Quote Originally Posted by iugmoh View Post
thanks alot skimask for your interesting information, I learn new things about open differential , I read it but I can't distinguish between straight and turn mechanisms and what happened and what is the thing make this machanisms straight or turn.

http://auto.howstuffworks.com/differential2.htm
Picture 2 half circles, for instance #1 having a radias of 500mm and #2 having a radias of 400mm, and both having the same exact center. now imagine those 2 half circles represent the tracks left by the wheels. the inner wheel travels a shorter distance than the outer wheel does. That is the purpose of the "open differential" . Does your motor have 1 set of 2 or 2 sets of 2 brushes? BTW a brushed motor is commonly referred to as a Universal motor as it can operate from A/C or D/C.