Try to use a rotary damper actuator for ventilation systems,,, Belimo, Siemens,, Honeywell all have them,, thy need to be whit out spring return,,,, thy have huge turning force,, and run slow,,
you can also use a Linear actuator same like for closing gates and elevating hospital beds,,,
also BOSCH have a new slow mowing motor that can eazy turn 2000 eggs the name is
D.C. motors with transmission
VMC | 24 V 0.22 W
Part number 0 132 801 141
Nominal voltage 5 24 V
Nominal power p 0,22 W
Nominal current Á ) 55 mA
Maximum current  250 mA
Nominal speed á 6 minÉ
Nominal torque À 40 Ncm
Breakaway torque à ( 140 Ncm
Reduction i 405 : 1
Direction of rotation L/R
max. axial â ) 30 N
max. radial Ä ) 50 N
Type of duty S 1
Weight approx. 0,12 kg
as a timer you can use a small hovabator turner motor with roller switch to control any other motor , it has perfect timing