A long time ago on the research for the pumps of my Vic I realised that all drawings of first and second rates at NMM from a certain date on show at least two of the four chain pumps reaching the middle deck.
This started about 1760 to 1780. All the drawing showing details have a cistern on the lower deck even for the pumps reaching the middle deck, mostly showing something that appears like an exhaust for a dale or hose.
From about 1810 both pairs of pumps reached the middle deck, both having a cistern and an "exhaust" on both decks.
Searching for quite a while already I just found one source apart from the drawings - the model of the Princes Royal. Here one pair of pump is reaching the upper deck, also showing the cistern, but no details of the mechanism is revealed.
The only reason so far I can see is that the double amount of man could man the handles. But no idea whatsoever how the technical side worked. Where these one chain running though the lower deck (as it seems to me) or were those two different chains for each pump? Was the cistern on the lower deck a water tight "passing through" cistern?
As usual - question over question ...
I just add some pictures of what I mean, some drawings out of NMM and of the Princess Royal.
Edited by dafi, 12 November 2014 - 09:42 PM.