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Building the rear triangle
I had a spare lugless bottom bracket that I used to set up the chainstays. First, I mitered the chainstays where they fit against the bottom bracket, getting them as close as I could. Then, I cut them equal lengths (for an 18" chainstay length), and mitered the end that fits at the dropout (they are "Breezer" dropouts, purchased from Gaerlan, see the 4th photo down).
 The proper 135mm spacing is drawn in pencil on this flat piece of plywood; I used the drawing on this plywood to line it all up.
I needed to crimp the inside of the chainstays to provide extra room for fenders and tires. I drilled a 7/8" hole in a piece of redwood, and sawed it in half (the stay is 7/8" at the fat end). Then I placed the tube in the channel, and put the dents in it, using the item in the photo above (which I found on the highway on a bike ride). It has a rounded shape that worked well with this task. I put a piece of cloth first aid tape against it in an effort to keep the dent smooth.
 It took about 20 hits with the hammer, as I moved along the area that I needed the clearance in.
After all that mitering and denting, I have the tubes together, braced at the bottom bracket, and held with bricks  at the dropout end, and finally, a short chainstay bridge at the proper distance in the middle.  This bridge I tacked in place; then removing the assembly and brazing it all around on both sides. I ended up with a pretty accurate chainstay assembly. There is some sheet metal there to keep a fire from starting on the plywood when I did the tacking.
Next, I put the dropouts in a properly dished wheel, and lined them up together, and tightened the quick release. Then, I placed it on top of the already mitered chainstay assembly, checking for alignment. It was perfect- the wheel was right in the center. So I brazed the dropouts in place, and this is how it looked. Some framebuilders would recommend tig welding this connection, since there is not a lot of room for laying brass up. Brazing was all I could do, and it seems to hold up fine after many thousands of miles, so I'm not worried about it.
 This Breezer dropout allows one to simply miter the tubes against it and braze. There is no slotting like the standard dropouts. Also, you don't need to flatten the inner chainstay in the area next to the freewheel cog, to get the required clearance, which is something one must do for the slotted dropouts. Salsa makes a similar dropout.
Okay! Now I am checking for the alignment of the rear wheel with the top tube. The rear wheel with it's chainstays are balanced; resting on top of the bottom bracket.  I would put a straight edge in front of my line of vision to make sure.   It is off, as you can see in this photo.  I filed the left (non-freewheel side) chainstay where it meets the bottom bracket a bit more, and finally got it centered, so that the wheel was directly in line with the top tube. After brazing (if I had to)  I could always cold set these tubes, so that the wheel would be parallel with the seat tube. But I couldn't change the chainstay length. With these vertical dropouts, I had to get it right. With horizontal dropouts, it wouldn't have mattered as much, since the wheel can be adjusted after it is fitted in.
Now is the time when I braze the chainstays onto the bottom bracket. I put the wheels on the bike, and I have the fork installed with the headset. The wheels are on with the  tires inflated. I have a clamp holding the chainstays against the bottom bracket. The piece of wood props up the bottom bracket so that the center of it is 10 1/4" from the ground (or flat board, as is the case here). This will provide the proper bottom bracket drop. The tires chosen are the smallest width I intend to use, so a larger tire would result in a higher bottom bracket. I checked the alignment of the rear wheel with the seat tube- and it looked exactly parallel. This is my last chance to change the head tube/seat tube angle, at the expense of the bottom bracket height.
 The angles looked accurate, and the miters looked tight, and the rear wheel  was aligned properly, so I prepared to braze. I fluxed the whole area well, and brazed the outside of the chainstays to the outside edge of the bottom bracket, making sure brass flowed into the crotch of the joint, but not building it up yet. Then I carefully took the wheels out and positioned the bike for completion of the chainstay brazing (with the chainstays pointing up to minimize gravitational forces on the presently weak connection during reheating). I lay down fillets at the chainstay/bottom bracket joint. Then I finished the seat tube brazing where it meets the bottom bracket at the same time.
 When it was all done, everything was is good alignment, and I didn't need to do any cold setting. The installed rear wheel was in excellent alignment with the seat tube and top tube. Again, I just eyeballed it with a straightedge held against the wheel.
Now all I had to do was to cut, miter, and drop the seatstays in the space provided.  I cut them a bit long,, and mitered the end that fit against the seat cluster. I did this for both of them, making sure they were equally spaced apart, and with enough clearance for my intended tires and fenders.
Looking into the seatpost opening you can see the results of what a rather dull reamer will do-- there is some scoring visible. More patience with smaller adjustment increments and extra cutting oil could have left a smoother result, too. The clamping strength will be adversely affected, but not enough to make any difference on this bike.
The connection at the dropout took more time, as I could only file it shorter, and it had to fit a steep angle at the dropout. Here it is, ready to flux and braze.
How I learned to brass braze:  I learned that the brass follows heat and gravity. In time, I had a feel for the proper tube temperature by the red color of the tube, and the appearance of the flux. If the brass did not flow easily onto the tube, the tube was not hot enough. If it sizzled and danced, it was too hot. I could make a little of it go uphill by moving it with the heat, but for the bigger fillets, I found I needed to arrange the tubes so that the brass could lay down and rest with gravitys help. This had me moving the tubes around as I was brazing, and it made having a bike stand rather invaluable.
 First I got my tanks and Victor torch, with a 00, 0, 1, and a big #3 tip. The  00  I used for braze ons, and small tubes. The  0  I used for main tubes. The  1  I used for the bottom bracket area; a bigger tip with more heat made it easier there. The  #3  I used for a big flame to heat bigger castings, like the fork crown, and I held it back further than usual (like 3 - 5 inches). I started with hardware store flux-coated rods first. The flux from those rods was really hard to remove. Then I got some Welco #17 flux that Mr. Patereck recommended, and used 1/16 bare bronze rods. .This left a residue that was much easier to remove, with a 10 min. hot water soak and a wire brush.
. Later, safety became important, and I installed a fan, pushing fresh air into the work area so I would breathe less fumes. I would have a hose turned on and ready to put out a fire (that never happened).
 Just like mitering, brazing takes plenty of of practice. There is more than one "right" way to do it. It is considered to be easier to learn that TIG welding. Since you need to do at least some brazing on a frame anyways,  you could just as easily use brass for the whole bike. Using lugs is an excellent construction method also, but more time consuming, and limited to finding the desired lug, with it's size and angle.
  The Framebuilder archives on the internet is an excellent source of advice and information.
I put the wheel in as a reference. I wanted to make sure I had enough clearance for big tires and fenders, as previously mentioned.
After finishing the seat stay installation, I started work on the brake bridge. This is a brake bridge I got from Gaerlan. Putting the brake bridge in was easy enough, but time consuming. First I cut it down (it was quite long). Then I mitered it, and kept mitering until  it fit in the increasingly narrow space, as I moved it upwards. The pads of this long reach brake at full extension needed to be at the right place on the rim. The brake was left in place, acting as a jig, while I tacked the brake bridge. I removed it to complete the small fillets around the bridge.
It's going to need a long bolt to clamp the seat post.  I cut the slot with the angle grinder, and will drill a small hole at the base of the cut, for stress relief.
 
The brake bridge is crooked- how did I let that happen?! I suppose the brake being in the way during tacking obscured my view. It's not noticeable with the brake installed, though.
The seatpost clamping is really solid, and I can't see the slot  coming together at all when I tighten it. I had one frame where the seatpost clamp deteriorated under pressure, and the ears met without holding the post. That will never happen to this one.
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