Here we have a Serrota built Yo that is getting a modern face lift; disc tab and brace added, canti's removed, new cable routing, and a Team Violet paint finish.
Mike should be glad he paid upfront on this, cause had I known what a pain in the arse this job was going to be I'd have given him a price that would have scared the notion right out of him ;)
The big issue is that the bullet stay treatment with the tab dropouts leave adding a disc tab a challenging job. You see, since the stay is pushed to the outermost position and the tab inserted in the inside, the position leaves the disc tab half hanging in the air with nothing to attach to. I ended up machining a custom tab that follows the shape of the stay/cone, dropout and over the rack eyelet to insure 100% support.
Next up I broke out the 4 inch grinder with cut off disc and CAREFULLY began to cut away at the canti bosses...don't try this at home kids. One slip and you'll be through the thin stays and your day will spiral towards suicidal thoughts. The stays cleaned up pretty well, the left stay will need a touch of silver for an undercut area from canti welding.
Buzzing off the cable stops...
Unlike a lot of builders, I just can't stand it when folks slam a straight piece of tubing in for a disc brake. The frame has all kinds of sexy curves that should be complimented with the brace so that the whole thing flows and looks original. So I bent up some .75" tubing and hit the hard angle miter so that the bend matches that of the chainstays.
All the Fats have sealed tubes which mean that I need to vent them prior to welding on the brace to prevent gas blowback from increased pressure inside the structure due to heat. When originally made, a small hole is left until all the welding is completed and then closed with a bit of silver. I'm putting some vent holes inside the brace so that they will not be seen but still be protected.
When you work by yourself, it helps to have a few extra hands...toe straps are great!