I have been working with 6061 for the past few weeks and having a blast. I just finished a BMXish 24" wheeled bike and have a few track bikes going now with aerodynamic tubing. Ill get the track bikes up when I get a little further along.
I made many of the parts of this BMX frame. It has a butted top tube and seat tube but the balance is drawn straight gauge. The dropouts are slotted 12mm through-axle with built in tugs but only the set-up parts are shown.
30 418 by
frankthewelder, on Flickr
30 419 by
frankthewelder, on Flickr
By flipping a brake adapter around I was able to make a brake mount that allows over 25mm of wheel adjustment with good pad coverage but rotating the assembly on a slot.
30 420 by
frankthewelder, on Flickr
30 421 by
frankthewelder, on Flickr
massive 49mm head bearing holes and shaped gusset.
30 422 by
frankthewelder, on Flickr
30 426 by
frankthewelder, on Flickr