Johnwasser, Thank you for your answer. I now understand why I need those diodes. Is a 1N4001 good for this purpose ? Or any diode will do ? What parameter should I look for when selecting a diode to use as fly-back?
Thank you for your answer, kf2qd. I see how using a continuous rotation servo would help me in reducing the complexity of the project, but unfortunately the servos are expensive in my coutry, specially the continuous rotation ones. One servo costs as much as a Tamiya gearbox... and i'll need two servos. Therefore, due to the low cost character of the project, I think I'll stick with DC motors.