1. The problem statement, all variables and given/known data I changed the problem, because I understood my error I forgot a force. It's the same problem with one motor. A motor drives two disks on a support. The support is turning clockwise at w1. Disks turn at w at start. The motor M gives a force F and a counterclockwise torque Fd/2 to the red disk. The motor M gives a force F and a counterclockwise torque Fd/2 to the magenta disk. The images shows rings but it's disks. There is friction at points A and B between disks, the force of friction is F/2. http://imageshack.com/a/img908/4925/N672Ta.png [Broken] 1) Draw all forces 2) Calculate the torque on each disk 3) Calculate the torque on the support 2. Relevant equations -- 3. The attempt at a solution 1) I drawn all forces: http://imageshack.com/a/img540/4338/6D0fx5.png [Broken] http://imageshack.com/a/img540/7663/cN4A9b.png [Broken] I noted all forces but: |F1|=|F2|=|2F3|=|2F4|=|2F5|=|2F6|=|F7|=|F8|=|F| The color shows where goes the force, magenta -> to the magenta disk, red -> to the red disk, blue -> from the motor M to the support. Prime forces, like F4 -> F4' are forces that must be reported to the axis. I'm not sure about my forces ! 2) Each disk receives a torque +FR/2-F(R-d)/2=Fd/2 from other disk and -Fd/2 from a motor. So the torque on each disk is 0. 3) If my forces are correct there is no torque on the support from disks. But the motor gives a clockwise torque Fd/2, so the support receives a clockwise torque Fd. Is it correct ?