Quote Originally Posted by plungefrog View Post
What I am not sure of is if they also drive the take up spool -I wouldn't think the film would wind up tightly any other way but I may be wrong. Which brings me to driving the spool at a suitable speed so that the film will wind up smoothly, but not so much as to force the film to slip past the transport drum, or to cause the drum to rotate faster.
The take-up spool can have a tensioning motor. You basically want to have something which holds a tension, and as that tension is relieved (i.e. the drum advances film), the take-up mechanism brings the tension back to par. This can be done using a clockwork mechanism. Perhaps it may be easier just to have a torque sensor which automagically (dis)engages the take-up motor.