Per R18 (Game Manual Section 4.6) when you open your bag before an event, anything added to the bag counts against your 30lb withholding allowance for that event, with the exception of:
- Commercial off the Shelf (COTS) items in the condition you received them from the manufacturer
- Fabricated parts produced during the current robot access period.
From your post, it sounds like you have two mechanisms that you would like to add to your bag, one weighing 10lbs and one weighing 30lbs. (Removing something from the bag has no effect on this.) So, how do you fit 40lbs of robot into a 30lb withholding allowance? My best piece of advice would be to remove any COTS components from the two mechanisms before you unbag. You can reassemble them once the bag is open, and as long as the COTS parts were in their original state (e.g. gear boxes fully disassembled) when you opened the bag they will not count against your 30lbs. You could also try taking advantage of #2 by manufacturing some components for these mechanisms while your bag is open.