In the time past there have been questions about gear generation.
I have made a pair of parametric gear wheels based on the grafical method.

It function only if the four CONTROL_xx...  parametres is changed by using the 
f(x) botton at the right vertical tool bar.
 
Never acces the parametres via the sketch or the browser, because the  equations will be spoiled.
There are a malfunction in the equation editor.
Those failures and the functionality of the editor have been discussed in one of the forum groups.

The gear pair moves when the Constraint Angle of the driving wheel is edited.

Kind regards 
OLdbelt.

Do it right first time.