Originally Posted by
mikeread
Does this sound practical? Would it be better to use brass or silver? - I will be filleting the top tube with brass
Am I worrying unnecessarily - might it be easier than I think?
Would it be better to shorten the top end of the sleeve to just beyond the tube junction and then use a seat-tube collar/clamp at the top and leave the bit in between 0.6mm?
Any other suggestions?
What you show is how I do most of my non-lugged frames.
I have tried drilling a TT vent hole and pucker hole in the sleeve before brazing it to the ST. I could then use those holes to add filler when brazing the sleeve onto the ST - to get full penetration with long sleeves . It required drilling the holes twice though.
I remember reading somewhere that some guys don't go for full penetration on the sleeve. Just soaking the filler in an inch or so was enough in their experience. Since I turn my sleeves down to around .040" I prefer to have full penetration. If I was leaving the walls at the full .058" (1.48mm!), I might feel differently.
I use 56% silver inside the sleeve. Silver keeps heat down minimizing distortion which makes reaming easier and it's easier to flow all the way through and to clean up the flux. Generally, I try to use silver for this whole joint except the binder boss. Just a lot of good stuff comes from using silver here.
Before I braze on the sleeve, I 'groove' it longitudinally with a course round file. You don't have to go crazy but a few hard strokes around the inside of the sleeve will create little channels to help the filler to wick down between the sleeve and ST. I would trim the excess from the top to save silver and make it easier to flow the filler through the sleeve. You could also shorten the part that extends below the TT for the same reasons. I have done a few that extend a couple inches below the TT and when I look at them now, they look a little out of proportion. The flip side is that a bit of extra length in the sleeve adds some mass so the TT fillet is a bit easier . Using brass on the TT fillet might make sense depending on how you attach the seatstays.
I like a point at the top of the seattube and contour both the ST and sleeve together as the final step before cutting the ST slot. If using a clamp, place the clamp on the outside of the sleeve, not on the .6mm walled seattube above the shoreline of the sleeve. I haven't really looked at what clamps sizes are available though so, that would be my first step. You don't want to cut the sleeve walls down then find there aren't any clamps that fit!