Dimensions of downtubes on step through frames
I've already posted this question on the folding bikes section, but it strikes me that one or two of you might be able to help me out as well. I am currently doing a project at University on the influence of shape on the downtube of step through frames and am stuck for data.
What I need is the shape of the tube (i.e. circular, oval, square, rectangular, etc.) and the dimensions, both internal and external. My hope is that if someone here has made a step-through frame or has one in the process of being made or has plans to make one then they might be able to give me those measurements. I don't particularly care what kind of bike it is for, although it would help if you let me know the purpose, material and basic manufacture process. Approximations are fine, just take the value at the midpoint, even if it is variable geometry. This isn't an exact analysis by any means. Having a multiple tube downtube is fine, but I'll need the distance between the tubes.
I've emailed some manufacturers for the same data, but no joy yet and the deadline is at the end of next week (typical disorganisation on my part I'm afraid).
Thanks in advance and sorry for bothering you (and for copying and pasting much of my previous post!)