Since it's been about 35 years since I took strength of materials in college I would like to ask for a little help. I am building a tricycle to be both peddle powered and assisted with an electric drive and planing on using A36 steel tubing for the frame. I found the calculator on this site for the section properties of square and rectangular tube, but for the life of me I can't figure out what to do with the results when it comes to inputting them into the beam bending calculator. My options are 2x1(.065 or .095 wall) or 1.5 square tube. I think the wall thickness may be off from what I have seen listed on the net but that is what the supplier gave me when I called for a quote.

I am attaching a rough sketch of what I ultimately am planning, for now though if someone could just tell me what I need input into the beam calculator for 1.5 and 2x1 tube it would be appreciated. After I figure that out I can divide the load between the multiple beams. Total loading will be in the range of 500# with two passengers and batteries etc.

Thanks,