Brazing Tab Type Dropouts

[William Chitham]

In a strictly amateur capacity I'm inching towards a first frame and am currently practicing brazing tabbed type front dropouts. I assumed when I started that the space between tab and tube should be entirely filled but I'm finding it very difficult to fill very far up and having cut up a couple of old factory made fork ends to find very little filler in them at all I'm wondering if I'm trying too hard. Photo shows an early attempt, I've done another half a dozen since with varying success. Any advice on how to tackle this joint would welcome.
Thanks,

William.

IMG_3463.jpg

[e-RICHIE]

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. There's no magic bullet. Use a big flame and according to my opinion a hot flame.

[William Chitham]

There's no magic bullet. Use a big flame and according to my opinion a hot flame.

Not too much finesse then, eg trying to "plug" it in deep then backfill as it were, just get plenty in?

[Eric Estlund]

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



*Better to have to file some away than starve the joint.

[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.

[e-RICHIE]

Not too much finesse then, eg trying to "plug" it in deep then backfill as it were, just get plenty in?

It's 100% finesse atmo. Channel Hendrix lighting his guitar on fire, and willing the flames in the direction he wants. Then, do it with a torch and flowing brass.

[William Chitham]

Thanks, I'll give it a go. Move over Rover....

W.

[William Chitham]

Tadaaa - loadsa brass:IMG_3504.jpg

But a bit cooked:IMG_3505.jpg

It takes some time to get all the filler in and I'm finding it tricky to keep the heat under control but I heard practice makes perfect...

Thanks for the help.

William.

[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.