Rear Triangle!

Over the last week I've gotten the rest of the rear triangle done.  Step one was getting the other chainstay installed and adjusted to keep the rear wheel straight.  I was pretty close and it only took a bit of bending to get it to 90 degrees.  As before, I referenced the head tube to try to keep everything in line.

Then it was on to the seatstays.  I really like a particular kind of scalloped end cap.  It's made by brass brazing a piece of 31.8 tubing to the end, then cutting it out and filing it down.  I use brass because it won't melt when silver brazing the finished piece on the side of the seat lug.

Miter template and rough cut.

Finished miter and notch.
The notch increases the
surface area of the braze.

Trimming the excess, post brazing.

Stays: completed.

Attaching the stays was pretty straightforward.  A little pressure at the top and a pin in each dropout kept things in place while I got the first two brazes done, then I moved the clamp down to braze the tops.  Both were done with 50N silver because the bottom was a bit gappy and the top needed to build up a bit of a fillet for strength.

Brazed!

Jig Interlude

This is a quick one, but there'll be more this weekend.

Here's my home made jig.  I've got the front triangle (already brazed) clamped in it.  I'm using my incredibly intricate chain-stay angle/length tool to set it up for brazing on the chainstays.  I use a digital angle gauge while I jostle it around to find the point where the angles match up with my rattlecad diagram.  

Two quick points: 

1) This works way better with a rigid piece of metal.

2) Referencing off of the head tube instead of the seat tube should yield better results (with a little math).  If the seat tube is forward or back a half degree, you'll most likely be able to account for it with the fore-aft position of your saddle.  If the relative angle of your head tube and chainstays is off, your bottom bracket height will change as will some of the steering characteristics.

Cheers, have a good week.

HIGH TECH!