Seat stay attachment - newbie question

[mayan42]

Frame number 1 is progressing, and I'm at the point where I need to attach the seat stays. The frame is a lugged 700c road/cross/gravel bike, I've used sif bronze 101 brass for the lugs, but I have a couple of questions re joining the seat stays (which I've already attached to the caps and intend to join them to the side of the seat lug.)

I've used brass for the seat lug, I also have 37% silver which I've used for the bottle bosses and will use for the other braze ons. I've read that the lower melting temp of silver will prevent the brass in the seat lug melting when I heat the seat lug for attachment, but will the brass be stronger for what seems to be a slightly compromised method of joining the seat stay to the seat tube?

Also, vent holes, I'd prefer to keep the vent holes hidden, so is it sensible / possible to put vent holes feeding into the seat stay bridge? Presumably then I'll need to vent the bridge when I attach that? Can I make that hole a 2mm hole and then simply pop a rod in the hole and seal it after I've brazed in the bridge?

So, in brief, silver or brass for attaching the seat stay to the seat lug?
And where do I put the vent holes in the seat stays?

Thanks,

[Andrew R Stewart]

For a first timer I'd say brass for the stay/lug joints. Brass is 'more forgiving" for prep, fit up (and I'm not sure the 37% silver's spec anyway). As long as you don't really cook the joint you won't likely see any brass flow out of the previously done lug. My advice might be different if you had used silver for the lug.

As to vent holes, I have used a number of painters over the years and one of the constants has been their dislike for vent holes. Liquids and blasting media get trapped inside tubes and no mater how well you try you mask off or clean out karma says that something will trickle out at the worst time. So place vent holes where you can seal them if you don't want to see them. I now use two per tube. Allows best clean out of flux and such then for the stays/blades i plug them. For the main triangle i use larger holes and leave them open. For stays my vent holes are near the ends and rotationally located to make plugging and finishing the plug easy. Andy.

[mayan42]

Thanks Andy,
I was leaning towards brass, from my limited experience, I cant imagine it would be easy to build a fillet around the seat stay cap with silver - I'll try not to cook the joint!

So if I put 2 vent holes in the stays, on the inside (wheel side), one at the bottom and one at the top, can I place the bridge (a short tube) over the upper holes to hide them, and also allow the bridge to vent during attachment? Then seal the lower holes after I've finished the bridge?

[Andrew R Stewart]

Yes, you can do the vents as you describe. But I won't any longer. The hidden hole will still be able to take in soak tank liquids or blast media. I say to either seal all (which is what i do) or leave two relatively large holes (allowing the flushing out of any stuff that does get inside). Andy.