Represent gear with fixed gear ratio
The Simple Gear block represents a gearbox that constrains the two connected driveline axes, base (B) and follower (F), to corotate with a fixed ratio that you specify. You can choose whether the follower axis rotates in the same or opposite direction as the base axis. If they rotate in the same direction, ωF and ωB have the same sign. If they rotate in opposite directions, ωF and ωB have opposite signs.
The Simple Gear imposes a single constraint, specified by the fixed gear ratio gFB, on the motions and torques of the two axes:
±gFB = ωB/ωF = τF/τB
The plus and minus signs refer to the axes corotating in the same or opposite directions.
If the Simple Gear represents two coupled gear wheels, the gear ratio is related to the ratio of the radii r of the gear wheels and the ratio of the number N of teeth on each gear wheel:
gFB = rF/rB = NF/NB