Sum of torque

[EOW]

Magenta disk has a velocity around red point and around blue point too at start, this energy is gave. At t=0, 2 disks are like figure, with friction between 2 disks. Magenta disk increase rotationnal velocity of grey disk. Grey disk turn around blue point only. Magenta disk decrease its velocity around blue point but decrease its velocity around red point too. The sum of energy is not 0. Black arm is force to turn like grey disk.

[EOW]

A disk with radius R turn at w1 around red axis of rotation. A cylinder inside the disk of radius r turn at w2 around black axis of rotation. Black axis of rotation is supported by disk. At start, disk and cylinder are turning. Friction exist between cylinder and disk, this friction give torque F1/F2 and -F1/-F2. Like radius of disk is different of radius of cylinder torques not works the same value, because it's possible to have the same angle when choose good value w1 and w2. The works of torques can be positive with good value and friction add energy too.

F1/F2 works with a radius r on cylinder. -F1/-F2 works with a radius R on disk.

[EOW]

2 disks are turning together. Blue disk turn at w1 and yellow disk turn at w2. With w2<w1. A support not drawn aplly forces like image shows. torque on blue disk don't change energy because forces pass to axis of rotation. In the contrary, forces on yellow disk increase energy like (w1-w2)², like w1>w2, when w2 decrease, the energy increase. Friction add energy too. For maintain yellow disk at contact of black walls, this need to add a spring or something like that.

[EOW]

 Maybe like that ? N disks all around disk1. Each disk (except disk1) receive a torque that slow down rotationnal velocity of diskX, so the energy increase is W1 > Wx with X from 2 to N. And N the number of disks (except disk1). W1 is clockwise, Wx are anticlockwise. W1 don't decrease because forces pass through axis of rotation (blue point in center of grey disk1)

Friction create forces. Each disk except disk1 receive a torque, this torque decrease rotationnal velocity and increase energy because energy is a function of (W1-Wx)². W1 > Wx. Disk1 turn faster than others disks.

[EOW]

At start the system is turning freely (no axis of rotation), the system turn around its center of gravity. w2 > w1 like that when w2 slow down, the energy increase, energy if a function of (w1-w2)².