Moment of Inertia

The original base frame was made of 2×4’s sandwiched between 3/4″ plywood. I hired a structural engineer to estimate the uniform load capacity for the 7′ length of a sistered 2×4 beam and it was only rated for about 500lbs. Since then I have gone back to the drawing board and determined the relative strengths based on Moment of Inertia:

2×4: 5.36
4×4: 12.505
2×6: 20.8 (almost 4x as strong as 2×4)
2×8: 52.73 (almost 10x as strong as 2×4)
2×10: ~115 (more than 20x as strong as 2×4)

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