Bronze welding

[bowser]

Very interesting - thanks for that.

Is a flux paste used on the tubes prior to brazing or bronze welding ?? If so, what is it ??

Thanks.

Bob.

Yes, is the simple anwser, flux is used for the same purpose as sheilding gas on mig or tig welding, it cleans off and prevents oxidization of the surface. Normaly a powder or paste form if powder then it should normally be mixed into a paste, when you have finished you will often find a clear glass like material covering the surface and that is the hardend flux after its done its job.
Also helps to clean off the surfaces first although without flux it will start to oxide as soon as you start to heat it.
There are general purpose flux but you should get the right one for the job, a flux for mild steel, would not be good for stainless, ali, or silver. However if your having a go then the sort of place you can get the flux from will normaly have somone with the right knowledge to recommend the correct sort for the job at hand.

 

[dean0n0]

Some frames were silver soldered, which, I believe, has a lower melting point, inducing less stress in the tubing.

 

[ChasF]

We are talking in general, and ideal situations there is some cross over from one to the other.

Brazing and Braze Welding (bronze Welding) are almost the same, brazing most usualy uses brass filler rod (alloy of copper and zinc) the the other bronze (copper and tin) the melting point of both is roughly similar. But you can braze with silver, special stainless, and plastic welding is effectivley braze welding with plastic, but I will only refer to steel/brass and bronze here.

Brazing would most usualy be used where joints are socketed such as in push bike frames or old harley/brit bikes where you had pre made joints into which the tubes were inserted.

Braze Welding would most usualy be used where the tubes are butted together.

either is used in applications where some give is required and a normal welded joint would crack, although strictly speaking the weld is stronger than the original material, and cracks normaly appear to one side of the weld site or the other. With either type of brazing the steel to be brazed is not heated as hot therefore does not harden in the same way and the filler is flexible as opposed to a steel filler.

A bronze welded joint appears as the bike frame at the start of the thread, a more usual brazed joint is the picture below. In a proper brazed joint you should only see a thin line of filler, in a welded joint you should see the "stack of coins" pushed over look, even were it has all been filled down if you see a big broad band of filler then it should be welded.

Your problems arise when people braze with brass when they should be welding with bronze, there are lots of people who dont appreciate that there is a difference.

Without seeing your frame I would suggest that it should be bronze welded, and I would clean off any plating prior, the nickel will only be a thin coat, and it would have been applied after the original jointing of the tubes.

Either brazing or braze welding can be used to join disimilar metals such as
Mild Steel - Galvanized Steel
Stainless Steel - Copper
Mild Steel - Stainless Steel
Stainless Steel - Copper-Nickel
Mild Steel - Cast Iron

The technique to use should be dictated by the way in which the tubes are jointed together.

Thanks for all this information. I've taken a closer look at the CCM frame and the joints do look very similar to those in the first post although possibly not quite as exagerated (see photo below).

It sounds from your description as if it takes a fair bit of practice to get the heat just right for bronze welding as unlike brazing it doesn't rely on the capillary action. I'm going to see if I can get hold of the right flux and filler locally but wonder if there are any good online suppliers.

As less heat is involved compared to ordinary welding would this be a good method in general for frame modifications - I'm thinking specifically about airhead frame bracing plates?

 

[desmo2]

For what it's worth , any quality after market racing frame you have ever seen will have been completely bronze welded . You do on occasion see some that have been tigged , or even migged and you think WTF !

 

[dean0n0]

Renolds have developed tubing specifically for modern welding techniques.

 

[Paul Rochdale]

"I'm thinking specifically about airhead frame bracing plates?"

Me too. I'm also going the bronze welding route.

 

[cheb]

Where does mig brazing fit into this?

As I understand it, it's a function on some mig welders but using bronze wire not steel.

 

[bowser]

Where does mig brazing fit into this?

As I understand it, it's a function on some mig welders but using bronze wire not steel.

Not somthing I have ever done as its fairly new, but its not really a "hobby" technique, as I understand it MIG brazing has been developed for the auto repair industry to repair high strength boron steels, the problem with boron steel is that its strength comes from the heat treatment which is destroyed by welding, hence MIG brazing however it is designed to take advantage of synergic MIG welding machines which are the top of the line expensive ones.

If your going to bronze weld then do it with oxy/acetylene, a bit of practice its not difficult.

here is one supplier of the relevent products online

http://www.wecs-ltd.co.uk/online-st...tion=com_virtuemart&page=shop.browse&vmcchk=1

 

[Paul Rochdale]

Bowser
Many thanks for your enlightening description of brazing and bronze welding, far more understandable than anything I've come across so far on the Net

I presume that nothing other than oxy would suffice so not really a DIY task? Nothing else would generate sufficient heat?

 

[(RIP) Tunneruk]

http://www.silverstonesuperbikes.co.uk/xr69_5.html

My links were taken from the above website, Trident Engineering.

I need to go and change my pants ......

..... they didn't paint over it after all either!

 

[bowser]

Bowser
Many thanks for your enlightening description of brazing and bronze welding, far more understandable than anything I've come across so far on the Net

I presume that nothing other than oxy would suffice so not really a DIY task? Nothing else would generate sufficient heat?

If you are prepared to do a bit of practice, you can use carbon arc brazing rods.
These are thick rods of carbon that are connected to the terminals of an arc welding set, you set the distance between the two ends so that when powered up you get a flame with which to braze rather than a spark that you would normaly get.
Its not quite as good but it is acceptable especially if you practice first.
I wouldnt try it on quater inch plate but on bike frame thickness tubing then it should be more than ok, its just a bit more difficult to do than with gas.
I think I got a carbon arc torch for about £30 a few years ago, the rods go in the end of the torch like a v and you adjust the distance between the rods at the tip of the v to form the arc. I have used it to weld 12 guage ERW tubing which is a bit thicker than normal jap bike frames which is normaly about 18 guage, never had an airhead frame apart so not sure what gauge of tubing they used, but its probably less than 12

WORD OF WARNING, its effectivly a carbon arc light, with shit loads of UV, ONLY do it with a full face mask and wear somthing that is UV resistant, leather welding jacket would be the best.

 

[bowser]

just to add to my last, you can braze with Mapp gas or oxy/propane but to be honest its somthing I might try on a bicycle frame but not on a motorcycle frame, it doesent heat up the two metals to be joined quickly enough, you really need proper gas welding kit, or use the carbon arc.

 

[Paul Rochdale]

Thanks, yes I used a set of carbon arc brazing rods many years ago on the floor of a Mini. It stuck metal to metal which was the kindest thing to say about it. Clumsy damned things to use as well.

 

[duckspeed]

Thanks, yes I used a set of carbon arc brazing rods many years ago on the floor of a Mini. It stuck metal to metal which was the kindest thing to say about it. Clumsy damned things to use as well.

Ohh yes I remember those mine repairs were minis also, bit like working using the inside bits of a world war two search light.

 

[Voyager]

Ohh yes I remember those mine repairs were minis also, bit like working using the inside bits of a world war two search light.

I've got a set that came with an Italian stick welder I bought nearly 40 years ago .

I have tried them a couple of times, but they require a lot of practice.

They came with a couple of flux-cored brazing rods if I remember correctly.

Scary stuff .

Bob.

 

[Brian.A]

Here are a few more pics of the frame







And michael dunlop winning the manx classic superbike on it last year

 

[Old Den]

Hi Vern,
I think we`d both give it a 8/10. But we know people who can do 10/10. Hope you`re well.
Take Care Den