is brazing patch panels in bad ?

[tchaika]

I cannot see the logic that causes the safety of a brazed fuel sender, a part that according to that paragraph is only under the load of the fuel in the tank and does not even see fuel on the pressurised side of the pump if that article is correct, infers that brazing is safe for joins that is going to be under considerable weight and shock loads. That's like saying you brazed a scratch in your hood ornament, therefore brazing is OK for structural work. That's more extreme but do you see the logical disconnect.

Also, that process does not use flux. flux is a major problem for paint adhesion and future rust if it is not removed very thoroughly. As the article says, it's a highly specialised manufacturing process that has probably had the hell tested out of it for safety. Good luck with mr too-lazy-to-fit-up-patches.

I think it is safe to infer from that article that it is safe to braze a patch in your bird bath...or hood ornament.

Remember, those joins have to survive a huge number of rather unpleasant shock loads. Just because it can stand up in the driveway until the cows come home, does not mean it will survive being driven on.

[TheTominator]

My point exactly, you guys just don't see logic. Free from a retired pro, versus whoever the shop owner decides to throw on your job, possibly the rawest recruit. One guy says brazing went out with Fred Flintstone, the next says outmoded technology, none of his pro friends seen a braze on a new car. Ford got the hell sued out of them in the 90's over pickups burning and fuel tank setup and location. Yet here they are installing BRAZED connections to transfer GASOLINE, I quit my research at this point, but did notice they use brazes elsewhere. I'm guessing the engineers at Ford know a little more about the science of brazing than we do. As to flux, You could clean it off with dirt if you wanted to, damn near all of it goes away in the smoke from the torch. The grinder got the rest. Why don't you guys just go braze something first, come back and comment later.
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[perrib]

The only trick to brazing is to bead blast and chemically clean off the flux. I would used USC All Metal over it for the first coat of bondo. Ive seen antiques my old boss did and 15 years later there were no issues. He took a year to switch to a mig the second year I worked for him, I used it the most the first year, He was comfortable with gas welding and brazing and got made when I welded a Q.P. in with it until he saw the lack of warpage at the seam. I've gas ,mig ,brazed and tig welded Tig is awesum but the equipment is also the most expensive. Let him use what he knows best.

[tchaika]

Argh. Lets pick an extreme example. Would you compare the loads that an unpressurised fuel hose comes under, to the loads a shock absorber mount has to withstand?

Which one comes under the most shock loads?

What is the effect of shock loads on joined metal?

What is the relative tensile strength in psi of a brazed weld to an oxy weld? Given a choice, which would you rather have?

Does gasoline eat brass any faster than steel?

Does "doesn't leak under the weight of ~150lbs of fuel applying a virtually static load" imply "can withstand repeated shocks applying more force than the weight of the car"?

Which join is likely to have been analysed and tested to be strong enough?

Does a run of braze ruin your ability to do any subsequent welds in the vicinity?

Is there a reason to braze other than to save time or make up for lack of skill?


???

You get what you pay for. I guess that applies to free advice too.

Sorry, this is just really getting on my nerves as a former victim of free expert metal work and person with grip of logic, and whose welds have passed destruction and pressure testing. Also, I have experience brazing. For example, I have brazed a cracked sump. But I don't call it a quality repair, I call it a fix to keep the car alive, since on this car I will have to pull the engine and strip the gearbox to change the sump. I would certainly use it on decorative or non stressed items.
I don't have access to a gas torch at the moment, but if I did, I could run out and braze/weld a couple of runs then show you how long each of them lasts in the press.

Modern "recruits" should have gone through multi years of training before they are let loose unsupervised on customer cars. If not, take your business elsewhere.

[Ipaintem]

You can braze brass to brass or brass to copper all day long for fluid transfer. Your not comparing apples to apples. Brass to cold rolled steel for structural repairs on a unibody car will fail.

[DrHAX]

I have a bit of experience with brazed body panels... there was 1939? chevy I did the quarter panel work on for a guy However the brazing was quite solid and lasted how ever long the car did before it was fielded. It was only when he blasted it did the evidence of the body repair occur. I took a four fender and made it fit onto a two door decently.

But thats not where I'm coming from here. I took a welding class and started off using a mig, then I went straight to tig. I Understand these methods of welding so I went to brazing next. I've had my brazes withstand quite a bit. I can see the advantage of brazing if you know what you're doing. I was able to get a 6G braze weld not once but twice. The teacher was amazed. Braze has the ability to flow which is something that welds flatout don't. I know about warpage and crap but on little tiny pieces of 20 gauge steel I was able to braze with very little issues. I had a T braze struck with a sledge hammer and shoved into a bench clamp and everybody in the class trying to break it.. It held up better then the metal did.

Honestly it all depends on wtf you want to do! If you're comfortable with having brazing done to your car (Honestly if you knock the F'er down you'd most likely be fine ) I've even had a few ideas of chopping the top of my 1968 volksrod and using brazing to show where all of the cuts were if it works on furniture in restaurants which can survive 200 pound fat people sitting it daily... Why won't it support the patch panel! Certain parts in nasa equipment is brazed together! We all focus on the horror stories of everything we hear. Also we focus on whats new, or best for the modern world not works! Honestly I'm the type of idiot who would pick up doing lead filler and brazing an entire volksrod together just so I could claim MN streetrod plates on it. So don't listen to me. I'm a maniac. I say go for it! If the works top notch its top notch! I'd go for it, and then have him teach me
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[Matt K.]

When people gas welded in the past it was pretty much what they had.I originally learned from a gentleman that was a customiser in '50's.....even when he taught me he was till gas welding.....I did it for some time until I switched to Mig welding.......it really depends on how the repair is done is to how long it will hold .
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[Dr OnHolliday]

Brazed joints must be overlapped. Attempted brazing of butt joints will fail virtually immediately.
Bondo does not stick to brass as well as steel. Perhaps epoxy primer would modify that result.

Really good and adequately sized brazed joint overlaps will work very well, but any approach other than fusion-welding the steel is second best.
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[Hyperspace]

The gentleman would use mild steel rods where he is not welding dissimilar metals or very crudy metal. The patch panels in my floor was brazed in, and I'm more than happy with them, allthough the bottom will take some maintenance. He wil likely rivet it first.
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[MMCCARTHY]

More important to me than how you weld a patch panel is how well you prep everything. Back in the 70's when I started working in a body shop I had brazing, a stick welder and an old Lenco spot welder that I used to repair panels , each had their uses. Brazing like others have said is not the best choice on something that has alot of stress put on it continuosly , but works pretty darn good for a patch panel when other options were not available . I always sand blasted every brazed panel and really rarely ever had a recheck due to paint or body filler failure. The biggest thing in Michigan was afterwards I always undercoated the backside of the patches if possible because all welding burns the backside of the repair and no matter how you weld it rust will begin as fast as you finnish welding it. I do still braze some things ( oil pickup externsions ect ) but I also mig, tig and lead panels depending on what what is best for that job. I would never braze any late model high tensel steel. .

[Northof49]

I don't think there are any joints in a beetle body or floor that would be compromised by brazing. Brazing, while weaker than steel, is still very strong. I did a fair bit of brazing on my Ghia, close to 30 years ago. Certainly none of the joints have failed. Whether the brazed joint contributed to paint flaking or bondo lifting isn't clear. There are a few spots where I see some blistering, but I haven't ground them down to see what is going on underneath. 98% of the brazed body work still looks perfect, so it might just be corrosion.

I suspect that because of the increased surface area of a brazed lap joint, it is overall stronger than the base metal and would not be the point of failure.

That said, I gave up brazing for bodywork decades ago. Brazing still does have its strengths on other applications, like joining dissimilar metals and flowing into gaps. It's an excellent repair for cast iron.
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[teveo]

Not a regular poster here but have been reading a few threads about brazing lately, have a bonnet section to transplate from one car to another (e-type bonnet bulge).

I think the opinions are a bit different across the pond, the modern CuSi3 wire seem excellent for MIG brazing.

Seems like modern (?) bondo or primer will stick even better to the copper silicon weld, cusi brazing is also how modern cars (high boron steel) are repaired as long as it is not a structural part.

Some good info on this UK site
http://www.mig-welding.co.uk/brazing.htm

Think this was my first post as well, am more of a 356 and XKE guy but Beetle's always been a passion, had quite a few including 181 and KG.

Just my 2 cents but well worth looking into modern MIG brazing.

[theKbStockpiler]

Apparently ,vw brazed in the joint of a super beetle wheel housing near where it attaches to the hood hinge. I have stripped this area down and It DOES not look like a weld but is gold in color. Worked fine in that situation.
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