ZenkiGarage

So, was looking at Smith torches and noticed they make a Acetylene/Atomospheric air torch. very nice unit as with all smith goods. Just curious if anyone has tried acetylene/air for filet brazing bike frames? Im sure its do-able as its possible to do with mapp/air. I guess just wondering how well? Just throwing around the idea, since it would be a nice compact, easy to use package if it works well.

unterhausen

I've seen videos of people brazing with Mapp, and it impresses me as a good way not to get full penetration because the heat is so marginal. I don't think you want to try this.

Cyclist0094

Acetylene/air burns around 2000c, Mapp/air is about 2200c. I have done more than a few fillets with Mapp and it is barely adequate on most joints with tube butts thicker than .8mm (Forget about trying to fillet a tube to a bottom bracket shell or 1.5 mm head tube)

Acetylene/Oxygen kits are pretty cheap these days. even a cheap Chinese made rig will work well with a bit of practice

ZenkiGarage

Thanks for the numbers. I was under the impression acetylene(air) burned hotter than mapp(air). i have a cheap chinese rig right now and am looking to upgrade to quality equipment and figures if it was hot enough would be nice and compact. Oh well, I'll keep looking. thanks again!

Cyclist0094

Some builders are using propane/ oxygen systems which they claim work great , Propane is certainly cheaper than acetylene.

I don't have any personal experience with prop/ox

NoReg

I have a propane oxygen system. I am not sure it is cheaper, though cheaper is part of my motivation for getting it. It's cheaper if you already have a propane tank for some pupose, and those tanks are somewhat cheaper to start with. But apparently propane uses up oxygen at a much more comsumptive rate. I forget though, some rocket scientist had an answer as to why that wasn't a problem. The good things about propane are that the gas is cleaner burning, both less sooty in the shop and less dirty on the work; it is colder, acet. is clearly too hot for this kind of work, 98% of the flame is just blasting the air all the time, though at the end of the day that probably doesn't really mater since people use it just fine; Accet is a safety nightmare, the training video is called "1000 Ways to Die". It really has no place in a home shop, as far as I am concerned. Whether propane does or doesn't belong, at least it is an everyday product around the home.

As far as cost is concerned for rigs, if you already have propane, then you only need one more bottle to run PO, no worse than one bottle of Accet. Whatever unit you try, you could use the same gages. I would only get good quality ones, for a host of reasons. That leaves the torch. The Meco torch is pretty cheap, and one of the nicest, though it probably doesn't handle quite the way a Smith does with the candle handle. Still, if you are outfitting a home shop the Meco is probably more versatile since it works very nicely for a little welding in many metals, has cheap nozzles you can switch, propane and accet nozzles, and so forth. Very nice little rig.

redtires

Are you talking about oxy/acetylene brazing? I've never heard it called atmospheric air, so maybe this is different. But I've built hundreds of bikes with an oxy/acetylene torch with no issues at all.

NoReg

Atmospheric air burners pull air from the atmosphere in to mix with the fuel. They can be pretty hot little torches, but nothing like ones that are fed bottled oxygen. So he has found something like the hardware store propane torch, but that uses accet. Didn't know there was such and animal or what it might be specifically useful for.

https://www.plumbersurplus.com/Cat/Sw...-Kits/791/List

Some interesting if distinctions made here, though the full meaning is not clear. Interesting point of lab burning temperature results, and heat transfer:

https://www.ganoksin.com/orchid/archi...4/msg00039.htm

redtires

Huh....well ya just learn something new everyday now don't ya.