Visibility is the answer. Once the cars exceeded the hieght of the cupola , the reason for the cupola went away. Also when it was no allowable to ride on top of the cars, seeing the brakemen on top of the cars wasn't necessary.
Dave H.
Dave H. Painted side goes up. My website : wnbranch.com
While not an official reason, space probably had something to do with the changeover, too. The cupola cabeese I have been in all feel like an hourglass (especially with a centered cupola): skinny in the middle. This is where the chair(s) to see out the top go, and underneath them are some closets. There may be 36" of aisle space under the cupola.
OTOH, a bay-window caboose feels more like a room. The closets can all be put at an end (or in the corners) and the rest of the length can enjoy the full width of the caboose. If a diagonal table is placed in the bay window, looking out does not require much internal space. The effect is like being in a smallish bedroom or a big walk-in closet.
Extra-cube boxcars started growing upwards and you can't build a cupola to see over them without getting a top-heavy caboose. You also have to rebuild every single bridge along the right-of-way to make the extra headroom. No railroad had that kind of money in the '50's, '60's, or '70's. (Also note that the 'Standard Northeast caboose' has a short cupola in the first place.)
For visual appeal, I still prefer the cupola caboose. But for utility, the bay window was the wave of the future.
Plus visibility...most wood cabooses were built to an 8' height, same as the boxcars and reefers that ran in front of them, so the cupolas allowed an unobstructed view ahead of the entire train. When 10' "highcars" started becoming common in the 30's-40's, the view ahead was blocked off - but the new cars weren't any wider, so the bay window gave you at least fairly good visibility down the side of the train.
In 1952 the DM&IR had a caboose designed and built for them that combined the two - essentially a caboose whose cupola was wider than the car body...the "Extended Vision" caboose.
This makes me wonder... What was the logic behind the switch to Bay Window cabooses please?
TIA
Andy Sperandeo MODEL RAILROADER Magazine
Just off the top of my head, I'd say 1950s for the steel bay window cabooses on the C&NW, and perhaps the 1940s for the wood bay window cabooses that were converted from cupola style. If I get the opportunity I'll look through old issues of North Western Lines to get more definitive data.
Dave Nelson