Doug Fattic 

Propane is an excellent choice as a fuel for building bicycle frames. It is much cheaper and way more convenient to buy and transport than acetylene. It burns cleaner and doesn’t give off soot. However to get the most out of it requires propane specific equipment. This includes a Victor UN-J or Smith AT-61 mixer/elbow (that fits their respective J-28 or AW1A torch handles). They have bigger and more numerous oxygen holes because propane requires more than acetylene.

Another improvement is multi-port tips that are tuned to burn propane (or natural gas) more efficiently. They provide a very sharp and long center flame surrounded by tiny flames that stabilize the center flame and keep it from blowing out easily. This can happen when the flame gets close to the work like when doing fillet brazing. The primary suppliers of these tips that work well for frame makers are Paige Tools or TM Technologies. Their primary market is jewelry makers. These tips have not been conveniently available for us until recently because their ¼” X 28 threading doesn’t fit either Victor (5/16” X 27 tpi) or Smith (1/4” X 32 tpi) mixer/elbows. They have always fit the Meco Midget torch handle. However not everyone likes Midget’s flat rectangular shape. Recently Paige tools has come out with an adaptor (called the NK) that changes Smith to Meco threading and allows the AW1A torch handle to use Multi-port tips. One for Victor and compatibles is coming out soon. Maybe. Call Richard at Paige Tools to ask how they are coming. They did the Smith adaptor at the request of framebuilders.

TM Technologies also makes an adaptor but it has to be brazed onto a Victor UN-J in order to work. This may be a little more complicated than some may want to tackle although it isn’t that difficult to do. It is a straight section of ¼” ø brass tubing with ¼” X 28 threading on one end. A 3/8” OD X 1” long bronze sleeve can be bought at most hardware stores in the bolts and nuts section. One end of its ¼” hole needs to be drilled out to 5/16” about half way through so it can fit over the UN-J. After cutting off some of each end of all 3 pieces (so the tip doesn’t stick out too far) they can be silver brazed together.

Multi-port tips work the best but others can work well with propane. Victor makes the TEN series of tips that screw directly onto their UN-J. They have a recessed end that helps prevent the propane flame from detaching from the tip (a common occurrence with propane). And besides wanting to detach it is also more difficult to see when you have the right fuel mixture. Unlike acetylene with sharp cone distinctions the ratio of oxygen to fuel has to be regulated mostly by the color of the flame. While the TEN series of tips are a lot better than using Victor acetylene nozzles like the1-W-J, they still don’t provide quite as sharp a flame and can blow out a bit more easily than multi-port tips.

One of the primary reasons propane is not more popular with bicycle frame builders is because most of us old timers learned using oxyacetylene and that is why it became the standard. Propane specific equipment has been available somewhere for years like the Smith AW405 nozzle no longer being made. However the ability to use multi-port tips with the most common aircraft style torch handles preferred by many builders has just now been possible without some kind of modifications with the new Paige NK adaptor that can connect their M series of multi-port tips to a Smith AT-61.

I should add that propane burns a little cooler than acetylene but for most readers finding this post helpful that is an advantage because it gives them just a bit more time to read what the heat is doing on the joint and adjust their flame accordingly. I learned how to hearth braze when I apprenticed in England in the 70’s as well as how to use an oxyacetylene torch. I started using propane about 15 years ago making transportation style of frames in Ukraine doing a charity bike project. I can use either easily but now prefer a multi-port propane flame for all frame brazing (including fillet brazing). The fact that it is much cheaper and easier to buy is just a bonus.

mikeread

For those in the UK you can get Oxy Propane multi-jet torches and nozzles at Welders Warehouse https://www.thewelderswarehouse.com/...t-Nozzles.html

I am not sure if they are exactly the same as what Doug uses but they worked OK for me - not that I am an expert. Easy to light and adjust and I haven't had a blow out yet.

unterhausen

Thanks Doug, I really want to make the switch

unterhausen

looked at this again and thought I would add a link to the Paige tools website page for their adapters. Photos
Wish they would sell the AT61. I think I have some meco tips, not sure.

calstar 

From Welders Warehouse site, multi-port propane tip