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.

[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.

[Michael Gordon]

It isn't too often that we have the opportunity to cut apart a frame built by one of the masters, but I had just that chance.

These pictures are from a Ron Cooper - 60th Anniversary Edition frame, I think from 2006. My friend who gave it to me was riding and got hit by a car, crushing the rear end. The seat stays were bend above the brake bridge, the wheel was shattered... squeezing together the dropouts, and the chain stays were bent shortly behind the chain stay bridge. The accident occurred in 2013, and when it took the computer apart it read some 12,000 miles. I'm not sure if they were all on this frame, but my point is that this frame was ridden a lot!!! He also has a Cooper from the 70's which he also rides, but now mainly as his indoor winter bike. Point being, his Coopers have held up.

After the accident, not a single joint failed, nor did they show any signs of stress (that I could see anyway). The pics below show the amount of filler material in a typical Columbus style tab style dropout, and the amount of filler material in the break bridge which had no reinforcing diamonds.

IMG_0856.jpgIMG_0858.jpgIMG_0859.jpgIMG_0860.jpgIMG_0862.jpgIMG_0864.jpg

[William Chitham]

Thanks Michael, interesting photos.

William.

[jclay]

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.

William,

Exactly how did you position the workpiece to accomplish that? With the stay horizontal and the dropout flat? If so, did you flip it over to do the other side.

Thanks

[EricKeller]

heh, you got enough brass in there all right. If you have some idea of how much you fed in on the over-filled side, you can back off by that much now.
I hold the stay vertically because that's the way I've always done it, and it allows access to the whole dropout at once. I never really thought about gravity, heat is what moves filler around for the most part.

[William Chitham]

I did try to put too much in on this one, if you never go too far to you never know how far you could have gone. I did do this with the "tab" horizontal, flipped over halfway through. It seemed the natural way to do it but I'll try one vertical next time.

William.

[bencooper]

I mostly do them vertically - get everything decently hot and it'll suck in beautifully. Get a reasonable amount in there but don't obsess about getting loads in - as the old frame up there shows, you don't really need an awful lot.

My rough rule-of-thumb for how much brass to use anywhere is that brass is about 1/3 the strength of steel, so use 3x as much of it. If the steel tube is 1.5mm thick, get a 5mm thickness of brass in there etc.

I've never seen a dropout fail because of lack of brass - they always fail at the thinnest point before they enter the tube.

[e-RICHIE]

Do them horizontally atmo. If nothing else, the flow of heat (rather than gravity) will draw the material. And more importantly, the HAZ will spread outward at a much slower rate of speed than if the object was held vertically. That's especially true on main tube joining as well.

[Dazza]

I have a collection of mild steel nail sizes in boxes in the drawers under my bench
I clean, cut , file and fit them to reduce the cavity to fill
I feel like a failure when pin holes appear, and I never expect the painter to cover my short comings with technique
so the steel fillers make a big difference to the fill
and it only takes 5 mins.
I used to do it horizontal but now do it vertical, more fun for me
That is my take.

[waterlaz]

I find it both funny and a bit disturbing but the more I braze the dropouts the more I struggle with each next one of them, or so it seems.
I think I'm starting to have problems when the joint gets full of brass and it becomes hard for me to control the heat, since the brass inside easily transmits heat all over the place.

[Andrew R Stewart]

I find it both funny and a bit disturbing but the more I braze the dropouts the more I struggle with each next one of them, or so it seems.
I think I'm starting to have problems when the joint gets full of brass and it becomes hard for me to control the heat, since the brass inside easily transmits heat all over the place.

It's the "more you know the more you know you don't know" thing. As you progress up the learning curve you have more and more to keep track of and it can be overwhelming. But in time you get more comfy with bits and aspects of the process, start to relax and work from muscle memory. Your brazing get's less anxiety filled, you see a step ahead and results get better/more consistent.

Keep practicing. Andy.

[Cynikal]

I have a silly question after reading this thread. I've only done socketed dropouts up to this point. Do you angle the slot when you cut it or do you bend the dropout after brazing?

[Clockwork]

I used to angle the slot but now I prefer to bend the dropout.

[Cynikal]

Thanks!