TheSamba.com :: View topic - Tunnel crack

Fri Dec 09, 2022 5:52 am

1961 bug. Pulled rear seat and found a crack in the tunnel. Any suggestions on fixing it properly? Welding for sure but how to make it structurally sound.

Fri Dec 09, 2022 6:23 am

weld the crack, grind flat, and then bridge the crack with a larger piece of steel and weld that. You'll have to trim the bridge so it doesn't get too close to the vin number, and take photos of before and after so nobody questions the authenticity of the vin number
I'd probably use some 1/8" for the bridge piece, and have it go about an inch past the crack where possible

Fri Dec 09, 2022 6:36 am

why would it crack there? is there likely to be damage elsewhere?

Fri Dec 09, 2022 10:00 am

That seems like an odd place for a crack without substantial damage somewhere else.

Fri Dec 09, 2022 11:14 am

I can honestly say I've never seen a crack there ever. Rust yes but never a crack. I would make darn sure there isn't something else bent or damaged before wasting my time fixing it only to find it was crooked to start. That must have been a hell of a wack to crack there.

Unless this is some family heirloom or special vin I would probably just get a new chassis and start fresh.

Fri Dec 09, 2022 1:57 pm

Thank you for the info. The car was hit square on the rear bumper. The bracket is bent an inch or so. The apron and rear fender had minor damage. I figure the accident jolted the chassis hard enough to crack the tunnel. Weird spot. The doors have normal operation and gaps.
I have the original matching numbers 36hp motor with it. Shame to scrap it.

Fri Dec 09, 2022 2:13 pm

Something else caused this damage.
The force path for a rear ender to that part of the chassis would be:
- bumper... body... body mount... chassis. But the body mount bolts would shear before this crack could form, and the whole rear body structure would be crushed
- engine...tranny...frame horns... chassis. But the engine would be utterly smashed by then.
This was dropped or otherwise impacted independent of a fender bender. I would go over the chassis and all its welds very carefully to look for the rest of the damage before dong anything else, preferably body-off.

Fri Dec 09, 2022 2:48 pm

Was this car parachuted out of a plane? Holy Moly!
The triangle shape with the missing shard on top, this thing took a real smack.

Fri Dec 09, 2022 4:38 pm

It almost looks like some one used a plasma cutter on it. Can you feel or see any slag on the back side of the crack? Likely a long shot, but worth a look.

Fri Dec 09, 2022 5:49 pm

What I would do...

1. Grab a fairly power magnet and hold it about 1/8 inch above the surface and pass it all around the crack and whole general area. I'm looking for other steel. I would concerned if I found a number of steel balls or steel filings on the magnet as that indicates previous repairs in the area.

2. I would clean that area up really good. I would light it up well and take a bunch of pictures. Now I'm documenting the "as discovered" state. If you you got any metal bits above photograph them too. If you need to look back while doing repairs it is nice to have documented the starting position. Not really that practical 30 years ago -- but I embrace this tech now!

3. Anything you can do to see inside the tunnel for damage and signs of previous repair. If you find it then you should try to figure out how to photograph it too.

4. Any underlying problems found should be fixed. If it is just body rust leaning on the frame too much that can wait, but a message has been sent.

5. Clean up the area around the crack to shiny steel. Drill the ends of the crack(s) with a 1/8 inch drill to "drill stop" them. Then weld that shit back together. Do it well and don't hide it, it will always be obvious from the reverse side because if all went well you will have through weld penetration.

6. Marvel at how tough these little old cars really are! You might mix this step in with all the steps above. WOW, I've never seen that crack.

Fri Dec 09, 2022 9:32 pm

Just a couple of things to note which I don't think have been mentioned yet....
That crack looks ancient, it's had plenty of time and movement to cause it to open up significantly; it's been there long enough to rust to the point where the fracture lines are no longer jagged, but sort of smoothed over; it's also old enough that it has accumulated quite a bit of dirt and debris. In the upper-left quadrant of the photo, where the crack transitions up from the vertical wall to the horizontal top surface of the tunnel, there almost appears to be a hole, as if someone tried to drill a hole to stop the progression of the crack long ago. And finally, the area at the lower-most part of the crack, down on the sidewall of the tunnel, has had time to bulge outward toward the battery area, which, along with the wide-open nature of the gap, suggests to me that the right frame horn and torsion tube have been flexing quite a bit and torquing on this area for a long time.

Those are just my observations. They don't change anything already suggested about repair options, but at at a minimum, if you plan to weld the crack, you really want to clear as much rust as possible from the cross sections of the metal (the actual fracture surfaces), the last thing you want is for the weld to be contaminated with iron oxide. And before that, some serious measurements of the frame horns, torsion tube, and general chassis/spring plate alignment verification.

Sat Dec 10, 2022 8:50 am

Loren wrote: It almost looks like some one used a plasma cutter on it. Can you feel or see any slag on the back side of the crack? Likely a long shot, but worth a look.

Yup. Or a torch that was running outta gas...

Lots of old Bugs have cuts in weird places. Lots of old Bugs were previosualy "parts cars" that have more recently been sold as restoration projects.

I've used my now classic first generation Lincoln SP100 to weld the equivalent of a bead around the equator something like eight times. I've repaired the ubiquitous big hole opposite the pedal cluster, the goober way to repair a broken clutch cable more times than I can count. And... badly rusted frame heads have become common within a couple hundred miles of Kennebunk, Maine.

My usual guarantee on welding cracks and cracked parts is the "tail lights" guarantee. I'll guarantee the weld until your tail lights go around the corner.

Having said that I can't recall anything I welded breaking again.

I don't know if my old SP100 settings translate to the newer Weld Paks. I'd set my little Lincoln to G 6 , run a nice solid weld up that crack and grind it flat. Anything that's properly restored should look "good as new" no matter where you look.

I might check it once in a while to be sure.

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Sat Dec 10, 2022 11:51 am

Busstom wrote:
Just a couple of things to note which I don't think have been mentioned yet....
That crack looks ancient, it's had plenty of time and movement to cause it to open up significantly; it's been there long enough to rust to the point where the fracture lines are no longer jagged, but sort of smoothed over; it's also old enough that it has accumulated quite a bit of dirt and debris. In the upper-left quadrant of the photo, where the crack transitions up from the vertical wall to the horizontal top surface of the tunnel, there almost appears to be a hole, as if someone tried to drill a hole to stop the progression of the crack long ago. And finally, the area at the lower-most part of the crack, down on the sidewall of the tunnel, has had time to bulge outward toward the battery area, which, along with the wide-open nature of the gap, suggests to me that the right frame horn and torsion tube have been flexing quite a bit and torquing on this area for a long time.

Those are just my observations. They don't change anything already suggested about repair options, but at at a minimum, if you plan to weld the crack, you really want to clear as much rust as possible from the cross sections of the metal (the actual fracture surfaces), the last thing you want is for the weld to be contaminated with iron oxide. And before that, some serious measurements of the frame horns, torsion tube, and general chassis/spring plate alignment verification.

Those are my thoughts too. That crack is definitely old, worn and displaced. I have never seen anything like that in that location either. If it were me, I would pull the body, engine and tranny and clean everything very well and check for alignment of the frame horns and check all dimensions. I would also inspect the inside of the tunnel for any rust thinning the metal or other contributing damage. It obviously took quite a hit to create that crack.

I would think that if that were caused by a collision with another vehicle, any body damage that would end up with a crack like that would have been massive and ended in the car being scrapped. The engine and tranny probably would have been damaged too. I have seen at least one car that got hit from the rear that broke the engine off of the bell housing and that car ended up being made into a baja due to the body damage.

My guess would be a drop from some height transferring all of the weight onto the right rear wheel or frame horn. Maybe it got dropped off a lift from a few feet, caused the crack but no body damage so the mechanic gave it back to the unsuspecting customer. Either that or it hit a massive pot hole at speed or ran off the road.

If the pan isn't structurally damaged, I would pull everything back into alignment and pull the crack back together andhave it welded by someone who knows how to weld. This is not something for a DIYer with a Harbor Freight MIG welder.

I definitely would stop driving it immediately.

Sat Dec 10, 2022 12:45 pm

It looks like a plasma cut to me as well. I think I'm seeing slag balls spread around the cut. Next to the triangle piece, it looks like it's welded back together in a spot. All the way to the right side of the cut, it looks like melted metal that wasn't blown all the way out by the torch.

Or I could just be seeing what I THINK I see. :lol:

Either way, that's a very strange place to see a crack, or a cut.

Sat Dec 10, 2022 12:56 pm

splitjunkie wrote: It obviously took quite a hit to create that crack.

I had more air time in my '67 than my brother had in his Cessna. I used to prowl the trails and back roads and look for things to launch it from.

While VWs eventually crack, they don't crack there.

splitjunkie wrote: I definitely would stop driving it immediately.

Years ago the frame head rusted through on my ex- girlfriend's '64. I had never seen that before. She said it needed welded so of course I offered to drive it to my secret laboratory 200 miles away and have at it.

First thing I noticed was an aggressive wobble that came on at 35mph. Couldn't call it a speed wobble, it was too slow for that. 200 miles @ 35mph in a wobbly POS, you gotta be kiddin'.

Hillbilly engineering says if something wobbles weigh it down until it doesn't. I pulled in next to a stream. I stuck the spare in the back seat and filled the spare tire well full of rocks. It worked! Approximately a hundred pounds of rocks got me up to 50mph. More rocks on top of the gas tank got me 55mph, good enough!

There really wasn't anything holding the front beam on when I got to my workshop, It was connected by the steering column, the brake hoses and gravity. Even the gas tank mounts were broken.

200 miles. Made it!

Anyone who is afraid of a little crack needs to earn their Ultimate Hoopdee Merit Badge. :twisted:

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Sat Dec 10, 2022 2:27 pm

As everybody seems to agree, an impact great enough to initiate such damage would've left other signs of damage. So in my opinion, I believe the most plausible explanation is just a defect in the manufacture of the raw material, totally undetectable when new. Then the passage of time and stresses just caused the defect to propagate to what it is now, and it just went unnoticed and/or disregarded for decades since the only time the average person lifts the back seat is to service the battery or shift coupling, for the most part. Out of sight, out of mind. Even if it was noticed, and depending on by who, they probably didn't worry enough to take action or consider it necessary to remedy. After all, it's still holding up, let the next guy (Razorrock) worry about it :)

Sat Dec 10, 2022 3:51 pm

Sat Dec 10, 2022 5:35 pm

Dusty1 wrote: splitjunkie wrote: It obviously took quite a hit to create that crack.

I had more air time in my '67 than my brother had in his Cessna. I used to prowl the trails and back roads and look for things to launch it from.

While VWs eventually crack, they don't crack there.

splitjunkie wrote: I definitely would stop driving it immediately.

Years ago the frame head rusted through on my ex- girlfriend's '64. I had never seen that before. She said it needed welded so of course I offered to drive it to my secret laboratory 200 miles away and have at it.

First thing I noticed was an aggressive wobble that came on at 35mph. Couldn't call it a speed wobble, it was too slow for that. 200 miles @ 35mph in a wobbly POS, you gotta be kiddin'.

Hillbilly engineering says if something wobbles weigh it down until it doesn't. I pulled in next to a stream. I stuck the spare in the back seat and filled the spare tire well full of rocks. It worked! Approximately a hundred pounds of rocks got me up to 50mph. More rocks on top of the gas tank got me 55mph, good enough!

There really wasn't anything holding the front beam on when I got to my workshop, It was connected by the steering column, the brake hoses and gravity. Even the gas tank mounts were broken.

200 miles. Made it!

Anyone who is afraid of a little crack needs to earn their Ultimate Hoopdee Merit Badge. :twisted:

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Sorry. I don't subscribe to the "I did something stupid once and lived to see another day so you'll be fine doing something stupid too" mentality.

As to whether they can crack there, I don't know how you can say with certainty just because you have never seen one crack there.

The part of the pan is clearly out of alignment with the rest and there is clearly a round hole that someone drilled at some point to try to stop the cracking that clearly didn't work because part of it on on one side and the rest is on the other. It is out of alignment, wait for it, by the width of the crack so something is bent to cause that. That wouldn't be the case if this was a plasma cut. If that was a plasma cut, the person who did it was clearly drunk.

I have highlighted the two halves of the hole and where the two parts are out of alignment. Continuing to driving a 60 year old car with a major crack like that would be foolish, no matter what anyone says. This displacement means that the right rear frame horn is bent downwards and there could be other cracking such as around the torsion housing among other places that the OP hasn't found yet.

Sat Dec 10, 2022 8:06 pm

splitjunkie wrote:
Sorry. I don't subscribe to the "I did something stupid once and lived to see another day so you'll be fine doing something stupid too" mentality.

As far as "stupid" goes I used my old '67 to de- construct and de- mystify nearly as many VW "urban legends" as the Berg's black '67. Like many offroad racers I have a good idea how hard you can beat on a VW before it breaks, how it's going to break and where it's going to break.

Unlike many internet forum "authorities" I know what I know from hands- on experience.

You might be horrified to know I've been through a few splits and early ovals.

splitjunkie wrote: As to whether they can crack there, I don't know how you can say with certainty just because you have never seen one crack there.

I've never seen a crack quite like that and I've never seen a crack in that location. You've never seen that crack, have you?

I have seen wavering plasma cuts and torch cuts that look like that.

If I want to see that actual "crack" I can probably drive over to Kennebunk and see it. I was over in Kittery and Berwick this time last week. OP knows there that is.

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Sat Dec 10, 2022 8:14 pm

Why would somebody even take a plasma cutter (that is, if they were even commonplace back in the day when this crack occurred on this vehicle) and just decide to say "Hey, I'm gonna go to the back of this pan tunnel, fire off my plasma torch and make a jagged, squiggly zig-zagged cutline, have a good laugh out of it, and then drop the seat back down and pat myself on the back, cuz I know how to use a plasma cutter"? Who would do that? Probably nobody.

That just makes absolutely ZERO sense at all. Yes, people have done stranger and stupider things, but I just can't believe that this is one of them. It has zero plausibility.