Saturday, June 30, 2012

Making Stays

The seat stays connect the dropouts for the rear wheel to the junction of the seat and top tubes.  On the dropout end, I attach a cap that slots into the rest of the dropout.  The inside of the cap has some curves to it, so I started by filing the stay to match.  I used calipers to determine the maximum distance that it could sink in, then measured that on the stay each time I made an adjustment.

Now, since the cap doesn't have a second open end, I had to do things a little differently to see if I'd filled everything properly.  If I were a pro, a blind braze like this wouldn't make me blink, but I'm still a bit paranoid.  On the suggestion of the internet, I curled up a little plug of silver, coated it in flux, and dropped it in the cap.  Then I added the stay and heated the whole end until the silver melted and was sucked up into the joint by capillary action.

For the other end, I wanted to make an abrupt but rounded cap.  I've already done this, so it didn't hold a lot of surprises.  It was a bit harder than last time because I spaced on drilling vent holes before brazing the end up.  That leaves heated air trying to push the filler out.  It worked out alright, but I'll be more careful next time.  I used brass so that the filler wouldn't melt when I braze them to the sides of the seat lug.

Also note that I notched the lug itself to increase the surface area that will hold things together.

The dropout caps go on the chainstays in about the same way as they go on the seat stays, but you have to line them up so that they're in the same plane as the oval in the stay.

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