Since the thing called Q-factor came from bikes I’d suggest that the bike definition be used. Even if the Q-factor is not really a factor but a distance.
Q factor is the overall width of an installed crankset, measured parallel to the bottom bracket shell from the outside of one pedal insertion point to the other. You can think of it like this: the larger the Q factor, the farther apart your feet will be.
The Q-factor is effected by the axle length and crank offset (sometimes probably incorrectly called the crank Q-factor).
