The expressions editor
uses a straightforward mathematical syntax comprising operators (+, -, *, /, etc.), constants (pi, e, etc.), RailClone's built in variables and inputs, and functions (that take one or more arguments and return a result). There are many built in functions, operators and constants available and these are all listed in the Expressions pane on the left hand side of the window. To see an explanation for each function, single click on it and a description and example syntax will display in the Expressions Help pane at the bottom of the interface.
I've just added this information to the documentation to help make it clearer. There are not currently any tutorials exclusively about the using expressions but you will find expressions used in the second half of the Counting Numbers
Another thing, when I adjust the global scale, the alignment of the gears totally offsets, why?
This is because the Global Scale value does not
affect the Fixed Size parameter, though it does
affect the Padding and Transform values. If you know you are going to use the Global Scale, then one solution is to use a very small Fixed Size value, for example 0.0001cm, and then position the objects using only the padding and transforms. You can then use Global Scale without problems.
I Hope that helps.