I need to repair a frame, not yer usual 531 frame though, this one’s a 1973 Cheney BSA B50 500 scrambler.
I’ve done a fair bit of oxy-acetylene welding in the past on Land Rover chassis, before I had access to a mig welder, but I’ve never done brazing or bronze welding.
It’s only a couple of seat mountings, not the main structure of the frame, so I thought I’d have a go myself.

These two brackets here, which a previous owner has cut off for some reason.

From what I’ve read so far, it seems mixing powdered flux to a paste, then painting it on before brazing with plain rods is preferable to using flux cored or coated rods.
I’ve also read that repairing nickel plated frames can be difficult because high copper content rods don’t stick to the nickel, I need high nickel rods. However, as it’s only a small area, I could probably manually remove any plating to get back to bare steel.

Any advice on exactly which flux and which rods I need?
We’ve got plenty of gas and scrap metal at work I can use to practice with. 😉

I can’t help you but holy-moly well done for taking that on!

Can we have an “after” picture too? 🙂

You can have a before picture.

And a what I want it to look like after picture.

Hopefully Ben Cooper will be along in a minute as he has more experience.

I’d just use regular unfluxed SIF No.1 or 101 rods.

Mechanically clean everything up (removing any plating). Paint on flux paste over everything. Any brazing flux works but one of the nicest to use is Cycle Designs LFB flux as it cleans off soaking in water and goes clear (handy indicator) when everything is starting to come up to temperature. A pot of flux (and also brazing rods) available from Ceeway. If you only need a bit I could probably post you a scoop in a bag.

SIF flux needs mechanical removal (blasting etc) but probably contains fewer chemical nasties.

Thanks, Mick. We’ve got oxy-acetylene burning gear a work which gets used regularly for cutting and heating.
I had a search around and found a tub of flux, some 2.4mm plain rods and a No5 & No10 welding nozzle all hidden away. 😀
I don’t know how long they’ve been there, I’ve never seen them used and didn’t even know we had them until I searched.
I’ll have a go with what we’ve got on some scrap metal and see how I get on.
I can always buy a different size nozzle or rods if I need to.

Firstly, set about that with a wire brush – you need lots of clean shiny steel for brazing. The wire brush, if vigorous enough, might remove the nickel too if there’s any left under that crud. If not then sand it off.

Your oxy gear will work, but try to find a smaller nozzle for it for fillet brazing stuff like this, you want a flame with an inner core around 5mm long, not a massive fire. This isn’t cutting gear, right? If it is, you can use the same mixer, but need to find the brazing and welding head for it.

Be a little careful with old brazing rods – a lot of them contained Cadmium, not nice stuff to breathe in.

It’s not really a hard skill to pick up, most people get the basics in 15 minutes, it just takes a while to get good at it!

Thanks Ben. Yes, I’ll use a twisted knot wire brush in the grinder to rip it right back to shiny steel.
We’ve got a cutting head on at the moment, but there is a welding head with two nozzles.
The brazing rods were loose in a welding rod tube, so I don’t know what they are exactly.

Her we go, my first attempt.

Things what I have learned so far;
I need smaller nozzle. I’ve got the number 5 turned right down as low as I can. I’ll buy a number 3.
I need some new goggles. They’re OK for cutting and heating but a bit scratched for when I need to actually see what I’m doing.

That’s decent for a first go – no blobbing, wetted out on the metal, good job.

That looks perfectly presentable – don’t forget to show off the finished bike repair!

I found some (sunglasses style) glasses actually labelled for brazing / soldering in Machine Mart for about £5 – they don’t list them in the catalogue and had just one pair bunged in with the welding goggles (too dark to just be tinted safety glasses). Must have been an old stock product but they are perfect and make it much easier to see the colour changes.