In my project, a little Nema11 stepper motor turns for max +/-90° an handle. When the windings of the motor are not energized, the handle can be manually rotated by a human operator.
The load is not big: the stepper offers max 19 N x cm of torque and the max load in the handle is around 3 Kg. The gear ratio is around 1 to 4. My goal is to reduce as much as I can the bad feeling of "clunkyness" and friction/resistance added by the gears when rotating the handle by hand.
What is the better? An "high" number of small teeth, or a small number of "big" ones? (I.e. a small m value versus a big m value, while keeping the pitch diameter the same.)
From an intuitive point of view, I could think that many small teeth have more probability to stay in close contact, increasing friction. While few "big" teeth stay more "away" one from the other. But I could be wrong...
I've read somewhere that efficiency of spur gears is substantially independent from the value of the modulus. It is strongly related to the value of the pressure angle α instead.
Is this true? It seems that I can simply choose almost the value m that I like more to build the gears (in acetal/Delrin).