Mechanical Monsters at the Fall of Gondolin?

[Aiwendil]

About the devising new dragons for the attack on Gondolin, I just wonder if the time that elapsed between Maeglin's plan to Melkor is long enough for the creation of such dragons. Do we have a time prediction of how long it take to breed a dragon?

That's an excellent point. If the dragons are no longer made of metal, can we still speak of 'devising' them? Or must they instead be 'bred', a far longer process that could not have been achieved between Maeglin's treachery and the fall of Gondolin? If we decide on the latter, then we need to rethink FG-D01 and FG-D02.

I'm not sure if the "of iron" is going to be used in the revised version of FOG.

No, that was just a fictitious sample of writing in the Q30 style intended to show that if the mechanical dragons had been retained at that point, the text could easily have said so.