War machine on Trajan\'s Column

[Timianus]

Looking at the blown-up image, there does not appear to be any connection between the "barrels" of one unit and the upper "wheel" of the next..I think the "lines" are part of the wall. It does indeed appear to be 3 separate engines. When viewed in that light, the first thing that came to my mind was some form of battering ram....but then on the machine farthest to the right, the "barrel" seems to be attached with an arm that is kinked at a 90 degree angle.

Very confounding.