Steve,
How much of the cab was filled by the boiler depended on the builder of the
cab. A good example is the Crystal River 103, an outside-frame 2-8-0
delivered with the backhead sticking out the back of the cab. The cab was
later replaced with a really long 3-window cab by new owner D&RG, who
renumbered it 375 (class C-25). The cab was extended back some to
(barely) enclose the backhead. Still later, they built yet another cab, a shorter
one that still extended just to the rear of the backhead. So, the cab moved
around on the boiler over the years.
The extreme example of this, of course, is the "camelback" type, where the
cab straddles the middle of the boiler, and the fireman stands out in the
weather. You'd think a design like that would have come with oil firing, but in
fact the cabs were moved forward to accomodate the huge Wootten type
anthracite-burning firebox, which was almost as wide as the loading gauge of
the line.
And just for completeness, what about the Forney type, which was intended
by Mathias Forney to run bunker first, boiler last (they were really 4-4-0s,
rather than 0-4-4s)? The cab is in front of the backhead on that one. ;-)
As you noted, some locos had the backhead closer to the front of the cab, but
that's not necessarily a universally standard arrangement. As in so many
things, the answer to the question "where does the cab sit relative to the
backhead?" is "It depends" -- on the loco, and the time in its life.
regards,
-vance-
Vance Bass
Albuquerque, New Mexico, USA
Small-scale live steam resources: http://www.nmia.com/~vrbass
