Brazing Tab Type Dropouts

[Ahmdo Molah]

When I used to use tabbed dropouts, at last 12" of brass rod would be fed into each joint (that's inside...). I never used gravity; the parts were always on their side, and filler metal was fed in, and heat would draw it in left/right or right/left. ...

First, thank you sir, for your kind generosity and guidance.

I'm surprised by the relative scarcity of (detailed) videos online demonstrating 'Brazing Tab Type Dropouts', particularly demonstrating how to 'fill the big gap under the arch'.
I did find a video demonstrating most of the prep and brazing processes;
https://ms-my.facebook.com/ChapmanCy...5401013849050/

I've mentioned the video above as a 'visual reference' to make our written communication a bit easier. About half way into the video he begins to add filler from the tips of the 'half-moon', and capillary action sucks filler into the slots. Unfortunately, the process of 'filling the big gap under the arch' is not shown in detail(skipped) in the video.

When you mention, "filler metal was fed in, and heat would draw it in left/right or right/left," how is your technique similar or different from that shown in the video?

How do YOU 'fill the big gap under the arch'? (i.e. aim the flame into the tube and touch rod onto the dropout inside under the arch and build up to the top of the arch inside? Or add filler from the top inside the arch and let it flow down and build up?) It seems that there would be a limit to how much can be further added (with ease) from the slots once the gaps are initially filled.

[e-RICHIE]

There are few videos online because most of framebuilding, the profession not the hobby, precedes the internet and also died a slow death before its arrival. I haven’t seen the video you link. How do you / how does one feed the filler material into the cavity so the joint has integrity? Practice. Line up some twenty assemblies and braze them. Do it again. Pay attention to the differences each time. Sounds expensive, maybe even tedious? It’s a lot less of an investment than working years for free or little money in order to leave with the same end result. PS Take a brazing class too. This will expedite the learning curve.

First, thank you sir, for your kind generosity and guidance.

I'm surprised by the relative scarcity of (detailed) videos online demonstrating 'Brazing Tab Type Dropouts', particularly demonstrating how to 'fill the big gap under the arch'.
I did find a video demonstrating most of the prep and brazing processes;
https://ms-my.facebook.com/ChapmanCy...5401013849050/

I've mentioned the video above as a 'visual reference' to make our written communication a bit easier. About half way into the video he begins to add filler from the tips of the 'half-moon', and capillary action sucks filler into the slots. Unfortunately, the process of 'filling the big gap under the arch' is not shown in detail(skipped) in the video.

When you mention, "filler metal was fed in, and heat would draw it in left/right or right/left," how is your technique similar or different from that shown in the video?

How do YOU 'fill the big gap under the arch'? (i.e. aim the flame into the tube and touch rod onto the dropout inside under the arch and build up to the top of the arch inside? Or add filler from the top inside the arch and let it flow down and build up?) It seems that there would be a limit to how much can be further added (with ease) from the slots once the gaps are initially filled.

[Ahmdo Molah]

The finesse isn't so much in getting it in there, as not getting it everywhere you don't want it on the outside. ... .

To fill the 'cavity'(between tube arch and tab), do you keep feeding rod from the outside in(?) via the gaps between the tab and tube's slot(?) or feed directly into the 'cavity' from inside, perhaps each tip of the 'half moon' (from the inner side), narrowing the cavity towards the center, then add a final dab to fill a central hole?

Thank you

[jclay]

To fill the 'cavity'(between tube arch and tab), do you keep feeding rod from the outside in(?) via the gaps between the tab and tube's slot(?) or feed directly into the 'cavity' from inside, perhaps each tip of the 'half moon' (from the inner side), narrowing the cavity towards the center, then add a final dab to fill a central hole?

Thank you

Eric is spot on!

It really is a "feel", experience thing. Unless you're just "the guy", or very lucky, it will take a while to get this figured out reasonably well.

Random things:

• Definitely practice on some cheap parts you'll toss
• I use an AW204 size tip; (I'd use a 203 if I didn't have a 204...and I sometimes think I'd rather use a 203)
• Preheat the "rest" of the DO enough that it doesn't heat sink the heat from the braze area; big flame for that tip for this step; you want to preheat with alacrity...don't dally; heat from multiple sides for this step
• Focus heat on the DO, at the feed area, avoiding (overheating) the stay as much as possible until very near filler flow temp, angling into the bore a bit
• I do them flat, just a skosh down slope in direction of desired flow
• Fixture so you can flip it over easily without putting the torch down; I clamp a flat piece of metal or a round file or similar in the vise and slide the fat end of the stay over it
• Once filler can start to flow I turn the flame down a bit (it's still sizeable, just not maximum), aim the flame generally into the cavity to encourage it in that direction
• MOL half a rod per entire DO (half for for all of one DO/chainstay...maybe 1/3 for seat stay)
• When meaningful amount of filler is inside I start heating the stay too, just far enough, and just enough to make room for more, still aiming flame largely into the bore....I sorta flame brush the filler down the tube while feeding a bit more filler into the end trying not to get it so hot the brass goes everywhere
• Big flame for preheat (of heat sink areas of DO and initially the feed areas), smaller (but not tiny by any stretch) for the actual brazing; not red hot but enough so the heat you're trying to put into the braze area isn't thermo sucked to the back of the DO
• Turn it down even more to fill any pock marks that develop at finish time
• I flux only the areas that are to get filler, plus a little "feed approach area" on the DO..."brass" likes to run everywhere; I no longer slather flux everywhere; I do apply and then finger wipe off flux down the stay for some inches, just as oxidation protection of the stay
• I'd hate to use LP for this operation...needs the heat well focused, not everywhere; many use LP but it certainly wouldn't make my life easier for this operation!
• Did I say to do some practice stays/DOs first? You'll be really, really glad you did.

[Ahmdo Molah]

Eric is spot on!

It really is a "feel", experience thing. ... it will take a while to get this figured out reasonably well.

Random things:

• ...
• Preheat the "rest" of the DO enough that it doesn't heat sink the heat from the braze area; big flame for that tip for this step...
• Focus heat on the DO, at the feed area, avoiding (overheating) the stay as much as possible until very near filler flow temp, angling into the bore a bit
• I do them flat, just a skosh down slope in direction of desired flow
• Fixture so you can flip it over easily without putting the torch down...
• Once filler can start to flow I turn the flame down a bit (it's still sizeable, just not maximum), aim the flame generally into the cavity to encourage it in that direction
• MOL half a rod per entire DO (half for for all of one DO/chainstay...maybe 1/3 for seat stay)
• When meaningful amount of filler is inside I start heating the stay too, just far enough, and just enough to make room for more, still aiming flame largely into the bore....I sorta flame brush the filler down the tube while feeding a bit more filler into the end trying not to get it so hot the brass goes everywhere
  ...
• I flux only the areas that are to get filler, plus a little "feed approach area" on the DO..."brass" likes to run everywhere; I no longer slather flux everywhere; I do apply and then finger wipe off flux down the stay for some inches, just as oxidation protection of the stay
• I'd hate to use LP for this operation...needs the heat well focused, not everywhere; many use LP but it certainly wouldn't make my life easier for this operation!
• Did I say to do some practice stays/DOs first? You'll be really, really glad you did.

Thank you sir, for the detailed clarifications above, as well as those in other threads such as your numerous counterpoint to Doug Fattic's clarifications. They will ever be kept in mind with gratitude.

I understand (in general terms) the importance of practice as you and Richard have mentioned and that, "it really is a 'feel', experience thing. ... it will take a while to get this figured out reasonably well."
Even after certification for structural TIG welding, it took me at least 2 years of intensive practicing with thin walled steel and aluminum, making custom purging hardware/heatsinks(for steel), cutting up & etching to check penetration, photo logging all dialed settings, and making note of particular points of progress, to get the 'feel' of gettin' it done well.

I have quite a bit of relatively cheap tubes and plates for use as DO-stay mock ups, and look forward to enjoying practicing A LOT to reach the point when I can say 'I got the feelin~ '...

Cheers~

[Eric Estlund]

I generally tack the tips of half moon then face fill onto the drop out to fill the chamber. You can practice my trying to close open small diameter tubes, and with that practice how deep you fill. You can fill say an 1/8" on one, and a half inch on another. This will also help you understand how much rod is going in and where it is going.

[Ahmdo Molah]

I generally tack the tips of half moon then face fill onto the drop out to fill the chamber. You can practice my trying to close open small diameter tubes, and with that practice how deep you fill. You can fill say an 1/8" on one, and a half inch on another. This will also help you understand how much rod is going in and where it is going.

Thank you Mr. Estlund.

After reading your response, I reviewed the video I linked of Brian Chapman brazing the front DO, stopping the video along the way to catch the very brief shots of filler dabbing, and realized that the very first tack he makes (to the front slot of the DO) is actually from inside the chamber along the slot & DO. Capillary action draws the filler inside-out and all around the joint between slot & DO. THEN, he dabs the tip of the 'half moon' towards the backside of the DO, but has the rod vertical and NOT aiming inside the chamber - this I think is due to the camera being in the way as he mentions shortly afterwards.

Also, I was able to catch a few very brief frames in which he points the flame (and the 'tongue tipped' rod) toward the chamber(as John mentioned). The frames are so brief it's not possible to make out how it looks when the chamber(cavity) is gradually filled up, but it's a good starting reference especially with clarifications in this thread.

[Ahmdo Molah]

BTW, if anyone has or encounters a detailed video of 'Brazing Tab Type Dropouts' (other than the one by Chapman Cycles linked above), I'd love to see it! Thanks~

[Eric Estlund]

Not sure if it will help, but :

https://www.flickr.com/photos/225387...in/dateposted/

https://www.flickr.com/photos/225387...in/dateposted/

https://www.flickr.com/photos/225387...in/dateposted/

https://www.flickr.com/photos/225387...in/dateposted/

[Ahmdo Molah]

Not sure if it will help, but :

https://www.flickr.com/photos/225387...in/dateposted/

https://www.flickr.com/photos/225387...in/dateposted/

https://www.flickr.com/photos/225387...in/dateposted/

https://www.flickr.com/photos/225387...in/dateposted/

Every minute detail helps greatly. Your flickr postings are a treat!
I see why a stationary camera would inevitably get in the way during this process, as you physically move around to heat, inspect, and add filler.
Perhaps a good way would be a forehead mounted GoPro/mini camera or similar to move with the brazer.

As I clicked play/pause repeatedly for intensive frame by frame inspection of your technique, I accidentally stumbled upon your source or inspiration;
https://www.flickr.com/photos/225387...n/photostream/

[Doug Fattic]

Jihoon, it has got to be said even though it is totally in my self-interest to say it. The easiest, fastest and best way available today to learn how to braze, file and build a frame is by taking a class from an experienced builder/teacher. I’ll use as an example the middle aged Korean/American (he came to the States 20 years ago) that just finished my 3 week class. Before he came he had no idea whatsoever how a frame was put together. Absolutely none. He had never heard of brazing before. He left with a professional quality frame because he was determined to learn how to get good results. Of course I had to help on some hard parts but after an explanation, demonstration and practice on each joint type, he did almost everything himself. There was a LOT of repetition involved before he did it for real. I’ll show you some pics of the frame he made starting with the brazing and filing he did on tab dropouts. We took a couple of extra days after class to paint it red.

IMG_3347 2.jpegIMG_3343 2.jpgIMG_3346 2.jpgIMG_3360 2.jpg

[Ahmdo Molah]

That's some fine teachin' ...! If you were within driving distance, not overseas, and the corona bug dropped dead, I'd probably be knockin' your shop door by now... mm!

[jclay]

Jihoon, it has got to be said even though it is totally in my self-interest to say it. The easiest, fastest and best way available today to learn how to braze, file and build a frame is by taking a class from an experienced builder/teacher.

As my self interest is limited to personal intellectual integrity I'll echo, with slight elucidation, what Doug said:

Quality instruction is always the most time efficient and easiest way to learn, regardless of the subject area.

I'd suggest that "best" is overly broad, a bit more fuzzy and depends upon circumstances, allied experience, proclivities and personal goals; whether or not instruction is more cost efficient, or even feasible, depends upon the same sorts of details.

Twenty years into amateur frame building and I don't know whether or not I'd have saved $$ by taking a class, and if money is limited then one has to weave that into the decision to spend a fair bit of it on a class. But there is no question that my current skill level would have been attained more quickly via a class like Doug's and I'd have enjoyed it immensely. Having said that, and knowing what I know now, if I could turn the clock back I'm not sure what my decision would be (and I can/could afford it). Sometimes just banging away and learning solo is gratifying in and of itself, and the $$ nice to have for other stuff. And then there often times the intangibles gained only by the uninstructed or poorly aimed arrow. Education, no matter whether via instruction or self directed, is never cheap!

If I was intent on trying to make a living in the frame building world, alacrity would be important to me and I'd certainly take a class....unless some wise person was able to convince me that doing so wasn't probably a terribly sound way to make a living! Few can pull that rabbit out of that hat, long term.

Aside from those sorts of details, I think Doug's class would be stellar and a boatload of enjoyment.

[Ahmdo Molah]

I've been practicing with mock-ups.

Mock-up Tab Dropouts (for Brazing Practice).jpg

Sample No.9.jpg

Sample No.9 (Internal).jpg

Recently, an air pocket on one side has been recurring in various sizes only on one side.

1. What is causing the air pocket and is there a way to prevent it?

2. Regarding the blackened flux spots, is this due to too much heat, lack of flux, and/or flame setting*?
* I try to set and maintain the flame on the 'border' of reducing & neutral.

3. If the blackened(hardened) flux occurs internally as in the sample above, could this (if left intact) cause an issue even if the flux is supposedly non-corrosive? And is there a method to remove such internal spots other than an acid treatment in a real tube/dropout joint?

[e-RICHIE]

Very cool!

I've been practicing with mock-ups.

Mock-up Tab Dropouts (for Brazing Practice).jpg

Sample No.9.jpg

Sample No.9 (Internal).jpg

Recently, an air pocket on one side has been recurring in various sizes only on one side.

1. What is causing the air pocket and is there a way to prevent it?

2. Regarding the blackened flux spots, is this due to too much heat, lack of flux, and/or flame setting*?
* I try to set and maintain the flame on the 'border' of reducing & neutral.

3. If the blackened(hardened) flux occurs internally as in the sample above, could this (if left intact) cause an issue even if the flux is supposedly non-corrosive? And is there a method to remove such internal spots other than an acid treatment in a real tube/dropout joint?

[Ahmdo Molah]

The following is Sample No.10.

Sample No.10.jpg

Sample No.10 (Internal).jpg

I think the 'air pockets' may have been caused by flux. In the example above, I luckily split a small ball of flux which did not get pushed back with the rest, which this time did not get toasted.

Perhaps I've been adding filler too soon before all the moisture of the flux had sufficient time to escape or before the flux was 'ready' internally?

I'm still a bit concerned about the flux that doesn't dissolve easily inside the joint. Perhaps I need to soak in hot water longer?

Or... perhaps the white/grey crusty stuff is zinc oxide (due to zinc vaporizing out of the filler)?

I'm at least relieved that there has been improvement with each sample.

[Doug Fattic]

it is difficult to diagnose a finished braze without seeing the brazing process itself. It appears you got your joint too hot. The evidence is that your surface around the black spots is not smooth and the cooper color is an indication the bronze got so hot the cooper separated out. There can be several reasons for this. Probably you held the flame on the joint too long before flicking it off. There are several ways to control the heat at the joint. A common way is to flick the flame off just when you see the metal is starting to get too hot. That is when the joint color is going from a cherry red to a lighter color. Use a compact motion because it only takes a nano second for the joint to cool down enough. Rookies tend to take too long to bring the flame back to the joint because they have moved their flame too far away.

Always the problem when brazing is that you are coordinating moving both of your hands at the same time. Most people can keep track of doing one or the other but not both at the same time. One of your hands needs to be moving by muscle memory.

Another heat control trick when doing dropout brazing is to move your flame back as your other hand holding the brass is moving forward as it melts. It is natural for 90% of my students to want to move their flame forward (increasing the heat on the joint) instead of back. It takes practice to unlock that natural trend for both your hands to want to move in the same direction at the same time. In Western culture people try to pat their head and rub their tummy in a circle at the same time and most who try get funny results.

Try this trick to show the problem and to practice unlocking your hands trying to move the same way. Point a left and right hand finger at each other. Start by making one finger circle the other. Then try to get the other finger go in the opposite direction. What happens is that your 2 fingers will be like 2 pursuit riders on a track. They will both be going the same direction. What you want is your fingers going in opposite directions like one rider turning left and the other turning right so if they were not careful they would crash head on. Try it. At first when someone finally gets their fingers to go in opposite directions, they will not be making a circle but rather an ellipse. Eventually with practice the circles get rounder.

[Ahmdo Molah]

I performed a second hot water soak and the white/grey matter in Sample No.10 dissolved confirming it was flux. On one of the spots(right half/left side) the dissolved flux revealed a small 'cave' from which the flux flowed (or where the filler got sucked out towards the side opening).

Sample No.10 (Internal 2nd Soak).jpg

it is difficult to diagnose a finished braze without seeing the brazing process itself. It appears you got your joint too hot. The evidence is that your surface around the black spots is not smooth and the cooper color is an indication the bronze got so hot the cooper separated out. There can be several reasons for this. Probably you held the flame on the joint too long before flicking it off. ...

Mock-Up Tab Joint On Ceramic(Alumnia) TIG Cups.jpg

I've been placing the mock-up tab joints on a pair of old TIG cups(alumina ceramic) joined by a bent steel welding rod. I'm brazing in my mini hearth and heating/filling while flipping with pliers to let one side cool a bit and work on the other side. I'm using the Meco(TM Technologies) OX No.3 tip on a Smith AW1A torch, the fuel is butane, and the oxygen is 93~94% O2 from my DeVilbiss 515 O2 concentrator.

The copper color has been buggin' me as it is a sign that the zinc is being zapped away.

I definitely have not been flicking off the flame quickly enough nor frequently enough as you suggest to keep the temperature steady with a dull("cherry") red, but rather tended to let it get bright("lighter") red then back to no glow at all during the flipping to the other side. It cools surprisingly fast, and my 'put down the rod then flip sample with pliers' can be distracted/delayed by 'sticky flux on the TIG cups' initially.

... Another heat control trick when doing dropout brazing is to move your flame back as your other hand holding the brass is moving forward as it melts. It is natural for 90% of my students to want to move their flame forward (increasing the heat on the joint) instead of back. It takes practice to unlock that natural trend for both your hands to want to move in the same direction at the same time. ...

I've been doing what 90% of your students have been doing - keeping the flame up close as I push down on the rod to fill. I think this is due to my TIG welding conditioning. I'll try the 'push-rod/pull-torch' on the next session.

Thanks Doug!

[steve garro]

E4DA654C-F921-45A6-83A5-81D1FF000A36.jpg

If you shove 1/2 a 1/16th" bronze rod evenly into one of those joints, it's all good.

- Garro.

[Ahmdo Molah]

E4DA654C-F921-45A6-83A5-81D1FF000A36.jpg

If you shove 1/2 a 1/16th" bronze rod evenly into one of those joints, it's all good.

- Garro.

Thanks for your pointer Steve. I'm using coiled 1/16" Gas Flux C-04 wire, measure cut and straightened to a rod's equivalent length, then splitting these standard rod lengths in half for each side of the tab, instead of using one continuous rod throughout the process, as this allowed me to keep track of how much got 'shoved' in per side(i.e. If I flipped the joint, I'd use the designated half rod for the current top side).

Therefore, in my samples above, I've been 'shoving' in twice as much as what you and John have advised(!). Oh dear... But of course my samples are mock-ups, not real chainstays(nor dropouts), so the cavity may be larger.

I was aiming to fill according to the Paterek Manual (as suggested in the drawing on p. 2-46 "Braze filled" Dropout Joint), with a bowl shaped internal fillet and a full fill all the way out to the opening of the joint.

Paterek Manual (Brazed Dropout Joints).jpg

The depth(length) of fill is not clearly defined in the drawing, so I assumed that the base of the bowl shaped internal fillet should start near or at the internal edge of the dropout (as is shown in the 'Simple braze' drawing).

In your joints and that of Eric's, the filler is not "topped off" to the very edge of the tube's half-moon openings. I assume this is because the strongest tensile strength is at and near the slots where the gap between the materials is least, and that the larger gap of the cavity is comparably of secondary concern, perhaps one more of aesthetic preference(?).