Here are some photos of the Lego Mindstorm film pulling mechanism I am using.

An overall picture of the setup (scanner is on the right of the picture). There are two Minstorm step motors, one of them is rotating the film reel and the other is pulling the film.

Closeup of the puller mechanism. The film moves between the two tyres that are rotated by motor. Note the push button that is used to detect when the film tightens and stops the motor that is rotating the film reel.

The puller from other side

The film puller from above. Note the Lego pieces used to guide the film so that it moves straight (luckily they have a hole that is exactly 8 mm wide!)