radius primary shaft

Another imporant part of the clutch is the primary shaft. It's the link between clutch and gearbox.

theoretical the torque produced by the motor is the same torque on the disc plate and the same as on the primary shaft.

calculation:
d= 11,65mm

the real situation: 24 mm

or there is something wrong in the calculations (probably) or there are some properties of the gearbox that influence the radius.