Just a little clarification:
AI_Robotics:
I am using servomotors torque: 40 kg/cm; power: 4,8 - 7 V.
Torque is force x distance, the unit is kgf-cm (kilogram force times centimetres).
The better unit is N-m (newton-metres). 1 N-m = 10.2 kgf-cm
Torque is actually really energy per unit angle, but is commonly thought of as
force times distance-from-axis.
Force is energy per unit linear distance which has a nice symmetry
with torque as energy per unit angle.
Force in newton == joule / metre
Torque == joule / rad == newton * metre / radian (sloppily == newton * metre)