Now that the choice is made to support the lower beam on the subframe using concept 3.5c,
the cross-sections of the both parts can be designed in more detail. In doing this, the most
important goal is to maximize the stiffness of the lower beam. Secondly, the subframe must
be sufficiently strong and also as stiff as possible within the design-limitations (see appendix
A.2 and A.3). This must be done within the outer dimensions of the lower machine section
(± 930 [mm] high, 200 [mm] thick) while using the steel efficiently to reduce the material-
costs. In order to fairly compare the different designs, the ratios of moment of inertia (I)
and cross-section surface (A) are compared (stiffness per kilo of steel). The I/A-ratio for the
current situation (figure 4.1a) is set to 1.