow for the pedal cluster mount to fit into the tunnel. I checked it with the already powder coated cluster mount and taped it with tape to protect it from scratches. Once satisfied with the clearance, I welded on the new piece. I used a copper bar behind it as I welded it to keep the weld from blowing out on the edges. I ground down the welds on the outside of the support plate and left the ones on the inside. I drilled holes in the tunnel rail replacement piece to weld to the support plate and then welded the fourth section in. I left the area covering the hole for the pedal cluster mount for now.

With the fourth section welded in and the welds ground down and dressed on the outside, I now had four feet of tunnel rail replaced on both sides. Next up is to continue and finish the tunnel rail replacement through the frame head and up to the frame head front plate.

Before I can continue replacing the rest of the tunnel rail, I need to patch a rusted out area on the driver side under where the Napoleon hat mounts. This damage also extends to the metal in front of the pedal cluster support plate. Rather than make a patch, I cut a section out of the tunnel from the first donor frame head. This matched perfectly. I cut out the tunnel to match the patch, drilled out several spot weld holes for the support plate, and welded the patch in on both sides. I then ground down and dressed the welds on the outside of the tunnel.

On the passenger side, I cut out the rest of the tunnel rail out up to the front plate of the frame head. With that area cut out, you can really see the severe rust damage on the frame head. This section is longer than the frame rail pieces that I made, so I had to use part of another one and weld them together. Then I welded the piece in completely on the inside and as much as I could access on the outside. With the frame head in the way, I could only get to about 2/3 of it. I will complete the rest of outside welds when the frame head is removed. I ground down and dressed the welds on the outside on the short section from the last section welded in up to the frame head.

This section of the driver side is shorter than the frame rail pieces that I made, due to the patch under the Napoleon hat and I was able to use the leftover piece from the passenger side. The cut-out on this section also exposes the rust damage to the frame head on this side. Just like on the passenger side, I welded this section completely on the inside of the tunnel and what was accessible on the outside. I will complete the outside as well once the frame head is removed. I also cut out the rest of the hole for the pedal cluster. I had a real sense of accomplishment with getting these 10' of tunnel rail replaced. I have once more section to replace on the curved portion of the driver side, but that will be in another post.

Below are pictures most of the metal cut out to replace the tunnel rail on both sides. I did use some of the better metal to make a couple of patches, this is the bulk of it. Since I took these pictures later, there are pieces included of the curved section that I cut out on the driver side.

I thought long and hard about removing this additional section of the tunnel bottom plate. I knew it would be a lot more work, but finally decided that I needed to for 2 reasons. The first reason is that I need to replace some more tunnel rail on the driver side. The problem with replacing this section is that it both curves out and down and is way more complicated than the straight sections I already replaced. The second reason is that this section is dented in and I have not come up with a valid method of removing those dents without removing it. I thought about using a slide hammer, but I don't think that I could do a satisfactory job that way. So out came the angle grinder with a cut-off wheel and the spot weld cutter. After cutting out 25 spot welds and one foot-long cut across the tunnel, this section has been removed.

I first tackled the dented areas. The dents were mainly in the raised ridges, so I thought that if I could raise these back up and get them straight again that maybe that would bring the surrounding metal back up with it. I used a body panel hammer with a wide, narrow tip, a big rawhide hammer, and a 4" x 4" scrap of wood to use as an anvil and hammered them back straight. This brought the flat areas around them back up as well. This actually turned out better than I had hoped. Next, the hard part.

I cut a pattern out of cardboard that was the same size as the rail replacement that I was going to use and bent it to match. Then I cut slits in the cardboard so that I could bend it to match the contour of the tunnel rail area. Each time I got the correct bend, I would tape over the cut to hold it in place. I continued this until I had the pattern matching the tunnel. When I was satisfied with the shape, I removed the tape and laid the pattern over the rail replacement. Each place that there was a slit in the cardboard, I scribed a line on the piece to mark where I needed to cut slits in it. I cut the slits one at a time, bent it, checked the fit, and then tack-welded the slit to hold it in place. I did this for all of the cuts. Of course, the welding process distorted the shape a little and I had to re-cut and adjust it a little. I did finally get it to match fairly well.

With the replacement part now ready, I cut the lip off of the tunnel so that I could match up the top flanges and know where to cut the out the rest of the tunnel to match the replacement. I clamped it to the tunnel and used the edge as a guide for the cut-off disk just like I did with the straight areas. I used smaller cut-off wheels so that I could make the curved cut without cutting out too much. I welded it in on both sides and then ground down and dressed the welds on the outside. I placed the bottom plate section on and checked the fit. Some of the spot welds that I cut out were really far in from the edge and miss the lip of the rail. I will probably fill those area in while the plate is still off of the tunnel as that will be much easier when I can get to both sides of the plate and I can also clamp a copper bar behind it and fill them in.