Welding Tips and Tricks

Hello,

New to welding, the forum, and much needed knowledge.....

This is my first post on the forum and since I know enough about welding to be considered extremely dangerous, I thought I would refer to the experts.

We are attempting to restore two 1968 Porsche 912's that are in need of some metal repairs. On this particular 912, I discovered that many, many years ago(25+) a repair was made to the front suspension pan. What was a shocking discovery was the method the repair was made. Instead of welding the panels together via the traditional ways, the parts were braised together. Who knows, maybe braising was the preferred method when this repair was made and the repair has held thus far. I estimate the repair to have been made that far back because there is evidence of metal rot along a lower body seam that will need to be addressed and this type of metal rot takes years to show its ugly head.

So what my question to you, the experts is how would you recommend I tackle this issue. I understand that I will need to remove the braising material before I can make a welded repair. I will attempt to attach some photos of what I have to work with and discovered as I dug into the interior of the trunk area.

Thanks for looking,

Cheers Trevor

Here are some more photos....

As you can see, the parts were all attached via the braising method.

These pictures are what I started with before I discovered that the front suspension pan was replaced many years before.

Hey,

Are you dead against using brazing to renew this part? I say this because im not sure if there is a really easy way to remove the bronze filler material. I have burned it out with an arc welder before but I am not recommending for anything good because it makes a hell of a mess. Brazing, in the hands of a skilled operator will be an acceptable method.

Mick

Welcome to the forum.

JT68912.

From the photos it 'seems' that the brazed joints did not corrode away nor did they break.
If they can be utilized, it would make sense to leave them intact.
They are also part of the 'history' of that vehicle.

Nothing inhibits you from using more than one process ... brazing and/or welding.

Alexa

Brazing was performed because it doesn't warp the panels as easily as welding.
The braze filler melts at a lower temperature than the base metal.

In many cases, braze filler is sufficiently strong for the intended design.
My hovercraft use brazing as the preferred method for the structural metal.

A company called http://muggyweld.com/ has some nice products.
https://www.youtube.com/watch?v=-oifC7fbQfY

The person who brazed this appears to have known what he was doing, despite the "less than uniform" appearance. All joints are lapped or scarfed to provide maximum surface wetting, which is why it has held this long.

Removing the bronze will be harder and more time consuming than replacing the structure again, and those scarfed joints in the heavier structural members present a problem creating a proper weld. You'll end up with a very wide bead to do it "right", and suffer the shrinkage and distortion that accomanies it.

I'd try very hard to leave the light-gauge lap-braze connections completely alone if the parent metal is solid.

The heavier main structure can be reinforced as-is, by grinding smooth and adding "fish plates" that bridge the brazed area, but you need a basic understanding of engineering, specifically load distribution and stress risers, to avoid doing more harm than good. The general rule is "nothing square", meaning the reinforcement is elliptical so the attaching weld does mot make a straight line across a "beam".

I assume this is not a "Concours" restoration...

Steve S

weldin mike 27 wrote:Hey,

Are you dead against using brazing to renew this part? I say this because im not sure if there is a really easy way to remove the bronze filler material. I have burned it out with an arc welder before but I am not recommending for anything good because it makes a hell of a mess. Brazing, in the hands of a skilled operator will be an acceptable method.

Mick

Hi Mick,

I am very green to welding and look forward to learning on my Millermatic 211. I would not go as far as to say that I am against using brazing for these parts. What little experience I have, has always directed me towards mig welding repairs to these cars. Over the past couple of years I have been doing research on these projects and the notorious suspension pan that is a common repair. I will say that in the hundreds of posts regarding this type of repair on these cars, I have not run across a single repair made by brazing. I know in my first posting, I stated that the repair held for 20+ years. In looking into the records of the car, it has only been driven approximately 5K while living the rest of the time in an open field.

My biggest concern with the brazing repair lies mostly with the tank support cross member. From what I have seen, aside from the 5" braze on each end on the left and right extreme sides, there appears to only be three braze spot welds on each side of the wide sections. Since I have never replaced this component in a 912 before, I can only quote what I have seen, read, and gleaned from the 912Registry Forum. The cross support member is usually punched with a Neiko(sp) style metal punch approximately every 5/8" to 1", literally putting a 100 +/- holes in the flange to be welded in during the mounting process. In my case, there are only three small braze welds where there usually is 50 +/-.

Cheers Trevor

Alexa wrote:JT68912.

From the photos it 'seems' that the brazed joints did not corrode away nor did they break.
If they can be utilized, it would make sense to leave them intact.
They are also part of the 'history' of that vehicle.

Nothing inhibits you from using more than one process ... brazing and/or welding.

Alexa

Thanks Alexa,

I did not consider keeping both processes in place. I just figured that I would have to completely remove the brazing material to mig weld the open areas and get a good solid repair. When I discovered the area in the photo I will attach, I figured that if the original person who did the repair was satisfied with the original spot welds drilled out and just left as is, I began questioning the structural integrity of the rest of the repair. It just looked like numerous short cuts were taken over the whole repair and then covered up with a metallic bondo type material and rubberized paint to hide the repair.

Trevor

Mike wrote:Welcome to the forum.

Thanks Mike,

Look forward to the vast wealth of knowledge from the other members on the forum.

Cheers,
Trevor

Otto Nobedder wrote:The person who brazed this appears to have known what he was doing, despite the "less than uniform" appearance. All joints are lapped or scarfed to provide maximum surface wetting, which is why it has held this long.

Removing the bronze will be harder and more time consuming than replacing the structure again, and those scarfed joints in the heavier structural members present a problem creating a proper weld. You'll end up with a very wide bead to do it "right", and suffer the shrinkage and distortion that accomanies it.

I'd try very hard to leave the light-gauge lap-braze connections completely alone if the parent metal is solid.

The heavier main structure can be reinforced as-is, by grinding smooth and adding "fish plates" that bridge the brazed area, but you need a basic understanding of engineering, specifically load distribution and stress risers, to avoid doing more harm than good. The general rule is "nothing square", meaning the reinforcement is elliptical so the attaching weld does mot make a straight line across a "beam".

I assume this is not a "Concours" restoration...

Steve S

Hi Steve,

You are correct in that this car is NOT going to be a concourse restoration. I like to think that myself and the wife are going to bring up good driving examples of the 912, structurally sound, safe, and complete. I have never foreseen myself the type to park on a golf course and rub a car down with a diaper while afraid to drive the car if there is so much as a cloud in the sky. I have seem more than a few owners get all twitter pated because someone breathed wrong on their car, and I'm not talking about a rare million dollar car either.

Thanks for the pointers on the welds and the elliptical plates along the seam. It make since on that since the curve of the plate is used for strength in the weld. It seems that the local community colleges welding classes fill up in the first hour with registration opens up for continuing students, making it damn near impossible to get a class. there is still so much for me to learn about the "ART" of good welding practices. I guess it all boils down to the simple fact I just do not know enough about brazing to tell between good, bad, or mediocre brazing.

Cheers

Many body seams in production cars were indeed brazed. Not saying those are factory, but all of the seams you find on older cars, that were caulked and painted were brazed. Drip checks above doors. . .brazed. The seams that go from the trunk to the rear windows were also usually brazed. The ductility of bronze in some situations is favorable over steel.