Here are the illustrations I promised regarding tuning the take-up motor for correct Torque/Speed characteristics when applied to an open-loop drive for the Kinograph.
Take a moment to absorb the principles shown in A and B, then the following 4 illustrations should make sense.
I get the impression that once this tuning is carried out, there will be no need to adjust the resistance again as requirements of speed and the tension employed are changed. It will just be a matter of readjusting the motor voltage. I make this assumption because the relationships between all the variables (speed, tension, reel diameters, etc.) all appear to be linear, there being no obvious second-order effects. The only thing I do not know is whether in the current Kinograph design the tension changes with speed. In the version I am building, the tension is controlled and held constant electronically via the supply reel motor, so the problem does not exist.
In a short while I will post the table of values that I mentioned earlier which will enable the true significance of that red line in the illustration with respect to the motor characteristics. BTW the motor characteristics are usually stated by the manufacturers as two values - no-load speed and stalled torque.
Have fun
Jeff