As you say weight is the issue. Iron is not a good solution for moving energy because it is so heavy. Aluminium would be a much better solution. See interesti

As you say weight is the issue. Iron is not a good solution for moving energy because it is so heavy. Aluminium would be a much better solution. See interesting chart of energy densities by weight and volume. https://en.wikipedia.org/wiki/Energy_density#/media/File:Energy_density.svg https://en.wikipedia.org/wiki/Energy_density#/media/File:Ene...