What was the principal behind the design. How did they work. Thank you.
Smoke deflectors of various shapes and sizes have been used on a number of types of steam engines on a number of roads, both in the US and elsewhere in the world. They do work, at least after a fashion… the idea behind the things is that they take air which is otherwise pushed sideways around the smokebox and force it to go more in an upwards direction, hopefully pushing the smoke up…
Not only UP Challengers, but also most Delaware and Hudson locomotives of all types, most NYC Mowhawks and all Niagras.
Thank you very much, my question was answered.
Also, not all UP Challengers had them. On the Northwestern districts, some Challengers were used in passenger service and those were the ones that got the smoke deflectors. Many of these also received 2 tone grey paint.
The later series UP Northerns came with double stacks. The idea was to reduce back pressure, but this resulted in excessive smoke driftinng into the cab under certain conditions. The smoke deflectors were added to solve this problem.