I have been thinking about a new way to build a module. From experience the
challenge is to make a light module that is strong both horizontally and vertically
and also resists twisting. I want the track sub-roadbed to be stiff and strong.

In large construction I would use an I beam. It is not practical to make an “I” beam,
I want the space under the track to be open for wires and switch machines.

My thoughts moved to a “C” channel. I used 3/4 ply for the sub-roadbed. I then used
1/8” Luan Ply (door skin) for the verticals on the “C” channel. I “notched" out the
end plates to take the sub-roadbed. I then routered out a grove on the bottom of
the sub-roadbed and the inside of the end plates to accept the luan. If a picture is worth 100 words, here are 4000.