Much too complex!!!
Let me refraise and simplify my question; (forget other posts)
I have one (1) cable, initial length = 100 quants.
It has to grow to 900 quants. (So it grows 800 quants).
The max. scale factor: 900 / 100 = 9
Growing factor: 3 * 16 = 48 quants/sec.
Total growing time: 800 / 48 = 16.67 sec.

I think I don't need this;
The map scale = 1 : 2.5
The speed of growing: 3 * 16 * 2.5 /100 = 1.2 m/sec.

The question is;
how much is the CableScaleFactor to be used in;
liftcable.scale_z += CableScaleFactor * time;

Regards,
Frits