so lets talk about .028
 

I saw it mentioned in another thread. Was it used in building a fillet brazed frame? was that the issue? I want to do a bi-lam frame with .028

I used a 0.028 top tube on my bilam. The sleeves more that doubles the wall so it should be fine for fillet brazing I think! Well I'm not experienced, so I hope.

it's a little on the thin side, but I suspect it's ok, particularly in a bi-lam frame with an experienced builder. I went with .035 in my daughter's bike, it's a little on the heavy side.

What is the question? Structural, working properties? All I really know about it is that they make ultralight aircraft out of the stuff, not just the ribs, but main structural spars. Based on this, and the fact it can be welded in these sizes I made the suggestion it was sorta stupid not to use it on frames which is what got me banned from Frameforums, back when you could be banned from them. At some level anything you can do with 6/4 you should be able to do with this stuff. I like to collect dimensions, and I was interested to note Rob English uses .028 in his 3/8" seat stays. I figured it could be .035 or larger, the Bontrager sizing is .058. and .035 in 5/8", stepped o 1/2" as far as I recall, so his scantling seems very small. I can do what I like though since I don't sell anything.

(.028 is a higher ratio of wall thickness on a 3/8" tube, which is a point worth noting in some application)

That's interesting PP1. I was just looking at an old Columbus catalogue. PS tubing, 0.71 mm straight gauge, i.e. 0.028". For track riding (sprint, 6 day, pursuit) and 58+ cm frames according to the brochure. But I guess track bikes don't go through pot holes and see heavy braking. Anyway. I might have done my bilam with a 0.028 seat tube as well (not downtube), but couldn't find one in 1.125". Perhaps that's a good thing.

Also, I really like the 50s CCM Flyers. 3/8" stays as well. I'll check the wall thickness next time.

I was on of the early employees at Yeti and we built everything from .035 wall 4130. Chainstays, seat tubes,downtubes. everything. and with no gussets. We buit bikes that won all the downhill races including the Kamakazi under myles, Missy and Tomac and I am pretty sure I have never seen a Yeti FRO missing any big frame parts.

For years I have been getting comments regarding all the damage TIG welding does to tube yet I am quite confident I could TIG weld a reliable .028 frame for road or MTB with some shaping and small gussets. It's interesting that someone would be flamed for suggesting straight gauge material. I wonder if brazed frames in .028 typically fail?

FT, what would be the standard tube set for those kinds of Bikes. So all in .035": 1.125 seat tube and top tube, down tube?; Seat stay (there is the bontrager but isn't the upper end .058"? Chainstay, would .875 be the norm?

To be fair to frame forum, I try to keep the sass out of posts, but I may have torqued my comments a little to suggest that since one ought to be able to assemble. 028 with TIG (and it goes without saying with the orther methods, though I leave that up to them to say), that there was something a little silly about all this butted tubing. I wasn't serious or all that sassy, but I think the guy over there was going through hot flashes where one day he was all open to any post, or vehemently opposed to anything that wasn't best UK practices from 1950.

I think we all can be a bit brusque from time to time. We used 1-1/8 seat tube (that started SG then collared then bulged later, 1-1/4" top tube (also the bi-round) and 1-3/8" down tube. We did all the rears in 3/4X .035 but had issues with the bends where they were stretched a bit.

I get email from one of those frame building groups. Lots of good information. There certainly is a faction of folks going for maximum correctness.

Ft thanks for the help!