Thank you, Mike! Your explanation of injectors is very clear and helpful.
Makes me wonder why any railroad would have chosen the "lifting" type.
Maybe it had to do with how different roads ran their engines, the profiles
of their lines, etc.
Regarding feedwater heaters: the Burlington's three Coffin-equipped O-3s
(5318, 5325, 5341) all had units that extended out from the smokebox front,
sort of like the giant eyebrow of a cyclops, so at least some of the
mechanism must have been outside the smokebox. But maybe enough of it was
still inside to make it as messy and dirty and troublesome to maintain as
you describe. An interesting fact about these engines is that when the
Coffins were removed, sometime between 1935 and 1952, they were not
replaced with Elesco or Worthington units. The engines reverted to using
injectors only. So the Coffins really must have been more trouble than they
were worth.
That got me to wondering about what kinds of engines were equipped with
feedwater heaters and why. A quick perusal of the rosters in Corbin and
Kerka shows that many, though not all, of the Burlington's mikados had
feedwater heaters. All of the Q's larger engines had them (all 4-8-2s,
4-6-4s, 2-10-2s, 2-10-4s, and 4-8-4s), but almost no smaller engines --
with the exception of the Pacifics, almost all of which were so equipped,
even the smaller S-1s. What this suggests to me is that the real advantage
of having a FWH was its ability to help sustained steaming, especially on
heavier trains. Hence its use on mainline passenger engines, some of which
produced considerably less tractive effort than the drag-freight 0-3s, some
of which used only injectors.
In the case of freight engines, the choice of whether to add a FWH probably
was determined by a combination of the engines' intended functions and the
terrain where they were assigned. Manifest freight engines, for instance,
would have benefited from feedwater heaters more than drag freight engines,
as would any and all heavy freight engines operating over uneven terrain.
Consider the Burlington's USRA O-4 mikados, all 15 of which had feedwater
heaters, versus the FW&D's corresponding E4A2s, which appear to have only
injectors. Presumably the pancake-like topography of central and west Texas
diminished the need for FWHs, while the grades of the Q's western
divisions, where the 0-4s hung out, made such appliances much more
important. It strikes me as significant that feedwater heaters seem not to
have been used much on the FW&D, compared to the Q -- or the C&S, where
all engines larger than a 2-8-0 had them.
Jonathan
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