RtR Tape reel size selection

[JediDude]

I was pondering what changes in a RtR deck when you select the large reel size, for 10.5" reels. My initial thought is that the supply reel exerts a lower back torque to keep tape tension within tolerable limits.
Am I right?
I suspect the takeup reel also runs with a lower torque for the same reason.

The particular deck that prompted my question is a Pioneer RT-1011L, in case it matters.

 

[dr*audio]

The torque goes higher, not lower.

 

[JediDude]

Interesting...
I thought that with a higher torque supplied by the motor, the tension in the tape would be higher. The 10.5" reels have a larger diameter to pull on the tape.

 

[dr*audio]

As the diameter increases the tension decreases. You can see this for yourself by comparing the tension on the tape at the beginning and end of the tape. Sophisticated machines sense the tension and adjust the torque to keep it the same. I believe the Technics RS-1500 does this. I used to know the Physics theory behind this but I have forgotten it.