Bofobo
M,Mizera(BOFOBO)
I believe ive found a solution this morning over coffee ...
I started with thinking about tractor exhaust flaps (name?) then some thing with a spring ... all the kinds of springs i have ... however its not sleek and springs get lost so i have another thought a stud welded to the inside of the pipe with a keyed plate and an r clip or a threaded stud possibly ideas?