I’m not sure why i didn’t put in a chainstay bridge before I finished the frame but with the excessively crimped chainstays (see pics) and the very light and thin Dedaccai zero uno S-bend stays…the rear triangle flex was noticeable. This bridge in effect, does hardly anything, but it helps. I used an old warped disc brake rotor because: (1) it looks kinda cool, (2) it’s easier to miter and fit into the dimple of the chainstays than a scrap piece of tube, (3) brazing it with silver would work well because you’re in and out very quickly — it allows you to NOT heat up the chainstays very much to braze it in there affecting alignment possibly, etc. (Silver brazes at a lower temperature than brass). Of course, it’s not the beefiest fillet (yes, maybe I should’ve used brass…) but it’s not exactly a spot of high stress, it’s just meant to support and stiffen the rest of the rear triangle. With such heavy wheels (after i weighed the front wheel with tire and tube and it came out at almost 8 lbs…I just couldn’t bare to weigh the rear wheel) I think I’ll have to do something different (stiffer) for the rear triangle next time. These chainstays are great because of the amount of tire clearance they allow, but wow…they are flexy!
In the end, took me half a day to get it all back to rideable (disassemble, remove paint, miter, clean, braze, soak off flux, check alignment, clean, paint, rebuild frame) and all is good again with the Rotundcycle!