I have flash arrestors at the regulator side. They double as check valves. I don’t think it matters which end and you only need one on each line. Pretty sure on my old set up I had them at the torch side because they also doubled as A to B fitting reducers.
2/3/4 should be fine, 2 should be small enough for racks and 4 is good for fork crowns, lugged BB shells and trying to unbraze lugs on frame repairs. Sometimes a rosebud can be handy for those same things.
5 is definitely too dark. I use 5 for torch cutting with O/A only. I use safety glasses in shade 3 for bronze brazing (fillets, slotted dropouts). The flux gives off a bit of a flash and the torch is usually cranked up higher. For silver brazing lugs and doing braze ons and stuff I just wear regular safety glasses since I want to see the colour changes. It’s way easier to overcook the flux when silver brazing. I see that safety glasses in shade 1.7 exist, maybe those would ideal for that. Torch flame doesn’t give off UV like arc welding does so the tint isn’t nearly as big of a safety thing.
I wear a P100 respirator when brazing as well. Unless you have a really open area with great ventilation, I’d recommend it. Flux fumes can leave a nasty feeling in your throat.
Ok, thanks for the tip on the shade, I thought 5 would be too dark.
I have a respirator but never wore it while brazing because I usually do it outside. My new setup will be right against a roll up door with a big fan pulling fumes out.
I’m interested to see how this comes together - last time I refilled my bottles the counter price for acetylene was crazy high and the guy asked me “you’re a contractor right, wink wink” and I said I was a plumber and got better pricing. Since maybe the next guy might not be as cool and to save some space oxy-pro sounds appealing.
I run a Victor J100C and use a #1 tip for almost everything. For racks I might drop down to a #0. I keep thinking of treating myself to lighter kevlar hoses but even in a prolific year I don’t really need the lighter setup.
100% from memory (you can ask an AI now, it probably knows more than i do) the commercially available bike tubing stainless steels are two kind of super expensive seamless ferritic / martensitic tubes and less super expensive KVA (also ferritic martensitic) which is 420 (braze it) ERW (it has a seam, and also is sort of susceptible to stress corrosion cracking), all of these can be brazed i think (or just tig welded). what makes them good bike tubing is that they can be cold worked and heat treated to be very strong.
2205 duplex can be cold worked, but is not “built” to be heat treated for high strength, it’s optimized for corrosion resistance, with a butt tonne of chrome, but less nickel the austenitizing alloying addition) than 300 series, giving the “duplex” structure of Austenite (susceptible to SCC) and ferrite (not susceptible) meaning SCC can’t propagate.
It’s not really the kind of super high strength work hardening bicycle tubing (high strength to allow thinner wall tubes and hence lower weight, you’r stuck tig welding it and even then you’re probably gonna struggle to get the weld to pass a G48 (metalurgists inside joke and irrelevant to bike frames unless you really like riding through vats of boiling magnesiul chloride solution). side note my wedding ring passed a G48 test (i made it out of a left over passing test specimen) making it resistant to way more environments than i am).
is anyone actually making a hardtail out of 2205 or did some kind of offshore platform for ants wash ashore and you want to re-cycle the tubing?
very quick search on https://www.matweb.com/ indicates ~550 MPa Yield Stress for 2205 on a good day (thin section like bike tubing) maybe this could be jacked up a bit, but then it also has to be welded and the welds will likely be weaker unless they have “turdly buttways” (or does that just mean straight wall?) anyway the more typical SS bike tubes could be in the order of 1000 MPa yield, which is probably up there with the fanciest not stainless bike steels, even the “cheap” 420 has all the mechanical properties, just not “seamless” (doesn’t matter, ERW is fine, don’t let the San Bruno pipeline explosion make you think welded tubes are bad, i mean they are whey they’re only half welded and made in the ‘50s and then you build a suburb on top of them, but this is a bike frame)
anyway i don’t think 2205 would do anything mechanical properties wise that all but the most lawn furniture grade recycled oil tanker carbon steel can’t already do for a fraction of the price (and to be fair a fraction of the corrosion resistance, but like paint and frame protector spray stuff are a thing)
I’m doing a written interview with Rufus from Sufur cycles. If anyone has any questions about his ideas or build then let me know and I might be able to squirrel them in. I don’t know anything about frame building as such but its different enough to be interesting to nerdy bikepackers.
