Aferg I will concede that my equations are in error, and that your equation does indeed give the correct answer.
I was able to prove the equation earlier today using the density of steel @490lbs/ft^3.
Now say that cube is the 1:18 representative of the full scale cube. Meaning the full scale cube would be 18ftx18ftx18ft=5,832ft^3.
It would weigh 5,832ft^3 x 490lbs/ft^3=2,857,680lbs
Using your formula to find the weight of a 1/18 representative 2,857,680lbs/(18^3)=490lbs.
Very nice formula, and it was a good exercise for my brain. I haven’t used it like that in a while.