Hi Bill,
I'm glad the drawing office figures were able to provide you with a check against your volumetric models. Even though I didn't go to the trouble you went to in calculating the internal volumes, I was suspicious of these numbers because they just seemed way too large, and suspected that they might be figures given for a fully filled vessel rather than one filled to the maximum proper level for steam production. Your analysis has evidently proved these suspicions to be well-founded! Of course, as always, this now brings up a new question to explore: I wonder what the optimum nominal fill height above the tubes was for these boilers, as well as the minimum and maximum operating levels.
Regarding the structure of Olympic and Titanic boiler versus those of the Britannic as shown the drawings published in "Engineering" and in "Verbal Notes...", I have compared the information presented with all of the information I have available to me, photographic and otherwise, and other than the one foot increase in length, all other features appear to be the same between the earlier D.E. boilers and those of the Britannic. Based on the figures provided for grate surface, the additional length seems to be added wholly to the furnaces, fire bars, tubes and stays, with the depth of the combustion chambers remaining the same. I don't have figures for the S.E. boilers on the Britannic, but given their primary purpose, I doubt that there was any change made in the design of these boilers.
Regards,
Scott Andrews