Author Topic: Sealing  (Read 1229 times)

Offline Sluggo

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Re: Sealing
« Reply #15 on: 29.06. 2017 21:43 »
" Bronze is never a good idea on anything that vibrates and it is really more of a glue than a hole filler"

Trevor, I am curious about your statement above,, (I am not arguing just asking for clarification)
As I have seen a LOT of gas and oil tanks with brazing on them, and in many cases many oil pipes and fuel lines seem to have been sweated together using brazing as well.  I have a vintage Triumph frame that was in an unfortunate fire many years ago sitting here as well, and the owner wants to restore it.  I did some testing and the metal is not excessively cooked but we plan to install the frame in a jig, check for straightness and re-braze all the joints and casting lugs.
I have some old printed articles here and they state that the factory for BSA & Triumph used a hearth system to build the frames and the castings were heated up in heath furnace and then the plain steel frame tubes were inserted with flux and brazing.  This is clearly visible on many frames when stripped.   I follow some metal fab and industrial engineering forums and tech (always trying to learn) and much discussion on such over the years... Some speciality builders are using Brazing as a signature artform method as well... for example check out this beauty.
(See Pix).

If I am off the mark here, feel free to correct me.

(Known as "Weld-nrop"  some fetishists find such craftsmanship stimulating)

See : http://www.blogofthebiker.com/2016/09/bare-minimum-brazed-frame-gsxr-racer.html

More on topic, a Japenese custom shops version of a BSA A7 Plunger bike using a lot of Brazing
See: http://sgrallying.blogspot.com/2014/06/cyclops-bsa-a7-plate-armor-bobber.html

*NOTE* I find it amusing that certain words are auto-edited on here,, funny that!  And on certain forums when discussing Machine shop P R O N, Crankshaft P R O N, or Welding  P R O N we spell it that way to avoid spam filters and email issues.. So much for "Taking the P**"
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Online Joolstacho

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Re: Sealing
« Reply #16 on: 30.06. 2017 01:13 »
"Bronze is never a good idea on anything that vibrates and it is really more of a glue than a hole filler"...

Wouldn't the same apply to tinmans solder?

- I've had good results with both brazing and silver solder.
If the hole is anything bigger than a pinhole I cut little copper patches and silver solder them over the hole.

Online Black Sheep

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Re: Sealing
« Reply #17 on: 30.06. 2017 06:52 »
Brazing is an excellent means of joining metals. Tinman's solder has its uses too. Look what happens if you send an early petrol tank off for powder coating. The oven melts the solder and you get back a small pile of bits of carefully shaped sheet metal. I like tinman's solder for fixing small leaks as it's simple for the home handyman without the skills or equipment for welding or brazing to use. And you aren't going to destroy the tank you are trying to fix as can happen with unskilled attempts to weld.
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Offline dave55

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Re: Sealing
« Reply #18 on: 30.06. 2017 09:23 »
It would be a shame to paint that frame sluggo its a real work of art.
Had a mate in the 70,s who built and raced sidecar outfits and many in the paddock including his were all brazed and some crashed with no failed welds. I remember as an apprentice being told that if done correctly brazing was as strong as the parent metal.....don't know if that's correct or not  *conf*
BSA Bantam D7 175  1961
BSA A10 650 Golden Flash 1955 Plunger
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Online Joolstacho

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Re: Sealing
« Reply #19 on: 30.06. 2017 10:30 »
There are blokes on here much more qualified to comment on this but... Brazing was used for lug/tube assemblies of course but, also for steel tube frames where welding would compromise structural integrity of the particular alloy steel of the tubing (Bluddy'ell that's a mind boggling concept, let alone the lingo!)

But those pics of the brazed joints (Sluggos) makes me feel err... queezy! Yes the braze joints are beautifully executed, But...
WTF? All that's surplus to requirements surely? Why not design and fabricate the frame so there are continuous but overlapping tube elements rather than cutting, and putting in all those little fillets etc. Surely that's the way to structural madness!!!
(- Just saying! imagine the improvement in structural integrity if those tubes were continuous, overlapping and brazed, instead of cut, shut, and brazed. Every cut joint is concentrating and magnifying the destructive forces.)

Offline coater87

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Re: Sealing
« Reply #20 on: 30.06. 2017 16:35 »
 If you are repairing cast iron, brazing is absolutely the way to go. Nirod welding does nothing but ruin future attempts to repair.

 The same way brazing does. If you have ever tried to weld something that was previously brazed you know what I mean. The metal that was brazed is contaminated with bronze, the weld just spits back at you. Lead does the same thing.

 So basically, once you lead or braze a repair, you are stuck trying the same method again and again even if it fails. Or making the original problem much worse by having to cut all the contaminated metal out. So a pinhole is now the size of a quarter etc.

 I believe brazing was an inexpensive and quick production assembly method. Once mig welding became economically viable, brazing was quickly replaced by a faster, stronger method. It did not hurt that someone could be taught to mig weld in minutes either.

 Lee
Central Wisconsin in the U.S.

Offline BSA_54A10

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Re: Sealing
« Reply #21 on: 01.07. 2017 11:10 »
A weld a braze a solder blob are all castings.
Metal melted onto a place and allowed to solidify.
The only difference between brazing & a casting is the absence of a mold.

SO the ultimate strength of the joint comes down to the strength of the alloy.
A brazed joint is always a lap type of joint between two very close fitting parts and the strength of the joint is determined by the amount of overlap.
So you have a forged frame lug with a machined hole into which goes 1/2 ( or more ) of tube.
A highly reducing flux is melted into the joint (usually borax based ) then metal is melted in and flows under capillary action to fill the void.
There is a tiny amount of penetration of the filler rod into the base metal but the phases formed are quite brittle and the braise metal is also quite brittle.
Some high alloy steels can not be welded because the heat causes phase changes or grain growth in thin sections.
Nearly all braisings fail through the filler metal.

I do not know what alloy your mates frame is made out of nor the alloy used to weld it but fillet brazing, some times called bronze welding is not particularly strong and has a very low fatigue strength.
The deposits themselves look nice, very neat  & uniform but have been done too cold and in too big a step.
If a student presented that to me he would be failed.


" Bronze is never a good idea on anything that vibrates and it is really more of a glue than a hole filler"

Trevor, I am curious about your statement above,, (I am not arguing just asking for clarification)
As I have seen a LOT of gas and oil tanks with brazing on them, and in many cases many oil pipes and fuel lines seem to have been sweated together using brazing as well.  I have a vintage Triumph frame that was in an unfortunate fire many years ago sitting here as well, and the owner wants to restore it.  I did some testing and the metal is not excessively cooked but we plan to install the frame in a jig, check for straightness and re-braze all the joints and casting lugs.
I have some old printed articles here and they state that the factory for BSA & Triumph used a hearth system to build the frames and the castings were heated up in heath furnace and then the plain steel frame tubes were inserted with flux and brazing.  This is clearly visible on many frames when stripped.   I follow some metal fab and industrial engineering forums and tech (always trying to learn) and much discussion on such over the years... Some speciality builders are using Brazing as a signature artform method as well... for example check out this beauty.
(See Pix).

If I am off the mark here, feel free to correct me.

(Known as "Weld-nrop"  some fetishists find such craftsmanship stimulating)

See : http://www.blogofthebiker.com/2016/09/bare-minimum-brazed-frame-gsxr-racer.html

More on topic, a Japenese custom shops version of a BSA A7 Plunger bike using a lot of Brazing
See: http://sgrallying.blogspot.com/2014/06/cyclops-bsa-a7-plate-armor-bobber.html

*NOTE* I find it amusing that certain words are auto-edited on here,, funny that!  And on certain forums when discussing Machine shop P R O N, Crankshaft P R O N, or Welding  P R O N we spell it that way to avoid spam filters and email issues.. So much for "Taking the P**"
Bike Beesa
Trevor

Offline chaterlea25

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Re: Sealing
« Reply #22 on: 01.07. 2017 20:47 »
Hi All
It seems to me that people here are confusing brazing and bronze welding  *????*

Lugs and tubes are brazed using brass filler

The racing frames "Harris" and the like are bronze welded, using a silicon bronze filler rod

John
1961 Super Rocket
1963 RGS (ongoing)

Offline BSA_54A10

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Re: Sealing
« Reply #23 on: 02.07. 2017 13:00 »
A bronze weld is just a braize with a stronger filler metal.
THe bronze does not alloy with the tube to form a join with consistant metallurgy from the HAZ through the "weld" to the opposite HAZ
The parent metal is not melted into the filler rod, the 2 remain totally seterate entities with the exception of some solid state diffusion .
It never was and never will be anywhere near as strong as a real steel weld.
Race frames in particular were only designed to do a single season and they still crack through the middle of the filler metal.
I have some race frames in the shed and they all have cracks in the joints.
Some are worse than others.
The problem is some one makes or designs a frame in plain 04 carbon steel tube then some one else copies it in light weight alloy tube but does not design the joints properly for "bronze welding" and expects the bronze to exhibit the same strength as a steel weld which of course it can not because it is still nothing more than a copper based alloy casting.
A welded frame can have members in tensin where as a brazed ( brass or bronze ) frame must have all members in compression so all the filler rod is actually doing is holding the parts in place which is why  you see one tube wrapping around another then held in place with the rod.
Bike Beesa
Trevor

Online Greybeard

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Re: Sealing
« Reply #24 on: 02.07. 2017 16:35 »
I must say, this forum is very educational!