acetylene vs propane

[nspace]

Oh, and sorry for the typos; I wasn't fast enough to go back and edit.

[Doug Fattic]

Nspace, nice to see your progress! A few pointers. It is difficult to see the subtleties of color and flux change when using any kind of darkened glasses when brazing with silver. This just makes learning more difficult. For short term learning purposes, it makes sense to use clear lenses. Of course when brazing brass the brightness of flux does require some kind of darkened eye protection. I use a #3 lenses but sometimes something lighter than that. For beginners that want to see as much as possible just sun glasses are fine. There is a tension between ultimate safety and seeing well enough to catch on.

Understandably you got the first lug joint too hot but of course a picture can’t tell the reason. It could be you got too close with the flame or held it in one spot too long. There are any number of mistakes rookies make that contribute to scorching a lug. The most common is that their torch hand freezes while moving their hand holding the brazing rod. Using both hands independent of each other is the learning curve struggle.

Getting clean shorelines is something not everyone has the skill to do. I spend a long time explaining and demonstrating how to do this in class. About 15 to 20% of my students still won’t be able to do it well. For them it requires too much hand eye coordination. Essentially you move the excess from where you don’t want it to someplace that still needs some or where it can be removed later. The general idea is that the point of your flame is concentrated just on the shoreline and you will move it at the speed the silver will melt like a surfer riding a wave. This blob has to be taken somewhere like the front band of a head lug where it can be drawn onto the section of head tube that will be cut off later. There is also a 2nd more general method when the lug is still very hot. You flick the flame on the shoreline to melt any milky flux to get a clearer view and make sure there is no excess and if there is, draw it with heat through the lug (instead of just moving it along the shoreline) to someplace that still needs silver or further on where it can be cut off later. There is a lot of subtlety to brazing techniques that are easiest learned from a pro.

[nspace]

Thanks so much for your reply, Doug. Your point about the torch hand freezing while concentrating on the filler rod is a valid one. I caught myself doing that on a number of occasions and probably exhausted the flux in a couple areas as a result. I thought about recording a video of myself just to see how often I do it so I can know when to correct it and how often I do it. I will keep practicing and will definitely try some clear glasses—I could see that helping a lot. I'll try to worry about the shorelines more so once I can braze the joint without scorching anything, seems to be the lesser of the two evils. I wanted to take some time off in the next year or so and make an effort to enrol in your course after reading so many of your helpful replies, but alas, I just found out my wife and I are having twins, so just being able to afford materials to practice at this point is going to be enough of a struggle for me, but maybe further out I can swing it. I don't have any local contacts either to ask, so I think it is going to be the trial and error method for a while. I really appreciate the feedback!

How long a piece of filler rod do you typically work with? I had a bundle of the wire in my hand with a section extended straight out to avoid cutting it, but I find I don't have very much control over the filler like this, and it gets kind of "springy", and I think it might be easier with a 12-14" piece of rod that I could control better.

I'll post some more photos once I do a few more practice runs :) Thanks again.

[veryredbike]

Quick newbie to newbie advice: I always scorch things because I worry that I'm taking too long, not because I'm actually taking too long. Nothing has improved my brazing more than just letting things come up to temperature naturally. Any time I want to jump in early or get the torch lot closer I muck things up. The flux burns fastest when you're trying to heat things faster.

[Doug Fattic]

How long a piece of filler rod do you typically work with? I had a bundle of the wire in my hand with a section extended straight out to avoid cutting it, but I find I don't have very much control over the filler like this, and it gets kind of "springy", and I think it might be easier with a 12-14" piece of rod that I could control better.

I just straighten out a length from the coil. But that isn’t necessarily what you should do starting out. One thing that is very important for beginners is to have as straight a piece of brazing rod as possible. Often students are a little lazy and their silver is a bit curved or wavy from straightening. This increases their difficulty and lowers their results. It requires more of their attention and greater coordination to keep the end of the rod right where it should be as it melts. Extra attention that should be focused on moving the flame in the best pattern. Rookies can’t keep track of both until some factors are in muscle memory. Sometimes it is best starting out to cut off a 1’ length and get it as straight as possible even though your can’t use the final inch or 2.

Another important starting point is to hold the angle of the rod to the works that allows it to stay right where you want it as it melts. If you have to think about how fast to move your rod hand to keep it at its entry point as it melts you are in the wrong position. And a 3rd critical point is keep the rod end very close to your work while heating up the joint. Students tend to drop their rod hand waiting for things to get hot and then when things are up to temperature, they scorch their lug in the time it takes to put the rod in position.

Try this exercise to teach both hands to move independently of each other. Point a finger from your left and right hand at each other. Now move them in opposite circles. You will find this difficult to do at first. They tend to want to follow each other like track bikers in a pursuit race.

[Simonhi]

Doug, you really need to write a book or do a video series. You explain things so well it is great reading your posts.

Really wish I could fly across the pond to attend one of your classes but with a 14 week baby at home my chances of doing that are very very slim.

Many thanks for taking the time to comment here, definitely the best thing about this site is that the experienced hands are so willing to share their craft on an open forum.

[Doug Fattic]

Doug, you really need to write a book or do a video series...Many thanks for taking the time to comment

Thanks. Writing a general framebuilding manual is on my bucket list. I don’t have to start from scratch, I’ve spent hundreds of hours over many years refining the multiple pages of my class manual that I hand out to each student. Having a detailed written account of all the steps to make a frame as well as descriptions of how to braze and file and design a frame is one of the perks I provide my students. I know that it will seem clear when it is explained and demonstrated in class but so much material is given in 3 weeks that much of it will be soon forgotten unless one is a genius sort. Something specific to refer back to later can be very helpful.

[nspace]

I would buy that manual in an instant. Just reading the other thread about the plug drop-outs, I was a bit confused, but as soon as I read what Doug wrote, it made perfect sense!

Thank you all for advice and suggestions so far! I'm sure people thought I was going crazy, spinning my fingers at my desk :)

One question I had, after reading a few threads. I hear people referring to silver and brass rings. My understanding is that you are basically putting some filler material into the tube above the dropout and sweating it out with heat. I'm assuming the reason for doing this is that you get a visual indicator that you have got full penetration compared to if you did it the opposite way and fed filler into the joint? I guess my main question is, the "ring" is that just a piece of rod bent into a circle/ring with pliers to fit the ID of a tube or socket?

[Doug Fattic]

One question I had, after reading a few threads. I hear people referring to silver and brass rings. My understanding is that you are basically putting some filler material into the tube above the dropout and sweating it out with heat. I'm assuming the reason for doing this is that you get a visual indicator that you have got full penetration compared to if you did it the opposite way and fed filler into the joint? I guess my main question is, the "ring" is that just a piece of rod bent into a circle/ring with pliers to fit the ID of a tube or socket?

Your assumption is correct. It is easiest to tell if your brazing is complete by sweating brazing material out rather than in. The only way you can know for sure, however, that silver or brass is covering every mm of surface area is by even heat coverage. It is possible for it to flow down one side and not the other but fool you because it makes a complete circle at the bottom. Students often make the mistake of not heating the stay evenly around its circumference.

Henry James dropouts come with a single ring of silver for each joint. So a pair of rear dropouts will come with 4 rings and front dropouts 2. Hank has simply made these out of a larger coil of 50N silver. 50N silver wets out a bit better on stainless than its 56% to 45% cousins (although they all work). You can make these rings yourself by bending 1/16” diameter silver coil around some kind of rod. I put a small notch in the rod to help hold the silver end in a vise while I am twisting the coil around it. I turn it as many times as the number of coils I need to make (i.e. 4 turns to make 4 coils). A joint doesn’t need more silver than that if you have a reasonable fit. I don’t make them one at a time unless I only need one.

After your newly made coil is cut apart, it is necessary to adjust its size to fit tight against the inside walls of the stay or blade. Usually it needs to be made smaller by squeezing it in a vise at various points around the circle. If it gets too small, I push it down a tapered center punch to enlarge its diameter. If you tried to braze up a plug dropout when the brazing material inside was not touching the walls, it might just ball up on top of the plug instead of running down the sides. That is why I bevel the plug a bit at its end to facilitate silver's travel.

[nspace]

Wow, thank you again. Your description of adding that taper/bevel answered my next question already while I was reading through your response. That is a great idea!

[Doug Fattic]

Now that I’ve been using my propane/w oxygen concentrator set up in the States for a couple of years, I’ve modified my tip sizes preferences a bit. I’ve been using propane for years in Ukraine without choice opportunities. I prefer using a Victor TEN-2 tip when fillet brazing. The Victor #3 provides just a bit too big of a flame for me to feel as in control of the brass puddle as much as I do with a #2. It (the #3) heats up a broader area then I like. YMMV. The TEN tip (as a reminder) is specifically designed for propane. I do think that fillet brazing is the one area where it is a little easier to use acetylene (where my preference is a #1 tip). However I’m still able to get just as good results with propane.

For brazing fork crowns to fork blades or seat tubes to socketed bottom bracket shells I like a TEN-4. For lugs I can use a #4 but my framebuilding class students tend to like a smaller #3 or even a #2. It is a pick your poison decision. The bigger tips provide more even coverage but requires more instant attention to heat control. The smaller tips allow more time to understand/evaluate and move the flame away/around before bad things happen but requires a more precise flame pattern to get even heat coverage. My observation is that most students are more comfortable with a smaller tip size while they are learning because a bigger flame makes them nervous. I prefer using a #2 for braze-ons.

Here is a story about selecting the right tip size when I was apprenticing at Ellis-Briggs in England in the 70’s. Jack Briggs had an old friend/framebuilder come late afternoon on Wednesdays to help. I think mostly this was just so they could stay connected. My 1st question to him was what tip size should I use. His answer kind of surprised me. He said it didn’t make that much difference to him. A good builder could adjust his technique to work with various tip sizes.

[nspace]

Gave the torch a go today for the first time with brass. The only two tips I purchased were the TEN2 and TEN3 (based on Doug's recommendation). I have been using the TEN3 for silver brazing with the lugs, and for this I used the TEN2. After playing around with a couple of scrap pieces I decided to try fashioning a seat stay cap. I was pretty pleased with the way it turned out for my first go.

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I tried to fashion some sort of ring so that I could sweat the brass out (wish I took a photo!), but it didn't work like I thought. My idea was to tack upright, and then once the cap was on the tube, I would flip it upside down so gravity was on my side, and sweat the brass. For something like this, how would you guys create a ring? Like a long oval shaped ring to match the opening on the seat stay? How do you get it to stay in place and allow the cap to sit flush on the miter? I imagine it works best when the ring is touching a tube. I think I was able to get some of the brass to flow out, but ended up flowing in some brass around all sides with the rod. The end result turned out half decent (despite being a bit of a mess prior to clean up), but I'm sure there is a more efficient way to make the ring internally that I haven't figured out yet.

13048337124_1baf650cbb_z.jpg

[nspace]

Silver slip brazing is improving. I did a few joins this weekend with much improved heat control. Trying to keep my torch arm moving without burning up the flux in one spot. Felt rewarding to consistently do 3 of these in a row and got the silver to pull through the entire way around. The top ring I cut in half and could see a small sliver of silver all the way around on the tube. Shorelines are bit less sloppy too.

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[Alistair]

I tried to fashion some sort of ring so that I could sweat the brass out (wish I took a photo!), but it didn't work like I thought. My idea was to tack upright, and then once the cap was on the tube, I would flip it upside down so gravity was on my side, and sweat the brass. For something like this, how would you guys create a ring? Like a long oval shaped ring to match the opening on the seat stay? How do you get it to stay in place and allow the cap to sit flush on the miter? I imagine it works best when the ring is touching a tube. I think I was able to get some of the brass to flow out, but ended up flowing in some brass around all sides with the rod. The end result turned out half decent (despite being a bit of a mess prior to clean up), but I'm sure there is a more efficient way to make the ring internally that I haven't figured out yet.

Personally, I wouldn't mess with ring brazing on a SS cap. Since you'll be hacking off all the excess I don't think you gain anything from the clean brazing that ring brazing can offer. Most of any filler that flashes out on the SS cap during brazing will be removed when you trim the cap material to match the elliptical shape of the stay end.

I just feed the bronze at a few points around the circumference of the joint and chase it around with the heat until I've got a continuous fillet.









Alistair.

[nspace]

Thanks! I tried a ring of silver, and the result didn't seem as good as the brass one I did, plus I imagine with silver I may loose the cap if I tried to braze it onto a seat lug. I'll stick with practicing the first method as you described. I just got in the mail a nice long piece of flat stock 0.8mm stock and going to try a couple more attempts in the next week or so.

[Davey Smalley]

Great thread Doug, really helpful and I've read it all,

I'm putting together a workshop having built a frame with Peter Bird / Rob Wade from Bicycles by Design last year.

I have found a supplier in England for the Victor J-28 torch and other parts as per your list.
They are recommending I consider the 'Harris LD1390 Propane Brazing Kit' as it's a stock item, whereas they'll be a lead time on the Victor product.

It looks good and they consider the two to be equally usable for fine work and a more popular choice in England.
I'd appreciate any comments you or others have with the Harris torch and tips for Oxy/Propane brazing.

Many thanks,
Davey

[Doug Fattic]

I have found a supplier in England for the Victor J-28 torch and other parts as per your list. They are recommending I consider the 'Harris LD1390 Propane Brazing Kit' as it's a stock item, whereas they'll be a lead time on the Victor product. It looks good and they consider the two to be equally usable for fine work and a more popular choice in England. I'd appreciate any comments you or others have with the Harris torch and tips for Oxy/Propane brazing.

It took me a bit of time researching propane specific Harris mixers, elbows and tips that fit their 19-6 handle (that is in the package you indicated). From their catalog, it appears that you need the H19-2-S mixer (for alternative fuels) and not the H19-2-E (which is for acetylene). I make this point because one UK supplier I googled included the H19-2-E mixer with the package they described as the “Harris LD1390 Propane Brazing Kit”. You would obviously want to make sure you got the S mixer and not the E.

I also tried to figure out if their alternative fuel 1390-N tips (that screw into the D-50-C neck that attaches to the H19-2-S mixer) had a recess on the end that does a better job of keeping a propane flame attached to the tip than their acetylene cousins that don’t have that recess. I finally found one image that had a bit of an end shot that indicated it did. If I were you I would want to confirm that their 1390-N tips had a recess. Propane flames like to get away from a heating tip when you are adjusting the flame.

In the States the Harris 19-6 Handle has the larger “B” fittings (9/16”–18). The Harris 15 torch handle has the smaller “A” fittings (3/8”–24). I don't know what size fittings UK handles have and if that is different from ones sold on the continent. From pictures it looks like the fittings on 19-6 handle sold in the UK are not as large as our B fittings. In the States one would definitely want to buy the 15 handle since A size check valves and hose fittings are much smaller and lighter than B fittings.

One of the most important pieces of equipment in a propane set-up that makes me happy is lighter hoses. They don’t resist flame adjustment motions like a standard rubber hose does. I’m not sure what is available in the UK but something like our TM Technologies hose that is rated “T” for propane must exist.

I’ve used a Harris 19-5 handle in Ukraine. From what I can tell it is approximately the same as the 19-6. It certainly is a bigger and heavier handle than the Victor J-28. It weighs on my Park Tool scale (with an acetylene mixer and tip attached) 357 grams. The J-28 (with the UN-J mixer/elbow and TEN-3 tip) weighted 294 grams and has a much smaller diameter handle. This extra size and weight may or may not be important to you. I certainly like my J-28 better but YMMV. Some of my framebuilding class students like a handle with a bigger diameter than the J-28 like the Uniweld 71. For Stateside readers, my Smith AW1A handle with the AT-61 mixer/elbow w/56 tip weighed 263 grams. The Uniweld 71 handle with the Victor UN-J mixer/elbow and TEN-3 tip weighed 257 grams. The difference in weight between the various models was noticeable in my hand.

In the States some companies will state that their equipment works with propane but that doesn’t mean it was designed for propane. The Harris 19-5 handle I used with an H-16-E mixer and number 2 tip worked okay with propane even though it was designed for acetylene. It just didn’t work as well as my Victor setup designed specifically for propane. In the States Harris equipment is a bit more expensive and less common than Victor so it doesn’t get nearly the attention its competitor does.

[jclay]

I'd suggest going with equipment commonly available in your part of the world.

I also think its worth noting that a lot of successful, long time builders use larger and heavier torches; most I'd guess. You'll adapt to whichever torch you select. I started with an AW1A, had a Meco Av-Jet and then got a Meco Midget. They're all nice, the Midget my fave, but if I had to use a standard size torch (which I did several decades ago) for brazing it would be fine. I certainly spent far more time thinking about the "best" torch to get than was warranted when I started framebuilding.

Having recently had my second set of lightweight Kevlar hoses develop a leak I got a conventional 25' hose set. It's heavier and less flexible but it isn't a problem, doesn't affect my work and the extra length is handy. It's also a lot more durable. Being able to position the work so you aren't in an awkard position is far more important in my view. I don't see another set of Kevlar hoses in my future.

Just my perspective. Good luck regardless.

[devlin]

I'll throw my 2c in here as a newb. Due to available budget I've spent a long time hesitating on getting set up. I have a Harris dealer down the road but were getting close to $400 for torch, one tip, hose and regs. I looked around a bunch and had a chance to get a close up look at one of these... Professional OXY LPG Welding Cutting KIT NEW Plumbers | eBay and felt the quality was high enough for me. ie. it felt very well finished. It probably has a little bit of weight in it and the mixing knobs are at the bottom but id does feel balanced in the hand, like a good rod and reel set up.

I am just using my bbq bottle and ended up getting a size E oxy bottle (it was $aus71 and from memory the bottle rent is $aus16pm). I was trying to get a used oxy conc. off ebay and when it got to $aus400 I bailed. The decent ones are hideously expensive here and I am loathe to get one of the cheaper ones in case it's not up to the job. So all up I've spent $aus300 to get going and not have to borrow.

Anyhow, I got it setup and flashed it up today with the marked No.3 tip (haven't measured it yet). As usual there is a bit of separation when the propane is flowing too fast but got it sorted and the flame adjusts really easily and smoothly. I grabbed a bit of scrap mild steel tubing and pointed the torch at it. I was blown away at how quickly this thing got up to orange hot. Without brazing with it yet I am quite happy with my purchasers and set up so far.

[jclay]

Due to available budget I've spent a long time hesitating on getting set up.

Used equipment is readily available, at least here in the US, and can often be an excellent value. Pawn shops, Craigslist and similar are good places to check. Be a careful buyer, inspect and test the gear first, confirm compatibility with the fuel gas you intend to use and/or do whatever else is necessary for a successful purchase. I wouldn't consider obviously ancient or non-mainstream gear and if in doubt then new gear is always an option.

Also note that oxygen consumption with LP is 2 or 3X that accompanying acetylene use. That may, or may not be, a logistical issue depending on circumstances. Cylinder exchange is a bit of a hassle for me; when I used LP it was quite obvious. Use of an oxygen concentrator renders it moot and sounds like an interesting way to go, regardless of the fuel.