Sum of torque

[EOW]

With 2 different radius and a belt.

Or 2 disk with the same radius and a circle with friction to accelerate the disks

[EOW]

The radius of the grey disk is lower than the red disk but the angle alpha of the grey disk is lower than the red disk, so the grey disk turns quickly than the red disk, the arm receives a clockwise torque.

[EOW]

Like that the spring increases its potential energy and the arm receive a positive torque. The horizontal torus turns at -w in the arm reference. The disk turns at -0.707w in the arm reference.

[EOW]

2 springs and 2 disks.

[EOW]

On the red arm I can put 2 spirals. The spiral1 will accelerate counterclockwise in the arm reference and it is correct because R1 becomes smaller more and more and R2 becomes higher more and more. So, the spiral1 accelerates in the laboratory reference.The spiral2 decelerates in the arm reference but it accelerates in the laboratory reference. There is a pressure from a gas outside the device.