Hi The belt drives over the surface of the tape so the tape speed is independent of the spindle speed ( as Tony mentioned ). The smaller spindle would revolve faster but that doesn't explain how it maintains tension. As Tony said, the belt runs over the surface of the tape at both spools. If every thing was equal, the tape would never have any tension on it and any slack would never be taken up. As one knows that has taken one apart, the belt is a little elastic and is stretched on. The place that the belt is stretched the most when moving would need to have a higher surface speed ( kind of like the Bernoulli principle ). This would cause that spool to turn a little faster than it would if the belt were non-elastic. Of course, the end of the belt that is close to the drive would have the most tension and that spool should have a tape speed slightly greater than the other spool until the tension of the tape brought the other spool to the same amount of stretch on the belt. It seems like I remember something about holding some tension on the tape when I was taking up the slack. As I recall, it seemed counter intuitive at the time but thinking about how the belt speed up the take-up spool, it makes sense. Joe, the next time you have to take up slack, maintain a little tension on the feeding spool and you should notice an increase in the rate that the take-up spool pulls the slack in. Dwight