Such great post should be posted thrice
Very easy reading and understandable - even though I know the subject in question this reading clarified some points to me.
A question which always makes me scratch my head and loose the rest of my hair is how on earth do some achive smooth transition between two soldered parts of brass tubes on a ventilator (one being straight and the other(s) at the angle). I tried that with paper model (with miserable results) and know that you can make an 'approximately' smooth transition between individual sections of a pipe (cylinder) while trying to represent a ventilator. As we can not use putty if we want 'bare-brass' ventilators or unpainted papermodel the question arises.
I knew guys who have done ventilators from metal just casting the metal (in special oven). While definitely a good method it is not for me as I will probably never have an access to such ovens. But how they do it without casting from individual tubes - I do not see any sort of transitions between sections on museum quality ventilators - probably they bend the pipe somehow...
Yevgeniy