Drum bakes: Brake pad holders. 
aluminium round
simple method to hold the round parallel to the middle
sawed and milled
brass bolts
 
fitted with springs
set up 
a little problem are the brake pads themself. after a lot of research i've found the tip that gasket paper (abil eg) was a pretty simple material
and really: it works perfect. 
mocked up
next and last part: bowden cable and the mechanics to activate the breaks.