[Justin Stiltner]

Also, in this application a 6lb weight will always exert 6lb force in the down direction. However the added force you need to lift this thing is due to the friction of whatever is holding it out away from the upright portion. you calculate that by summing the torque on the mechanism at a convenient point and finding the resulting force at the point of contact. Then you can approximate the actual force if you have some values for coefficient of friction for the materials. For more info look into a subject called "Statics"

Also as an aside thought, If you dont already, try to place a bearing at each place that contact is made between sliding surfaces, or at least some slippery plastic, that may help your motor some as well