A Climax question...

Gentelmen,
I'm sitting here pouring though my copy of "The Climax Locomotive" and looking at other source material from magazines on Climax locomotives and I'm scrathing my head about how the frame is con structed on the Class B and Class C engines.
It looks like a piece of square tubing. Then in some of the more detailed shots it looks like "I" Beam with stiffiner plates rivited onto the web. But to get that squared look those plates would have to be a couple of inches thick!
What am I seeing here? Can someone show me some photos of how Climax built their frames?
Thanks,
Curtis F.