The brass body could be in another material, but because it's screwed into an aluminium body, brass allow to not cause oxydation seisure with time. If I use an iron body, do the magnetic center field will be relocatd in the middle of the overall iron mass when electromagnet will be powered or if it remain the center of the coiling?

I'll try to double the volume/mass of the iron core. As I said, I'm pretty sure it's lightweight is pretty hard to keep attracted in the magnetic field.

 

Its more usual to design the rest of a device around the main working parts needed. In stead of trying to make the main working part fit the space.

 

You are right with this but it's because it's an upgrade of something already existing. That's why dimension and space are limited!

 

Common enough problem. Boss says, "Make it fit" and physics says, "You're an idiot".

New engineer sends me a transformer design wherein the windings will not physically fit inside the toroid. LOL!