| Posted by Dan I. on June 12, 2020 | |
I have often wondered why steam locomotives of the 1800's and some 1900's had such large funnel shaped smokestacks? And then a few decades later, a person only saw straight vertical stacks and some steamers had almost none at all as in the case of Union Pacific's "Challenger" and "Big Boy". Anybody out there in railfan-land know the answer? Just curious.
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Steam locomotive stacks which are anything other than straight are typically designed as spark arrestors, to catch either hot cinders or burning wood embers. The goal, of course is to prevent fires, and steam locomotives did set a lot of fires. It's also the reason why most preserved steam railroads today chase their trains with fire patrols, to look for line-side fires. In the case of B&O #25, she sports a version of what is known as a "Yankee-style" balloon stack, which is most definitely designed as a spark-catcher and would typically be found on a wood-burner (also on some modern-day replicas of wood-burners, which burn oil instead.) While construction varied, it is likely that there is an inverted cone inside there, covering the actual exhaust, to reflect any high-speed embers that were ejected and keep them rattling around inside that big stack. At the top, there would typically be a big screen, which would limit the size of anything actually leaving the stack with the smoke. Most such stacks have some sort of clean-out plug at the base, which is periodically used to prevent the build-up of debris inside. The 25 was originally designed as a wood-burner, and ended her operational career that way.
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