Bockscar 2.0

[PorkPie]

NICE

[Stainless1]

Work on the cage and cleanup continue... As an excuse for mediocre welding skills I think the self etching primer just does not all sand off...  the outside welded and the lower hole in the firewall welded to the tube... it ain't pretty... then it was time to attack the inside.  I have the lakester apart, lying on its side trying to get the extra cage bar welded on the inside... it's really tight to get 1 arm, the torch and the welding helmet in there... oh crap... then you need to feed filler rod.... I guess my hand is not steady enough to feed rod from 14 inches away... lots of starts and stops to uncontaminate the tungsten... a few spots that wondered off course... but it is welded and I'm sure I didn't make the original tubes weaker...
Hey ya know how some cars have a 15 ft paint job... those welds don't look too ugly from that distance 
next up is get the top firewall hole welded back up to seal the tube.

[WOODY@DDLLC]

My welding instructor always said, "Most good welds are somewhere between bubble gum that holds and pretty that breaks!"  :-P :clap :-P :clap

[Peter Jack]

I see good penetration and washed in at the edges. It's far better than a weld that's too cold. You may lose a few points for undercut but I would certainly consider it safe. 

Pete

[floydjer]

I was going to day if you are concerned with looks , you could do a wash pass over it......But Pete would go off on me.🤔...😁

[Stainless1]

Wash pass?... I already cleaned some of the smoke off of it with a wire brush 
Don't worry, I'm about to get the part of the firewall I cut out welded back in so it's about to get uglier.... of course that part won't be structural so I might be able to grind smooth the worst of it....
Ross suggested I work on my brazing skills... which might be a good idea for the non-structural closing of the hole in the firewall.

[floydjer]

Bob...Wash pass....You go back over the weld with just the tungsten arc..no filler. The weld lays down and you can blend the start/stop areas. You can also over heat the area and end up with shrinkage and cracking. And Pete would cuff you upside the noggin.

[Peter Jack]

Bob, DON'T use brass. Once you have brass in there you can't do a successful weld repair. The brass will contaminate any weld you try to make.

I've been known to use a wash pass, though not for quite a while. I've even been known to use filler rod on a wash pass. If you're using a wash pass with no filler the original weld was probably too cold. 

Pete

[Peter Jack]

A little more on the use of brazing in chassis fabrication.

The Europeans used brazing until the late '50s or early '60s because it was the most practical thing to use for space frame chassis construction. It was easy to teach apprentices to join metal with the process and there was sufficient strength for space frame construction. Once good equipment was available to employ the TIG welding process brazing quickly went by the board. A good TIG weld is far superior structurally to a brazed joint and is far superior for more exotic steel alloys. TIG can also be used to successfully join many other alloys.

Brazing still has its place among the welding processes but if there is a failure anywhere near a brazed joint the repair must be made using brass. A brass contaminated weld WILL fail.

Pete

[manta22]

Frankly, I prefer to do braze welding rather than fusion welding. Braze welding is done at a much lower temperature so the distortion is far less and it is possible to join dissimilar metals using an active flux. The nickel silver bronze rod produces a joint that is tough and as strong as the mild steel tubing that is being joined. 

Overheating the joint produces intermetallics and a weak, brittle joint so experienced weldors need to learn the new technique as it is not at all the same as they are familiar with. One disadvantage is that nickel silver bronze rod is expensive, particularly the ones containing a small percentage of silver but the silver promotes fluidity and is worthwhile. Finding this type of rod is not easy these days. It used to be commonly available from All-State, Eutectic, and others. The last 5 lbs I bought from Washington Alloys.

Braze welding forms a nice bead that distributes the joint stress over a wider area than TIG and its HAZ (heat affected zone) is not as dramatic if a gas torch is used. It is not as effective on 4130 according to an old Lockheed report that I found years ago.

[floydjer]

"Bird cage" Maserati chassis' were brazed....I wonder the difference in weight between steel filler rod ( had they welded them) and all of that bronze rod?

[Stainless1]

Well guys I wasn't thinking of brazing the roll cage parts, I was thinking I might braze the patch to reseal the firewall around the new tube... but I haven't decided to go that way yet.... I have not used a torch for 30 years... well to do anything but bend stuff...
Still thinking... occasionally 

[floydjer]

 Bah....Tig that rascal back in there.

[Stainless1]

yea, probably... started making the patch panels after my visit to the dentist...

[Stainless1]

Patch panels are made and ready to weld... the metal ones were a lot harder to make than the cardboard patterns... guess they are a lot less flexible