I'm mulling over something different in the way of formats. Traditionally locomotive books have been written class by class, which in many ways is the most logical way to do it. But the trouble is that its difficult to get a sense of how design developed. Say for instance, you're looking at GWR 0-6-0 freight engines. You list the 57 class and its history from a cabless domeless sandwich frame locomotive in 1855 with Gooch motion, then maybe the renewals around the mid 1870s which were almost new locomotives, domes boilers, Stephenson link etc, and then typical 1890s boilers, even Belpaire fireboxes before being withdrawn mostly in the 1910s. Then you jump back to the 79s in 1857, and a similar story, and so it proceeds, jumping between eras and what by the end of their lives are very different locomotives. Which is fine, and its conventional because it works for most people, but it makes it very difficult to gain a picture of how the design school was progressing. A Dean Goods at the end of the class service life in the 40s and 50s was a very different beast to the first built Dean Goods in the early 1880s, and maybe it makes as much or even more sense to look at it alongside a 2251 as opposed to an Armstrong Goods?
So then I got to thinking, OK, lets look at it over a time line. The most extreme version would be to use a format of annals - literally year by year, So sort of
Of the 60 locomotives built this year, most were transitional Dean/Churchward types with Churchward boilers. There were 10 Aberdares with Std 4 tapered boilers without top feed and slide valves. 27 Bulldogs, which mostly had second hand parallel barrel Std 2 boilers, although the last ten had short cone taper boilered Std 2s. The reason for the second hand boilers was that the original plan was for a sort of super Bulldog with a Std 4 boiler, but in the event these were used to upgrade Aberdares instead. The ten new Cities, fitted with Std 4 boilers were also built this year as were a further 10 of the 36xx 2-4-2Ts. Most notable, however, was the start of the Churchward revolution. The 2nd and 3rd prototype Saints 98 and 171, the 28xx, No 97 and the large Prairie No 99 all appeared this year, the first with the Churchward front end with integrated cylinders/saddle. The DeGlehn no 102 also made its first appearance this year. Arguably this was year the final form of the British steam locomotive appeared.
Then illustrations of a City and the Churchward prototypes perhaps."
An alternate approach would be to do periods of design, for instance Churchward/Dean Transition and Churchward Standards. That would separate the 36xx, Aberdare, Std boilers on 4-4-0s and the Std 2/4 boiler era from the true outside cylinder era, and in many ways would be a lot more readable, but on the other hand there would be big overlaps, with transition types like the Bird and Flower as late as 1908, but the outside cylinders starting in 1903. On the other hand it would be a lot more readable.
What do you think folks? Would you be more likely to purchase a book based on timelines? Rigidly as annals, or more flexible with eras?