apollodriver

Hello dear experts,

what do I actually need if I want to braze with propane? what is aimed: I want to build a racing bike frame

First of all: The question is: what do I actually need if I want to braze with propane?

What is aimed: i want to create a bikeframe.

So the question is: Do you definitely need oxygen, or does it also work with a so-called "air-breathing" burner?
In other words: without any special oxygene.

Can we also process brass solder, or just silver solder?

Note: air-breathing is the name given to all those burners which, in addition to the gas (let's say acetylene or propane), do not add pure oxygen, but only "utilize" air from the environment. The small disadvantages: If we re doing so: There is also nitrogen here. (see below)

Fuel flame temperature

to the temperatures: Flame temperature - Wikipedia
The literature usually states the highest temperature that can be measured in a flame under ideal conditions. Examples:



BTW: The fact that a lower flame temperature is reached with air than with pure oxygen is primarily due to the fact that the nitrogen contained has to be heated as well. In addition, the formation of nitrogen oxides requires heat as an endothermic reaction, which cools the burner flame. So if I take propane and (!!!) oxygen then: ....
... then you need adjustable pressure reducers with manometers, I think that this is at least 3 bar for both gases.

what is aimed: I want to build a racing bike frame

i chose a relatively easy project to start with. I build a racing bike frame from 25CrMo4 tubes (Columbus Thron) that is soldered in sleeves. Columbus Throne has a number of advantages for me as I have next to no soldering experience.

C. Thron is a CrMo steel that can be processed very easily with all common soldering agents (nickel silver, bronze ..)
C. Throne is not very strongly butted (0.9-0.6). There is no risk that the material will suffer disproportionately from excessively high temperatures. The pipe set is cheap and should I fail, filing, soldering, it doesn’t mess up too much money.

look forward to hear from you

Andrew R Stewart 

Agreed that Thron is a good starter tube set but disagree that it won't be affected by too much temp. My poor understanding about flame qualities and the various gasses that make up the flame is that there's more to it then max temp the flame is. One aspect is how the temp is spread within the flame. Acetylene/O can focus the high temp in a very small spot, propane/o less so.

Doug Fattic has posted a lot on his research and sourcing of propane specific torch parts. I suggest you search the archives for his advise. The last bit of free advise I can offer is that it's a poor design principle to work a system at it's limits for "normal" use. To invest in a flame/torch/set up that is being stretched to handle shells and crowns might be limiting in the long term. Andy

tuz

The key is heat, not temperature. You can melt steel with propane and a simple furnace. You can braze a frame with air-propane with brass and a hearth. But these are techniques from the late 1800's. I can't help you and I don't think many can.

I've made many frames with a bbq propane tank and an oxygen concentrator. Brass, silver, fillets, lugs. No regulator required for oxygen, just for the propane. Once you factor all the other costs involved in framebuilding, trying to use a plumber's torch is a false economy.

unterhausen

There are air-fuel torches that might work okay to build frames. Not the regular plumbing torches. I don't know why more people don't use them, but I imagine it's because they are a pain.
It's going to be difficult to use brass. Even with oxy/acetylene, brass takes more heat than a small torch can deliver.

N2deep

This guy is spot on. . Being able to control the temperature and size of the heat affected zone is paramount to obtain a quality weld. There is a lot more to braising than getting the solder to flow into the joint, the heat also changes the mechanical properties of the component. As stated, a propane or mapp gas torch may work but its the wrong tool for the task. Oxy-Acet torches come in all sizes from rosebuds that can heat a thick steel plate to small jewlers torches used to solder gold rings. I suggest going to your local college and take a class in braising/welding and get some experience before you purchase the torch. Braising or gas welding is an art form when properly performed.

Doug Fattic 

Apollodriver, where are you located? In North America or in Europe or someplace else?

Doug Fattic 

Here is the Cliff Notes version on using propane for brazing with oxygen. And you want to use pure oxygen with propane so you can get a nice sharp flame for much finer control. While acetylene equipment can work with propane, propane specific equipment works better. A propane flame is harder to light and stay light. Start by getting a propane specific mixer. They have a different ratio of fuel to oxygen mix. For the Smith torch that is a AT-61 and for Victor and compatibles it is the UN-J. Smith no longer makes propane tips. Victor makes its TEN series that screw onto the end of the UN-J. These tips have a recessed end that helps prevent flame blowout.

The best tips for propane are made by the Paige Tool company for the jewelry trade. These tips have little orifices around the center orifice so those extra little flames sharpen and stabilize the center flame. These tips work great. We (as in the bicycle frame making community) talked them into making adaptors for their tips that allow them to be used with a variety of torch handles and corresponding mixer/elbows. They provide a very sharp flame tip that contributes to precise control.

You also want T rated hose for propane instead of acetylene R rated hose. I recommend the light hose TM Technologies sells and extend its length with standard T rated rubber hose so the tanks are further away from the action.

In the frame builders section of Velocipede Salon, I have written extensively about using propane instead of acetylene for brazing. It has a lot of views so I assume that subject is interesting to a lot more people than hobby framebuilders.

apollodriver

hi there Andrew, Unterhausen, N2Deep and Doug,

here a quick answer - since i have to leave the house for catching the train.

Thanks for the ideas and for sharing your experience. I agree with you - and spend some more bucks for a nice system ;

Acetylene/O
my friend has got Propane / O

so i can make some tests and get more insihghts on both systems.

Again - many many thanks for all your great ideas. This forum is so awesome,. Keep it up - it is the best place for the topic Framebuilding.


have a great day

smontanaro 

There are a couple long-running threads in the VSalon forums which Doug started years ago. These might be helpful to OP:

acetylene vs propane

Finding the best torch handle and tips to work with propane

It's been a while since I checked in there, but as I recall they have plenty of info about brazing with propane, oxygen concentrators, torches and tips.

MassiveD

There is an interesting thread here, somewhere, about a guy from the UK who wanted information on how to use a torch supplied with compressed air. I thought I knew a lot about propane, and all that, so when he brought it up I was completely skeptical, turned out to be a standard technique. Never had heard of it then or since.

Welding, and brazing are hugely broad subjects, if you want to get it done, you can find a way, but if you want to do it like the pros, who tend not to be out of the box, you should just gear up with what they use, though personally I wouldn't touch acetylene in a domestic situation if it was free. And I very much doubt my insurance covers it.

squirtdad

Pretty clear OP is not in North america, I think Europe has lots more restrictions on things like acetylene and oxygen

Devin Rickey

I recently put together a propane/oxygen rig using the info from Doug on Vsalon (Thank you Doug Fattic !) I went with an oxygen concentrator, BBQ tank, TM hoses, Uniweld 71 torch, Smith fuel regulator, UN-J elbow, and Paige tools tips. Worked spot on, right out of the box! I have fillet brazed and silver soldered with it and am very happy with how it performs. Let me know if you need any part numbers. Happy brazing!!

Tandem Tom

Devin, I took Doug's course and I put together the same outfit.
Where did you get your UN-J elbow? Mine is leaking at the threads by the Paige tip. And I can't recall where I bought mine.
Thanks!

Devin Rickey

Hi Tom, I got it at Zoro (https://www.zoro.com/victor-universa...?q=victor%20un) They have them in stock and good pricing!

Tandem Tom

Thanks!