J.Higgins 

Hi Framebuilders. I'm thinking about getting a nice O/A brazing outfit to do repairs and add-ons for some of the factory frames that I've been rebuilding and customizing. For instance, I'll take an old Gary Fisher or Trek MTB frame, clean it up, sometimes have it powder-coated, and add all new wheels and components to it to make a new touring bike from it. What I'd want to do is to perhaps braze on disc brake mounts, or water bottle mounts or such.

I've got a lot of experience in tig, mig, and I've had training on O/A and brazing, and classes for all these. However, the only thing that I've ever had at my home shop is a Lincoln mig unit, and I've never had an O/A brazing/cutting outfit of my own. I was wondering if one of you kind folk could steer me in the right direction? Thanks!

Andrew R Stewart 

You'll likely get a lot of opinions, including using propane instead of acetylene. If I were to be starting up again I might give P/O a go but since I also find Ti to be cool I'd probably had gotten a TiG set up.


I have two torches. Set 1 is A-35cf, O-40cf, GOSS 42W. 32 is A-70, O-80, Purox W200. I use 25' 1/4" ID T type hoses although on the Purox set I have an additional 12' of 3/16 size because of the lighter weight and that the Purox uses A fittings and the smaller hose comes set up that way.


I use the Purox most of the time but I feel that the Goss puts out a small amount more energy so will use it for thick stuff. I do like the lighter hose/torch weight of the Purox set. (I have used Smith AW1 w/ Kevlar hoses which are really light and fragile). Both sets are very easy to carry in their separate parts although the bigger tanks want some focus for my 5' 6" body to lift and swing around. These are the largest I would consider if only for that reason. If I ever got a truck and a ground floor shop I'd use a size or two larger. I run check valves placed at the regulator ends of the hoses, I've found at the low flow pressures and rate I use a true Flashback Arrestors can have too much flow restriction for a consistent flame.


I do have a Gas Fluxer but haven't used it for a few years and it's not hooked up. It does make some aspects of brazing a little bit easier but both doesn't replace paste flux or good skills. Dealing with the liquid "flux" is a hassle, I store mine outside of the house.


I've never had reservations of safety with my O/A sets in the basement though. I follow good practice of assembly, testing, ventilation, opening up and then bleeding shut and decided years ago to get first grade equipment and not knocked about used stuff.


A common issue with local Craigs list finds is that they are usually intended for automotive, machine/fab shop or industrial use and have large torch handles and cutting tools that will never see a bike frame. Most sets I've seen will be "up graded" with bike frame building friendly torches/hoses and the big stuff will sit in a box. I would also strongly suggest that if you have a LWSS (local welding supplies shop) you consider buying from them for the non consumables.


The Gas Flux bronze rod, CO4, and their type "U" and "B" fluxes are used by many builders as they are easy to work with and are not too pricy. Cycle Design fluxes and fillers are well spoken for and some feel are a step better then the gas Flux products. I've not used any so I won't give any opinion.


Last item is mounting disk brakes on frames not intended for them. If this is only for yourself then fine. But if for customers (and this includes friends and family) then I'd reconsider. Oh, I'd also make sure I have liability insurance that covers my manufacturing a bicycle brake system because the bike manufacturer will bow out of the law suit given your mods. Andy.

unterhausen

I have never seen a craigslist O/A that was worth going to see. My favorite is people selling rental tanks. The gas places used to just charge a deposit, and you could keep them as long as you wanted. Those days are gone, but grandpa might have a set of tanks out in the barn that were acquired that way.

You can get a Smith A1WA for reasonable money, and J28 (or clone) as well. The J28 seems to have better selection of tips for propane. I think I would go to propane if I had to spend any money on my current setup. I really want an oxygen generator

J.Higgins 

Looks like I can get a Victor J28 for about $150. Do I need a special regulator for propane? What size propane bottle should I get? What size O2?

JohnDThompson 

You don't need a special regulator for propane, but propane, unlike acetylene, remains stable at high pressures; that's what makes it nice for cutting thick plate. So the "red line" found on acetylene regulators doesn't apply for propane.

At Trek, we ran propane through a manifold system with a main regulator between the tanks and the manifold and individual regulators at each work station. The manifold was run at fairly high pressure to maintain flow to all the workstations, and the main regulator was actually an acetylene regulator. I remember when a new supervisor was hired and glanced at the main regulator with the needle buried firmly in the red zone. He just about crapped his pants until we explained we were running propane, not acetylene.

Andrew R Stewart 

John- good points about A and P's different high pressure behavior. I remember a story that Albert E told us 9at a building class in 1979) about his neighbor at his shop in Oakland. This guy was doing some sort of torch cutting on a large scale. One day Al went next door and introduced him self, he noticed the A reg was set at around 15PSI... he then looked at the simple brick wall separating his shop from the cutter's. Andy.

unterhausen

when I was at Trek, we still used acetylene and we had pilot lights on the torches (whatever predated the smith a1wa). One day there was an explosion because someone let their pilot light go out. Shook the building. I was in the (attached) second building, I bet people had ringing ears over in the brazing area. Soon thereafter we got new torches without the pilot light. I have thought about brazing in my basement, but it does make a bit of a stink and I'd rather have an explosion in my garage. Storing the tanks outside is still something I might do. Propane is heavier than air, so basement use seems problematic. I know someone that makes glass beads with propane in their basement though.

elcraft

Storing propane ( Larger than 1 lbs disposable canisters) indoors is usually against local fire codes. It's heavier than air and can "settle" in pockets and cause nasty explosions. If you want to use Propane, the tank needs to be stored outside the building. You can buy Propane gas detectors/ alarms at RV supply centers. I have always dreamed of taking the alarm system and adapting it to "un -power" a solenoid valve (that is arranged to "fail safe" into the closed position. In other words, a electrified solenoid valve that closes if the Propane alarm detects any sizable amount of Propane. Alas, this system doesn't exist at the moment.
That being said, I use Propane for jewelery and goldsmithing while Imam indoors.

J.Higgins 

I have zero experience with propane. Its probably best that I leave it out of the equation in the beginning.

Doug Fattic 

“Airline” or “light duty” torch handles are the best type to get for brazing bicycle frames. They are characterized by their smaller size, have their adjusting knobs at the top of the handle and use smaller “A” size hose fittings. A light torch makes subtle and slight brazing motions more precise and comfortable. This group would include the Smith AW1A, Victor J-28 and the Uniweld 71. There are others. For most framebuilding applications a Victor #0 and #1 size torch tips are probably all you need

Using TM Technologies Ultra Light Weight Hose on the end of the torch handle reduces weight and, more importantly, torch resistance to movement. Like I said, frame brazing often requires slight and subtle hand motions and these lightweight flexible hoses makes any motion adjustments easier. Smith makes a kevlar hose which is even lighter but they are more fragile because even one drop of hot melted flux can burn a hole. Because these hoses are only 10 feet long, it can be a good idea to extend them with regular 3/16” rubber hose (the smallest diameter available). It is better to hang these hoses from the ceiling on their journey from the tanks to the work station then to have them lying on the floor getting dirty, worn and in danger of having hot flux drop on them. T grade hose can be used for either propane or acetylene and R rated hose only for acetylene.

For protection you will want a check valve on the end of the torch handle and flashback arrestors next to the regulators. There are 2 kinds of flashback arrestors so make sure you get the ones that go next to a regulator and not a torch handle. This will stop a flame from a cut hose caused by your errant flame from going into the tanks and making it a big bomb.

Somewhere you will need to convert the A fittings on your torch handle to the B fittings on your regulators. This can be done with the connector between the 2 hoses or the rubber hose can have an A fitting on one end and a B fitting on the other. TM hoses come with an A to B fitting adaptors.

Here is a a list of brazing equipment from the tank to the flame: 1. A regulator (most likely with “B” size fittings). 2. Flashback arrestor. 3. 3/16” rubber hose (it is smaller than the other common ¼” size). 4. A male to male hose connector. Whether this brass connector is an A/A or A/B or a B/B fitting depends on your hose fittings. 5. TM Technologies ultralight hose. It has A female fittings on both ends but comes with two A to B adaptors. 6. “A” size check valves. 7. An “aircraft” style torch handle. 8. Whatever mixer/elbow/tips fit your needs.

Because I teach framebuilding classes I have throughly investigated what equipment most likely works best for an amateur builder. Using propane as a fuel and an oxygen concentrator (those machines that convert air to mostly oxygen for those with reduced functioning lungs) are cheaper and more convenient and safer options. I have written extensively about this online. A google search will find them. But of course an oxyacetylene outfit works just fine too.

J.Higgins 

Thank you, Doug, for grabbing me by the scruff of the neck and spelling this out for me. I suspected that a light torch would be a good place to start. Now I'll have to look up "oxygen concentrator." Shall I take for granted that this setup will not require trips to get welding gasses - just the propane filled?

David Tollefson

The advantage of that oxy-propane set-up is that you indeed do not need to go get bottles filled. Using the standard bbq propane bottles, you can get them just about anywhere for a song. $50 for the first one, then exchanges for $20 or so. And they last a good long while.

Doug Fattic 

That’s right my propane BBQ tank lasts me about 3 times longer than my large acetylene tank that cost me something like $175 for the tank and $65 for a refill. The real reason I researched using propane with an oxygen concentrator is because regulations and/or restrictions in some cities don’t allow the delivery and use of oxyacetylene. Propane is allowed because of the popularity of barbequing and a concentrator isn't a potential bomb or unguided missile.

Oxygen concentrators can be found on Craigslist for an average of $200. If you are lucky even cheaper. I bought a refurbished one from M&M Medical in Beaverdale PA for $300 that came with a 3 year warranty. This is a similar price to buying an oxygen tank and regulator. You don’t need a regulator or flashback arrestor with a concentrator. They have drawbacks. You have to let them run for a few minutes until nearly pure oxygen has purged the line. They make noise and learning how to set the flow rates to light a flame has a bit of a learning curve. Actually propane has a longer lighting learning curve than oxyacetylene too.

J.Higgins 

@Doug Fattic are you saying that it does not need to be a special O2 concentrator made specifically for welding, but instead it can be a medical O2 concentrator?

Doug Fattic 

Yes a medical 5 liter per minute output concentrator works well for brazing bicycle frames. My DeVilbiss has a brass B fitting that I can screw my brazing hose directly onto. Some concentrators have a barb fitting designed to hold clear tubing. In that case a barb to B fitting is necessary. They are commonly available. Some pros that use a huge rosebud flame will not get enough oxygen output out of a single concentrator.