Next stage of the project is to define the distance between the axes. In the dialog box 'Axis distances', shown in the figure below, there are the following columns: pair number, pair wheels (wheels arranged in pair), actual wheel axis distance (the actual distance between the centers of the wheels for each pair) and required wheel axis distance (the determined distance between the centers of the wheels selected or entered by the user). The window has three tabs that can contain up to 30 pairs of wheels.



Some pairs of wheels can be associated with the same shafts, so the distance between their axes should be the same. In such cases, the change of distance between any pair of wheels in the column required wheel axis distance will cause a simultaneous change of distance to the other associated pairs.

The 'Axis distances' option can be used in three ways:

1. User doesn't make any changes, current and entered distances between axes are identical. The program during optimization is trying to keep the current distance between axes;

2. User modifies the distance between axes in the column required wheel axis distance, selects or puts values. During optimization, program aims to solve calculations for selected axes distance.

3. Selected check-box axis distance determined during optimization allows to change the distance between axes during calculation in correlation with the optimization criteria. 

The third method is superior to the others. If it is selected, it will determine the distance between axes, regardless any changes in the column required wheel axis distance.

It allows for the optimization of existing gear set (method 1), some modifications of distance between axes for an existing gear set (method 2) or searching for better or completely new solutions (method 3).