Some turning required please

[Jonathan]

I've just made a quick spreadsheet for calculating the inertia to demonstrate the difference:

Moment of inertia calculator.xls

I've entered the values for your original design as an example, so you could put the values in for the modified design and compare. You could also include the pulley and ballnut.

[drumsticksplinter]

Thanks for your advice Jonathan.

I know what you are saying that aluminium will decrease the moment of inertia as will reducing the radius. I've seen lots of designs that all go the other way and house the ballnut inside the bearing housing using larger bearings still, I'd agree that this is overkill.

This is the design I liked the look of:

castanha 25mm passo 10 da OBR com sistema giratório [rotating nut] - YouTube

What do you think?