The windshield stanchion for my a model is broken at the pivot cup. I could actually just run with it as it is but l thought l may as well give it a go at repairing it. My first attempt was a fail ,l tried a fluxed brazing rod that l had laying around but it just would not take. From what l could find on the www they are made from a cast bronze, Cheers
That's a job for a Tig welder and Silicon Bronz filler rod. Well at least that's my personal opinion.
I'm going to make the long story shorter. Oxy acetylene gas, Silver brazing alloy, BAg1. Final answer. Why, because not everyone owns a Gas Tungsten Arc Welder.
Question for those who know, why can't you braze it? The OP said he tried but it would not stick. I would think brass would melt into bronze, what gives.
Like NoelC said, get some 45% BAg1 silver braze wire and the proper flux. Put flux on both pieces, butt the parts together and clamp them so they can't move if you can. Start heating the joint and watch the flux, it will dry up first then it will turn to a clear syrup. This will indicate that you are close to the brazing temp. Add more heat and try to add the filler wire to the joint, when you have reached the correct temp, the silver braze will flow into the joint like solder. I use this silver braze to connect regular and stainless steel parts and it will make a repair that is as strong or stronger than the base metal.
You could actually, if you get it all hot enough. Key word hot enough. The difficulties will be the flux coated brass rod, RB CuZn-C and it's composition is it's high zinc, that burns off in the high heat required to melt it all, base metal and filler into a molten mass. They mention silicon bronze and GTAW, well it could as well be used with oxy acetylene. Almost the same issue. While of a different composition, heavy copper content instead of zinc. Most associate silicon bronze fillers with GTAW. But they also make GMAW silicon bronze wires.
In this case I might argue that a gas torch would be better, or a whole lot of gas preheat before TIG. Fairly hard to reliably pre-heat with a TIG torch.
I would Tig the areas that you can reach, and torch silver solder the valley that the Tig won't reach. That way it will look good where you see, and have the added strength in the middle.
My Granddad (he was a real Blacksmith) would tell me to throw it on the Forge and get er hot and I'll show ya one time sonny. It's all about what you have to work with, and do you know what you're doing with it.
Just as others have said, silver solder will do the trick. At one time I did it for a living, I used white low temp flux and a small gas torch. Even a Mapp Gas torch will work just fine in this case, which is what I now use at home. The mistake a lot of people make is thinking you need to get the base metal as hot as when you braze it, in my experience a big mistake.
When in doubt, or to the untrained find out the recommended flow temp for your fill rod. Get a temp stick for that range. Now bring your base part up to it and get busy.
If that is cast bronze... There is a possibility is was made for Wescotts in the 1970's-1990's, if so it is aluminum bronze (for high strength) and will require special attention with a tig welder to get a good weld. (pia to machine also).
I used to do a lot of Silver Solder, with Borax flux. It depends on what they call “bronze”. Some alloys have something in them that will never stick with a torch and flux. I say need to find a TIG welder with experience.
Darn shame there wasn't 3 or 4 broken ones, to be fixed. Yea...then we could vote on which repair turned out best. Really, when you say, this is what I got, what I can afford, what will work, what will be the least amount of work, what will require the least refinishing, do the job, serve the purpose, please the critics and with in the skill set to accomplish the task, 3 or 4 may not be enough? But when it comes down to probably have around, will do the job, simple clean up, not much effort, work like a charm, most would be impressed, and the average Joe can do it...JB weld and tuck tape shouldn't be ruled out. I'm still voting for silver brazing.
Just because l have oxy/acy available that’s the method l went with. Got hold of some silicone bronze wire 1.6mm and flux to suit. Definitely didn’t have enough heat into the first time around so l cranked it up a bit. The silicone bronze didn’t flow like silver solder would and l was worried about the amount of heat that l was putting into the stanchion as it was well past cherry red to get wire and base material to meld together. I cleaned it up and it turned out ok, could be better but good for me I reckon it’s a weak spot in the design so wouldn’t be surprised for it to crack again ]