RE: What's the minimum amount of torque that can be used for aileron direct drive?
Servos for ailerons -
The original setup of one servo -plus bellcranks is superior to any sevo in wing setup -
Problem - sloppy cheap linkages .
Ailerons try to deflect up/down depending on air loading and centering is bad.
So - IF the original setup (one servo coupled to both) , was perfect -- the load on the servo would be nothing --unless you input info for deflection.
Individual , inexpensive servos can easily be pushed up or down , around center.- try it -
Very strong digital servos hold the center far better - even cheap digitals are much better at holding position than any non digital .
has to do with providing power at the slightest variation.
Real world -
done right with max servo travel and minimum aileron deflection - any decent setup will do the job for a good sport/scale.