yo jonathan.... sounds interesting, a bit complex for a simple soul like me id need walking through the whole procedure

have you had any joy with the brake ? i found a vid on youtube where someone had used a mechanical calliper on a disk
Actuated pneumatically,,, id prefer to use a motor and screw with a spring as a buffer

if you have any old slit saws you could use one of these as the disk
i havnt desided whether ill take the simple road and use a rotary table or build a fast mover with a disk brake