Cut and weld options

[BenL]

Hi all,

This would be my first post here, I have read of LOT of posts and found some great advice on here so thanks in advance for any help.

I am working on a VW Beetle and part of the chassis is not in good shape. One specific section that needs to be replaced extends out from the main part of the chassis (not my car below) both the top and bottom parts are rusted.

The part you see also has a bottom section, that is rusted also. My question is should I do a straight cut through both as per below (bottom section not shown) or stagger the cuts so the new welded piece is not one line?

I am leaning towards staggering the cut between the top and the bottom sections, what other options are there?

 

[tom2207]

always better not to stack joints if its avoidable ,
and I clean off the black coating on both sides before welding , have a wee practice on some off cuts first to check your happy with your settings.
with some imaginatin you should be able to weld the inside of that box section too , always handy when you can get to something from both sides , obviously not once the lower sections welded in place too.

 

[Robert Mullins]

Old school ship builders used to stagger the shell-butt welds around the ship, but with the advance of metalurgy, weld technology, shell-butt cutting and alignment, you'll find single sided and back-gouged shell butts running in a straight line all the way from the keel upto the gunnel bar:
I reckon, what's good in a shipyard, is just dandy on a car

 

[johnser]

Ends of the "Napoleons hat". Not sure I'd be too concerned with staggering, more important to ensure the body mounting holes on the ends are going to line up with the body (front of the heater channels). That might mean dropping the body on to check. And that you can get good enough access everything to ensure decent welds are achieved.

 

[BenL]

Ends of the "Napoleons hat". Not sure I'd be too concerned with staggering, more important to ensure the body mounting holes on the ends are going to line up with the body (front of the heater channels). That might mean dropping the body on to check. And that you can get good enough access everything to ensure decent welds are achieved.

Thanks, your point is a good one. I spent a considerable amount of timing measuring where the holes should be to line up for when the body is put back on. I have reference points from various sections and a template of the bottom. One side at a time gives me a good reference.

 

[Shedendman]

Those two photos,am i right in saying they're (not my car below),so thats not what you've done?

Welds look a little to cold to me

 

[BenL]

Those two photos,am i right in saying they're (not my car below),so thats not what you've done?

Welds look a little to cold to me

Correct, they are just photos I found on the net quickly to show what I was waffling about. The first one is pretty much the amount of metal to cut off to be more than clear of the rust.

 

[Shedendman]

Correct, they are just photos I found on the net quickly to show what I was waffling about. The first one is pretty much the amount of metal to cut off to be more than clear of the rust.

Ok fair enough,but can you show us the real thing,if possible?

 

[BenL]

Not the best photo but it might help.

 

[Shedendman]

Theres a lot more IMHO that need cutting out than that
You've clean up well to the best you can,but,to get something back in as a replacement isn't going to be easy,thing is ask yourself,is there something solid to weld to?

 

[BenL]

Away from what you see there is it good and solid, they are notorious for rusting in that area. Both the bottom and the "hat" can be bought as straight replacements. I figure buy both and cut off what I need to replace.

I haven't put much time into that section just in case it needed to be replaced as a whole unit, the rest of the chassis is rust free.

 

[Matchless]

I think that Beetle has been sleeping with a Land Rover!

 

[BenL]

I think that Beetle has been sleeping with a Land Rover!

Haha yer, it was marked as off the road for 12 years at least!

 

[ChrisBailey]

I had to do the same job on my vw chassis a few months ago. I installed an after market pedalbox so I had to notch the napoleon hat.

Im a begginner myself so made all the mistakes.
I made some napoleon hat ends from sheet steel rather than buying the real ones, mostly because im tight but i had the sheet metal lying about.

I also recomend you cut more of the rusted steel out. You will find the discoloured bits are really thin and porous. As soon as the mig wire touches it, it will melt into blobs.

In the bolt holes on the outer edge, the holes contain steel inserts which are used to stop the box section folind up when you tighten the bolts up. Those inserts will probly fall out when you weld around them as the rusted thin steel melts.

I would recomend you buy and weld in a new frame head bottom skin. That would be easier than patching up what you have.

If you are tight like me, buy some sheet steel and make little patches.

Your life will be much easier than mine was since you have really easy access to the frame head.
I did mine with the body still on, welding from thecwhhel arch on my knees.

 

[BenL]

Yer you are right there, I looked last weekend and have cut back quite a fair way past the rusted steel to be sure. Both the frame head bottom and hat are on the list. At this point, I am still undecided if I should replace the entire bottom as that looks to be a real pain and is it good shape or just cut and use the section I need.

The budget is not too much of an issue right now, the funds have been approved by the better half bean counter BUT later on with money spent the interior will be made out rug offcuts, bubble wrap, and old office chair from a random skip!

 

[BenL]

It has been quite the learning curve and there is still a lot to do but here is the progress so far.

I cut out the bad sections plus extra to be sure the metal was good, the cuts were stagged so I had some overlap between the top and the bottom sections. The pattern parts were not perfect but good enough so I cut out the parts I needed and welded them in, by my measurements from before the cutting the new parts are spot on and line up correctly.

Next, I will finish grinding down the welds and carry on cleaning up the frame head.

The spot welds were 3cm apart, is that enough spacing or too much? or was it 2cm.. I forget!