the seat tube isnt welded to the rear triangle.. simply the rear triang is shaped like a u and is formed around the seat tube and is open to the rear so that the seat tube can move freely. its probly a single pivot centered around the bb for no chain growth aswell.
Why give turb0 negative props? He is right the pivot is around the bottom bracket, I am almost positive that its one of Brooklyn's designs. ive been to their shop they have a bunch like this. And plus why put a 5 to 600 dollar avalanche rear shock on there for looks?
well it just looks like there is no way the frame can bend according to the shock direction
and it is just fixed to the frame as you can see there would be no picot round the bb
Doc made this bike in 1997 along with a few others. Look at this picture and stop arguing that there is no pivot around the bb because there clearly is.
you are correct there is a pivot round the bb very strange but from perspective of this picture on pink bike it looks like the rear swing arm is just stuck to the frame